Fabry Cardiomyopathy: Current Practice and Future Directions

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Review Fabry Cardiomyopathy: Current Practice and Future Directions

Jeffrey Yim 1 , Olivia Yau 2, Darwin F. Yeung 3,*,† and Teresa S. M. Tsang 3,*,†

1 Department of Medicine, University of British Columbia, Vancouver, BC V6H 0A5, Canada; [email protected] 2 Faculty of Medicine, University of British Columbia, Vancouver, BC V6H 0A5, Canada; [email protected] 3 Vancouver General Hospital and University of British Columbia Echocardiography Laboratory, Division of Cardiology, University of British Columbia, Vancouver, BC V6H 0A5, Canada * Correspondence: [email protected] (D.F.Y.); [email protected] (T.S.M.T.) † These authors are co-senior authors.

Abstract: Fabry disease (FD) is an X-linked lysosomal storage disorder caused by mutations in the galactosidase A (GLA) gene that result in deficient galactosidase A enzyme and subsequent accumulation of glycosphingolipids throughout the body. The result is a multi-system disorder characterized by cutaneous, corneal, cardiac, renal, and neurological manifestations. Increased left ventricular wall thickness represents the predominant cardiac manifestation of FD. As the disease progresses, patients may develop arrhythmias, advanced conduction abnormalities, and heart failure. Cardiac biomarkers, point-of-care dried blood spot testing, and advanced imaging modalities including echocardiography with strain imaging and magnetic resonance imaging (MRI) with T1 mapping now allow us to detect Fabry cardiomyopathy much more effectively than in the past. While enzyme replacement therapy (ERT) has been the mainstay of treatment, several promising therapies are now in development, making early diagnosis of FD even more crucial. Ongoing initiatives involving artificial intelligence (AI)-empowered interpretation of echocardiographic images, point- of-care dried blood spot testing in the echocardiography laboratory, and widespread dissemination of point-of-care ultrasound devices to community practices to promote screening may lead to more Citation: Yim, J.; Yau, O.; Yeung, D.F.; timely diagnosis of FD. Fabry disease should no longer be considered a rare, untreatable disease, Tsang, T.S.M. Fabry Cardiomyopathy: but one that can be effectively identified and treated at an early stage before the development of Current Practice and Future irreversible end-organ damage. Directions. Cells 2021, 10, 1532. https://doi.org/10.3390/cells10061532 Keywords: Fabry cardiomyopathy; Fabry disease; lysosomal storage disorder

Academic Editor: Ritva Tikkanen

Received: 6 May 2021 Accepted: 15 June 2021 1. Introduction Published: 17 June 2021 Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the α- galactosidase A (GLA) gene that result in deficient α-galactosidase A (α-Gal A) enzyme and the Publisher’s Note: MDPI stays neutral accumulation of globotriaosylceramide (Gb3) and associated glycosphingolipids throughout with regard to jurisdictional claims in the body [1]. The accumulation of Gb3 in lysosomes leads to metabolic dysfunction and published maps and institutional afﬁl- subsequent cellular death in various organs, leading to a multisystemic clinical presentation iations. that includes cutaneous, corneal, renal, neurological, and cardiac manifestations. Fabry disease has long been considered a rare disease with limited diagnostic and treatment options. However, the condition is likely underdiagnosed, with newborn screening programs around the world showing much higher prevalence of GLA mutation than Copyright: © 2021 by the authors. previously described [2,3]. Furthermore, we now have more effective tools to diagnose FD Licensee MDPI, Basel, Switzerland. in a more timely fashion [4–7]. The development of novel effective therapies has made the This article is an open access article early diagnosis of FD and prompt institution of therapy even more important. distributed under the terms and The purpose of this review is to provide an overview of the cardiac manifestations of conditions of the Creative Commons Fabry disease, methods of screening and diagnosis, currently available and investigational Attribution (CC BY) license (https:// treatments, ongoing challenges in management, and future directions to improve the care creativecommons.org/licenses/by/ of patients with this condition. 4.0/).

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2. Clinical Presentation of Fabry Disease The typical presentation of Type I ‘classical FD’ is a male patient of the first and second decades of life who presents with acroparesthesia (burning pain in the extremities), gas- trointestinal symptoms (including nausea, diarrhea or constipation, and abdominal pain), and angiokeratoma corporis (distinct cutaneous abnormality characterized by vascular papules distributed in the inguinal, hip, and periumbilical areas) [8]. Patients subsequently develop more severe cardiac, renal, and neurologic complications in the third and fourth decades of life [8]. Classical FD has a typical disease onset of childhood or early ado- lescence and is described in hemizygous male FD patients or heterozygous female FD patients with skewed X-chromosome inactivation of the normal GLA allele [9]. Classical FD patients are characterized by a nearly absent level of α-Gal A activity. In contrast to other lysosomal storage diseases, a large number of patients with FD have the late-onset Type II ‘non-classical FD’ phenotype, remaining asymptomatic during very first few decades of life due to residual α-Gal A activity. Recently, sub-classifications of FD including “cardiac variants” with isolated cardiac findings have been identified [10,11].

3. Fabry Cardiomyopathy Cardiac manifestations of FD include increased left ventricular (LV) wall thickness, conduction abnormalities, arrhythmias, valvular disease, and aortic dilatation, which result from glycolipid deposition and subsequent fibrosis of contractile cardiomyocytes, conductive cardiomyocytes, valvular interstitial cells, and smooth muscle cells of the cardiovascular system (Table1). Eventually, complications such as hypertension, myocardial infarction, and cardiac death may occur, with heart failure being the most common first cardiovascular event in FD [12]. Compared to other organs, the heart appears to be the most susceptible to low levels of α-Gal A. The FD-related cardiovascular injury is thought to be due to a combination of Gb3 accumulation, the accumulation of trophic factors, and microcirculatory ischemia, which contribute to inflammation and ultimately result in myocardial fibrosis [13]. Patients with FD-related cardiac involvement tend to be asymptomatic from a cardiac perspective during the first four decades of life, then present with non-specific cardiac symptoms such as angina, dyspnea, palpitations, or syncope. Since there is no pathognomonic cardiac manifestation of FD, the non-specific findings often make FD-related cardiac involvement difficult to diagnose.

Table 1. Cardiac manifestations of Fabry disease.

Structural abnormalities detected by cardiac imaging

• Increased LV wall thickness. Morphologies include concentric hypertrophy (most common), asymmetric septal hypertrophy, eccentric hypertrophy, and apical hypertrophy. Associated LV outflow tract obstruction may be present but often not [4] • LV ejection fraction often preserved but may be reduced with advanced disease [4] • Biatrial enlargement due to chronic diastolic dysfunction or underlying atrial myopathy [4] • Prominent papillary muscles [4] • Reduced LV longitudinal strain on echocardiography and T2 elevation (suggesting inflammation) or late gadolinium enhancement (suggesting fibrosis) on MRI in the basal inferolateral segment [4] • Reduced native T1 values on MRI [4] • Abnormal LV diastolic function [4] • Binary sign (no longer considered sensitive or specific for Fabry cardiomyopathy) [4] • RV wall thickness may be increased [4] • Thickening and redundancy of the valves with some degree of valvular regurgitation, although often not significant enough to warrant intervention [4] • Aortic dilatation [4] Electrophysiologic abnormalities detected by ECG or prolonged rhythm monitoring

• Short PR interval in younger patients, prolonged PR interval in older patients [14] • Bradycardia from chronotropic incompetence [15] • Sinus node dysfunction [15] • Varying degrees of AV block [15] • Atrial arrhythmias including atrial tachycardia, atrial ﬂutter, or atrial ﬁbrillation [15] • Ventricular arrhythmias including non-sustained VT and sustained VT [15] Abbreviations: AV, atrioventricular; ECG, electrocardiogram; LV, left ventricular; MRI, magnetic resonance imaging; RV, right ventricular; VT, ventricular tachycardia. The hallmark feature of FD cardiomyopathy is increased LV wall thickness [6,9]. Increased right ventricular wall thickness and impaired right ventricular function have Cells 2021, 10, 1532 3 of 13

also been reported [16]. Increased LV wall thickness is rarely present in children with FD, tends to be more severe in male FD patients, and is usually not evident until the third or fourth decade in classical FD patients [4,17]. However, the ﬁnding of increased LV wall thickness is not speciﬁc for Fabry cardiomyopathy, and it is important for clinicians to consider the differential diagnoses of other causes of increased LV wall thickness (Table2).

