Abstract
Arterial pressure is an important diagnostic parameter for cardiovascular disease. However, relative contributions of individual ventricular and arterial parameters in generating and augmenting pressure are not understood. Using a novel experimental arterial model, our aim was to characterize individual parameter contributions to arterial pressure and its amplification. A piston-driven ventricle provided programmable stroke profiles into various silicone arterial trees and a bovine aorta. Inotropy was varied in the ventricle, and arterial parameters modulated included wall thickness, taper and diameter, the presence of bifurcation, and a native aorta (bovine) versus silicone. Wave reflection at bifurcations was measured and compared with theory, varying parent-to-child tube diameter ratios, and branch angles. Intravascular pressure-tip wires and ultrasonic flow probes measured pressure and flow. Increasing ventricular inotropy independently augmented pressure amplification from 17% to 61% between the lower and higher systolic gradient stroke profiles in the silicone arterial network and from 10% to 32% in the bovine aorta. Amplification increased with presence of a bifurcation, decreasing wall thickness and vessel taper. Pulse pressure increased with increasing wall thickness (stiffness) and taper angle and decreasing diameter. Theoretical predictions of wave transmission through bifurcations werre similar to measurements (correlation: 0.91, R2 = 0.94) but underestimated wave reflection (correlation: 0.75, R2 = 0.94), indicating energy losses during mechanical wave reflection. This study offers the first comprehensive investigation of contributors to hypertensive pressure and its propagation throughout the arterial tree. Importantly, ventricular inotropy plays a crucial role in the amplification of peripheral pressure wave, which offers opportunity for noninvasive assessment of ventricular health.NEW & NOTEWORTHY The present study distinguishes contributions from cardiac and arterial parameters to elevated blood pressure and pressure amplification. Most importantly, it offers the first evidence that ventricular inotropy, an indicator of ventricular function, is an independent determinant of pressure amplification and could be measured with such established devices such as the SphygmoCor.
Highlights
NEW & NOTEWORTHY The present study distinguishes contributions from cardiac and arterial parameters to elevated blood pressure and pressure amplification
The pulse pressure (PP) was higher with the higher inotropy (Fig. 4, A and B), it should be noted that cardiac output was maintained between the ventricular contribution tests by changing the portions of systolic verus diastolic time
Contributions to arterial pressure generation and peripheral amplification from various ventricular and arterial parameters were investigated in a novel experimental model
Summary
NEW & NOTEWORTHY The present study distinguishes contributions from cardiac and arterial parameters to elevated blood pressure and pressure amplification. Pressure wave reflections have received substantial attention as an important contributor to pressure [20] Such reflections are created at changes in arterial impedance such as bifurcations [21], tapering [29], and changes in aortic stiffness [22], and its arrival back to the heart is signaled by the first systolic shoulder [19]. Distal waveforms (typically brachial or femoral pressure), can too be analyzed as the sum of many Fourier components The ratio of these Fourier components determine the amplification of certain frequencies and are indicative of the popular pressure transfer function used to derive central pressure waveforms from distally measured ones [13, 17]. Amplification is up to 70% in young subjects (Ͻ20 yr old) and down to 20% in subjects over 80 yr old [18]
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