Heart Rate Dependency of Large Artery Stiffness

Abstract

Tan et al Heart Rate Dependency of Large Artery Stiffness 237 Hemodynamic MeasurementsBrachial BP, central aortic BP, and cfPWV were determined by cuffbased pulse wave analysis (SphygmoCor XCEL, AtCor, Sydney, Australia). Brachial BP was obtained by oscillometric method with a brachial cuff positioned on the right arm, and central aortic waveform was derived from the brachial BP volume displacement waveform using a validated transfer function. 16 For measurement of cfPWV, the carotid and femoral pulse waveforms were obtained by tonometry on the skin above the right carotid artery and by a cuff placed on the right upper thigh, respectively. 17,18 Subtraction method for path length was used to calculate cfPWV, whereby the path length was calculated as the distance between the sternal notch and the carotid site subtracted from the distance between the sternal notch and top of the thigh cuff. 17 In a subset of the study's cohort (n=45), beat-to-beat stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR) were determined from the finger arterial pressure waveform using the Modelflow method (Finometer PRO, Finapres Medical Systems, Amsterdam, The Netherlands). 19 Study ProtocolSubjects were advised to refrain from caffeine and fatty meals 4 hours before their study appointment, but to continue with their prescribed medications. There were no current tobacco users in the cohort. After 10 minutes of seated rest, seated brachial BP was measured in duplicate (SphygmoCor XCEL). After a further 10 minutes of supine rest, finger arterial pressure waveform was measured from the left middle finger (Finometer PRO) to obtain SV, CO, and TPR. Brachial and central aortic BP and cfPWV were then obtained (SphygmoCor XCEL). Subjects were then paced in a randomized sequence at 60, 70, 80, 90, and 100 bpm using their prescribed pacemaker settings, with BP and cfPWV measurements repeated at each pacing step after 3 minutes of stabilization. ECG was also acquired continuously for the duration of the study for monitoring of HR (PowerLab acquisition system, LabChart software, ADInstruments, Dunedin, New Zealand), and SV, CO, and TPR from the Finometer PRO device were also recorded via PowerLab and LabChart. The average duration for study protocol completion was 60 minutes. Data AnalysisFor pulse wave analysis, brachial and central aortic BP waveforms were averaged >5 s, and cfPWV was averaged >10 s. Observations with measured HR differing from the paced rate by >5 bpm were excluded from the analysis, and the lowest pace rates of 60 and 70 bpm were not achievable in some subjects because of a higher unpaced resting HR. A linear mixed model with maximum likelihood was used to determine the effects of HR on each measured variable, with paced HR modeled as the fixed effect and the random effect modeled as the intercept for each individual (Equation 1).where Yij denotes the outcome measure at a particular paced HR for one individual, ε ij , the residual of variances, and u j , the random effect becase of individual subjec...

Association of Morning Hypertension Subtype With Vascular Target Organ Damage and Central Hemodynamics

“…The explanation for the different interaction of morning hypertension subtype with aortic stiffness is unclear. Previous studies have demonstrated a significant association of increased heart rate with PWV . Although the mechanism behind this phenomenon has yet to be firmly established, passive decrease in arterial compliance due to reduced time for elastic recoil has been suggested to be an explanation for this phenomenon .…”

“…Previous studies have demonstrated a significant association of increased heart rate with PWV. 30,31 Although the mechanism behind this phenomenon has yet to be firmly established, passive decrease in arterial compliance due to reduced time for elastic recoil has been suggested to be an explanation for this phenomenon. 31,32 We postulate that the effect of nocturnal hypertension and morning hypertension on arterial stiffening is accentuated in arteries passively stiffened by increased baseline heart rate.…”

“…30,31 Although the mechanism behind this phenomenon has yet to be firmly established, passive decrease in arterial compliance due to reduced time for elastic recoil has been suggested to be an explanation for this phenomenon. 31,32 We postulate that the effect of nocturnal hypertension and morning hypertension on arterial stiffening is accentuated in arteries passively stiffened by increased baseline heart rate. With regard to the significant association of morning hypertension related to nocturnal hypertension with central aortic BP and aortic PWV, we postulate that the increased hemodynamic stress that is related to nocturnal/morning hypertension over time will result in increased aortic stiffness, which, in turn, will increase central aortic BP and vice versa.…”

Effects of cardiac timing and peripheral resistance on measurement of pulse wave velocity for assessment of arterial stiffness

“…In this study, three constant values of elastic modulus were used for three major arterial types, and it was demonstrated that there was only a slight effect of HR on PWV. As to a positive HR dependency of PWV 6 , the frequency dependent elastic modulus E( ω ) should be considered in future research. However, realistic E( ω ) values for specific arteries are not available, even though some studies have addressed this field 34–37 .…”

Options for Dealing with Pressure Dependence of Pulse Wave Velocity as a Measure of Arterial Stiffness: An Update of Cardio-Ankle Vascular Index (CAVI) and CAVI0

“…We recently set out to quantitatively assess the physiological confounders of PWV [1], investigating the magnitude of their effect and ways to correct for them. These confounders included blood pressure [6,7,8], heart rate [9,10], and axial stretch [11]. This mini-review will concentrate on blood pressure as a confounder of PWV, and will discuss several options to deal with the confounding effect.…”