Table 2. Differential diagnosis of increased LV wall thickness and common ﬁndings on patient history, ECG, echocardiography, and CMR.

Patient History ECG Echocardiography CMR

• Angiokeratoma corporis • Prominent • LGE and T2 increase • Acroparesthesia • Short PR interval • PMBinary sign in basal • • • Fabry Cardiomyopathy Diarrhea Prolonged QRS Loss of base-to-apex inferolateral wall • Stroke • High voltage QRS circumferential • Shortened T1 • Chest pain strain gradient relaxation time • Heart failure

• Concentric LVH • History of • Diastolic • High voltage QRS • Absence of LGE Hypertension hypertension dysfunction • Reduced LV GLS

• Asymptomatic • Normal • Ventricular • History of sporting • Absence of LGE • Possible high hypertrophy and Athlete’s Heart activity • Normal LV SVI voltage QRS dilatation • Resting bradycardia

• Chest pain • High voltage QRS • Aortic stenosis • Dyspnea • Left atrial • Focal mid-wall LGE Aortic Stenosis • Concentric LVH • Syncope enlargement

• Asymmetric septal • High voltage QRS hypertrophy • Left atrial • Patchy mid-wall Hypertrophic • Chest pain • LVOT obstruction enlargement LGE Cardiomyopathy • Dyspnea • Systolic anterior • Atrial ﬁbrillation motion

• Heart failure • Bi-atrial enlargement • Global • Bilateral carpal • Diastolic subendocardial LGE tunnel • Low voltage QRS dysfunction • Abnormal Cardiac Amyloidosis • Nephrotic syndrome • Atrial ﬁbrillation • Abnormal LV GLS in myocardial and • Macroglossia • Pseudo-infarct mid and basal walls blood-pool • Peripheral with apical sparing gadolinium kinetics neuropathy Abbreviations: CMR, cardiovascular magnetic resonance imaging; ECG, electrocardiogram; GLS, global longitudinal strain; LGE, late gadolinium enhancement; LV, left ventricular; LVH, left ventricular hypertrophy, LVOT, left ventricular outﬂow tract; PM, papillary muscle; SVI, stroke volume index.

Electrophysiologic abnormalities represent other common cardiac manifestations of FD [9]. Advanced conduction disease is thought to be caused by glycolipid accumulation in cardiomyocytes of the atrioventricular (AV) node, bundle of His, and the left and right bundle branches [18]. In contrast, accelerated AV conduction is common in younger FD patients and is reflected as shortened PR intervals on the electrocardiogram (ECG), while prolonged PR interval may be observed in older FD patients [18]. Atrial and ventricular arrhythmias are also relatively common and may be due to atrial myopathy, atrial dilatation from longstanding diastolic dysfunction, and atrial and ventricular fibrosis. Atrial arrhythmias such as atrial fibrillation are more common than ventricular arrhythmias. In addition, valvular diseases such as aortic, mitral, and tricuspid regurgitation are common in patients with FD due to mild thickening of the valves, although valvular regurgitation significant enough to require intervention is uncommon and stenotic lesions attributed to Fabry disease alone are rare [19]. Thickening of papillary muscles in FD patients has been proposed as a mechanism of mitral regurgitation in FD. Fabry disease can Cells 2021, 10, 1532 4 of 13

also lead to aortic dilatation, especially in males, where its prevalence increases with age. Aortic dilatation in FD has been shown to be independent of elevated blood pressure [20] and has been attributed to degenerative changes in the aortic media due to excessive glycolipid substrate deposition [21]. Signiﬁcant aortic dilatation due to Fabry disease resulting in acute aortic events has yet to be reported. Fabry cardiomyopathy may not be as rare as we once thought as it has been shown to be responsible for up to 4% of unexplained hypertrophic cardiomyopathy (HCM) cases [22,23] and up to 12% of unexplained increased LV wall thickness in other selected cohorts [9]. When assessing for pathogenic mutations only, the prevalence of GLA mutation in LVH or HCM clinics is 0.94% in males and 0.90% in females [24]. In fact, the cardiac variant is the most common form of FD in some countries such as Taiwan [25]. This is of particular concern as cardiovascular complications represent the predominant source of FD-related mortality and morbidity [8,26].

4. Screening and Diagnosis A diagnosis of FD is made by demonstrating reduced or absent α-Gal A activity in hemizygous males. In females, genotyping is required as random inactivation of X- chromosome results in mosaicism, resulting in partial expression of the mutated allele that allows for normal levels of α-Gal A activity but still results in Gb3 build-up [27]. The prevalence of FD in males was previously estimated to be 1 in 117,000 [28]. However, various newborn screening initiatives around the world such as in Taiwan and Italy have demonstrated a much higher prevalence of disease-causing variants, ranging from 1:1250 to 1:4600, suggesting that FD may be underdiagnosed elsewhere [2,3]. The screening and diagnosis of FD have been simplified with the use of dried blood spot (DBS) testing. Dried blood testing identifies reduced enzyme activity using artificial fluorescent tag substrates linked to an analog of the natural substrate [7]. If enzyme activity is found to be low in male patients, a confirmatory genetic analysis is sent. For female patients, enzyme activity is not a reliable measure of disease activity and therefore all DBS samples are sent for genetic analysis.

5. Diagnosis of Fabry Cardiomyopathy Awareness of the cardiac manifestations of FD may lead to earlier recognition of the condition and differentiation from other causes of increased LV wall thickness. Sensitive cardiac biomarkers and advanced cardiac imaging modalities such as echocardiography with strain imaging and MRI with T1 mapping are essential for the diagnosis and staging of FD.

5.1. Echocardiography Echocardiography is an effective noninvasive method of assessing the degree of cardiac involvement in FD (Figure1). A concentric pattern of increased LV wall thickness is the hallmark finding of Fabry cardiomyopathy, although other morphologies such as an asymmetric thickening of the interventricular septum, eccentric hypertrophy, and apical hypertrophy have also been described [4]. Other echocardiographic features of Fabry cardiomyopathy include prominent papillary muscles, increased right ventricular wall thickness, atrial enlargement, and the ‘binary sign’. The ‘binary sign’ is a finding characterized by a hyperechogenic endocardial surface composed of glycolipid-enriched smooth muscle cells adjacent to a hypoechogenic subendocardial layer relatively devoid of glycolipids, although recent studies have shown poor sensitivity and specificity of the sign to detect FD [29]. Cells 2021, 10, x 5 of 13

with strain imaging and MRI with T1 mapping are essential for the diagnosis and staging of FD.

