Electrical stimulation of the heart in patients with ventricular tachycardia.

SUMMARY The initiation and termination of tachyeardias were studied in five patients who suffered from recurrent attacks of ventricular tachycardia. In four, coronary artery disease with old myocardial infarction was present. A ventricular tachycardia could be initiated in all patients by a single right ventricular premature beat given during regular driving of the right ventricle. The tachycardia could be terminated by a single right ventricular premature beat, or two right ventricular premature beats given in close succession. In four of our patients an early right ventricular premature beat was followed by the next QRS complex of the tachycardia after an interval shorter than compensatory. Our results favor reentry as the causal mechanism for the tachyeardias in our patients. Possible pathways for circus reentry leading to ventricular tachycardia can theoretically be composed of (1) the bundle branches, (2) Purkinje fibers with or without adjacent ventricular myocardium, (3) infarcted or fibrotic ventricular tissue, and (4) combinations of (1), (2), and (3). ELECTRICAL STIMULATION of the heart has enabled us to study the initiation and termination of tachyeardias directly in the human heart. With help of these technics initiation and termination of supraventricular tachyeardias have been studied in patients with and without signs of preexcitation.1-5 Using these methods we studied five patients who suffered from recurrent attacks of ventricular tachyear-dias. Methods All the patients studied suffered from recurrent attacks of ventricular tachycardia. As shown in table 1, coronary heart disease with myocardial infarction was present in four. The fifth patient had myocarditis at the age of 19 years. Table 2 lists the electrocardiographic findings in these 216 patients, both during sinus rhythm and tachycar-dia. By use of the Seldinger technic four electrode catheters were passed under local anesthesia through the femoral veins and positioned at the desired intracavitary location. Two bipolar cath-eters were used for stimulation of the right atrium and right ventricle, respectively. A tripolar electrode catheter was used to record the electrogram of the His bundle.6 The fourth catheter was used for registering the unipolar intracavitary atrial complex. A description of our stimulator and methods of stimulation have been given previously.' The duration of the stimulus was 2 msec, the stimulus strength two times diastolic threshold. The protocol of the investigation in each patient consisted of: (1) The study of A-V conduction. This was done by way of a premature stimulus to the right atrium once after eight beats of a …