Cycle length alternation in circus movement tachycardia using an atrioventricular accessory pathway. A study of the role of the atrioventricular node using a computer model of tachycardia.

The possible role of the atrioventricular nodal (AVN) function curve during tachycardia as a cause of cycle length alternation was investigated using a computer model of circus movement tachycardia utilizing an atrioventricular accessory pathway. Two types of AVN function curves during tachycardia were entered into the computer: straight lines of various gradients and representative examples of patient-based AVN function curves obtained during clinical electrophysiologic studies. Perturbations of the tachycardia model were induced by introducing a short cycle, by suddenly prolonging a conduction interval, or by moving the AVN function curve relative to that in stable tachycardia. Using the straight line AVN function curves, stable, sustained cycle length alternation could be induced by perturbation of the tachycardia cycle if the gradient of the line was -1 (slope = 45 degrees). If the gradient was more than -1 (slope less than 45 degrees), the perturbation was damped. If the gradient was less than -1 (sl...