Accuracy of the Single Cycle Length Method for Calculation of Aortic Effective Orifice Area in Irregular Heart Rhythms

Abstract

In irregular heart rhythms, echocardiographic calculation of aortic effective orifice area (EOA) requires averaging measurements from multiple cardiac cycles. Whether a single cycle length method can be used to calculate aortic EOA in aortic stenosis with nonsinus rhythms is not known. Transthoracic echocardiograms of 100 patients with aortic stenosis and either atrial fibrillation (AF) or frequent ectopy (FE) were retrospectively reviewed. The aortic valve velocity time integral (VTIAV) and the left ventricular outflow tract VTI (VTILVOT) were measured by two methods: the standard method (averaging multiple beats) and the single cycle length method. The latter matches the R-R intervals for VTIAV and VTILVOT. Stroke volume, EOA, and Doppler velocity index were calculated by both methods in all patients. The single cycle length method was used for short and long R-R cycles in AF and for postectopic beats (long R-R cycles) in FE. In AF, long R-R cycles resulted in larger stroke volumes (73±21 vs 63±18mL; P≤.0001) but no difference in EOA (0.84±0.27 vs 0.82±0.27cm2; P=.11), whereas short R-R cycles resulted in smaller stroke volumes (55±18 vs 63±18mL, P≤.0001) but a larger EOA (0.86±0.28 vs 0.82±0.27cm2; P=.01). In FE, the postectopic beat led to larger stroke volumes (96.1±28 vs 78±23mL; P<.0001) and a larger EOA (0.99±0.32 vs 0.94±0.32cm2; P=.0006) and Doppler velocity index (0.24±0.07 vs 0.23±0.07; P<.001). In AF patients, the single, long cycle length method of calculating EOA can be used instead of averaging multiple cardiac cycles. The single cycle length method used on a postextrasystolic beat results in a larger EOA than a normal sinus beat and may have utility in clinical decision-making.