The Effect of Heart Rate on Aortic Valve Area Calculated by Continuity Equation

Gwon, Hyeon Cheol; Choi, Kee Joon; Kim, Hyo Soo; Sohn, Dae Won; Oh, Byung Hee; Lee, Myung Mook; Park, Young Bae; Choi, Yoon Sik; Seo, Jung Don; Lee, Young Woo

Abstract

BACKGROUND
Recent investiogations have shown that aortic valve area derived by continuity equation as well as Gorlin formula varied with transvalvular volume flow rate. This study was designed to investigate the effect of heart rate on aortic valve area calculated by continuity equation.
METHODS
We studied 10 patients of with cath-proven aortic stenosis. Patients underwent echocardiography recording during right atrial pacing with 80, 100 and 120 beats/min. Flow rate and continuity equation valve area were obtained at each heart rate by doppler echocardiography.
RESULTS
Transvalvular flow rates were 194+/-30 ml/sec, 208+/-38 ml/sec and 200+/-39 ml/sec with pacing at 80, 100 and 120 beats/min respectively, and there was no significant change in flow rate with heart rate. Aortic valve areas derived by continuity equation were 0.77+/-0.14cm2, 0.81+/-0.14cm2and 0.86+/-0.15cm2with pacing at 80, 100 and 120 beats/min. There was signifcant increase in aortic valve area between heart rate 120 and 100 beat/min(p=0.02), and between heart rate 120 and 80 beas/min([=0.003). there was no significant change in aortic valve area between heart rate 100 and 80 beat/min.
CONCLUSION
Although there was no significant change in transvalvular flow rate with heart rate increase, aortic valve area derived by continuity equation significantly increased with increased heart rate. This relation should be considered when interpretion continuity equation valve area in aortic stenosis.