The valvuloarterial impedance (Zva), an estimate of global left ventricular (LV) afterload, has been shown to be associated with LV dysfunction and poor outcome in aortic stenosis (AS). In this situation, whether the Zva may affect the net atrioventricular (A-V) compliance has never been examined. This study was, thus, undertaken to assess the impact of Zva on A-V compliance in patients with severe AS.Two dimensional, tissue Doppler imaging and Doppler transthoracic echocardiography were performed in 37 consecutive patients with severe AS (70±13 years, 65% of male, valve area, 0.68±0.3 cm 2 , mean gradient, 44±14mmHg). Concomitantly, plasma BNP level was measured. A-V compliance is defined as the change in volume shift between the left atrium and the LV during diastole divided by the change in transmitral pressure gradient [Cn = 1270 x (mitral valve area/mitral E-wave downslope)]. Zva was calculated by dividing the estimated LV systolic pressure (systolic arterial pressure + aortic mean transvalvular gradient) by the LV stroke volume index. Mean A-V compliance was 9.2±5.3 ml/mmHg (median, 8 ml/mmHg). A-V compliance was well correlated with aortic valve area (AVA) (r=0.61, p=0.003), Zva (r=0.57, p=0.002), septal E/Ea ratio (r=0.66, p < 0.0001) and BNP (r=0.61, p=0.0003). Moreover, patients with low A-V compliance (<8 ml/mmHg) had lower AVA (p=0.0005) and higher Zva (p=0.004), septal E/Ea ratio (p<0.0001) and BNP (p=0.005). On multivariate analysis, after adjustment for age and LV ejection fraction, septal E/Ea (r 2 =0.50, p=0.0001) and AVA (r 2 =0.15, p=0.005) were independently associated with A-V compliance. Zva was also an independent determinant of A-V compliance (r 2 =0.11, p=0.02) when excluding AVA from the model. Interestingly, symptomatic patients (63%) had significantly lower A-V compliance than asymptomatic patients (7.7±4.9 vs. 11.9±5ml/mmHg, p=0.03).In patients with severe AS, the net A-V compliance is related to LV filling pressure and global LV afterload (valvular and arterial). Further studies are needed to evaluate the impact of A-V compliance on outcome.