Mitral regurgitation and left atrial phasic function and atrioventricular coupling in patients with myocardial infarction: a cardiac magnetic resonance imaging study

Background: Mitral regurgitation (MR) after myocardial infarction (MI) may increase left atrial (LA) pressure and contribute to cardiac dysfunction. This study evaluated the incremental association of MR with LA phasic function and strain and identified independent factors associated with LA deformation in patients with MI. Methods: This retrospective study included 189 patients with MI (111 without MR and 78 with MR: mild, 27; moderate, 33; severe, 18) and 86 normal controls who underwent 3.0-T cardiac magnetic resonance (CMR). MR severity was graded by the CMR-derived MR fraction: mild <30%, moderate 30% to <50%, and severe ≥50%. CMR-derived LA phasic function and strain (reservoir strain, epsilon-s; booster strain, epsilon-a; conduit strain, epsilon-e), left ventricular (LV) function and strain, infarct size, and MR fraction were measured. Between-group comparisons were performed using one-way analysis of variance or the Kruskal-Wallis test with post hoc correction, and multivariable linear regression was used to identify independent factors associated with LA strain. A two-sided P<0.05 was considered statistically significant. Results: Patients with MI and MR had lower LA reservoir strains [22.14%±10.91% vs. 28.65% (22.78%, 38.30%) vs. 41.70% (36.15%, 53.15%)], booster strains [11.52%±6.19% vs. 13.80% (10.20%, 19.80%) vs. 19.25% (15.10%, 24.05%)], and conduit strains [9.40% (6.03%, 14.85%) vs. 14.60% (9.60%, 20.50%) vs. 22.55% (17.75%, 30.43%)] than patients with MI without MR and controls (all P<0.05). They also had higher LA maximum volume [68.43 (57.44, 91.51) mL] and minimum volume [35.93 (24.43, 61.15) mL] and lower LA total ejection fraction (45.39%±14.97%) than the other groups (all P<0.05). In multivariable analysis, MR degree was independently associated with reservoir strain (β=−0.194, P=0.048) and conduit strain (β=−0.208, P=0.038). Anterior wall MI (reservoir strain: β=−0.245, P=0.014; booster strain: β=−0.231, P=0.028; conduit strain: β=−0.224, P=0.027) and posteromedial papillary muscle infarction (reservoir strain: β=−0.329, P=0.004; booster strain: β=−0.370, P=0.003) were also independently associated with LA strain. Conclusions: MR was associated with further deterioration of LA myocardial strain in patients with MI. Posteromedial papillary muscle infarction, anterior wall MI, beta-blocker use, and dual antiplatelet therapy with aspirin plus clopidogrel were independently associated with LA strain. CMR-derived functional and strain parameters may help characterize LV-LA coupling and support risk stratification in this population.