Left ventricular hypertrophy is often found very early in the course of autosomal dominant polycystic kidney disease (ADPKD). Diastolic dysfunction has been shown in hypertensive adult patients with ADPKD with increased left ventricular mass (LVM), but there are no data about diastolic function in the young ADPKD population without hypertension and with normal renal function. To evaluate very early alterations in cardiac structure and diastolic function in young normotensive patients with ADPKD, color Doppler echocardiography was performed in 46 young normotensive patients with ADPKD and 35 healthy subjects. LVM, transmitral pulsed Doppler flow (diastolic function), and valvular abnormalities were studied. Patients with ADPKD showed higher LVM indices (LVMIs) than controls (89.7+/-17.3 v 68.5+/-17.2 g/m2; P < 0.0001). Peak early diastolic velocity (E wave) deceleration time and isovolumic relaxation time were significantly prolonged in patients with ADPKD compared with controls (E wave deceleration time, 182.5+/-51.3 v 149.4+/-34 msec; P=0.002; isovolumic relaxation time, 97.7+/-17.5 v 79+/-15 msec; P=0.0001). No differences were found in valvular abnormalities in the two groups. In conclusion, young normotensive patients with ADPKD showed increased LVMIs and Doppler abnormalities consistent with early diastolic dysfunction.