5.1. Echocardiography Echocardiography is an effective noninvasive method of assessing the degree of cardiac involvement in FD (Figure 1). A concentric pattern of increased LV wall thickness is the hallmark finding of Fabry cardiomyopathy, although other morphologies such as an asymmetric thickening of the interventricular septum, eccentric hypertrophy, and apical hypertrophy have also been described [4]. Other echocardiographic features of Fabry cardiomyopathy include prominent papillary muscles, increased right ventricular wall thickness, atrial enlargement, and the ‘binary sign’. The ‘binary sign’ is a finding characterized by a hyperechogenic endocardial surface composed of glycolipid-enriched smooth muscle Cells 2021, 10, 1532 cells adjacent to a hypoechogenic subendocardial layer relatively devoid of glycolipids,5 of 13 although recent studies have shown poor sensitivity and specificity of the sign to detect FD [29].

Figure 1. Structural abnormalities detected on echocardiography in patients with Fabry cardiomyopathy. (A) Parasternal Figure 1. Structural abnormalities detected on echocardiography in patients with Fabry cardiomyopathy. (A) Parasternal long-axis view shows increased left ventricular wall thickness (the hallmark feature of Fabry cardiomyopathy) along with long-axis view shows increased left ventricular wall thickness (the hallmark feature of Fabry cardiomyopathy) along with thickening of the aortic and mitral valves as well as aortic dilatation. (B) Parasternal short-axis view shows prominent papillarythickening muscle of the and aortic binary and sign mitral (hyperechogenic valves as well endocardial as aortic dilatation. layer of (glycolipid-enrichedB) Parasternal short-axis smooth view muscle shows cells prominent adjacent topapillary a hypoechogenic muscle and subendocardial binary sign (hyperechogenic layer relatively endocardial devoid of glycolipids). layer of glycolipid-enriched (C) Severe biatrial smooth enlargement muscle cells with adjacent a device to leada hypoechogenic seen in the right-sided subendocardial chambers layer for relatively treatment devoid of advanced of glycolipids). conduction (C) Severe disease. biatrial (D) Reduced enlargement longitudinal with a device strain lead in theseen basal in the inferolateral right-sided segment chambers charac for treatmentteristic of of Fabry advanced cardiomyopathy. conduction disease. (D) Reduced longitudinal strain in the basal inferolateral segment characteristic of Fabry cardiomyopathy. Strain imaging is a sensitive method in identifying subclinical cardiomyopathy. Pa- tients Strainwith Fabry imaging cardiomyopathy is a sensitive methoddemonstrate in identifying lower global subclinical longitudinal cardiomyopathy. strain and cir- Pa- cumferentialtients with Fabry strain cardiomyopathy compared to healthy demonstrate subjects lower[30]. Reduced global longitudinal longitudinal strain strain and in the cir- basalcumferential inferolateral strain segment compared as well to healthyas loss of subjects the base-to-apex [30]. Reduced circumferential longitudinal strain strain gra- in dientthe basal have inferolateralbeen suggested segment as specific as well LV as de lossformation of the base-to-apexpatterns of Fabry circumferential cardiomyopathy strain comparedgradient have to hypertrophic been suggested cardiomyopathy as specific LV deformation[31]. patterns of Fabry cardiomyopathy comparedThe application to hypertrophic of artificial cardiomyopathy intelligence [(AI)31]. to the echo assessment of patients with increasedThe applicationLV wall thickness of artificial may intelligenceone day faci (AI)litate to the the diagnosis echo assessment of FD given of patients the known with challengesincreased LVof accurate wall thickness LV wall may thickness one day measurement facilitate the diagnosis[32]. Artificial of FD intelligence-based given the known myocardialchallenges texture of accurate analysis LV wall was thicknesssuggested measurement as a means of [differentiating32]. Artificial intelligence-basedhypertrophic car- diomyopathymyocardial texture from hypertensive analysis was heart suggested disease as and a means uremic of differentiatingcardiomyopathy hypertrophic [33]. Artificial cardiomyopathy from hypertensive heart disease and uremic cardiomyopathy [33]. Artificial intelligence models have also previously been shown to augment the detection of cardiac intelligence models have also previously been shown to augment the detection of cardiac amyloidosis and assist in the diagnosis and risk stratification of patients with hyper- amyloidosis and assist in the diagnosis and risk stratification of patients with hypertrophic trophic cardiomyopathy [34–36]. The role of AI in assessment of patients with increased cardiomyopathy [34–36]. The role of AI in assessment of patients with increased wall thick- wall thickness including patients with possible FD is ongoing in our echocardiography ness including patients with possible FD is ongoing in our echocardiography laboratory. laboratory. 5.2. Magnetic Resonance Imaging Several MRI findings have been described in Fabry cardiomyopathy. Late gadolinium enhancement (LGE) in the basal inferolateral segment is a common MRI finding in Fabry cardiomyopathy and is observed in 50% of affected patients [5]. Shortened myocardial T1 relaxation time can discriminate Fabry cardiomyopathy from other causes of LVH and may be seen in Fabry cardiomyopathy prior to the development of LVH [37,38]. Chronic local T2 elevation in the basal inferolateral segment may indicate myocardial inflammation from Fabry cardiomyopathy and is associated with worse Fabry stabilization index (FASTEX) score [39]. Cardiac MRI can also be helpful in identifying increased right ventricular wall thickness, atrial enlargement, and prominent papillary muscles.

5.3. Laboratory Tests Various laboratory biomarkers have been proposed for use in staging patients with Fabry cardiomyopathy. Troponin level has been correlated with the degree of ﬁbrosis measured by LGE on MRI in patients with Fabry Cardiomyopathy [40]. Increased symptom and disease burden is correlated with elevated levels of CRP, NT-proBNP, and IL-6 [41–43]. Cells 2021, 10, 1532 6 of 13

5.4. Cardiopulmonary Exercise Test Patients with FD have been shown to have decreased heart rate, indexed oxygen pulse, blood pressure, and max VO2 at peak exercise during cardiopulmonary exercise testing using treadmill test and cycle ergometer [44–46]. There may be a small improvement in exercise tolerance in patients receiving ERT [44,47].

6. Fabry Disease Severity Scores Several validated scoring systems for FD is available. Fabry disease severity scoring system (DS3) is a validated scoring system utilizing 4 clinical domains: peripheral nervous system, renal, cardiac, and a patient-reported domain. Fabry DS3 has been demonstrated to correlate very well with overall clinical picture of patients with FD using clinical global impression of severity score by FD experts [48]. The Mainz Severity Score Index (MSSI) is another scoring system used to grade severity of disease in FD [49]. The MSSI is composed of four sections (general, neurological, cardiac, and renal) related to symptoms of FD. After one year of treatment with ERT in patients with FD, MSSI was signiﬁcantly reduced in all patients [49]. The Fabry Stabilization index (FASTEX) is a scoring system developed to assess for clinical stability in patients with FD. The FASTEX was created using consensus weighted score in 28 patients with FD, where the score is based on three domains (nervous system, renal, and cardiac). A worsening global score of ≥20% was suggested to indicate that the patient is clinically unstable [50].

