Trivia: Sudden Arrhythmia Death Syndrome (SADS)

Sudden arrhythmia death syndrome (SADS) can be caused by a number of diseases that interfere with the heart's normal rhythm or function. Each year, about 400,000 Americans die suddenly and unexpectedly due to cardiac arrhythmias, of which 3,976 are under age 35. Although the number of young people at risk for SADS is small, increased awareness regarding the conditions that predispose people to SADS can prevent young patients from going undiagnosed or misdiagnosed. Once diagnosed, most cardiac arrhythmias or structural heart defects can be treated or managed.

Most cases of SADS are caused three conditions: hypertrophic cardiomyopathy (HCM), arrhythmogenic right ventricular dysplasia (ARVD), and Long QT syndrome (LQTS). SADS can also be triggered by a number of other medical conditions. According to a SADS Foundation fact sheet, SADS occurs in about 240 people per 100,000. Of those, about 200 have HCM, about 20 have ARVD, and about 20 have LQTS.

Hypertrophic Cardiomyopathy (HCM): HCM is a hereditary disease which causes the heart muscle to become excessively thick, and also leads to the haphazard arrangement of heart muscle fibers. People with HCM are prone to potentially fatal heart rhythms, such as ventricular fibrillation or ventricular tachycardia. HCM can be treated using drugs, specialized pacemakers, and sometimes surgery.

Arrhythmogenic Right Ventricular Dysplasia (ARVD): ARVD is a genetic heart condition where the muscle of the right ventricle is gradually replaced by fat and fibrosis, which leads to abnormal heart rhythms. ARVD is estimated to affect one in 5,000 people, and may account for up to one-fifth of cases of sudden cardiac death in people under age 35. ARVD is difficult to diagnose and usually requires many different tests, including an ECG, a signal averaged ECG (SAECG), an echocardiogram, an exercise stress test, a cardiac MRI, and 24 hours of Holter monitoring. The majority of patients with ARVD are asymptomatic for many years. If arrhythmias develop, they can usually be controlled by antiarrhythmic drugs. Many patients receive an ICD.

Long QT Syndrome (LQTS): LQTS is caused by genetic mutations in the ion channels of the heart, which affects the electrical signals that cause the heart to beat. There are seven types of LQTS, and 95% of patients have Long QT 1, 2, or 3. Long QT 1 and 2 are caused by underactive potassium channels, and Long QT 3 is caused by overactive sodium channels. When screened with an ECG, most people with the condition have a longer "QT interval" (the time between depolarization and repolarization). LQTS can also be diagnosed using an exercise ECG or a Holter. Beta-blocker medications are the most common treatment for LQTS and are effective in 90% of cases. High-risk patients may need pacemakers or ICDs. Patients with LQTS should avoid strenuous sports and physical activity, caffeine, and over-the-counter stimulants, such as cold medication.

Anyone who experiences one or more of the following symptoms should consult his or her doctor:

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