Challenge to conventional treatment for myocardial failure-mechanical assist

Use of a prosthesis for temporary or permanent circulatory support in left ventricular failure has been investigated by our group for over 12 years. Experiences with both a U-shaped mechanical auxiliary ventricle (MAV) and the intraaortic balloon pump showed that in-series devices can stabilize the failing circulation. Studies with a MAV based on the balloon pump, the dynamic aortic patch (DAP) indicated that this system too is hemodynamically effective. In addition, data from extensive in vivo studies indicated that when its intravascular surface is made of Electrolour (Dacron velour backed by polyurethane with a negative electrical charge), the frequency of thromboembolism is greatly diminished. Following initial activation of the DAP in a patient with advanced chronic congestive failure, his hemodynamic parameters rapidly approached normal values: mean pulmonary artery and end-diastolic pressures were reduced, cardiac output increased, and myocardial metabolism changed from anaerobic to aerobic. The patient's cardiac function gradually improved, allowing his return to his home. The patient died on the 96th postoperative day after three months of improved cardiac function. Autopsy disclosed the DAP to be functional. A stable fibrin layer had formed on its intravascular surface; there were no signs of embolization. The DAP represents a promising approach to long-term ventricular support. For more than twelve years, our group has been interested in the possibility of using a mechanical prosthesis, not for total heart replacement, but rather for partial temporary or permanent circulatory support. In the first several years of work following this approach, we concentrated on the development of a permanently implantable system for in-series ventricular assistance. This work led to the study of several configurations of a mechanical auxiliary ventricle which gave effective circulatory support in laboratory and clinical studies [1,2]. The problem of achieving satisfactory interaction between blood and prosthesis was not resolved in these studies, but we were sufficiently encouraged by the hemodynamic effects to look into the possibility of working with the temporary support system initially proposed by Moulopoulos, Topaz, and Kolff [3].