An overview of arrhythmogenic cardiomyopathy Understanding conditions that can cause this disorder will help nurses educate and care CNE for patients. 1.5 contact hours By Fidelindo Lim, DNP, CCRN; LEARNING O BJECTIVES Chris Noah Hsiao, BSN, RN; and Navi Johal, BSN, RN, CEN, PMD 1. Compare the causes of arrhythmogenic cardiomyopathy (ACM) as to pathophysiology, clinical course, and management. 2. Discuss nursing implications for patients with ACM. The authors and planners of this CNE activity have disclosed no rel- evant financial relationships with any commercial companies per- taining to this activity. See the last page of the article to learn how to earn CNE credit. Expiration: 8/1/24 6 American Nurse Journal Volume 16, Number 8 MyAmericanNurse.com ARAN*, an otherwise healthy 16-year-old Brugada brothers in Spain, is a genetic dis- South Asian male, arrives at the emergency de- ease of the cardiac ion channel function. The partment with paramedics after having a syn- syndrome causes dysfunction in the ion copal episode while watching a soccer game. channels via up or down regulations, de- The initial ECG shows polymorphic ventricular pending on the genetic mutation or variant tachycardia, which requires cardioversion in involved, which can lead to arrhythmias. Pa- the field. Slight ST-elevations in the right pre- tients with the disease can experience syn- cordial leads are noted but no T-wave inver- cope, ventricular tachycardia (VT), ventricu- sions. Aran denies any cardiac history, but a lar fibrillation (VF), cardiac arrest, or SCD. cardiology consultation with his parents re- The most common ECG manifestations are veals a family history of sudden cardiac death right bundle branch block (RBBB) and ST- (SCD) and that the father has had peri-synco- segment elevations in the right precordial pal and syncopal episodes. leads. BrS affects more men than women and An electrophysiologic study shows an easily especially those of South Asian or Japanese inducible Type 1 ST-elevation, and pro- descent. El Sayed and colleagues report that grammed electrical stimulation induces ven- overall prevalence is 5:10,000. The disease is tricular tachycardia. Aran is diagnosed with the leading cause of SCD in men under 40 Brugada syndrome (BrS). An implantable car- years and accounts for 12% of all SCD world- diac monitor is placed with plans for an im- wide. (Web resource: SADS.org) plantable cardioverter defibrillator (ICD), pro- phylactic quinidine, regular follow-ups, and Pathophysiology genetic testing. No clear pathophysiology for BrS exists, but genetic links are well established. When the disease was initially discovered, and up until Our understanding of the major risk factors a decade ago, most thought it was a condition of cardiovascular disease—such as diet, elevat- of an otherwise structurally normal heart. Re- ed blood pressure, high body mass index, in- cent advances in higher resolution–computed creased total cholesterol, high fasting glucose tomography (CT) and cardiac magnetic reso- level, smoking, and sedentary lifestyle—has nance imaging (MRI) have revealed some increased, but little was known about arrhyth- structural abnormalities. However, because no mogenic cardiomyopathy (ACM) until recently. pathognomonic pattern exists, the debate ACM is defined as an arrhythmogenic dis- lingers as to whether the abnormalities cause order of the myocardium not secondary to BrS or are a result of it. ischemic, hypertensive, or valvular heart Genetically, an SCN5A mutation affecting disease. Because of the low prevalence of the sodium channel flow is the most common conditions that lead to ACM, many health- (up to 30%) BrS variant. The mutation causes care providers may not be familiar with a decrease in the early peak current in the car- managing the disease or identifying those at diac muscle and slows or blocks the conduc- risk. In 2019, the Heart Rhythm Society tion rate in parts of the heart, allowing for (HRS) issued a comprehensive consensus wave-break, which leads to arrhythmias. Ac- report on ACM management. This article pro- cording to Brugada and colleagues, other ge- vides an overview of selected genetic (BrS, netic variants affecting the cardiac sodium, left ventricular noncompaction), systemic (sar- potassium, or calcium channel subunits ac- coidosis, cardiac amyloidosis), infiltrative (car- count for 2% to 5% of inherited BrS cases. Es- diac amyloidosis), and infectious (Chagas dis- timates show that in up to 70% of patients ease) disorders that can lead to ACM. with the inherited disease, no genetic variant Although these conditions may result in a host has been identified. of systemic complications, the discussion will focus on cardiac pathology and the role of Clinical course nurses. BrS is diagnosed