The Mechanical Auxiliary Ventricle Demonstrates Biocompatibility in up to 25 Months of Intermittent Cardiac Support in Calves

The mechanical auxiliary ventricle (MAV) is an avalvular prosthesis that is permanently implanted in the descending thoracic aorta. It is counterpulsated like the intraaortic balloon pump (IABP); however, the MAV, with its larger pumping chamber, can provide greater hemodynamic effects than the IABP. The IABP is an accepted therapy for alleviating acute pharmacologically refractory congestive heart failure (CHF). The beneficial actions of the MAV in advanced CHF have been documented, using an earlier version of the system [Kantrowitz A, Krakauer JS, Zorzi G, Rubenfire M, Freed PS, Phillips S, Lipsius M, Titone C, Cascade P, Jaron D (1971) Current status of the intraaortic balloon pump and initial clinical experience with an aortic patch mechanical auxiliary ventricle. Transplant Proc 3:1459] These studies also confirmed that the MAV, because of the small surface area of artificial material in contact with the blood, is minimally thrombogenic, allowing the system to be turned off at will and permitting the patient to be untethered when physiologically appropriate. However, these studies also demonstrated that the MAV’s percutaneous access device had led to infection. The MAV system was therefore redesigned, necessitating in vitro and in vivo studies to determine the reliability of the reconfigured prosthesis. In this report, the results of in vivo tests of biochemical and hematological studies of four calves with long-term, intermittently activated, MAVs are presented. Four animals were pumped intermittently for 2-h sessions, 5 days a week, for 22, 26, 60, and 112 weeks, respectively. In the aggregate, the four animals were pumped for 3790 h. During this time, the blood pumps were activated for more than 20 million cycles and were restarted after inactivation of hours or days more than 1700 times. No aberrations of clinical significance were discovered. The results of other tests, including an exhaustive search for thromboemboli and other pathological responses to the MAV, also proved negative. These results provide evidence that turning the MAV ‘Off’ and ‘On’ does not activate the host’s hemostatic mechanism. In clinical application, with the MAV ‘Off,’ the patient can be free of any external connection, or have the option of a standby wearable drive unit weighing <5 lbs with batteries. If clinical trials prove successful, clinicians would then have at their disposal a nonobligatory, avalvular LVAD for selected CHF patients, with the advantages of quality of life, reliability, and safety.