MITRAL-VALVE REPLACEMENT - TECHNIQUES TO ELIMINATE MYOCARDIAL RUPTURE AND PREVENT VALVULAR DISRUPTION

Twenty fresh canine hearts were used to compare the peak left ventricular pressures required to disrupt prosthetic mitral valves sutured in place with horizontal mattress sutures using either subannular or supraannular placed pledgets. Separate groups were developed to determine the effect of leaving the whole mitral valve apparatus or only the posterior leaflet apparatus intact and what effect, if any, each had on the ventricular pressure required to disrupt the implanted prosthetic mitral valve. Group 1 consisted of 10 hearts with the entire mitral apparatus left in place (5 valves implanted with supraannular pledgets and 5 with subannular pledgets). Group 2 consisted of 10 hearts with only the posterior leaflet apparatus left in place (5 valves implanted with supraannular pledgets and 5 with subannular pledgets). A 29-mm Medtronic mitral valve was secured in the mitral position with a fixed number of ten pledgeted sutures in each annulus. The aorta was cannulated and normal saline solution infused into the left ventricle until end-point rupture occurred. The peak pressure and mechanism of any disruption were then noted. No specimen exhibited subannular myocardial rupture or left atrial wall dissection. Similar protection was provided by leaving the posterior leaflet only or the entire mitral valve. In each case peak left ventricular pressure resulted in only paravalvular leaking around the limited number of sutures as the end point. In each of these four groups the peak left ventricular pressures required for end-point rupture were not significantly different. These data would indicate that preservation of either the posterior leaflet or the entire mitral valve eliminates the incidence of myocardial rupture that was routinely present with total excision of the valve and supraannular suture placement in the same animal model in previous studies. This should certainly support leaving at least the posterior leaflet apparatus of the mitral valve in place, which could also improve ventricular function.