This article needs additional citations for verification . (February 2009) (Learn how and when to remove this template message) |
Arrhythmogenic cardiomyopathy | |
---|---|
Other names | arrhythmogenic right ventricular cardiomyopathy (ARVC), arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C), right ventricular dysplasia |
Photomicrograph of an ACM heart. | |
Specialty | Cardiology |
Arrhythmogenic cardiomyopathy(ACM), arrhythmogenic right ventricular dysplasia (ARVD), or arrhythmogenic right ventricular cardiomyopathy (ARVC), is an inherited heart disease. [1]
ACM is caused by genetic defects of the parts of heart muscle (also called myocardium or cardiac muscle) known as desmosomes, areas on the surface of heart muscle cells which link the cells together. The desmosomes are composed of several proteins, and many of those proteins can have harmful mutations.
A genetic disorder is a genetic problem caused by one or more abnormalities formed in the genome. Most genetic disorders are quite rare and affect one person in every several disease thousands or millions. The earliest known genetic condition in a hominid was in the fossil species Paranthropus robustus, with over a third of individuals displaying Amelogenesis imperfecta.
Cardiac muscle is one of three types of vertebrate muscles, with the other two being skeletal and smooth muscles. It is an involuntary, striated muscle that constitutes the main tissue of the walls of the heart. The myocardium forms a thick middle layer between the outer layer of the heart wall and the inner layer, with blood supplied via the coronary circulation. It is composed of individual heart muscle cells (cardiomyocytes) joined together by intercalated discs, encased by collagen fibres and other substances that form the extracellular matrix.
A desmosome, also known as a macula adherens, is a cell structure specialized for cell-to-cell adhesion. A type of junctional complex, they are localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes. Desmosomes are one of the stronger cell-to-cell adhesion types and are found in tissue that experience intense mechanical stress, such as cardiac muscle tissue, bladder tissue, gastrointestinal mucosa, and epithelia.
The disease is a type of nonischemic cardiomyopathy that primarily involves the right ventricle, though cases of exclusive left ventricular disease have been reported. It is characterized by hypokinetic areas involving the free wall of the ventricle, with fibrofatty replacement of the myocardium, with associated arrhythmias often originating in the right ventricle. The nomenclature ARVD is currently thought to be inappropriate and misleading as ACM does not involve dysplasia of the ventricular wall. Cases of ACM originating from the left ventricle lead to the abandonment of the name ARVC.
Cardiomyopathy is a group of diseases that affect the heart muscle. Early on there may be few or no symptoms. As the disease worsens, shortness of breath, feeling tired, and swelling of the legs may occur, due to the onset of heart failure. An irregular heart beat and fainting may occur. Those affected are at an increased risk of sudden cardiac death.
A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The atrium primes the pump.
Hypokinesia refers to decreased bodily movement. One of the two categories of movement disorders, hypokinesia is characterized by a partial or complete loss of muscle movement due to a disruption in the basal ganglia. Patients with hypokinetic disorders like Parkinson's disease experience muscle rigidity and an inability to produce movement. It is also associated with mental health disorders and prolonged inactivity due to illness, amongst other diseases.
ACM can be found in association with diffuse palmoplantar keratoderma, and woolly hair, in an autosomal recessive condition called Naxos disease, because this genetic abnormality can also affect the integrity of the superficial layers of the skin most exposed to pressure stress. [2] :513 [3]
Naxos disease is a cutaneous condition characterized by a palmoplantar keratoderma. The prevalence of the syndrome is up to 1 in every 1000 people in the Greek islands.
ACM is an important cause of ventricular arrhythmias in children and young adults. It is seen predominantly in males, and 30–50% of cases have a familial distribution.
Up to 80% of individuals with ACM present have symptoms like syncope and dyspnea.The remainder frequently present with palpitations or other symptoms due to right ventricular outflow tract (RVOT) tachycardia (a type of monomorphic ventricular tachycardia).
Symptoms are usually exercise-related. In populations where hypertrophic cardiomyopathy is screened out prior to involvement in competitive athletics, it is a common cause of sudden cardiac death.
