Does changes in heart rate by isoproterenol affect aortic stiffness in patients with hypertension?

Rhee, Moo Yong; Kwon, Na Young; Kim, Jae Deok; Song, Seung Ho; Yoon, Young Won; Lee, Myoung Yong; Kim, Young Kwon

Abstract

BACKGROUND: Increased aortic stiffness (AS) is an independent risk factor of cardiovascular disease in patients with hypertension. Elevation of blood pressure (BP) or sympathetic tone increases AS. It was reported that acute changes in heart rate by artificial pacemaker did not affect AS. However, it is unknown whether changes in HR by sympathomimetics can affect AS in patients with hypertension. We investigated the effect of changes of HR by isoproterenol (ISO) on AS in 17 hypertensives (mean age: 59+/-9 years).
METHODS
All vasoactive drugs were discontinued at least 3 days before the study. Carotid-to-femoral pulse wave velocity (PWV) was measured by foot-to-foot method. Pulse wave recordings were done at baseline and at every increase of HR by 5 to 10 bpm with gradual increase of dose of ISO. BPs were measured simultaneously by the fluid-filled manometer system through the side arm of arterial sheath of femoral artery. HR was measured by electrocardiography. Compliance (C) and compliance index (Ci) were calculated from PWV, pulse pressure, systolic and diastolic blood pressure by established formulas. For analysis, HR, PWV, C and Ci were converted as percent changes (delta) from the baseline values. Percent changes of parameters of AS, i.e., deltaPWV, deltaC, and deltaCi, were grouped by every 10% increase in HR.
RESULTS
There was no significant difference among groups in deltaPWV, deltaC and deltaCi (p>0.05 for each). With simple regression analysis, deltaPWV and deltaC showed no significant correlation with deltaHR (r=0.18, 0.13 respectively, p>0.05 for each). deltaCi was weakly correlated with deltaHR (r=0.22, p<0.05). However, only 4.6% of deltaCi could be referable to deltaHR (r2=0.046).
CONCLUSION
AS was not affected by changes in heart rate by isoproterenol, suggesting that it is not necessary to consider changes of HR when measuring aortic PWV.