Myocarditis in the Athlete: Arrhythmogenic Substrates, Clinical Manifestations, Management, and Eligibility Decisions
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Journal of Cardiovascular Translational Research https://doi.org/10.1007/s12265-020-09996-1 REVIEW ARTICLE Myocarditis in the Athlete: Arrhythmogenic Substrates, Clinical Manifestations, Management, and Eligibility Decisions Riccardo Vio1 & Alessandro Zorzi1 & Domenico Corrado1 Received: 3 October 2019 /Accepted: 24 March 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020 Abstract Myocarditis is as an important cause of sudden cardiac death (SCD) among athletes. The incidence of SCD ascribed to myocarditis did not change after the introduction of pre-participation screening in Italy, due to the transient nature of the disease and problems in the differential diagnosis with the athlete’s heart. The arrhythmic burden and the underlying mechanisms differ between the acute and chronic setting, depending on the relative impact of acute inflammation versus post-inflammatory myocardial fibrosis. In the acute phase, ventricular arrhythmias vary from isolated ventricular ectopic beats to complex tachy- cardias that can lead to SCD. Atrioventricular blocks are typical of specific forms of myocarditis, and supraventricular arrhyth- mias may be observed in case of atrial inflammation. Athletes with acute myocarditis should be temporarily restricted from physical exercise, until complete recovery. However, ventricular tachycardia may also occur in the chronic phase in the context of post-inflammatory myocardial scar. Keywords Myocarditis . Athletes . Sport . Ventricular ARVC Arrhythmogenic right ventricular cardiomyopathy tachycardia . Ventricular fibrillation . Atrial fibrillation . Atrioventricular block . Sudden death Introduction Abbreviations Myocarditis is an inflammatory disease of the heart muscle AM Acute myocarditis most often caused by infectious agents (infective myocar- SCD Sudden cardiac death ditis), autoimmune conditions, or pharmacological and en- EMB Endomyocardial biopsy vironmental toxins (non-infective myocarditis) [1]. LGE Late gadolinium enhancement Infective myocarditis due to viral agents (coxsackievirus, CMR Cardiac magnetic resonance adenovirus, parvovirus, and herpes virus) is fairly the most AV Atrioventricular common form of the disease and is usually characterized LV Left ventricular by a benign prognosis [2]. The majority of patients with AF Atrial fibrillation acute myocarditis (AM) have a mild and transient cardiac VF Ventricular fibrillation involvement, most often mimicking the clinical features of VT Ventricular tachycardia acute coronary syndromes, and a favorable clinical course ICD Implantable cardioverter defibrillator with a complete clinical recovery; acute heart failure and sudden cardiac death (SCD) are less common clinical pre- Associate Editor Domingo A. Pascual-Figal oversaw the review of this sentations [1, 3, 4]. Post-inflammatory myocardial article sequelae are not so rare and consist of repair subepicardial-midmural myocardial fibrosis which occurs * Domenico Corrado [email protected] as a result of the healing process of a previous acute myo- cardial lesion [5]. There is growing evidence that non- 1 Department of Cardiac, Thoracic, Vascular Sciences and Public ischemic myocardial scar, either post-myocarditis or due Health, University of Padova, Via Giustiniani, 2, 35128 Padova, Italy to other myocardial diseases, may act as a substrate of J. of Cardiovasc. Trans. Res. life-threatening ventricular arrhythmias and arrhythmic Challenges in the Diagnosis of Acute Myocarditis cardiac arrest, mostly in young people and athletes [6]. in the Athlete The present article reviews the etiology, pathogenesis, clin- ical manifestations, risk stratification, and management of Definitive diagnosis of AM relies on histologic demonstration myocarditis occurring in the athlete, with particular reference of myocardial inflammatory infiltrates and myocyte degener- to the different arrhythmogenic substrates and mechanisms ation and death on endomyocardial biopsy (EMB). However, acting in the acute and chronic disease settings. the use of EMB is uncommon in the routine clinical practice and according to current guidelines the invasive approach for histologic examination of myocardial samples is reserved to Myocarditis in the Athletes selected clinical scenarios that do not include most common benign and self-limiting presentation [26]. In the absence of Although definite evidence is lacking, athletes may be EMB confirmation, the clinical diagnosis of myocarditis is at higher risk of developing myocarditis than the gener- strongly suspected or highly probable in the presence of ≥ 2 al population. Sports activity can influence the suscep- criteria including compatible clinical symptoms, electrocar- tibility