(P127) EARLY ADAPTATION OF THE MITRAL VALVE AFTER ST-ELEVATION MYOCARDIAL INFARCTION

Background: Ischemic mitral regurgitation (IMR) is a frequent complication after myocardial infarction (MI) and its presence is associated with worse outcomes and higher mortality. Clinical observations and experimental data have shown that mitral valve leaflets have the potential to enlarge over time to compensate left ventricular remodeling and prevent IMR. Previous animal studies have demonstrated that MI is associated with fibrotic changes in the mitral valve leaflets and prevent this adaptive compensation. However, the timing of mitral valve geometric changes are not well described. While previous data shows an increase in leaflet size at 6 and 12 months after MI, its short-term evolution after an ischemic event is not well documented.

METHODS AND RESULTS: Twenty-two patients with ST-elevation myocardial infarction and initial left ventricular ejection fraction less than or equal to 45% were enrolled in Quebec Heart and Lung Institute. Participants had 3D transthoracic echocardiography (TTE) at baseline and 3 months, as well as cardiac magnetic resonance (CMR) at 3-month follow-up. Mitral valve leaflet size was measured from the 3D TTE using a custom software (Omni4D). CMR was used to derive left ventricular volumes, function and mitral regurgitant volume. Since mild IMR has been shown to interfere with adverse outcome, significant IMR was defined as a mitral regurgitant fraction ≥ 15% derived from the 3-month CMR. Twenty-one of the 22 patients completed the imaging follow-up. Left ventricular ejection fraction at 3 months was 53 ± 10% (range from 37 to 69%). Eight patients (38%) had mild IMR at 3 months. Mitral valve surface area was significantly increased at 3-month follow-up compared with baseline for patients without IMR (10.96 ± 1.78 cm2 vs 9.51 ± 1.62 cm2; p = 0.001). Valve enlargement in comparison with baseline was significantly greater in patients without IMR (+17 ± 13% vs -5 ± 4% for those with IMR at follow-up, p=0.0007).

Conclusion: Mitral valvular surface increases within the first few months after MI, but not in all patients. Adequate valve enlargement seems related to the absence of IMR at 3 months. Understanding the mechanisms underlying this adaptation could lead to new therapeutic interventions to prevent IMR.