Abstract
The pressure phase plane (PPP), defined by dP(t)/dt versus P(t) coordinates has revealed novel physiologic relationships not readily obtainable from conventional, time domain analysis of left ventricular pressure (LVP). We extend the methodology by introducing the normalized pressure phase plane (nPPP), defined by 0 ≤ P ≤ 1 and −1 ≤ dP/dt ≤ +1. Normalization eliminates load-dependent effects facilitating comparison of conserved features of nPPP loops. Hence, insight into load-invariant systolic and diastolic chamber properties and their coupling to load can be obtained. To demonstrate utility, high-fidelity P(t) data from 14 subjects (4234 beats) was analyzed. PNR, the nPPP (dimensionless) pressure, where –dP/dtpeak occurs, was 0.61 and had limited variance (7%). The relative load independence of PNR was corroborated by comparison of PPP and nPPP features of normal sinus rhythm (NSR) and (ejecting and nonejecting) premature ventricular contraction (PVC) beats. PVCs had lower P(t)max and lower peak negative and positive dP(t)/dt values versus NSR beats. In the nPPP, +dP/dtpeak occurred at higher (dimensionless) P in PVC beats than in regular beats (0.44 in NSR vs. 0.48 in PVC). However, PNR for PVC versus NSR remained unaltered (PNR = 0.64; P > 0.05). Possible mechanistic explanation includes a (near) load-independent (constant) ratio of maximum cross-bridge uncoupling rate to instantaneous wall stress. Hence, nPPP analysis reveals LV properties obscured by load and by conventional temporal P(t) and dP(t)/dt analysis. nPPP identifies chamber properties deserving molecular and cellular physiologic explanation.
Highlights
The gold standard for characterization of chamber properties utilizes high-fidelity, micromanometric left ventricular (LV) pressures (P) as a function of time
Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society
In concordance with previous results (Carroll et al 1983), we found that Pmax, +dP/dtpeak, and –dP/dtpeak were significantly lower in magnitude in the premature ventricular contraction (PVC) beats (P < 0.01)
Summary
The gold standard for characterization of chamber properties utilizes high-fidelity, micromanometric left ventricular (LV) pressures (P) as a function of time. For isovolumic relaxation (IVR) characterization, P from just after –dP/dtpeak to just before mitral valve opening is fit using a 2 or 3 parameter assumed exponential relationship (Weiss et al 1976). Eucker et al (2001) adopted the phase plane analysis method familiar in nonlinear dynamics (Strogatz 2008) to analyze LVP in the pressure phase plane (PPP) (Eucker et al 2002). Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.
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