Performance of an abdominal left ventricular assist device during induced tachycardias and dysrhythmias

Experiments were designed to assess the performance of an intracorporeal (abdominal) left ventricular assist device (ALVAD) in the presence of induced tachycardias, multiple premature ventricular contractions (PVC's), and ventricular fibrillation in calves. Performance criteria were the degree of left ventricular unloading and the per cent cardiac output assumed by the ALVAD. During synchronous pumping, left ventricular unloading was complete and the entire cardiac output was captured by the device. During induced tachycardias up to rates of 120 beats per minute, these degrees of performance were maintained. At rates in excess of 120 beats per minute, performance declined due to decreased biologic stroke volumes and prosthetic filling times. In the presence of induced PVC's, performance during synchronous pumping decreased because of erratic R-wave sensing. Left ventricular unloading was complete but irregular, and the total cardiac output was captured. When asynchronous pumping was utilized, mean left ventricular systolic pressures increased, but total cardiac output was still captured. During induced ventricular fibrillation, ALVAD actuation maintained cardiac outputs equal to control values for periods up to 5 1/2 hours. These experiments indicate that, during normal sinus rhythm, synchronous pumping is optimal; asynchronous pumping is optimal during complex dysrhythmias; and either can be utilized to support the circulation with varying degrees of left ventricular unloading.