Agents Used in Cardiac Arrhythmias

Agents Used in Cardiac Arrhythmias

Cardiac arrhythmias are a common problem in clinical prac-tice, occurring in up to 25% of patients treated with digitalis, 50% of anesthetized patients, and over 80% of patients with acute myocardial infarction. Arrhythmias may require treat-ment because rhythms that are too rapid, too slow, or asyn-chronous can reduce cardiac output. Some arrhythmias can precipitate more serious or even lethal rhythm disturbances; for example, early premature ventricular depolarizations can precipitate ventricular fibrillation. In such patients, antiar-rhythmic drugs may be lifesaving. On the other hand, the hazards of antiarrhythmic drugs—and in particular the fact that they can precipitate lethal arrhythmias in some patients— has led to a reevaluation of their relative risks and benefits. In general, treatment of asymptomatic or minimally symptom-atic arrhythmias should be avoided for this reason.

Arrhythmias can be treated with the drugs discussed and with nonpharmacologic therapies such as pacemakers, cardioversion, catheter ablation, and surgery.

 CASE STUDY

69-year-old retired teacher presents with a 1-month history of palpitations, intermittent shortness of breath, and fatigue. She has a history of hypertension. An ECG shows atrial fibrillation with a ventricular response of 122 bpm and signs of left ventricular hypertrophy. She is anticoagulated with warfarin and started on sustained-release metoprolol 50 mg/d. After 7 days, her rhythm reverts to normal sinus spontaneously. However, over the ensuing month, she continues to have intermittent palpita-tions and fatigue. Continuous ECG recording over a 48-hour period documents paroxysms of atrial fibrillation with heart rates of 88–114 bpm. An echocardiogram shows a left ven-tricular ejection fraction of 38% with no localized wall motion abnormality. At this stage, would you initiate treat-ment with an antiarrhythmic drug to maintain normal sinus rhythm, and if so, what drug would you choose?