7. Treatments in Fabry Disease The current approach to the treatment and management of FD aims to either prevent or delay the progression of FD to irreversible tissue damage and organ failure. There is currently no curative treatment for FD. To date, treatments available for FD include disease-modifying therapies used in conjunction with non-specific therapies that treat symptoms caused by multi-organ injury. The advantages and disadvantages of currently available as well as investigational FD therapies are summarized in Table3. Enzyme replacement therapy (ERT) is currently the standard treatment for males with classical FD and Type 2 non-classical FD, and females with classical FD. Enzyme replacement therapy became available in 2001 and represents the first treatment developed for FD. Two formulations of ERT currently exist: agalsidase α (Replagal) administered at a dose of 0.2 mg/kg intravenously every two weeks and agalsidase β (Fabrazyme) administered at a dose of 1 mg/kg intravenously every two weeks. Agalsidase α is generated from a continuous human cell line with the activation of the GLA gene, while agalsidase β is generated from a Chinese hamster ovary mammalian cell expression system transduced with the human GLA sequence. Enzyme replacement therapy has been shown to effectively reduce glycolipid substrates including Gb3 in the urine, plasma, and tissues of patients with FD [51]. With respect to FD-related cardiac injury, ERT has been shown to effectively reduce Gb3 inclusions in endothelial cells, with less clear evidence regarding Gb3 clearance from cardiomyocytes [52]. In addition, observational studies have reported a reduction in LV wall thickness in patients treated with ERT [53,54]. The limitations of ERT include the short plasma half-life of the recombinant enzyme, thus necessitating bi-weekly infusions and that it can only delay the progression of FD. Enzyme replacement therapy also has limited efficacy in later stages of Fabry cardiomyopathy, when fibrosis is already present [53], and it is unclear whether or not ERT slows the progression of fibrosis [55]. Additionally, anti-drug antibodies against the recombinant replacement enzyme in ERT has been reported to develop in 64–88% of FD patients [52,56], thereby attenuating the effect of ERT. Finally, ERT demonstrates uneven biodistribution, with the liver taking up the majority of the recombinant replacement enzyme, whereas the most severely affected cell types in the body such as cardiomyocytes and podocytes take up lesser amounts of the replacement enzyme [55]. Cells 2021, 10, 1532 7 of 13

Table 3. Comparison of approved and investigational disease-modifying therapies for Fabry disease.

Disease-Modifying Therapy Advantages Disadvantages

• Lifelong biweekly intravenous infusions • Anti-drug antibodies may developExpensive • Nearly two decades of clinical experience • Less clear evidence regarding Gb3 clearance First-generation ERT • Applicable to most patients with FD from cardiomyocytes • Effectively reduces Gb3 in urine, plasma, • Uneven biodistribution resulting in limited • Agalsidase α (Replagal) tissues, and endothelial cells uptake in cardiomyocytes and podocytes • Agalsidase β (Fabrazyme) • Reduction in LV wall thickness seen in • Unclear effects on ﬁbrosis possibly limiting observational studies its efﬁcacy in later stages of FD • Non-curative

• Only applicable to certain GLA variants Oral chaperone therapy • Oral route of administration • Approval limited to certain countries • Increases α-Gal A activity • Variable therapeutic response • Decrease Gb3 inclusions • Migalastat • Non-curative

Second-generation ERT • Possible monthly (vs. biweekly) schedule • Intravenous route of administration • Improved biodistribution compared with • Currently in preclinical phase • Pegunigalsidase-α ﬁrst-generation ERT • Non-curative • Moss-aGal

Substrate reduction therapy • Cannot be used as a monotherapy • Oral route of administration • Currently in preclinical phase • Can be used as adjunctive therapy to ERT • Venglustat • Non-curative • Lucerastat

• Longer lasting therapeutic effects • Uncertain long-term adverse effects Gene therapy • Potentially curative although • Currently in pre-clinical phase still uncertain

There is currently no evidence demonstrating the superiority of agalsidase α over agalsidase β and vice versa in clinical endpoints [57,58]. Specifically, in the Canadian Fabry Disease Initiative, a comparison of agalsidase α and agalsidase β demonstrated no statis- tical difference in clinical endpoints including death, cardiac events, acute neurological events, and others [58]. However, there were differences in the biochemical response between patients treated with agalsidase α and agalsidase β, with a higher risk of developing anti-drug antibodies and a greater decrease in the plasma globotriaosylsphingosine levels in patients treated with agalsidase β. In addition, there was a greater reduction in the left ventricular mass in patients treated with agalsidase β [59]. Oral pharmacologic chaperone therapy, namely Migalastat, is an alternative treatment option for FD. However, since Migalastat is protein-variant specific, it is only used for patients with amenable GLA gene variants [60]. These specific GLA variants produce highly unstable mutated α-Gal A proteins. Migalastat binds to these α-Gal A variants, thus stabilizing the enzymes by enhancing correct folding [55]. This stabilization allows the mutated enzymes to be properly trafficked to lysosomes, where Migalastat dissociates, allowing it to catabolize the accumulated Gb3 substrates [61]. This therapy has been demonstrated to both increase α-Gal A activity and decrease Gb3 inclusions [62,63]. Despite disease-modifying FD treatments described, equal attention and care should be given to non-FD specific treatments directed towards the multi-system consequences of the condition. Due to the clinical heterogeneity of FD, a multidisciplinary clinical team with a cardiologist, nephrologist, neurologist, genetic counselor, and a medical geneticist should ideally be in place for the holistic care of FD patients. General preventative measures including pharmacological stroke prophylaxis with an antithrombic agent and lifestyle modifications such as avoidance of extremes of temperature to prevent painful crises, exercise prescription, diet, and smoking cessation should be appropriately advised. Other co-morbidities such as hypertension and dyslipidemia should be managed diligently. The management of the cardiac manifestations of FD has been summarized in Table4. Cells 2021, 10, 1532 8 of 13

Table 4. Management of the cardiovascular manifestations of Fabry disease.

Structural abnormalities that can be present on cardiac imaging • Identiﬁcation/treatment of hypertension to prevent further increase in LV wall thickness • Cautious use of medications with negative inotropic effects (e.g., beta-blockers, non-dihydropyridine calcium channel blockers, disopyramide) if LVOT obstruction present • Regular surveillance of valvular regurgitation and aortic dilatation Electrophysiologic abnormalities detected by ECG or rhythm monitoring • Atrial arrhythmias may require treatment with rate control strategy (using AV nodal blockers) or rhythm control strategy (with anti-arrhythmic agents or catheter ablation) • Anticoagulation for stroke risk reduction is indicated in the setting of atrial ﬁbrillation • Ventricular arrhythmias may require treatment with either beta-blockers, anti-arrhythmic agents, catheter ablation, or ICD therapy • Amiodarone should only be considered when other therapeutic options have failed since it may promote glycolipid accumulation and attenuate the effects of ERT • Symptomatic bradyarrhythmias including sinus node dysfunction or advanced AV block may require permanent pacing Other cardiovascular considerations in patients with Fabry disease • ACE inhibitors or ARBs should be considered for patients with chronic kidney disease • Beta-blockers or non-dihydropyridine calcium-channel blockers should be used with caution given the higher prevalence of sinus node dysfunction or advanced AV block • Antiplatelet therapy may be indicated for primary or secondary prevention of ischemic stroke in selected patients • Heart failure can be treated with diuretics or LV enhancement therapy if LVEF is reduced in accordance with contemporary consensus-based guidelines • Chest pain due to large-vessel or microvascular disease can be managed with standard anti-anginal therapy with cautious use of AV nodal blockers as previously described

Abbreviations: ACE, angiotensin converting enzyme; ARB, angiotensin II receptor blocker; AV, atrioventricular; ERT, enzyme replacement therapy; ICD, implantable cardioverter-deﬁbrillator; LV, left ventricular; LVEF, left ventricular ejection fraction; LVOT, left ventricular outﬂow tract.

