Physiologic variables, such as heart rate, affect the noninvasive indexes of left ventricular filling, complicating the interpretation of these indexes for clinical assessment of diastolic function. We compared the effect in normal subjects of increased heart rate provoked by both exercise and amyl nitrite on noninvasive velocity and volumetric indexes of left ventricular filling. Velocity indexes were affected in a different pattern with exercise compared with amyl nitrite because peak E wave velocity and relative atrial contribution to filling increased with exercise. In contrast, the volumetric index of rapid left ventricular filling increased similarly with both mechanisms. These findings demonstrate the importance of recognizing the different effects on indexes of left ventricular filling when heart rate is increased by different methods.