Hypertrophic cardiomyopathy (HCM) is a condition in which a portion of the heart becomes thickened without an obvious cause. This results in the heart being less able to pump blood effectively. Symptoms vary from none to feeling tired, leg swelling, and shortness of breath. It may also result in chest pain or fainting. Complications include heart failure, an irregular heartbeat, and sudden cardiac death.
The first clinical signs of ACM are usually during adolescence and early adulthood. However, rarely, signs of ACM have been demonstrated in infants.
It is usually inherited in an autosomal dominant pattern, with variable expression. Only 30% to 50% of individuals affected by ACM will test positive to one of the known genetic mutations in chromosomal loci associated with the disease. [4] [5] Novel studies showed that mutations (point mutations) in genes encoding for desmosomal proteins (see intercalated disc) are the main causatives for the development of this disease. Recently it has been shown, that mutations in the desmin DES gene could cause ACM. [6] Desmin is an intermediate filament protein, which is linked to the desmosomes. Different DES muations cause an abnormal aggregation of desmin and associated proteins. [7] The penetrance is 20–35% in general, but significantly higher in Italy. Seven gene loci have been implicated in ACM. It is unclear whether the pathogenesis varies with the different loci involved. Standard genetic screening test are currently tested and evaluated in different state of the art cardiovascular research centres and hospitals. Types include:
Type | OMIM | Gene | Locus | Reference |
---|---|---|---|---|
ARVD1lpl | 107970 | TGFB3 | 14q23-q24 | [8] |
ARVD2 | 600996 | RYR2 | 1q42-q43 | [9] |
ARVD3 | 602086 | ? | 14q12-q22 | |
ARVD4 | 602087 | ? | 2q32.1-q32.3 | |
ARVD5 | 604400 | TMEM43 | 3p23 | [10] [11] |
ARVD6 | 604401 | ? | 10p14-p12 | |
ARVD7 | 609160 | DES | 10q22.3 | [12] [13] |
ARVD8 | 607450 | DSP | 6p24 | [14] |
ARVD9 | 609040 | PKP2 | 12p11 | [15] |
ARVD10 | 610193 | DSG2 | 18q12.1-q12 | [16] [17] |
ARVD11 | 610476 | DSC2 | 18q12.1 | [18] [19] |
ARVD12 | 611528 | JUP | 17q21 | [20] [21] |
ILK | 11p15.4 | [22] | ||
LMNA | [23] |
The pathogenesis of ACM is largely unknown. Apoptosis (programmed cell death) appears to play a large role. It was previous thought that only the right ventricle is involved, however recent cohorts have show many cases of left ventricular disease and biventricular disease. The disease process starts in the subepicardial region and works its way towards the endocardial surface, leading to transmural involvement (possibly accounting for the aneurysmal dilatation of the ventricles). Residual myocardium is confined to the subendocardial region and the trabeculae of the ventricles. These trabeculae may become hypertrophied.
Aneurysmal dilatation is seen in 50% of cases at autopsy. It usually occurs in the diaphragmatic, apical, and infundibular regions (known as the triangle of dysplasia). The left ventricle is involved in 50–67% of individuals. If the left ventricle is involved, it is usually late in the course of disease, and confers a poor prognosis.
There are two pathological patterns seen in ACM, Fatty infiltration and fibro-fatty infiltration.
The first, fatty infiltration, is confined to the right ventricle. This involves a partial or near-complete substitution of myocardium with fatty tissue without wall thinning. It involves predominantly the apical and infundibular regions of the RV. The left ventricle and ventricular septum are usually spared. No inflammatory infiltrates are seen in fatty infiltration. There is evidence of myocyte (myocardial cell) degeneration and death seen in 50% of cases of fatty infiltration.
The second, fibro-fatty infiltration, involves replacement of myocytes with fibrofatty tissue. A patchy myocarditis is involved in up to 2/3 of cases, with inflammatory infiltrates (mostly T cells) seen on microscopy. Myocardial atrophy is due to injury and apoptosis. This leads to thinning of the RV free wall (to < 3 mm thickness) Myocytes are replaced with fibrofatty tissue. The regions preferentially involved include the RV inflow tract, the RV outflow tract, and the RV apex. However, the LV free wall may be involved in some cases. Involvement of the ventricular septum is rare. The areas involved are prone to aneurysm formation.
