Preoperative factors affecting the outcome of isolated mitral valve replacement: A 10 year review

The outcome after mitral valve replacement is influenced not only by the skill and experience of the surgical team and the type of prosthesis used but also by preoperative factors. This study was performed to assess the effect of such factors on early and late mortality and the rate of thromboembolism after isolated mitral valve replacement in 545 patients. A Starr-Edwards prosthesis was used in 292 and a porcine heterograft in 253 patients. The overall operative (1 month) mortality rate was 7 percent. Age at operation (19 or less versus 20 to 54 versus 55 or more years), type of mitral valve lesion, and heart rhythm did not influence operative or 3 year survival or rate of thromboembolism. A large cardiothoracic ratio (75 percent or greater) on standard anteroposterior chest radiograph was associated with a reduced operative survival rate (81 versus 95 percent, p < 0.005) that was still evident at 3 years (67 versus 84 percent, p < 0.005) and a higher incidence rate of thromboembolic events (90 versus 98 percent thromboembolism-free rate, p < 0.05) in the perioperative period. A large left atrial diameter (12 cm or more) was also associated with a reduced operative survival rate (85 versus 95 percent, p < 0.05) but did not influence late survival or rate of thromboembolism. Cardiac catheterization was performed in 387 patients. A depressed cardiac index (1.5 liters/min per m² or less), elevated systolic pulmonary arterial pressure (100 mm Hg or greater), pulmonary vascular resistance (10 units or greater) or left ventricular end-diastolic pressure (20 mm Hg or greater) were not individually associated with an increased mortality or thromboembolism rate. However, when grouped according to the presence or absence of one or more severely abnormal hemodynamic variables, patients with poor hemodynamics had a reduced operative survival (91 versus 97 percent, p < 0.02), but survival at 3 years and rate of thromboembolism were not significantly different in the two groups. Thus (1) patients with a large cardiothoracic ratio, large left atrium or poor hemodynamics have a reduced operative survival and should be managed with great care in the perioperative period because their late postoperative survival is not significantly different from that of patients without these derangements; and (2) thromboembolic events after mitral valve replacement are largely unrelated to preoperative factors.