Potential Effects of Mild Atrial Secondary Mitral Regurgitation in Patients With Isolated Atrial Fibrillation

BACKGROUND: Patients with only moderate atrial secondary mitral regurgitation (asMR) frequently develop heart failure (HF). Mechanisms of HF with moderate asMR and the impact of mild asMR remain unclarified. Although mild/moderate primary mitral regurgitation is compensated by left ventricular (LV) dilatation, the LV is not dilated in asMR. We hypothesized that patients with mild asMR without LV dilatation may have impaired hemodynamics and higher risks of subsequent symptomatic HF deterioration. METHODS: Stroke volume, cardiac output, and systolic pulmonary artery pressure were measured by echocardiography in 142 patients with isolated atrial fibrillation and 30 healthy controls. The prognosis of patients with isolated atrial fibrillation was followed up. RESULTS: In the 142 patients with isolated atrial fibrillation, asMR was no/trivial in 55, mild in 83, moderate in 4, while none had severe asMR. Compared with controls and patients with no/trivial asMR, LV end-diastolic volume index was not increased and hemodynamic parameters were abnormal in patients with mild asMR (LV end-diastolic volume index, 65±6 versus 58±8 versus 60±8 mL/m²; stroke volume index, 42±4 versus 35±4 versus 29±6 mL/m²; P <0.001 versus other 2 groups; cardiac output index, 2.8±0.4 versus 2.8±0.5 versus 2.3±0.6 L/min per m²; P <0.001; systolic pulmonary artery pressure, 21±3 versus 26±5 versus 37±9 mm Hg; P <0.001). Although the event-free rate of HF symptomatic deterioration or hospitalization in patients with no/trivial asMR during a median 13.9 months follow-up was 86.9% and 100%, the rate in mild asMR was 59.4% and 85.0% ( P <0.001 or P =0.032), respectively. CONCLUSIONS: In the presence of isolated AF and no compensatory LV dilatation, impaired hemodynamics and higher risks of symptomatic HF deterioration were associated with mild asMR, requiring further studies of causalities.