8. Future Directions in the Management of Fabry Disease There are three potential future treatment options currently undergoing preclinical investigation: (1) second-generation ERT; (2) substrate reduction therapy (SRT); and (3) gene therapy. Todate, two formulations of second-generation ERTshave been developed: pegunigalsidase- α and moss-aGal. These second-generation ERTs are plant-derived with different phar- macokinetic properties that may lead to better biodistribution in the body compared with first-generation ERTs. Substrate reduction therapy including Venglustat and Lucerastat are potential future oral treatments for FD. Substrate reduction therapy limits the formation of pathogenic metabolites such as Gb3, thus limiting its accumulation in tissues throughout the body [64]. Substrate reduction therapy may have a potential role as an adjunctive therapy used alongside ERT [64]. Gene therapy may be a treatment option that enables FD patients to receive fewer treatments with more permanent effects. This novel therapy involves the encapsulation of mRNA into lipid nanoparticles that target hepatocytes where endogenous protein translation, glycosylation, and intracellular trafficking of α-Gal A occurs. Functional α-Gal A enzymes are then subsequently secreted into the circulation, which can be taken up by affected cells [65]. Recently, the first gene therapy trial for FD was conducted, where classical FD patients were infused with lentivirus-transduced hematopoietic stem cells engineered to express α-Gal A [51]. All patients produced α-Gal A to near normal levels within one week of therapy with observations of reduced plasma and urine Gb3 [51]. Several challenges exist in the early identification of individuals with FD. Many non-classic FD patients are asymptomatic in their early years of life, resulting in delayed diagnosis. Additionally, remote centers may not have the capacity for advanced imaging. Cells 2021, 10, 1532 9 of 13

Even when presented with imaging findings of FD, clinicians may not readily diagnose FD due to the non-specific findings and unfamiliarity with the clinical manifestations of FD. To overcome these challenges, our echocardiography lab has undertaken several initiatives that aim to achieve earlier detection of Fabry cardiomyopathy, including the development of artificial intelligence (AI)-empowered detection of increased LV wall thickness, the use of DBS testing at the time of echocardiography when an unexplained increase in LV wall thickness is identified, and the dissemination of point-of-care ultrasound devices to community healthcare providers to promote widespread screening for the presence of cardiomyopathies [66–68]. The use of AI to effectively identify increased LV wall thickness and differentiate between the many possible etiologies is a promising area for further research. An AI approach based on 12-lead ECG has been shown to be 87% sensitive and 90% specific in identifying hypertrophic cardiomyopathy [69]. Fully automated echocardiographic interpretation has also been shown to be capable of detecting hypertrophic cardiomyopathy and cardiac amyloidosis with C-statistics of 0.93 and 0.87 respectively [36]. An AI strategy based on late gadolinium enhancement (LGE) patterns on cardiac MRI demonstrated 88% diagnostic accuracy in detecting cardiac amyloidosis [70]. Further research is needed to determine the potential role of AI in the diagnosis of Fabry disease.

9. Conclusions and Call to Action Our understanding of the pathophysiology, diagnosis and treatment of FD continue to rapidly evolve. We now have not only the capability to more effectively diagnose FD using various laboratory and imaging modalities, but also effective treatment options for the condition. Clinicians should have an understanding of the clinical manifestations of FD and consider it as part of the differential diagnosis when presented with unexplained increased LV wall thickness. Fabry disease should no longer be considered a rare, untreatable disease, but one that can and should be identiﬁed and treated in a timely manner.

Author Contributions: Conceptualization, D.F.Y. and T.S.M.T.; writing—original draft preparation, J.Y. and O.Y.; writing—review and editing, D.F.Y. and T.S.M.T.; supervision, D.F.Y. and T.S.M.T. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Acknowledgments: The authors would like to thank Jamie Hyerim Chun for creating the illustration for the graphical abstract. Conﬂicts of Interest: The authors declare no conﬂict of interest.

Abbreviations a-Gal A α-galactosidase A ACE Angiotensin converting enzyme ARB Angiotensin II receptor blocker AI Artiﬁcial intelligence AV Atrioventricular DBS Dried blood spot ECG Electrocardiogram ERT Enzyme replacement therapy FD Fabry disease Gb3 Globotriaosylceramide HCM Hypertrophic cardiomyopathy ICD Implantable cardioverter-deﬁbrillator Cells 2021, 10, 1532 10 of 13

LGE Late gadolinium enhancement LV Left ventricular LVEF Left ventricular ejection fraction LVOT Left ventricular outﬂow tract MRI Magnetic resonance imaging RV Right ventricular SRT Substrate reduction therapy VT Ventricular tachycardia