to infections, depending on the intensity and du- diographic abnormalities, elevation of myocardiocytolysis ration of the physical exercise. While moderate physical markers, evidence of non-ischemic morphofunctional ventric- activity may improve immunological defenses [7–9], in- ular abnormalities, and increased T2 signal for myocardial tense and prolonged training and competition lower the edema/regional late gadolinium enhancement (LGE) at cardi- immunity by reducing salivary secretory immunoglobu- ac magnetic resonance (CMR) [1]. lin A, lactoferrin, and lysozyme and altering the T cell Personal and family history, physical examination, and 12- response, all mechanisms that may increase the vulner- lead ECG are crucial in the initial evaluation of athletes with ability of athletes to viral infections [7, 8, 10–14]. Non- suspected myocarditis. Symptoms, such as chest pain, dys- infective myocarditis, i.e., immune-mediated and toxic pnea, and fatigue, possibly start after a respiratory or gastro- myocarditis, may also be favored. intestinal infection. Sports activity may also worsen the pathobiological At the electrocardiogram, repolarization abnormalities are course of AM [15–18]. Murine models of myocarditis by the most common alterations in AM, being detected in 40% of coxsackievirus B3 showed a striking augment in the viru- patients; ST segment elevation (typically concave and diffuse lence of the pathogen agents when the animals were forced without reciprocal changes) is more frequent than ST segment to swim [15]. The acceleration of coxsackie B3 myocardi- depression (6% vs 2%), and negative T waves (36%) are ob- tis course induced by exercise was also reported by Kiel served mainly in lateral leads [27]. These ECG changes are et al., who observed that exercise increased both the extent typically transient in AM [28], and even when present, their of myocardial cell necrosis and overall mortality [16]. significance might be uncertain since athletes frequently show Worsening of the myocardial pathological damage can oc- repolarization abnormalities (i.e., early repolarization) [29]. cur not only in viral myocarditis but also in autoimmune The most notable ECG feature of early repolarization is ST myocarditis as demonstrated by the increase of both hu- segment elevation, which may vary on morphology, location, moral and cellular immunities against the heart muscle in anddegree;Twaveinversioncanalsobeobservedparticular- mice exercised by treadmill [19]. ly in black athletes but confined to leads V1-V4 [30]. Myocarditis has been traditionally regarded as cause of Pathologic Q waves are reported in 13% of patients with life-threatening ventricular arrhythmias and SCD in the AM [27], whereas they are rare in athletes [31]. PR segment athletes. The incidence of SCD due to AM in the athlete depression and low voltages can reveal the existence of peri- ranges from 2 to 12% of all fatalities [20–24]. Data from cardial inflammation and effusion and tend to disappear the registry of juvenile SCD of the Veneto region of Italy throughout the healing process. Other ECG changes include showed that the mortality did not significantly change atrioventricular (AV) and bundle branch blocks. before and after the implementation of systematic pre- Electrocardiographic differential diagnosis between AM and participation screening in Italy (from 0.3/100.000 to athlete’s heart is summarized in Table 1. 0.15/100.000, p =0.42)[25]. Failure to identify athletes Biomarkers indicative of myocardial injury are usually el- with myocarditis by pre-participation screening reflects evated in myocarditis; however, the majority of healthy ath- the acute and unpredictable nature of the inflammatory letes after prolonged exercise show values of cardiac troponin process, which often is clinically silent and may lead to above the 99th percentile [32]. electrical ventricular instability and cardiac arrest in oth- Echocardiography may solve the dilemma, identifying erwise asymptomatic individuals. Furthermore, highly signs of the disease such as global left ventricular (LV) en- trained athletes tend to underestimate or hide symptoms largement and dysfunction, localized wall motion abnormali- to avoid limitations to competitive sports eligibility. ties, and relaxation alterations suggestive of the presence of J. of Cardiovasc. Trans. Res. Table 1 Electrocardiographic differential diagnosis between acute myocarditis and athlete’sheart Acute myocarditis Athlete’sheart Repolarization abnormalities - ST segment elevation Diffuse Localized (usually in the anterior leads) or diffuse - ST segment depression Possible Absent - T wave inversion Mainly in lateral or inferior leads Confined to V1-V4 in Afro-Caribbean athletes Q waves Pathological (amplitude ≥ 25% of the ensuing R wave Non-pathological (≥ 4 mm in depth but