Risk-adjusted mortality rate cumulative sum analysis based on the Japan SCORE represents a learning curve in mitral valve reparative surgery

Abstract

We calculated the cumulative sum analysis of an individual surgical learning curve for mitral valve reconstructive surgery to monitor quality control. Between April 2003 and March 2009, 25 consecutive patients underwent mitral valve reconstructive surgery for mitral regurgitation (MR). All operations were performed by a single surgeon. We analyzed the operative variables, mortality, and major morbidities and calculated the learning curve, using descriptive statistics and cumulative sum analysis based on the Japan SCORE calculator. In this series, the Japan SCORE calculator predicted a 30-day operative mortality rate of 3.07 ± 3.48 % and a 30-day operative mortality and morbidity rate of 14.9 ± 9.58 %s. In reality, there was no operative or in-hospital death and the major postoperative morbidity rate was 6.0 % (two patients). The risk-adjusted cumulative sum analysis revealed that the learning curve for mortality and morbidity shifted downward below the lower confident interval for all the patients, on completion of mitral valve repair. Coefficient analysis revealed a significant negative correlation between the aortic cross-clamp time and the cardiopulmonary time and case load. There was no correlation between the operation time and the case load. Routine reconstructive mitral valve surgery for MR can be performed at the professionally permissive level from the beginning, even in low-volume case loads.