Impact of Rhythm Transition from Sinus Rhythm to Atrial Fibrillation on Mean Gradient Assessment in Aortic Stenosis

Background Aortic stenosis (AS) severity assessment relies on Doppler-derived mean gradient (MG), which is flow dependent. Atrial fibrillation (AF) causes stroke volume variability, which may lower measured gradients despite unchanged anatomic valvular severity. Guidelines recommend averaging MG over 5 cardiac cycles in AF, but this may underestimate true severity compared with sinus rhythm (SR). We evaluated the impact of transition from SR to AF on MG in AS. Methods We retrospectively studied adults with AS undergoing transthoracic echocardiography. Patients had paired SR and AF studies within 3 months, left ventricular ejection fraction ≥50%, and no more than mild valvular regurgitation. MG was measured by averaging over 3 cycles in SR and 5 cycles in AF, and the highest single-beat MG meeting quality criteria. Paired comparisons were performed with statistical testing. Agreement was assessed using intraclass correlation coefficient (ICC) and Bland-Altman analysis. Results Thirty patients were included (mean age 77 ± 10 years; 33% female). Left ventricular ejection fraction remained preserved in both rhythms. Averaged MG was lower in AF than SR (23.4 ± 12 vs 28.3 ± 12 mm Hg, P < .001). In contrast, the highest single-beat MG in AF was similar to SR (27.3 ± 11 vs 28.4 ± 12 mm Hg, P = .29). Agreement with SR was moderate for averaged MG (ICC 0.792, 95% CI 0.612-0.895) and higher for single-beat MG (ICC 0.897, 95% CI 0.797-0.949). Conclusions Averaging MG over 5 AF cycles underestimates AS severity. The highest single-beat MG better reflects SR measurements and may more accurately represent true severity.