Assessment of Arterial Distensibility by Monitoring the Timing of Korotkoff Sounds

The timing of Korotkoff sounds, blood pressure and heart rate can now be monitored in the ambulatory patient: the QKD interval is the time between the onset of the depolarization on the electrocardiogram (Q) and detection of the last Korotkoff sound (K) at the level of brachial artery during cuff deflation, corresponding to diastolic blood pressure (D). Because this interval is inversely related to pulse wave velocity, this recently developed device enables evaluation of the influence of blood pressure on arterial rigidity, providing valuable information on the properties of the arteries. In this study, we examined the influence of hypertension and age on the above parameters and their correlations to left ventricular mass. QKD interval, blood pressure, and heart rate were monitored over a period of 24 h (four measurements/hour) in 33 normotensive and 70 untreated essential hypertensive patients. The slopes of the plots of QKD interval versus systolic and pulse pressure during the 24 h were calculated for each patient. The influence of age and hypertension on these slopes was tested by comparison of matched groups and multivariate analysis. Moreover the relationships between these parameters and echocardiographically assessed left ventricular mass were studied in 37 patients. We found a reduction in mean QKD interval with age and hypertension, reflecting the recognized higher pulse wave velocity in these patients. The slopes of the plots of QKD interval versus blood pressure were also lower in these patients, indicating the smaller influence of a change in blood pressure on pulse wave velocity in patients with stiffer arteries. Both average 24-h systolic blood pressure and the slope of QKD interval versus pulse pressure were significantly and independently correlated to left ventricular mass index. The influence of blood pressure on arterial rigidity can be evaluated by this new monitoring device. Our results showed that pulse wave velocity was less affected by a change in blood pressure in the patients with the stiffer arteries. Am J Hypertens 1994;7:228–233