through analysis of an ECG. Three ECG patterns have been identified as Brugada syndrome hallmarks of the disease, all having ST eleva- tions in the precordial leads; the most com- BrS, which is named after the cardiologist mon is type 1 coved ST elevation. Under the MyAmericanNurse.com August 2021 American Nurse Journal 7 HRS guidelines, BrS is confirmed when a type myocardium gradually compacts from the epi- 1 ST elevation is observed either spontaneous- cardium inward. When this fails, LVNC can re- ly or after I.V. administration of a sodium sult. Mutations in MYH7 and MYBPC3 genes channel blocker in at least one right precor- have been found in 30% of patients with dial lead (V1 and V2) combined with at least LVNC. These genes play a role in the function one of the following: documented VF or poly- of sarcomeres, the structure within muscle morphic VT, inducibility of ventricular ar- fibers that causes contraction. rhythmias with programmed electrical stimula- tion, family history of SCD before age 45, Clinical course history of non-vasovagal syncope, or noctur- LVNC diagnosis requires echocardiography or nal agonal breathing. cardiovascular MRI to measure the ratio of Patients with BrS can remain asymptomatic thickness, mass, or volume of the noncom- for life, but those who have symptoms, which pacted layer of the left ventricle to the com- Left can vary from syncope to SCD, frequently pacted layers. If the ratio of X (distance from ventricular start to experience them close to the mean epicardial surface to trough of trabecular re- age of 40 years. Certain factors, such as med- cess) to Y (distance from epicardial surface to noncompaction ication or fever, can induce arrhythmias asso- peak of trabeculation) is <0.5, the patient (LVNC), also ciated with BrS. meets diagnostic criteria. Although some pa- tients are asymptomatic, others may experi- known as Management ence SCD, blood clots, frequent premature honeycomb Treatment options for patients with BrS are ventricular complexes, ventricular tachycar- limited and guided by risk stratification. The dia, palpitation, and exercise intolerance be- myocardium, recommended pharmacologic intervention is cause of the ventricle’s inability to contract is a heart quinidine, which suppresses arrhythmias. De- and relax normally. According to Towbin and finitive treatment is an ICD. New research and Jefferies, two-thirds of individuals with LVNC muscle current medical investigations are showing develop heart failure (HF). Except for dilated disorder in promising results in using ablation to stop fre- and hypertrophic cardiomyopathy, LVNC fre- quent arrhythmic storms. quently presents with features similar to those which the left found in pulmonary atresia and intramyocar- ventricle Left ventricular noncompaction dial hematoma. becomes thick Left ventricular noncompaction (LVNC), also Management and spongy, known as honeycomb myocardium, is a heart For the most part, LVNC treatment is symptom- muscle disorder in which the left ventricle be- specific, and HF is the most common reason leaving the comes thick and spongy, leaving the heart for hospitalization. Treatment guidelines for heart weak weak and unable to contract or relax proper- HF should be applied on the basis of the pa- ly. The National Institute of Health estimates tient’s clinical scenario; treatment may include and unable to that LVNC affects eight to 12 patients per 1 beta-blockers, ACE inhibitors, angiotensin-II contract or million annually; however, because of the receptor blockers, diuretics, and aldosterone sometimes-hidden clinical manifestations, its antagonists. Antidysrhythmic therapy, such as relax properly. true prevalence may be underreported. Epi- ICD implantation and ablation, is recommend- demiology is also hampered by the lack of ed for patients with life-threatening dysrhyth- consensus on a diagnostic standard. The con- mia, especially those with nonsustained VT. In dition usually affects the left ventricle, but in patients with atrial fibrillation or presence of 22% to 38% of patients, the pathology is atrial or ventricular clots, oral anticoagulation found in both ventricles. (Web resource: is recommended. The risks and benefits of cardiomyopathy.org/left-ventricular-non heart transplant also should be explored. compaction/intro) Sarcoidosis Pathophysiology Although the exact cause of LVNC is un- Sarcoidosis is a multisystem, inflammatory dis- known, it’s thought to result from a disruption ease that primarily targets the lymph nodes of the compaction process during left ventri- and lungs. The hallmark manifestation is the cle myocardium development. Normally, the accumulation of noncaseating granulomas 8 American Nurse Journal Volume 16, Number 8 MyAmericanNurse.com (nonsolidifying areas