References 1. Germain, D.P. Fabry disease. Orphanet J. Rare Dis. 2010, 5, 30. [CrossRef][PubMed] 2. Hwu, W.L.; Chien, Y.H.; Lee, N.C.; Chiang, S.C.; Dobrovolny, R.; Huang, A.C.; Yeh, H.Y.; Chao, M.C.; Lin, S.J.; Kitagawa, T.; et al. Newborn screening for fabry disease in taiwan reveals a high incidence of the later-onset GLA mutation c.936 + 919G > A (IVS4 + 919G > A). Hum. Mutat. 2009, 30, 1397–1405. [CrossRef] 3. Spada, M.; Pagliardini, S.; Yasuda, M.; Tukel, T.; Thiagarajan, G.; Sakuraba, H.; Ponzone, A.; Desnick, R.J. High incidence of later-onset Fabry disease revealed by newborn screening. Am. J. Hum. Genet. 2006, 79, 31–40. [CrossRef] 4. Yeung, D.F.; Sirrs, S.; Tsang, M.Y.C.; Gin, K.; Luong, C.; Jue, J.; Nair, P.; Lee, P.K.; Tsang, T.S.M. Echocardiographic Assessment of Patients with Fabry Disease. J. Am. Soc. Echocardiogr. 2018, 31, 639–649.e2. [CrossRef] 5. Pieroni, M.; Moon, J.C.; Arbustini, E.; Barriales-Villa, R.; Camporeale, A.; Vujkovac, A.C.; Elliott, P.M.; Hagege, A.; Kuusisto, J.; Linhart, A.; et al. Cardiac Involvement in Fabry Disease: JACC Review Topic of the Week. J. Am. Coll. Cardiol. 2021, 77, 922–936. [CrossRef] 6. Seydelmann, N.; Wanner, C.; Störk, S.; Ertl, G.; Weidemann, F. Fabry disease and the heart. Best Pract. Res. Clin. Endocrinol. Metab. 2015, 29, 195–204. [CrossRef] 7. Chamoles, N.A.; Blanco, M.; Gaggioli, D. Fabry disease: Enzymatic diagnosis in dried blood spots on ﬁlter paper. Clin. Chim. Acta 2001, 308, 195–196. [CrossRef] 8. Mehta, A.; Clarke, J.T.R.; Giugliani, R.; Elliott, P.; Linhart, A.; Beck, M.; Sunder-Plassmann, G. Natural course of Fabry disease: Changing pattern of causes of death in FOS-Fabry Outcome Survey. J. Med. Genet. 2009, 46, 548–552. [CrossRef] 9. Linhart, A.; Germain, D.P.; Olivotto, I.; Akhtar, M.M.; Anastasakis, A.; Hughes, D.; Namdar, M.; Pieroni, M.; Hagège, A.; Cecchi, F.; et al. An expert consensus document on the management of cardiovascular manifestations of Fabry disease. Eur. J. Heart Fail. 2020, 22, 1076–1096. [CrossRef] 10. Nakao, S.; Takenaka, T.; Maeda, M.; Kodama, C.; Tanaka, A.; Tahara, M.; Yoshida, A.; Kuriyama, M.; Hayashibe, H.; Sakuraba, H.; et al. An Atypical Variant of Fabry’s Disease in Men with Left Ventricular Hypertrophy. N. Engl. J. Med. 1995, 333, 288–293. [CrossRef][PubMed] 11. Hsu, T.R.; Hung, S.C.; Chang, F.P.; Yu, W.C.; Sung, S.H.; Hsu, C.L.; Dzhagalov, I.; Yang, C.F.; Chu, T.H.; Lee, H.J.; et al. Later Onset Fabry Disease, Cardiac Damage Progress in Silence: Experience With a Highly Prevalent Mutation. J. Am. Coll. Cardiol. 2016, 68, 2554–2563. [CrossRef][PubMed] 12. Shah, J.S.; Hughes, D.A.; Sachdev, B.; Tome, M.; Ward, D.; Lee, P.; Mehta, A.B.; Elliott, P.M. Prevalence and clinical signiﬁcance of cardiac arrhythmia in Anderson-Dabry disease. Am. J. Cardiol. 2005, 96, 842–846. [CrossRef][PubMed] 13. Weidemann, F.; Sanchez-Niño, M.D.; Politei, J.; Oliveira, J.P.; Wanner, C.; Warnock, D.G.; Ortiz, A. Fibrosis: A key feature of Fabry disease with potential therapeutic implications. Orphanet J. Rare Dis. 2013, 8, 1–12. [CrossRef] 14. Omahony, C.; Coats, C.; Cardona, M.; Garcia, A.; Calcagnino, M.; Murphy, E.; Robin, L.; Atul, M.; Derralynn, H.; Perry, M.E. Incidence and predictors of anti-bradycardia pacing in patients with Anderson-Fabry disease. Europace 2011, 13, 1781–1788. [CrossRef] 15. Namdar, M. Electrocardiographic Changes and Arrhythmia in Fabry Disease. Front. Cardiovasc. Med. 2016, 3, 7. [CrossRef] 16. Niemann, M.; Breunig, F.; Beer, M.; Herrmann, S.; Strotmann, J.; Hu, K.; Emmert, A.; Voelker, W.; Ertl, G.; Wanner, C.; et al. The right ventricle in Fabry disease: Natural history and impact of enzyme replacement therapy. Heart 2010, 96, 1915–1919. [CrossRef] [PubMed] 17. Kampmann, C.; Linhart, A.; Baehner, F.; Palecek, T.; Wiethoff, C.M.; Miebach, E.; Whybra, C.; Gal, A.; Bultas, J.; Beck, M. Onset and progression of the Anderson-Fabry disease related cardiomyopathy. Int. J. Cardiol. 2008, 130, 367–373. [CrossRef] 18. Mehta, J.; Moller, J.H.; Desnick, R.J.; Ph, D. Electrocardiographic and vectorcardiographic abnormalities in Fabry’s disease. Am. Heart J. 1977, 93, 699–705. [CrossRef] 19. Linhart, A.; Paleˇcek,T.; Bultas, J.; Ferguson, J.J.; Hrudová, J.; Karetová, D.; Zeman, J.; Ledvinová, J.; Poupˇetová, H.; Elleder, M.; et al. New insights in cardiac structural changes in patients with Fabry’s disease. Am. Heart J. 2000, 139, 1101–1108. [CrossRef] [PubMed] 20. Barbey, F.; Qanadli, S.D.; Juli, C.; Brakch, N.; Palaek, T.; Rizzo, E.; Jeanrenaud, X.; Eckhardt, B.; Linhart, A. Aortic remodelling in Fabry disease. Eur. Heart J. 2010, 31, 347–353. [CrossRef][PubMed] 21. Desnick, R.J.; Blieden, L.C.; Sharp, H.L.; Hofschire, P.J.; Moller, J.H. Cardiac valvular anomalies in Fabry disease. Clinical, morphologic, and biochemical studies. Circulation 1976, 54, 818–825. [CrossRef] Cells 2021, 10, 1532 11 of 13

