The closing velocity of Baxter Duromedic heart valve prostheses

The closing velocity of a mechanical heart valve (MHV) leaflet has been conventionally related to the valve sound, and possibly to recently observed MHV cavitation phenomenon. Presently, the MHV leaflet terminal closing velocity has been indirectly assessed either by listening to the valve sound and/or averaging over the closing period. Leaflet motion during the closing phase is not uniform. Using a laser sweeping technique developed in this laboratory, an experimental study was carried out to analyze the closing motion of Baxter Duromedic (DM) 29 mm mitral MHVs. The results were compared with that of a St. Jude Mechanical (SJ) 29 mm mitral MHV, using the same technique. The in vitro experiment was carried out by mounting the testing MHV at the mitral position of a mock circulatory testing facility, with heart rates ranging from 70-120 beats/min, ventricular pressure slopes (dp/dt) from 1800-5600 mmHg/sec, and cardiac outputs from 5.0-7.5 liters/min. This paper introduces the laser sweeping technique developed for precision monitoring of MHV leaflet motion, and presents the detailed leaflet motions within the last 3 degrees before final closure. The experimental results showed that the final closing velocity of DM, which is known to generate a louder valve sound and has a shorter closing period than that of SJ, actually has approximately the same closing velocity within the range of the experiment. Theoretical analysis further confirms that a short closing period may not lead to a higher leaflet final closing velocity.