Prognostic factors in aortic valve replacement associated with narrow aortic roots:An Analysis Using the Proportional Hazard Model

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Abstract
In 80 patients who underwent aortic valve replacement with implantation of a small (21 mm) Medtronic-Hall prosthesis over a period of c. 7 1/2 years, beginning in 1977, prognostic factors were evaluated with use of the proportional hazard model. Twelve variables were considered. Four of them entered the regression model in a time-independent mode. These were preoperative NYHA function class, aetiology (endocarditis), diagnosis (‘pure’ aortic regurgitation) and aortic cross-clamping time. None of the parameters entered the model in time-related mode. Another multifactorial approach to the proportional hazard model, using a stepwise regression analysis, showed the variables with prognostic value to be aortic cross-clamp time and preoperative NYHA class. Based on this model, predicted 3-year survival ranged from 92% to 45% from the most to the least favourable combination of these prognostic variables. A patient-specific prediction of 3-year survival was formulated.