Impact of Significant Mitral Regurgitation on Assessing the Severity of Aortic Stenosis.

BACKGROUND: Significant mitral regurgitation (MR) may reduce a pressure gradient of aortic stenosis (AS) by decreasing forward stroke volume. The study objective was to evaluate whether significant MR can cause inconsistency when assessing the severity of AS.

METHODS: Among 5,355 patients diagnosed with AS from 2000 to 2015, 68 were retrospectively found to have concomitant significant (moderate or greater) MR and normal left ventricular ejection fractions in normal sinus rhythm (AS with MR). As a control group, 136 patients with trivial or no MR were selected who were matched by age, gender, and left ventricular end-systolic volume (AS without MR). Nonlinear regression was performed for data pairs (aortic valve area [AVA] vs mean pressure gradient [MPG]) using the formula AVA = a + b/√MPG. Composite clinical events were defined as aortic valve surgery warranted by the development of symptoms or left ventricular dysfunction, admission because of heart failure, and death.

RESULTS: The forward stroke volume index was significantly lower in the AS with MR group than in the AS without MR group (43.8 ± 8.3 vs 49.2 ± 10.2 mL/m2 , P < .004). A significant group difference was found with respect to the relationship between (indexed) AVA and MPG (AVA, 0.02 + 4.43/√MPG vs -0.06 + 5.60/√MPG [P for interaction = .04]; indexed AVA, 0.03 + 2.66/√MPG vs -0.03 + 3.47/√MPG [P for interaction = .01]). An AVA of 1.0 cm2 corresponded to MPGs of 20.3 and 28.2 mm Hg for the groups with and without MR, respectively. Conversely, an MPG of 40 mm Hg corresponded to AVAs of 0.72 and 0.83 cm2 for the groups with and without MR, respectively. Among patients with MPGs < 40 mm Hg, clinical event rates were significantly higher in those with MR compared with those without MR (P = .009).

CONCLUSIONS: This quantitative analysis demonstrated that AS severity assessed by MPG measurement may be underestimated, and thus AVA measurement is essential in patients with combined significant MR.