Recently, some studies have identified strenuous exercise as a novel risk for accelerated progression of the disease. One retrospective study on 301 patients conclusively demonstrated that the subpopulations participating in strenuous physical activity (professional athletes for example) had an earlier onset of symptoms and earlier mortality compared to other populations. [24]
Ventricular arrhythmias due to ACM typically arise from the diseased right ventricle. The type of arrhythmia ranges from frequent premature ventricular complexes (PVCs) to ventricular tachycardia (VT) to ventricular fibrillation (VF).
While the initiating factor of the ventricular arrhythmias is unclear, it may be due to triggered activity or reentry.
Ventricular arrhythmias are usually exercise-related, suggesting that they are sensitive to catecholamines. The ventricular beats typically have a right axis deviation. Multiple morphologies of ventricular tachycardia may be present in the same individual, suggesting multiple arrhythmogenic foci or pathways.
Right ventricular outflow tract (RVOT) tachycardia is the most common VT seen in individuals with ACM. In this case, the EKG shows a left bundle branch block (LBBB) morphology with an inferior axis.
The differential diagnosis for the ventricular tachycardia due to ACM include:
In order to make the diagnosis of ACM, a number of clinical tests are employed, including the electrocardiogram (EKG), echocardiography, right ventricular angiography, cardiac MRI, and genetic testing.
90% of individuals with ARVD have some EKG abnormality. The most common EKG abnormality seen in ACM is T wave inversion in leads V1 to V3. However, this is a non-specific finding, and may be considered a normal variant in right bundle branch block (RBBB), women, and children under 12 years old.
RBBB itself is seen frequently in individuals with ACM. This may be due to delayed activation of the right ventricle, rather than any intrinsic abnormality in the right bundle branch.
The epsilon wave is found in about 50% of those with ACM. This is described as a terminal notch in the QRS complex. It is due to slowed intraventricular conduction. The epsilon wave may be seen on a surface EKG; however, it is more commonly seen on signal averaged EKGs.
Ventricular ectopy seen on a surface EKG in the setting of ACM is typically of left bundle branch block (LBBB) morphology, with a QRS axis of −90 to +110 degrees. The origin of the ectopic beats is usually from one of the three regions of fatty degeneration (the "triangle of dysplasia"): the RV outflow tract, the RV inflow tract, and the RV apex.
Signal averaged ECG (SAECG) is used to detect late potentials and epsilon waves in individuals with ACM.
Echocardiography may reveal an enlarged, hypokinetic right ventricle with a paper-thin RV free wall. The dilatation of the RV will cause dilatation of the tricuspid valve annulus, with subsequent tricuspid regurgitation. Paradoxical septal motion may also be present.
Fatty infiltration of the RV free wall can be visible on cardiac MRI. Fat has increased intensity in T1-weighted images. However, it may be difficult to differentiate intramyocardial fat and the epicardial fat that is commonly seen adjacent to the normal heart. Also, the sub-tricuspid region may be difficult to distinguish from the atrioventricular sulcus, which is rich in fat.
Cardiac MRI can visualize the extreme thinning and akinesis of the RV free wall. However, the normal RV free wall may be about 3 mm thick, making the test less sensitive.
Right ventricular angiography is considered the gold standard for the diagnosis of ACM. Findings consistent with ACM are an akinetic or dyskinetic bulging localized to the infundibular, apical, and subtricuspid regions of the RV. The specificity is 90%; however, the test is observer dependent.
Transvenous biopsy of the right ventricle can be highly specific for ACM, but it has low sensitivity. False positives include other conditions with fatty infiltration of the ventricle, such as chronic alcohol abuse and Duchenne/Becker muscular dystrophy.
False negatives are common, however, because the disease progresses typically from the epicardium to the endocardium (with the biopsy sample coming from the endocardium), and the segmental nature of the disease. Also, due to the paper-thin right ventricular free wall that is common in this disease process, most biopsy samples are taken from the ventricular septum, which is commonly not involved in the disease process.
A biopsy sample that is consistent with ACM would have > 3% fat, >40% fibrous tissue, and <45% myocytes.
A post mortem histological demonstration of full thickness substitution of the RV myocardium by fatty or fibro-fatty tissue is consistent with ACM.
