Diastolic ventricular-vascular stiffness and relaxation relation: elucidation of coupling via pressure phase plane-derived indexes

Abstract

Because systole and diastole are coupled and systolic ventricular-vascular coupling has been characterized, we hypothesize that diastolic ventricular-vascular coupling (DVVC) exists and can be characterized in terms of relaxation and stiffness. To characterize and elucidate DVVC mechanisms, we introduce time derivative of pressure (dP/dt) vs. time-varying pressure [P(t)] (pressure phase plane, PPP)-derived analogs of ventricular and vascular "stiffness" and relaxation parameters. Although volume change (dV) = 0 during isovolumic periods, and time-varying left ventricular (LV) stiffness, typically expressed as change in pressure per unit change in volume (dP/dV), is undefined, our formulation allows determination of a PPP-derived stiffness analog during isovolumic contraction and relaxation. Similarly, an aortic stiffness analog is also derivable from the PPP. LV relaxation was characterized via tau, the time constant of isovolumic relaxation, and vascular (aortic pressure decay) relaxation was characterized in terms of its equivalent (windkessel) exponential decay time constant kappa. The results show that PPP-derived systolic and diastolic ventricular and vascular stiffness are strongly coupled [K(Ao)(+)=1.71(K(LV)(+)) +154, r=0.86; K(Ao)(-)=0.677(K(LV)(-))-5.53, r=0.86]. In support of the DVVC hypothesis, a strong linear correlation between relaxation (rate of pressure decay) indexes kappa and tau (kappa = 9.89tau - 90.3, r = 0.81) was also observed. The correlations observed underscore the role of long-term, steady-state DVVC as a diastolic function determinant. Awareness of the PPP-derived DVVC parameters provides insight into mechanisms and facilitates quantification of arterial stiffening and associated increase in diastolic chamber stiffness. The PPP method provides a tool for quantitative assessment and determination of the functional coupling of the vasculature to diastolic function.

Ventricular–vascular coupling in hypertension

“…Experimental data demonstrate the functional coupling between the left ventricle and the arterial tree not only during the systolic phase but also in diastole. 136 This is probably mainly related to the impact of reflected pressure waves on myocardial fibre relaxation process and on coronary perfusion. 137 Several observations in different populations reported the dependence of ventricular diastolic function on timing and amplitude of reflected pressure waves.…”

Acute and Chronic Ventricular-Arterial Coupling in Systole and Diastole

“…The current findings are also consistent with a recent study describing diastolic VA coupling based on analysis of pressure phase plane-derived indices in humans. 32 …”

New Methods of Assessment of Subclinical Changes in the Cardiovascular System in Arterial Hypertension

“…Экспериментальные данные указывают на то, что функ-циональное взаимодействие между ЛЖ и артериаль-ной системой происходит не только в систолу, но и в диа-столу. Это, вероятно, связано, главным образом, с воздействием отраженных волн на процессы релакса-ции миокардиальных волокон и на коронарную пер-фузию [44].…”

“…Данные нескольких исследований в разных по-пуляциях указывают на взаимосвязь между диастоли-ческой функцией ЛЖ и амплитудой и временем отра-женных волн [44]. Следовательно, уменьшение ам-плитуды волны Е и изменение отношения E/A, которое обычно наблюдается при трансмитральном доппле-ровском исследовании, при АГ может быть отражени-ем физиологической реакции миокардиальных воло-кон на резкую перегрузку вследствие раннего возвра-та отраженной волны (расслабление миокарда, зави-симое от нагрузки).…”