[Experience in the use of porcine heterologous grafts of the Hancock type for replacement of the mitral valve. 4 years of continuous use].

We present a statistical analysis on the use of the Hancock porcine heterograft for mitral valve replacement in 151 consecutive cases. A 14% early, and 3.9% late mortality rate is found. An evaluation of the factors contributing to this figure shows that the most important is the degree of myocardial derangement prior to surgery, with 3.5% mortality for stage III and 32% for stage IV (New York Heart Association classification). Our rate for thromboembolism is 9%. Study of other conditions favoring this complication indicates that factors other than valve replacement are present in all cases, making the evaluation of the thrombogenic qualities of these prosteses difficult. In a period of study of 4 832 patient-months (21 average) or 5 526 valve-months (19 average) which nicludes all our Hancock prosteses. There have been no failures that can be traced to mechanical derangement nor biological deterioration. This fact together with their favorable hemodinamic characteristics, make us recommend this model for clinical use.