ACM is an autosomal dominant trait with reduced penetrance. Approximately 40–50% of ACM patients have a mutation identified in one of several genes encoding components of the desmosome, which can help confirm a diagnosis of ACM. [25] Since ACM is an autosomal dominant trait, children of an ACM patient have a 50% chance of inheriting the disease causing mutation. Whenever a mutation is identified by genetic testing, family-specific genetic testing can be used to differentiate between relatives who are at-risk for the disease and those who are not. ACM genetic testing is clinically available. [26]
There is no pathognomonic feature of ACM. The diagnosis of ACM is based on a combination of major and minor criteria. To make a diagnosis of ACM requires either 2 major criteria or 1 major and 2 minor criteria or 4 minor criteria.
Major criteria
Minor criteria
The goal of management of ACM is to decrease the incidence of sudden cardiac death. This raises a clinical dilemma: How to prophylactically treat the asymptomatic patient who was diagnosed during family screening.
A certain subgroup of individuals with ACM are considered at high risk for sudden cardiac death. Associated characteristics include:
Management options include pharmacological, surgical, catheter ablation, and placement of an implantable cardioverter-defibrillator.
Prior to the decision of the treatment option, programmed electrical stimulation in the electrophysiology laboratory may be performed for additional prognostic information. Goals of programmed stimulation include:
Regardless of the management option chosen, the individual is typically advised to undergo lifestyle modification, including avoidance of strenuous exercise, cardiac stimulants (i.e.: caffeine, nicotine, pseudoephedrine) and alcohol. If the individual wishes to begin an exercise regimen, an exercise stress test may have added benefit.
Pharmacologic management of ACM involves arrhythmia suppression and prevention of thrombus formation.
Sotalol, a beta blocker and a class III antiarrhythmic agent, is the most effective antiarrhythmic agent in ACM. Other antiarrhythmic agents used include amiodarone and conventional beta blockers (i.e.: metoprolol). If antiarrhythmic agents are used, their efficacy should be guided by series ambulatory holter monitoring, to show a reduction in arrhythmic events.
While angiotensin converting enzyme inhibitors (ACE Inhibitors) are well known for slowing progression in other cardiomyopathies, they have not been proven to be helpful in ACM.
Individuals with decreased RV ejection fraction with dyskinetic portions of the right ventricle may benefit from long term anticoagulation with warfarin to prevent thrombus formation and subsequent pulmonary embolism.
Catheter ablation may be used to treat intractable ventricular tachycardia. It has a 60–90% success rate. [27] Unfortunately, due to the progressive nature of the disease, recurrence is common (60% recurrence rate), with the creation of new arrhythmogenic foci. Indications for catheter ablation include drug-refractory VT and frequent recurrence of VT after ICD placement, causing frequent discharges of the ICD.
An ICD is the most effective prevention against sudden cardiac death. Due to the prohibitive cost of ICDs, they are not routinely placed in all individuals with ACM.
Indications for ICD placement in the setting of ACM include:
Since ICDs are typically placed via a transvenous approach into the right ventricle, there are complications associated with ICD placement and follow-up.
Due to the extreme thinning of the RV free wall, it is possible to perforate the RV during implantation, potentially causing pericardial tamponade. Because of this, every attempt is made at placing the defibrillator lead on the ventricular septum.
After a successful implantation, the progressive nature of the disease may lead to fibro-fatty replacement of the myocardium at the site of lead placement. This may lead to undersensing of the individual's electrical activity (potentially causing inability to sense VT or VF), and inability to pace the ventricle.
Heart transplant may be performed in ACM. It may be indicated if the arrhythmias associated with the disease are uncontrollable or if there is severe bi-ventricular heart failure that is not manageable with pharmacological therapy.
All first degree family members of the affected individual should be screened for ACM. This is used to establish the pattern of inheritance. Screening should begin during the teenage years unless otherwise indicated. Screening tests include:
There is a long asymptomatic lead-time in individuals with ACM. While this is a genetically transmitted disease, individuals in their teens may not have any characteristics of ACM on screening tests.
Many individuals have symptoms associated with ventricular tachycardia, such as palpitations, light-headedness, or syncope. Others may have symptoms and signs related to right ventricular failure, such as lower extremity edema, or liver congestion with elevated hepatic enzymes.
