September 20, 2017
Twenty years ago is approximately when the first dual-chamber defibrillators were available for use. Up to that point, defibrillators had undergone some advances, including antitachycardia pacing, biphasic shock waveforms and using the implantable cardioverter defibrillator can as an electrode, but only provided ventricular backup pacing from a single ventricular lead. These were not very good at preventing the heart from going too slow, so sometimes we needed to insert a separate pacemaker and defibrillator in the same patient.
In 1997, patients who received implantable cardioverter defibrillators more commonly needed them for secondary prevention, ie, they previously had cardiac arrest or sustained ventricular tachycardia. We were just beginning to put devices in after we had done an electrophysiologic study to prove that someone had the potential to develop ventricular tachycardia. These primary prevention ICDs were mostly used for patients with coronary disease and poor ejection fraction.