22. Sachdev, B.; Takenaka, T.; Teraguchi, H.; Tei, C.; Lee, P.; McKenna, W.J.; Elliott, P.M. Prevalence of Anderson-Fabry disease in male patients with late onset hypertrophic cardiomyopathy. Circulation 2002, 105, 1407–1411. [CrossRef] 23. Maron, M.S.; Xin, W.; Sims, K.B.; Butler, R.; Haas, T.S.; Rowin, E.J.; Desnick, R.J.; Maron, B.J. Identification of Fabry Disease in a Tertiary Referral Cohort of Patients with Hypertrophic Cardiomyopathy. Am. J. Med. 2018, 131, 200.e1–200.e8. [CrossRef] 24. Doheny, D.; Srinivasan, R.; Pagant, S.; Chen, B.; Yasuda, M.; Desnick, R.J. Fabry Disease: Prevalence of affected males and heterozygotes with pathogenic GLA mutations identified by screening renal, cardiac and stroke clinics, 1995–2017. J. Med. Genet. 2018, 55, 261–268. [CrossRef][PubMed] 25. Lin, H.Y.; Chong, K.W.; Hsu, J.H.; Yu, H.C.; Shih, C.C.; Huang, C.H.; Lin, S.J.; Chen, C.H.; Chiang, C.C.; Ho, H.J.; et al. High incidence of the cardiac variant of fabry disease revealed by newborn screening in the Taiwan Chinese population. Circ. Cardiovasc. Genet. 2009, 2, 450–456. [CrossRef] 26. Baig, S.; Edward, N.C.; Kotecha, D.; Liu, B.; Nordin, S.; Kozor, R.; Moon, J.C.; Geberhiwot, T.; Steeds, R.P. Ventricular arrhythmia and sudden cardiac death in Fabry disease: A systematic review of risk factors in clinical practice. Europace 2018, 20, f153–f161. [CrossRef] 27. Echevarria, L.; Benistan, K.; Toussaint, A.; Dubourg, O.; Hagege, A.A.; Eladari, D.; Jabbour, F.; Beldjord, C.; De Mazancourt, P.; Germain, D.P. X-chromosome inactivation in female patients with Fabry disease. Clin. Genet. 2016, 89, 44–54. [CrossRef] 28. Meikle, P.J.; Hopwood, J.J.; Clague, A.E.; Carey, W.F. Prevalence of lysosomal storage disorders. J. Am. Med. Assoc. 1999, 281, 249–254. [CrossRef] 29. Mundigler, G.; Gaggl, M.; Heinze, G.; Graf, S.; Zehetgruber, M.; Lajic, N.; Voigtlander, T.; Mannhalter, C.; Sunder-Plassmann, R.; Paschke, E.; et al. The endocardial binary appearance (‘binary sign’) is an unreliable marker for echocardiographic detection of Fabry disease in patients with left ventricular hypertrophy. Eur. J. Echocardiogr. 2011, 12, 744–749. [CrossRef] 30. Gruner, C.; Verocai, F.; Carasso, S.; Vannan, M.A.; Jamorski, M.; Clarke, J.T.R.; Care, M.; Iwanochko, R.M.; Rakowski, H. Systolic myocardial mechanics in patients with Anderson-Fabry disease with and without left ventricular hypertrophy and in comparison to nonobstructive hypertrophic cardiomyopathy. Echocardiography 2012, 29, 810–817. [CrossRef] 31. Labombarda, F.; Saloux, E.; Milesi, G.; Bienvenu, B. Loss of base-to-apex circumferential strain gradient: A specific pattern of Fabry cardiomyopathy? Echocardiography 2017, 34, 504–510. [CrossRef] 32. Hindieh, W.; Weissler-Snir, A.; Hammer, H.; Adler, A.; Rakowski, H.; Chan, R.H. Discrepant Measurements of Maximal Left Ventricular Wall Thickness Between Cardiac Magnetic Resonance Imaging and Echocardiography in Patients With Hypertrophic Cardiomyopathy. Circ. Cardiovasc. Imaging 2017, 10.[CrossRef] 33. Yu, F.; Huang, H.; Yu, Q.; Ma, Y.; Zhang, Q.; Zhang, B. Artificial intelligence-based myocardial texture analysis in etiological differentiation of left ventricular hypertrophy. Ann. Transl. Med. 2021, 9, 108. [CrossRef][PubMed] 34. Goto, S.; Mahara, K.; Beussink-Nelson, L.; Ikura, H.; Katsumata, Y.; Endo, J.; Gaggin, H.K.; Shah, S.J.; Itabashi, Y.; MacRae, C.A.; et al. Artificial intelligence-enabled fully automated detection of cardiac amyloidosis using electrocardiograms and echocardio- grams. Nat. Commun. 2021, 12.[CrossRef][PubMed] 35. Augusto, J.B.; Davies, R.H.; Bhuva, A.N.; Knott, K.D.; Seraphim, A.; Alfarih, M.; Lau, C.; Hughes, R.K.; Lopes, L.R.; Shiwani, H.; et al. Diagnosis and risk stratification in hypertrophic cardiomyopathy using machine learning wall thickness measurement: A comparison with human test-retest performance. Lancet Digit. Health 2021, 3, e20–e28. [CrossRef] 36. Zhang, J.; Deo, R.C. Response by Zhang and Deo to Letter Regarding Article, “Fully Automated Echocardiogram Interpretation in Clinical Practice: Feasibility and Diagnostic Accuracy”. Circulation 2019, 139, 1648–1649. [CrossRef] 37. Sado, D.M.; White, S.K.; Piechnik, S.K.; Banypersad, S.M.; Treibel, T.; Captur, G.; Fontana, M.; Maestrini, V.; Flett, A.S.; Robson, M.D.; et al. Identification and assessment of anderson-fabry disease by cardiovascular magnetic resonance noncontrast myocardial T1 mapping. Circ. Cardiovasc. Imaging 2013, 6, 392–398. [CrossRef] 38. Pica, S.; Sado, D.M.; Maestrini, V.; Fontana, M.; White, S.K.; Treibel, T.; Captur, G.; Anderson, S.; Piechnik, S.K.; Robson, M.D.; et al. Reproducibility of native myocardial T1 mapping in the assessment of Fabry disease and its role in early detection of cardiac involvement by cardiovascular magnetic resonance. J. Cardiovasc. Magn. Reson. 2014, 16, 99. [CrossRef] 39. Augusto, J.B.; Nordin, S.; Vijapurapu, R.; Baig, S.; Bulluck, H.; Castelletti, S.; Alfarih, M.; Knott, K.; Captur, G.; Kotecha, T.; et al. Myocardial edema, myocyte injury, and disease severity in Fabry disease. Circ. Cardiovasc. Imaging 2020, 13, 10171. [CrossRef] 40. Seydelmann, N.; Liu, D.; Krämer, J.; Drechsler, C.; Hu, K.; Nordbeck, P.; Schneider, A.; Störk, S.; Bijnens, B.; Ertl, G.; et al. High-sensitivity troponin: A clinical blood biomarker for staging cardiomyopathy in fabry disease. J. Am. Heart Assoc. 2016, 5. [CrossRef] 41. Yogasundaram, H.; Nikhanj, A.; Putko, B.N.; Boutin, M.; Jain-Ghai, S.; Khan, A.; Auray-Blais, C.; West, M.L.; Oudit, G.Y. Elevated inflammatory plasma biomarkers in patients with fabry disease: A critical link to heart failure with preserved ejection fraction. J. Am. Heart Assoc. 2018, 7.[CrossRef][PubMed] 42. Altarescu, G.; Chicco, G.; Whybra, C.; Delgado-Sanchez, S.; Sharon, N.; Beck, M.; Elstein, D. Correlation between interleukin-6 promoter and C-reactive protein (CRP) polymorphisms and CRP levels with the Mainz Severity Score Index for Fabry disease. J. Inherit. Metab. Dis. 2008, 31, 117–123. [CrossRef][PubMed] 43. Coats, C.J.; Parisi, V.; Ramos, M.; Janagarajan, K.; O’Mahony, C.; Dawnay, A.; Lachmann, R.H.; Murphy, E.; Mehta, A.; Hughes, D.; et al. Role of serum N-terminal pro-brain natriuretic peptide measurement in diagnosis of cardiac involvement in patients with anderson-fabry disease. Am. J. Cardiol. 2013, 111, 111–117. [CrossRef][PubMed] Cells 2021, 10, 1532 12 of 13

