Mechanisms of hemolysis after mitral valve repair: Assessment by serial echocardiography

Background : Recently, fluid dynamic simulation models have identified distinct patterns of regurgitant flow disturbances in patients with mitral prosthetic hemolysis which were associated with high shear stress and may therefore produce clinical hemolysis. Rapid acceleration, fragmentation, and collision jets were associated with high shear stress and hemolysis whereas deceleration and free jets were not. Objectives : The aim of this study was to determine, using serial echocardiography, the hydrodynamic mechanisms involved in the occurrence of severe, symptomatic hemolysis after mitral valve repair in 13 consecutive patients who were referred for re-operation between January 1985 and December 1996. Methods : Serial echocardiographic studies of these patients were reviewed and the site, severity and hydrodynamic characteristics of the regurgitant jet noted. Results :The median time interval between initial repair and diagnosis of hemolytic anemia was 2.9 months (range= 25 days to 6.8 months). Mitral regurgitation was mild in 1, moderate in 4, moderately severe in 5, and severe in 3 patients. The regurgitant jet was central in 12 patients and para-ring in 1, multiple jets were seen in 5 patients. Hydrodynamic mechanisms of regurgitation included collision in 10, rapid acceleration in 3, and fragmentation in 1 patient. No patient had either a free jet or slow deceleration. These "culprit " jets were present in the intraoperative post-bypass TEE study in only 1 patient. Collision commonly occurs when the regurgitant jet was directed at the annuloplasty ring. Twelve patients underwent reoperation (replacement in 8, re-repair in 4), with resolution of hemolysis in all patients. At reoperation, the initial repair was found to be grossly intact in 9 patients. Conclusion : Distinct patterns of regurgitant flow disturbances associated with high shear stress were found in patients with hemolysis after mitral valve repair. Majority of these color flow disturbances were not present in the post-bypass TEE study and subsequently developed in the early period after mitral valve repair.