ARVD is usually diagnosed in older children and adults (usually after age 10 and less than 40 years) and may cause sudden cardiac death in athletes. Symptoms may include:

• Irregular heart rhythms that start in the lower chambers of the heart (ventricular arrhythmias). The most common is ventricular tachycardia.
• Fluttering in the chest due to abnormal heart rhythms (palpitations)
• Dizziness, lightheadedness or fainting caused by irregular heart rhythms
• Sudden cardiac death − can be the first sign of ARVD
• Heart failure − shortness of breath with activity, inability to carry out normal activities without fatigue, swelling in the legs, ankles and feet (edema)

The cause of ARVD in family members has been linked to genetic changes in a type of protein. It occurs in about one in 5,000 people. ARVD can occur without a family history, although it often runs in families. A family history of ARVD is present in at least 30 to 50 percent of cases. When one parent has ARVD, a child has a 50 percent chance of inheriting the condition. The symptoms and age of onset may be different between family members.

Family members may also get a form of ARVD called Naxos disease. In addition to the symptoms seen in ARVD, these individuals have a thickening of the skin on the palms of the hands and soles of the feet and thick wool-like hair.

It can be hard to diagnose ARVD since the changes to the heart muscle may be subtle. ARVD is diagnosed based on medical history, physical exam, and tests (electrocardiogram, Holter monitor, electrophysiologic testing, echocardiogram, cardiac MRI, and/or cardiac CT scan, genetic testing).

Cardiac magnetic resonance imaging (MRI) is recommended for the diagnosis of ARVD because the heart muscle of the right ventricle can be seen. This imaging test can detect the abnormal features found in the heart muscle of the right ventricle. If image quality is poor related to an irregular heart rhythm, then a cardiac CT scan can be done. Unlike MRI, a CT scan can be performed if the patient has an implanted device (pacemaker, defibrillator).

The diagnosis of ARVD may include the following findings:

• Abnormal function of the lower right chamber (ventricle) of the heart
• Fatty or fibrous-fatty deposits in the right ventricle heart muscle (myocardium)
• Abnormal ECG
• Abnormal heart rhythms (supraventricular tachycardia, ventricular tachycardia or ventricular fibrillation, especially with exercise)
• Family history of ARVD

A family history of ARVD is present in at least 30 to 50 percent of cases. It is recommended that all family members (parents, siblings, children, grandchildren, uncle, aunt, nephew, niece) be evaluated carefully for this form of cardiomyopathy, even if they have no symptoms.

There is no known cure for ARVD. Treatment is usually directed at controlling the patient's abnormal heart rhythms and managing their heart failure. The primary goal of treatment is preventing continued ventricular arrhythmias and/or sudden death. Antiarrhythmic drug therapy is the most frequently used therapy. Frequent ventricular arrhythmias that have not been successfully treated with medical therapy may be treated with radiofrequency ablation. Patients who are thought to be at risk for sudden death are usually treated with an implantable defibrillator (ICD).

Patients with ARVD need to ask their physicians about exercise or participation in sports.