44. Lobo, T.; Morgan, J.; Bjorksten, A.; Nicholls, K.; Grigg, L.; Centra, E.; Becker, G. Cardiovascular testing in Fabry disease: Exercise capacity reduction, chronotropic incompetence and improved anaerobic threshold after enzyme replacement. Intern. Med. J. 2008, 38, 407–414. [CrossRef][PubMed] 45. Bierer, G.; Kamangar, N.; Balte, D.; Wilcox, W.R.; Mosenifar, Z. Cardiopulmonary exercise testing in fabry disease. Respiration 2005, 72, 504–511. [CrossRef] 46. Powell, A.W.; Jefferies, J.L.; Hopkin, R.J.; Mays, W.A.; Goa, Z.; Chin, C. Cardiopulmonary fitness assessment on maximal and submaximal exercise testing in patients with Fabry disease. Am. J. Med. Genet. Part A 2018, 176, 1852–1857. [CrossRef] 47. Bierer, G.; Balfe, D.; Wilcox, W.R.; Mosenifar, Z. Improvement in serial cardiopulmonary exercise testing following enzyme replacement therapy in Fabry disease. J. Inherit. Metab. Dis. 2006, 29, 572–579. [CrossRef] 48. Giannini, E.H.; Mehta, A.B.; Hilz, M.J.; Beck, M.; Bichet, D.G.; Brady, R.O.; West, M.; Germain, D.P.; Wanner, C.; Waldek, S.; et al. A validated disease severity scoring system for Fabry disease. Mol. Genet. Metab. 2010, 99, 283–290. [CrossRef] 49. Whybra, C.; Kampmann, C.; Krummenauer, F.; Ries, M.; Mengel, E.; Miebach, E.; Baehner, F.; Kim, K.; Bajbouj, M.; Schwarting, A.; et al. The Mainz Severity Score Index: A new instrument for quantifying the Anderson-Fabry disease phenotype, and the response of patients to enzyme replacement therapy. Clin. Genet. 2004, 65, 299–307. [CrossRef] 50. Mignani, R.; Pieruzzi, F.; Berri, F.; Burlina, A.; Chinea, B.; Gallieni, M.; Pieroni, M.; Salviati, A.; Spada, M. FAbry STabilization indEX (FASTEX): An innovative tool for the assessment of clinical stabilization in Fabry disease. Clin. Kidney J. 2016, 9, 739–747. [CrossRef] 51. Khan, A.; Barber, D.L.; Huang, J.; Rupar, C.A.; Rip, J.W.; Auray-Blais, C.; Boutin, M.; O’Hoski, P.; Gargulak, K.; McKillop, W.M.; et al. Lentivirus-mediated gene therapy for Fabry disease. Nat. Commun. 2021, 12.[CrossRef] 52. Eng, C.M.; Guffon, N.; Wilcox, W.R.; Germain, D.P.; Lee, P.; Waldek, S.; Caplan, L.; Linthorst, G.E.; Desnick, R.J. Safety and Efficacy of Recombinant Human α-Galactosidase A Replacement Therapy in Fabry’s Disease. N. Engl. J. Med. 2001, 345, 9–16. [CrossRef] 53. Weidemann, F.; Niemann, M.; Breunig, F.; Herrmann, S.; Beer, M.; Störk, S.; Voelker, W.; Ertl, G.; Wanner, C.; Strotmann, J. Long-term effects of enzyme replacement therapy on fabry cardiomyopathy. Evidence for a better outcome with early treatment. Circulation 2009, 119, 524–529. [CrossRef][PubMed] 54. Weidemann, F.; Breunig, F.; Beer, M.; Sandstede, J.; Turschner, O.; Voelker, W.; Ertl, G.; Knoll, A.; Wanner, C.; Strotmann, J.M. Improvement of cardiac function during enzyme replacement therapy in patients with fabry disease: A prospective strain rate imaging study. Circulation 2003, 108, 1299–1301. [CrossRef][PubMed] 55. Van der Veen, S.J.; Hollak, C.E.M.; Van Kuilenburg, A.B.P.; Langeveld, M. Developments in the treatment of Fabry disease. J. Inherit. Metab. Dis. 2020, 43, 908–921. [CrossRef][PubMed] 56. Schiffmann, R.; Kopp, J.B.; Austin, H.A.; Balow, J.E.; Brady, R.O. Enzyme Replacement Therapy in Fabry Disease: A Randomized Controlled Trial. N. Engl. J. Med. 2001, 285, 2743. [CrossRef][PubMed] 57. El Dib, R.; Gomaa, H.; Carvalho, R.P.; Camargo, S.E.; Bazan, R.; Barretti, P.; Barreto, F.C. Enzyme replacement therapy for Anderson-Fabry disease. Cochrane Database Syst. Rev. 2016.[CrossRef] 58. Sirrs, S.M.; Bichet, D.G.; Casey, R.; Clarke, J.T.R.; Lemoine, K.; Doucette, S.; West, M.L. Outcomes of patients treated through the Canadian Fabry disease initiative. Mol. Genet. Metab. 2014, 111, 499–506. [CrossRef] 59. Arends, M.; Biegstraaten, M.; Wanner, C.; Sirrs, S.; Mehta, A.; Elliott, P.M.; Oder, D.; Watkinson, O.T.; Bichet, D.G.; Khan, A.; et al. Agalsidase alfa versus agalsidase beta for the treatment of Fabry disease: An international cohort study. J. Med. Genet. 2018, 55, 351–358. [CrossRef] 60. Germain, D.P.; Hughes, D.A.; Nicholls, K.; Bichet, D.G.; Giugliani, R.; Wilcox, W.R.; Feliciani, C.; Shankar, S.P.; Ezgu, F.; Amartino, H.; et al. Treatment of Fabry’s Disease with the Pharmacologic Chaperone Migalastat. N. Engl. J. Med. 2016, 375, 545–555. [CrossRef] 61. Germain, D.P.; Fan, J.Q. Pharmacological chaperone therapy by active-site-specific chaperones in Fabry disease: In vitro and preclinical studies. Int. J. Clin. Pharmacol. Ther. 2009, 47, S111–S117. [PubMed] 62. Hughes, D.A.; Nicholls, K.; Shankar, S.P.; Sunder-Plassmann, G.; Koeller, D.; Nedd, K.; Vockley, G.; Hamazaki, T.; Lachmann, R.; Ohashi, T.; et al. Oral pharmacological chaperone migalastat compared with enzyme replacement therapy in Fabry disease: 18-month results from the randomised phase III ATTRACT study. J. Med. Genet. 2017, 54, 288–296. [CrossRef][PubMed] 63. Germain, D.P.; Nicholls, K.; Giugliani, R.; Bichet, D.G.; Hughes, D.A.; Barisoni, L.M.; Colvin, R.B.; Jennette, J.C.; Skuban, N.; Castelli, J.P.; et al. Efficacy of the pharmacologic chaperone migalastat in a subset of male patients with the classic phenotype of Fabry disease and migalastat-amenable variants: Data from the phase 3 randomized, multicenter, double-blind clinical trial and extension study. Genet. Med. 2019, 21, 1987–1997. [CrossRef][PubMed] 64. Ashe, K.M.; Budman, E.; Bangari, D.S.; Siegel, C.S.; Nietupski, J.B.; Wang, B.; Desnick, R.J.; Scheule, R.K.; Leonard, J.P.; Cheng, S.H.; et al. Efficacy of enzyme and substrate reduction therapy with a novel antagonist of glucosylceramide synthase for fabry disease. Mol. Med. 2015, 21, 389–399. [CrossRef] 65. Nabhan, J.F.; Wood, K.M.; Rao, V.P.; Morin, J.; Bhamidipaty, S.; Labranche, T.P.; Gooch, R.L.; Bozal, F.; Bulawa, C.E.; Guild, B.C. Intrathecal delivery of frataxin mRNA encapsulated in lipid nanoparticles to dorsal root ganglia as a potential therapeutic for Friedreich’s ataxia. Sci. Rep. 2016, 6, 20019. [CrossRef][PubMed] 66. Fabregat-Andrés, Ó.; Pina-Buded, S.; Valverde-Navarro, A.A. Feasibility and diagnostic performance of including point-of-care ultrasound (POCUS) in preparticipation screening of young competitive athletes. Cardiol. Young 2020, 30, 1970–1972. [CrossRef] Cells 2021, 10, 1532 13 of 13

67. Fox, J.C.; Lahham, S.; Maldonado, G.; Klaus, S.; Aish, B.; Sylwanowicz, L.V.; Yanuck, J.; Wilson, S.P.; Shieh, M.; Anderson, C.L.; et al. Hypertrophic Cardiomyopathy in Youth Athletes: Successful Screening with Point-of-Care Ultrasound by Medical Students: Successful. J. Ultrasound Med. 2017, 36, 1109–1115. [CrossRef] 68. Moulson, N.; Jaff, Z.; Wiltshire, V.; Taylor, T.; O’Connor, H.M.; Hopman, W.M.; Johri, A.M. Feasibility and Reliability of Nonexpert POCUS for Cardiovascular Preparticipation Screening of Varsity Athletes: The SHARP Protocol. Can. J. Cardiol. 2019, 35, 35–41. [CrossRef] 69. Ko, W.Y.; Siontis, K.C.; Attia, Z.I.; Carter, R.E.; Kapa, S.; Ommen, S.R.; Demuth, S.J.; Ackerman, M.J.; Gersh, B.J.; Arruda-Olson, A.M.; et al. Detection of Hypertrophic Cardiomyopathy Using a Convolutional Neural Network-Enabled Electrocardiogram. J. Am. Coll. Cardiol. 2020, 75, 722–733. [CrossRef] 70. Martini, N.; Aimo, A.; Barison, A.; Della Latta, D.; Vergaro, G.; Aquaro, G.D.; Ripoli, A.; Emdin, M.; Chiappino, D. Deep learning to diagnose cardiac amyloidosis from cardiovascular magnetic resonance. J. Cardiovasc. Magn. Reson. 2020, 22.[CrossRef]