Reduced Left Ventricular Apical Rotation: A Novel Pathophysiological Correlate Underlining Acute Ischemic Mitral Regurgitation.

Background: Functional mitral regurgitation (or backward flow to the left atrium with an anatomically normal valve) is associated with adverse outcomes, yet its pathophysiology is not fully understood. We set out to investigate the association between reduced apical rotation and functional mitral regurgitation in patients presenting with first acute ST-elevation myocardial infarction.

Methods: Retrospective analysis of first echocardiographic images for patients with first acute ST-elevation myocardial infarction undergoing percutaneous coronary intervention from July 2019 to October 2022. Patients with significant (moderate or worse) functional mitral regurgitation were compared to those with less functional mitral regurgitation for baseline characteristics, myocardial infarction parameters, and myocardial features including apical rotation. Logistic regression analyses were performed to assess determinants of functional mitral regurgitation.

Results: Of the 200 initially identified subjects, 164 were included in the final analysis. Significant functional mitral regurgitation was observed in 14 patients (8.5%). Reduced apical rotation was significantly associated with functional mitral regurgitation (2.2 ± 1.7° compared with 5.7 ± 3.3°, P < .001), independent of other variables. Other echocardiographic findings in patients with significant functional mitral regurgitation were mildly reduced ejection fraction (43% ± 10% vs 48% ± 8%, P = .010), mildly enlarged left ventricular diameter (5.1 ± 0.5 cm vs 4.8 ± 0.5 cm, P = .022), and enlarged left atrial diameter (4.2 ± 0.5 cm vs 3.8 ± 0.4 cm, P = .004). In an adjusted model including clinically relevant variables, the probability of significant acute functional mitral regurgitation increased by 2.14 (95% confidence interval 1.35-3.40, P = .001) for every degree decrease in apical rotation.

Conclusion: This study highlights for the first time a significant correlation between reduced apical rotation and acute post- ST-elevation myocardial infarction functional mitral regurgitation, posing a possible novel pathophysiological mechanism.