Any physician implanting pacemakers must be familiar with the American College of Cardiology/American Heart Association/North American Society Pacing Electrophysiology (now termed the Heart Rhythm Society) Guidelines that are published intermittently in their various journals. Only a brief summary of basic concepts is discussed here. | Temporary pacing may be useful in the management of drug-resistant ventricular arrhythmias. Unfortunately, there is no panacea for resistant ventricular tachycardia, which usually occurs in a setting of severe left ventricular failure, often with associated myocardial ischemia. In selected patients who are resistant to drug therapy, however, overdrive suppression by using a temporary ventricular pacemaker, either alone or in association with drugs, may be helpful. This treatment has been especially effective for Torsade de pointes, a form of polymorphic ventricular tachycardia with changing electric vectors, only occurring in a setting of prolonged QT interval. Torsade de pointes is often due to toxicity resulting from quinidine, disopyramide, or other drugs that lengthen the QT interval. Overdrive suppression works by establishing a heart rate of 10 to 40 bpm above the resting heart rate. This pacing rate physiologically shortens the QT interval and the refractory period of the ventricle. Ventricular ectopy often begins at a slow intrinsic heart rate that is fairly reproducible; that is, a patient may have ectopy begin at a heart rate of less than 60 bpm that no longer occurs when the heart rate increases to 90 bpm. By increasing the heart rate and shortening the QT interval, a rhythm is established that prevents ectopic ventricular beats. Generally, temporary atrial or ventricular pacing at 30 bpm above the resting rate is attempted. This approach is used much less commonly now that it has been learned that intravenous magnesium generally can suppress Torsade de pointes by shortening the QT interval.