ACM is a progressive disease. Over time, the right ventricle becomes more involved, leading to right ventricular failure. The right ventricle will fail before there is left ventricular dysfunction. However, by the time the individual has signs of overt right ventricular failure, there will be histological involvement of the left ventricle. Eventually, the left ventricle will also become involved, leading to bi-ventricular failure. Signs and symptoms of left ventricular failure may become evident, including congestive heart failure, atrial fibrillation, and an increased incidence of thromboembolic events.
The prevalence of ACM is about 1/10,000 in the general population in the United States, although some studies have suggested that it may be as common as 1/1,000. Recently, 1/200 were found to be carriers of mutations that predispose to ACM. [28] Based on these findings and other evidence, it is thought that in most patients, additional factors such as other genes, athletic lifestyle, exposure to certain viruses, etc. may be required for a patient to eventually develop signs and symptoms of ACM. [29] It accounts for up to 17% of all sudden cardiac deaths in the young. In Italy, the prevalence is 40/10,000, making it the most common cause of sudden cardiac death in the young population. [30]
Brugada syndrome (BrS) is a genetic disorder in which the electrical activity within the heart is abnormal. It increases the risk of abnormal heart rhythms and sudden cardiac death. Those affected may have episodes of passing out. The abnormal heart rhythms seen in those with Brugada syndrome often occur at rest. They may be triggered by a fever.
Ventricular fibrillation is when the heart quivers instead of pumping due to disorganized electrical activity in the ventricles. It is a type of cardiac arrhythmia. Ventricular fibrillation results in cardiac arrest with loss of consciousness and no pulse. This is followed by death in the absence of treatment. Ventricular fibrillation is found initially in about 10% of people in cardiac arrest.
A premature ventricular contraction (PVC) is a relatively common event where the heartbeat is initiated by Purkinje fibers in the ventricles rather than by the sinoatrial node, the normal heartbeat initiator. PVCs may cause no symptoms at all, but they may also be perceived as a "skipped beat" or felt as palpitations in the chest. Single beat PVC abnormal heart rhythms do not usually pose a danger.
Dilated cardiomyopathy (DCM) is a condition in which the heart becomes enlarged and cannot pump blood effectively. Symptoms vary from none to feeling tired, leg swelling, and shortness of breath. It may also result in chest pain or fainting. Complications can include heart failure, heart valve disease, or an irregular heartbeat.
Ventricular tachycardia is a type of regular, fast heart rate that arises from improper electrical activity in the ventricles of the heart. Although a few seconds may not result in problems, longer periods are dangerous. Short periods may occur without symptoms, or present with lightheadedness, palpitations, or chest pain. Ventricular tachycardia may result in ventricular fibrillation and turn into sudden death. It is found initially in about 7% of people in cardiac arrest.
Desmin is a protein that in humans is encoded by the DES gene. Desmin is a muscle-specific, type III intermediate filament that integrates the sarcolemma, Z disk, and nuclear membrane in sarcomeres and regulates sarcomere architecture.
Ventricular hypertrophy (VH) is thickening of the walls of a ventricle of the heart. Although left ventricular hypertrophy (LVH) is more common, right ventricular hypertrophy (RVH), as well as concurrent hypertrophy of both ventricles can also occur.
Tachycardia-induced cardiomyopathy (TIC) is a disease where prolonged tachycardia or arrhythmia causes an impairment of the myocardium, which can result in heart failure. People with TIC may have symptoms associated with heart failure and/or symptoms related to the tachycardia or arrhythmia. Though atrial fibrillation is the most common cause of TIC, several tachycardias and arrhythmias have been associated with the disease.
Desmoplakin is a protein in humans that is encoded by the DSP gene. Desmoplakin is a critical component of desmosome structures in cardiac muscle and epidermal cells, which function to maintain the structural integrity at adjacent cell contacts. In cardiac muscle, desmoplakin is localized to intercalated discs which mechanically couple cardiac cells to function in a coordinated syncytial structure. Mutations in desmoplakin have been shown to play a role in dilated cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, striate palmoplantar keratoderma, Carvajal syndrome and paraneoplastic pemphigus.
