Significance and Consequences
of Arrhythmias

The function and efficiency of the cardiac pump under ordinary circumstances is not affected if the rhythm becomes irregular: the heart can adapt to an irregularity, even to the absence of effective atrial contraction. Arrhythmias frequently affect normal hearts in healthy individuals: monitor studies have shown that single ectopic beats can be found in almost one-half of the general population. Occasionally, healthy subjects display groups of ectopic beats (short runs of tachycardia), and even more complex arrhythmias sometimes appear. However, arrhythmias are more frequent in patients with heart disease and may produce serious consequences. The importance of arrhythmias in general is in its effect on cardiac function, its relationship to the underlying disease, and its role as a harbinger of life-threatening arrhythmias.

The function of the heart may be compromised if the heart rate is very fast or very slow. Tolerance of rapid tachycardia or slow bradycardia varies from person to person: in healthy populations only extremes in heart rate are likely to affect cardiac function; patients with cardiac disease, however, may be sensitive even to a moderate increase or decrease in heart rate, which may have serious consequences. The more common instances of arrhythmias in patients with organic heart disease, as already mentioned, may be an unimportant by-product of the underlying disease. But in some cases arrhythmias may accentuate the symptoms of the disease and affect cardiac function; in still others they may produce cardiac emergencies.

Perception of arrhythmias as palpitations is one of the symptoms that lead patients to seek medical care. As such, they may be a clue to the discovery of previously unknown, significant cardiac disease. Both healthy individuals having arrhythmias and patients with cardiac disease may be aware of the irregularity of their heartbeat. Even simple premature ectopic beats are often perceptible: ectopic ventricular beats usually cancel the next normal beat, producing a longer than usual pause that the affected person can feel as a skipping of heartbeats. Tachycardias often are perceived as palpitations or pounding of the heart. Yet some people, with or without heart disease, may be totally unaware of even the most complex arrhythmias.

Ventricular arrhythmias are potentially more serious than atrial arrhythmias, even though they are common in healthy persons. Since the most severe variety of ventricular arrhythmia is fibrillation—that is, cardiac arrest—some such arrhythmias need to be carefully studied to determine whether the patient is at a high risk of developing a fatal arrhythmia and thus requires aggressive treatment.