5.3.7 Tachycardia-induced cardiomyopathy

Prolonged tachycardia with heart rates exceeding 100 beats per minute may induce systolic and/or diastolic ventricular dysfunction. "Tachycardia-induced cardiomyopathy" may occur in conjunction with any type of tachycardia such as atrial fibrillation, atrial flutter, atrial tachycardia, or atrioventricular tachycardia. It has also been observed in sustained ventricular tachycardia. How long the ventricle tolerates a high heart rate depends on several factors:

the actual heart rate
underlying structural disease
age
coexisting medical conditions

By definition, tachycardia-induced cardiomyopathy is reversible once heart rate and/or heart rhythm is brought under control. Therefore, the diagnosis can only be established retrospectively. The time until recovery of left ventricular function may vary; it may return to normal in a few days, or may take several weeks in some patients.

In clinical practice it may be difficult to determine left ventricular function in the presence of tachycardia. Watch for beats with a long RR interval. Estimation of left ventricular function from these beats will enable you to determine whether left ventricular function merely appears reduced (due to the short cycle length) or whether contractility is actually reduced.

Tachycardia-induced cardiomyopathy should be suspected in all patients with heart rates above 100 beats per minute and reduced left ventricular function. It may be a challenge, in terms of diagnosis, to determine whether atrial arrhythmias are the cause or the result of cardiomyopathy.

Tachycardia-induced cardiomyopathy. The patient has atrial fibrillation with a heart rate between 100-130/bpm.

Reduced left ventricular function during tachycardia (left). Left ventricular function recovers after control of heart rate (right)

Cardiomyopathy may also be induced by frequent premature ectopic beats (PEB). Myocardial dysfunction is probably related to the dyssynchronous contraction caused by such beats (see also Chapter 23). There is evidence that a premature ectopic beat burden of more than 24% is associated with reduced left ventricular function.