Ventricular Tachycardia and Sudden Cardiac Death in Hypertrophic Cardiomyopathy
The major cause of death in patients with hypertrophic cardiomyopathy may be serious life-threatening arrhythmias called ventricular tachycardia or ventricular fibrillation. It should be emphasized that most patients with hypertrophic cardiomyopathy will never have a serious or life-threatening ventricular arrhythmia. In fact, many studies indicate that the overall survival of patients with hypertrophic cardiomyopathy approximates that of the general population.
Why, then, are we concerned about ventricular tachycardia and hypertrophic cardiomyopathy? There is a subset of patients with hypertrophic cardiomyopathy in whom ventricular arrhythmias are the major cause of death. In fact, in many families, the first evidence of hypertrophic cardiomyopathy is the existence of a death in an individual due to hypertrophic cardiomyopathy.
Once patients are given the diagnosis of hypertrophic cardiomyopathy, how do we determine if they are at increased risk of these serious ventricular arrhythmias? In addition to a complete family history, physical examination and history, there are number of tests that are usually performed: exercise stress testing, ECG monitoring for 24 hours or more (often called Holter or ambulatory ECG monitoring).
There are a number of criteria that are used: history of prior cardiac arrest (ventricular tachycardia or ventricular fibrillation requiring an electrical shock to restore normal heart rhythm), nonsustained ventricular tachycardia (a series of fast heart beats from the lower heart chamber) on ECG monitoring, episodes of loss of consciousness (without clear explanation), decrease in blood pressure or failure of blood pressure to rise during exercise testing, massive heart wall thickness (30mm is often used but some physicians may select another cut-off value), family history of sudden death.
If patients have one or more of these criteria, physicians will discuss with patients the option of a special device called an implantable cardioverter defibrillator (ICD) and determine if this treatment is right for the patient.
History of prior cardiac arrest non-sustained ventricular tachycardia episodes of loss of consciousness decrease in blood pressure or failure of blood pressure to rise during exercise testing, massive heart wall thickness family history of sudden death.
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