Sinoatrial and atrioventricular nodal reentry tachycardias

Sinus node re-entry tachycardia, atrioventricular nodal re-entry tachycardia, atrioventricular reciprocating tachycardia, and paroxysmal junctional tachycardia are included in this category as all can be treated in a similar fashion. Because of the re-entry circuit, carotid sinus massage will either terminate the arrhythmia or have no effect. The next treatment of choice is adenosine which has a very short half-life and is as effective as verapamil. An initial dose of 6 mg is given by rapid intravenous bolus; if this is ineffective, a dose of 12 mg may be administered. Calcium-channel antagonists such as verapamil and diltiazem may be used; however, the patient must be closely monitored for hypotension when using these agents. Other medications that may be used acutely are b-blockers and digitalis. However, the onset of action of cardiac glycosides is delayed by about 30 min when given intravenously. Overdrive pacing has also been shown to be effective in terminating re-entry tachycardias, and this can be accomplished by atrial or esophageal pacing. If the patient is hemodynamically unstable, electrical cardioversion is indicated, with a voltage of 25 to 50 J usually being effective.

Any precipitating factors should be corrected and, if chronic therapy is required, verapamil, diltiazem, b-blockers, and digitalis, as well as class IA and IC antiarrhythmics, may be used. Patients with known atrioventricular reciprocating tachycardia with an accessory pathway should not be given verapamil or digitalis on a chronic basis since they may also exhibit atrial fibrillation and/or atrial flutter.

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