Discrepancies between catheter and Doppler estimates of aortic stenosis: The role of pressure recovery evaluated 'in vivo'

BACKGROUND AND AIM of the study: Wide discrepancies are often observed between catheter- and Doppler-derived gradients and valve areas. The study aim was to verify if these measurements could be attenuated in a clinical setting by taking into account pressure recovery. METHODS: Between 1st January 2000 and 31st March 2005, a total of 259 patients with an aortic valve area (AVA) < or =2 cm(2) was prospectively collected. During a standard diagnostic catheterization, the aortic valve gradient was taken as: [peak left ventricular pressure-- peak aortic pressure]. The AVA was calculated using the Gorlin formula (AG). Echocardiography was performed within 30 days of this procedure. Transvalvular gradients were measured using the Doppler technique, and the AVA was computed using the continuity equation (ACE). The diameter of the ascending aorta was monitored in the parasternal long-axis view, and the values averaged. The ascending aorta sectional area (AA) was then computed according to geometric formulae. In order to correct for pressure recovery, an energy loss coefficient (ELCO) equation was used [ELCO = (AA x ACE)/(AA -ACE)]. Correlations between AG, ACE and ELCO were evaluated by linear regression analysis. As cardiac output affects the estimates of valve areas, the correlation was calculated separately for patients with a median cardiac index (CI) above and below 2.7 1/min/m(2). RESULTS: A good linear correlation was found between AG and ACE with regression coefficient 0.88, independent of cardiac output. A similar correlation was present between AG and ELCO, with correlation coefficient 0.99 in patients with CI >2.7 1/min/m(2), and