What causes arrhythmogenic right ventricular dysplasia?
The pathogenesis of arrhythmogenic right ventricular dysplasia is largely unknown. Apoptosis (programmed cell death) appears to play a large role. It is unclear why only the right ventricle is involved. 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 RV). Residual myocardium is confined to the subendocardial region and the trabeculae of the RV. 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 arrhythmogenic right ventricular dysplasia, 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 < 3mm 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.
Ventricular arrhythmias due to arrhythmogenic right ventricular dysplasia 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 ARVD. In this case, the EKG shows a left bundle branch block (LBBB) morphology with an inferior axis.
In order to make the diagnosis of ARVD, a number of clinical tests are employed, including the electrocardiogram (EKG), echocardiography, right ventricular angiography, and cardiac MRI.
More information on cardiomyopathy
What is cardiomyopathy? - Cardiomyopathy is an alteration in the function of the heart muscle. Cardiomyopathy is the deterioration of the cardiac muscle of the heart wall.
What're the symptoms of cardiomyopathy? - The symptoms of cardiomyopathy include fatigue, shortness of breath, fainting, leg swelling, and an enlarged and tender liver.
How is cardiomyopathy diagnosed? - Cardiomyopathy can be diagnosed by characteristic physical findings, electrocardiogram, echocardiogram, cardiac catheterization and radionuclide angiography.
What is dilated cardiomyopathy? - Dilated cardiomyopathy (DCM) is the commonest form of cardiomyopathy, and one of the leading indications for heart transplantation.
What causes dilated cardiomyopathy? - No exact cause can be found for cardiomyopathy. Up to 30% of cases of dilated cardiomyopathy can be linked to heavy drinking.
What're the symptoms of dilated cardiomyopathy? - Typical signs and symptoms of dilated cardiomyopathy include fatigue, weakness, shortness of breath, and swelling of the legs and feet.
What're the treatments for dilated cardiomyopathy? - Treatment for dilated cardiomyopathy is focused on relieving the symptoms and the extra load on the heart. Lifestyle changes, medicines, and surgery may be needed.
What is hypertrophic cardiomyopathy? - Hypertrophic cardiomyopathy (HCM) is the second most common type of cardiomyopathy and results in excessive thickening of the heart walls.
What causes hypertrophic cardiomyopathy? - Hypertrophic cardiomyopathy is caused by the mutation in one of a number of genes that encode for one of the sarcomere proteins.
What're the symptoms of hypertrophic cardiomyopathy? - Symptoms of hypertrophic cardiomyopathy include shortness of breath, chest pain (angina), palpitations, dizziness and fainting attacks.
What's the treatment for hypertrophic cardiomyopathy? - Treatment of hypertrophic cardiomyopathy is directed towards decreasing the left ventricular outflow tract gradient and to abort arrhythmias.
What's arrhythmogenic right ventricular dysplasia? - Arrhythmogenic right ventricular dysplasia (ARVD) is a type of nonischemic cardiomyopathy that involves primarily the right ventricle.
What causes arrhythmogenic right ventricular dysplasia? - The cause of arrhythmogenic right ventricular dysplasia is largely unknown. Apoptosis appears to play a large role.
What's the treatment for arrhythmogenic right ventricular dysplasia? - Pharmacologic treatment of arrhythmogenic right ventricular dysplasia involves arrhythmia suppression and prevention of thrombus formation.
What is restrictive cardiomyopathy? - Restrictive cardiomyopathy (RCM) is the least common cardiomyopathy. Restrictive cardiomyopathy can be caused by a number of diseases.
How restrictive cardiomyopathy is diagnosed? - The diagnosis of restrictive cardiomyopathy is usually based on a physical examination, echocardiography, and other tests as needed.
What's the treatment for restrictive cardiomyopathy? - There is no effective treatment for restrictive cardiomyopathy. Treatment of a causative disease may reduce or stop the damage to the heart.
How is cardiomyopathy treated? - Beta-blocker medicines, and calcium antagonist medicines are the mainstay of treatment for cardiomyopathy. Surgery may be indicated for hypertrophic cardiomyopathy.