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. The Role of Exercise
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. Ventricular arrhythmias
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.
It is seen predominantly in males, and 30–50% of cases have a familial distribution. Signs and symptoms
Those affected by arrhythmogenic cardiomyopathy may not have any symptoms at all despite having significant abnormalities in the structure of their hearts. If symptoms do occur, the initial presentation is often due to abnormal heart rhythms (arrhythmias) which in arrhythmogenic cardiomyopathy may take the form of palpitations, or blackouts. Sudden death may be the first presentation of ACM without any preceding symptoms. These symptoms often occur during adolescence and early adulthood, but signs of ACM may rarely be seen in infants. As ACM progresses, the muscle tissue within the ventricles may dilate and weaken. The right ventricle typically weakens first, leading to fatigue and ankle swelling. In the later stages of the disease in which both ventricles are involved shortness of breath may develop, especially when lying flat.The first clinical signs of ACM are usually during adolescence and early adulthood. However, rarely, signs of ACM have been demonstrated in infants. Causes
Genetics
ACM 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. 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.