Abstract 18230: Impact of Significant Mitral Regurgitation on Assessing the Severity of Aortic Stenosis: a Cause of Low Severe Aortic Stenosis

Introduction: A significant mitral regurgitation (MR) may reduce a pressure gradient of aortic stenosis (AS) by decreasing forward stroke volume. However, a quantitative impact of MR on evaluation of AS severity by measuring pressure gradient has not been demonstrated. Methods: From 2000 to 2013, 3,075 patients who were diagnosed with AS were retrospectively detected from our echocardiographic database. Among patients in normal sinus rhythm and with normal left ventricular (LV) systolic function, 51 patients were found to have a concomitant significant (≥moderate) MR (Group A). As a control, 102 patients without MR were selected who were matched with Group A by age, gender and LV end-diastolic volume (Group B). Non-linear regression was performed for data pairs [aortic valve area (AVA) by continuity equation vs. mean pressure gradient (MPG) across the aortic valve] based on the formula; AVA = a/√MPG. Generalized estimating equation was used for assessing the interaction between the groups and the fitted curves. Results: The stroke volume index was significantly lower in Group A than in Group B (43.2±7.9 vs. 48.0±9.7 ml/m 2 , p=0.004). A significant interaction was seen between the groups (A and B) and the fitted curves (AVA, 3.386/√MPG vs. 5.552/√MPG, interaction p=0.005; indexed AVA, 2.214/√MPG vs. 3.483/√MPG, interaction p=0.003, Fig.). An AVA of 1 cm 2 corresponded to a MPG of 16.5 and 27.5 mmHg for Groups A and B, respectively. An indexed AVA of 0.6 cm 2 /m 2 corresponded to a MPG of 19.2 and 29.1mmHg for Groups A and B, respectively. Conversely, a MPG of 40 mmHg matched with a AVA of 0.70 and 0.82 cm 2 , and an indexed AVA of 0.44 and 0.51cm 2 /m 2 in Groups A and B, respectively. Conclusions: This quantitative analysis demonstrated that AS severity assessed by MPG measurement may be underestimated and thus AVA measurement is essential in patients with a combined significant MR.