Do acute changes in heart rate by isoproterenol affect aortic stiffness in patients with hypertension?
Increased aortic stiffness is a independent risk factor of cardiovascular disease in patients with hypertension. Acute changes of the heart rate (HR) have been reported not to affect the aortic stiffness in pacing. However, it is unknown whether acute changes in HR caused by sympathomimetics can affect the aortic stiffness in patients with hypertension. We investigated the effect of acute changes in HR produced by isoproterenol on the aortic stiffness in 17 hypertensive patientss (mean age: 59 +/- 9 years). All vasoactive drugs were discontinued at least 3 days before the study. The carotid-to-femoral pulse wave velocity (PWV) was measured by the foot-to-foot method. The pulse waves were recorded at the baseline and at every increase of HR by 5 to 10 bpm with a gradual increase of the dose of isoproterenol. The blood pressures and HR were measured simultaneously. For the analysis, HR, PWV, compliance (C), and compliance index (Ci) were converted as percent changes (delta) from the baseline values. Percent changes of the parameters of the aortic stiffness, i.e., deltaPWV, deltaC, and deltaCi, were grouped by every 10% increase in deltaHR. There was no significant difference among groups in deltaPWV, deltaC and deltaCi (p>0.05 for each of the group). The regression analysis showed no significant correlation of deltaHR with deltaPWV and deltaC (r = 0.18, 0.13 respectively, p>0.05 for each). deltaCi had a poor correlation with deltaHR (r = 0.22, p<0.05). However, only 4.6% of deltaCi could be referred to deltaHR (r2 = 0.046).
Aortic stiffness was not affected by acute changes in HR produced by isoproterenol which suggests that it is not necessary to consider acute changes in HR when measuring aortic PWV.