Drug therapy before and after the electroversion of cardiac dysrhythmias

Abstract

Synchronized DC shock is the treatment of choice for atrial rhythm disturbances and ventricular tachycardia, but it is important that patients be chosen carefully for this form of therapy. In addition, the success and safety of treatment depend not only on the correct procedure for the electrical therapy itself but also on the choice and dose of drugs used before and after DC shock. The following guidelines can be recommended: 1. (1) Patient anxiety and pain should be prevented by using diazepam routinely in incremental intravenous doses before the shock. 2. (2) Anticoagulant cover should be used as a routine unless contraindicated and should be maintained for 1 mo after successful electroversion, since the incidence of reversion back to the dysrhythmia is highest during this time. 3. (3) Atropine 1–2 mg intravenously should precede DC shock to enhance sino-atrial pacemaker activity in any patient known to be in atrial fibrillation for 5 yr or longer and in whom an attempt at DC conversion is still to be made. It should also precede DC shock in any patient with an atrial rhythm disturbance and a slow ventricular response (60/min or less) to protect against asystole, which may result from parasympathetic stimulation produced by the transmyocardial shock. The routine use of lidocaine, quinidine, procainamide, or propranolol without atropine in these patients is dangerous for these drugs all inhibit any further pacemaker activity. 4. (4) Ventricular premature beats, tachycardia or fibrillation leading to death may follow DC shock at usual energy level settings even when synchronized in the heavily digitalized or digitalis-toxic patient, particularly when the myocardial potassium content is lowered by diuretic therapy. Whenever possible, elective DC shock should be postponed until all signs of digitalis toxicity have passed and the serum potassium level is adequate. In addition, these patients should be protected against ventricular dysrhythmias by an intravenous injection of lidocaine 50–100 mg just before DC shock and by reducing the initial energy level setting to 5 joules. 5. (5) The incidence of tachydysrhythmias following DC shock can be lessened by using the smallest energy setting needed to depolarize the heart and by administering lidocaine 50–100 mg, procainamide 50–100 mg, or diphenylhydantoin 50–100 mg intravenously should extrasystoles follow the initial shock before proceeding to higher energy levels. 6. (6) In patients in whom sinus rhythm is hemodynamically important for adequate cardiac performance, maintenance on quinidine or procainamide with additional propranolol in those not in severe cardiac failure can be used in an attempt to prolong sinus rhythm following electroversion, although the long-term results of such treatment are unfortunately less than ideal. Electroversion of cardiac dysrhythmias is an exciting advance, but much greater effort is needed to uncover basic mechanisms of cardiac rhythm disturbances, to develop more physiologic approaches to their treatment, and particularly to the maintenance of sinus rhythm thereafter.