Estimation of the End of Ejection in Aortic Stenosis

Abstract

Background— All indices of aortic stenosis (AS) rely on measurements of mean transvalvular pressure gradient ( ΔP ) and flow rate. Because the gradient is reversed during late ejection, the late systolic left ventricular (LV)–aortic pressure crossover may be an erroneous landmark of end-ejection. The aortic incisura should be a better reference to calculate indices of AS invasively. Methods and Results— The accuracy of the pressure crossover and the incisura to define end-ejection was assessed in a chronic AS experimental model (9 dogs) with the use of an implantable flowmeter and Doppler echocardiography as reference. In 288 hemodynamic recordings analyzed (aortic valve area [AVA]: 0.74±0.46 cm 2 ), ejection ended 37±29 ms after the pressure crossover but almost simultaneously with the incisura (2±17 ms). Pressure crossover error accounted for significant errors in the measurement of ΔP (95% limits of agreement, +0 to +7 mm Hg) and AVA (−0.1 to +0.2 cm 2 ). These errors were reduced to less than half with the use of the incisura to define end-ejection. Additionally, the agreement with Doppler-derived AS indices was best with use of the incisura. Pressure crossover error was maximal in situations of higher output, moderate orifice narrowing, higher arterial compliance, and lower vascular resistance. In 32 consecutive patients undergoing cardiac catheterization for AS, the pressure crossover induced a clinically important overestimation of the ΔP from +22 to +50%. Errors in AVA estimation were considerably smaller (−2% to +6%) because of simultaneous and offsetting errors in the measurements of ΔP and flow. Conclusions— The aortic incisura and not the second pressure crossover should be used to obtain invasive indices of AS.