Plakoglobin, also known as junction plakoglobin or gamma-catenin, is a protein that in humans is encoded by the JUP gene. Plakoglobin is a member of the catenin protein family and homologous to β-catenin. Plakoglobin is a cytoplasmic component of desmosomes and adherens junctions structures located within intercalated discs of cardiac muscle that function to anchor sarcomeres and join adjacent cells in cardiac muscle. Mutations in plakoglobin are associated with arrhythmogenic right ventricular dysplasia.
Non-compaction cardiomyopathy (NCC), is a rare congenital cardiomyopathy that affects both children and adults. It results from the failure of myocardial development during embryogenesis.
Ryanodine receptor 2 (RYR2) is a protein found primarily in cardiac muscle. In humans, it is encoded by the RYR2 gene. In the process of cardiac calcium-induced calcium release, RYR2 is the major mediator for sarcoplasmic release of stored calcium ions.
The following outline is provided as an overview of and topical guide to cardiology, the branch of medicine dealing with disorders of the human heart. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Physicians who specialize in cardiology are called cardiologists.
Desmocollin-2 is a protein that in humans is encoded by the DSC2 gene. Desmocollin-2 is a cadherin-type protein that functions to link adjacent cells together in specialized regions known as desmosomes. Desmocollin-2 is widely expressed, and is the only desmocollin isoform expressed in cardiac muscle, where it localizes to intercalated discs. Mutations in DSC2 have been causally linked to arrhythmogenic right ventricular cardiomyopathy.
Plakophilin-2 is a protein that in humans is encoded by the PKP2 gene. Plakophilin 2 is expressed in skin and cardiac muscle, where it functions to link cadherins to intermediate filaments in the cytoskeleton. In cardiac muscle, plakophilin-2 is found in desmosome structures located within intercalated discs. Mutations in PKP2 have been shown to be causal in arrhythmogenic right ventricular cardiomyopathy.
Transmembrane protein 43 is a protein that in humans is encoded by the TMEM43 gene. TMEM43 may have an important role in maintaining nuclear envelope structure by organizing protein complexes at the inner nuclear membrane. Required for retaining emerin at the inner nuclear membrane. However, the localization of TMEM43 in myocardial tissue is controversial discussed. Franke et al. demonstrated that TMEM43 is localized at the intercalated disc but not at the nuclear envelope. In contrast Christensen et al. have shown that TMEM43 is mainly localized at the sarcolemma. Mutations in TMEM43 are associated with ARVD and EDMD7.
Boxer cardiomyopathy is a disease of the myocardium primarily affecting Boxer dogs. It is characterized by the development of ventricular tachyarrhythmias, resulting in syncope and sudden cardiac death. Myocardial failure and congestive heart failure are uncommon manifestations of the disease.
Heart arrhythmia is a group of conditions in which the heartbeat is irregular, too fast or too slow. A heart rate that is too fast – above 100 beats per minute in adults – is called tachycardia, and a heart rate that is too slow – below 60 beats per minute – is called bradycardia. Many types of arrhythmia have no symptoms. When symptoms are present, these may include palpitations or feeling a pause between heartbeats. In more serious cases, there may be lightheadedness, passing out, shortness of breath or chest pain. While most types of arrhythmia are not serious, some predispose a person to complications such as stroke or heart failure. Others may result in sudden death.
Frank I. Marcus is an American cardiologist and Emeritus Professor of Medicine at the University of Arizona Health Sciences Center, the author of more than 290 publications in peer-reviewed medical journals and of 90 book chapters. He is considered a world expert on arrhythmogenic right ventricular cardiomyopathy (ARVC) and has been or is a member of the Editorial/Scientific Board of 14 Cardiovascular Journals as well as a reviewer for 26 other medical publications.
The Association for Inherited Cardiac Conditions is the UK national professional body for experts in genetics and cardiology dealing with inherited diseases of the heart. These include heart muscle diseases such as hypertrophic cardiomyopathy, dilated cardiomyopathy, noncompaction cardiomyopathy, and arrhythmogenic cardiomyopathy, as well as inherited arrhythmia disorders such as long QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia (CPVT). The AICC also represents experts in aortic disease such as Marfan syndrome and other systemic diseases which affect the heart or circulation.
Classification | |
---|---|
External resources |
Wikimedia Commons has media related to Arrhythmogenic right ventricular dysplasia . |