Changes in transmitral velocities with heart rate.

Sir, During a study ofchanges in afterload induced by the cold pressor test, Smith et al (1989;61:344-7) recognised a relation between heart rate and transmitral velocities derived from pulsed Doppler recordings. We specifically studied the relation between transmitral velocities and differing RR intervals during exercise and respiration in healthy men.'2We found a clear cut linear change in peak early transmitral velocity and late (active) transmitral velocity with increasing heart rate and decreasing RR interval. Early velocity increased on average by 16% when heart rate increased from 53 beats per minute to 94 beats per minute but active velocity increased by 89%. This led to a linear decrease in the ratio ofpeak early diastolic velocity to peak atrial velocity (E/A) (correlation coefficient r= 099). Similarly, with respiratory induced sinus arrhythmia, the E/A ratio cycled in the opposite direction to the RR interval, so that as the heart rate increased the ratio fell.2 Doppler derived indices of left ventricular diastolic dysfunction that rely on transmitral velocities must take into account the relation with heart rate.