The influence of heart rate on augmentation index and central arterial pressure in humans

Abstract

Arterial stiffness is an important determinant of cardiovascular risk. Augmentation index (AIx) is a measure of systemic arterial stiffness derived from the ascending aortic pressure waveform. The aim of the present study was to assess the effect of heart rate on AIx. We elected to use cardiac pacing rather than chronotropic drugs to minimize confounding effects on the systemic circulation and myocardial contractility. Twenty‐two subjects (13 male) with a mean age of 63 years and permanent cardiac pacemakers in situ were studied. Pulse wave analysis was used to determine central arterial pressure waveforms, non‐invasively, during incremental pacing (from 60 to 110 beats min−1), from which AIx and central blood pressure were calculated. Peripheral blood pressure was recorded non‐invasively from the brachial artery. There was a significant, inverse, linear relationship between AIx and heart rate (r=−0.76; P < 0.001). For a 10 beats min−1 increment, AIx fell by around 4 %. Ejection duration and heart rate were also inversely related (r=−0.51; P < 0.001). Peripheral systolic, diastolic and mean arterial pressure increased significantly during incremental pacing. Although central diastolic pressure increased significantly with pacing, central systolic pressure did not. There was a significant increase in the ratio of peripheral to central pulse pressure (P < 0.001), which was accounted for by the observed change in central pressure augmentation. These results demonstrate an inverse, linear relationship between AIx and heart rate. This is likely to be due to alterations in the timing of the reflected pressure wave, produced by changes in the absolute duration of systole. Consideration of wave reflection and aortic pressure augmentation may explain the lack of rise in central systolic pressure during incremental pacing despite an increase in peripheral pressure.

Diastolic blood pressure is an important determinant of augmentation index and pulse wave velocity in young, healthy males

“…10,11 A number of nonpathological factors influence augmentation index and PWV. It has been consistently reported that age, 1,12 height, 13,14 heart rate 15,16 and gender 12,14 influence augmentation index, whereas PWV appears to be a more robust stiffness measure influenced by fewer factors including age 1,5 and heart rate. 17 However, despite the wide use of both augmentation index and PWV, there are controversial results in the literature regarding the relation between both stiffness measures and blood pressure, the classical haemodynamic parameter.…”

Impact of passive vibration on pressure pulse wave characteristics

“…We noted a 7.1% reduction in AIx that is comparable to those reported by others after single bouts of exercise longer than 10 min. As the AIx is inversely related to HR and is influenced by Tr, 26,29 it can be argued that the post-exercise reduction in AIx may be partially mediated by changes in these factors. However, as opposed to previous studies that have shown reductions in the AIx along with increases in HR 30 min after exercise, 9-11 HR and Tr did not change in response to PV, and hence, they did not influence the AIx response.…”

“…AIx was normalized to a heart rate (HR) of 75 beats min À1 (AIx@75) as it is influenced by HR. 26 Transit time of the reflected wave (Tr) indicates the round-trip travel of the forward wave to the peripheral reflecting sites and back to the aorta. 25 AIx and Tr have been used as markers of wave reflection and aortic stiffness, respectively.…”

Contribution of abnormal arterial function to cardiac syndrome X: a study of pressure waveform analysis and exercise haemodynamics

“…The lower heart rate in CSX patients is unlikely to entirely account for the AIx increase because (1) ejection duration was similar between groups, (2) significant differences in AIx remained between groups after statistical correction for heart rate and (3) the heart rate difference between groups (8 b.p.m.) would only account for about 3% AIx, 11 whereas the actual difference was a statistically significant 7%. Moreover, MAP and height are well known to correlate with AIx, but these associations were only demonstrated in the controls and not the CSX patients.…”