Acute loss of mitral annular dynamics predicts development of functional mitral regurgitation after myocardial infarction in a swine model

Abstract

Objective

Functional mitral regurgitation is identified in approximately 40% of patients after myocardial infarction, adversely affecting their prognosis. Predicting functional mitral regurgitation development after the onset of myocardial infarction remains challenging, yet early intervention could potentially enhance patient outcomes. In this study, we developed porcine models with consistent lateral wall infarction to investigate the morphological and functional differences between animals with functional mitral regurgitation and those without.

Methods

Twenty-two Yorkshire pigs underwent myocardial infarction induction through occlusion of the left circumflex coronary artery. Epicardial echocardiography and pressure-volume loop analysis were performed before and after myocardial infarction induction. Three months after myocardial infarction, mitral regurgitation quantification was conducted with epicardial echocardiography via mini left thoracotomy, and the animals were classified into 2 groups based on mitral regurgitation severity: no/mild mitral regurgitation (lower mitral regurgitation, n = 11) and moderate/severe mitral regurgitation (greater mitral regurgitation, n = 11). The left ventricle and mitral valve geometry and function immediately after myocardial infarction were compared between the 2 groups.

Results

The infarction area was comparable between the groups, with no significant differences observed in invasive hemodynamic parameters after myocardial infarction. However, the change in the mitral annular anteroposterior diameter (diastolic anteroposterior minus systolic anteroposterior) immediately after myocardial infarction was significantly lower in the greater mitral regurgitation group (2.02 ± 1.19 vs 4.34 ± 0.93, P < .01), and it was strongly correlated with effective regurgitant orifice area (r = −0.7873, P < .01), regurgitant volume (r = −0.7585, P < .01), and regurgitant fraction (r = −0.7290, P < .01) at the 3-month follow-up after myocardial infarction.

Conclusions

Reduced anteroposterior diameter shortening from diastole to systole, indicative of impaired annular dynamics, immediately after myocardial infarction can serve as a new predictor for the subsequent development of mitral regurgitation.