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

INTRODUCTION: 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.

METHODS: 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.

RESULTS: In AF, long R-R cycles resulted in larger stroke volumes (73 ± 21 vs 63 ± 18 mL; P ≤ .0001) but no difference in EOA (0.84 ± 0.27 vs 0.82 ± 0.27 cm2 ; P = .11), whereas short R-R cycles resulted in smaller stroke volumes (55 ± 18 vs 63 ± 18 mL, P ≤ .0001) but a larger EOA (0.86 ± 0.28 vs 0.82 ± 0.27 cm2 ; P = .01). In FE, the postectopic beat led to larger stroke volumes (96.1 ± 28 vs 78 ± 23 mL; P < .0001) and a larger EOA (0.99 ± 0.32 vs 0.94 ± 0.32 cm2 ; P = .0006) and Doppler velocity index (0.24 ± 0.07 vs 0.23 ± 0.07; P < .001).

CONCLUSIONS: 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.