The quest for load‐independent left ventricular chamber properties: Exploring the normalized pressure phase plane

• Published in: Physiological reports Vol. 1; no. 3; pp. e00043 - n/a
• Main Authors: Ghosh, Erina, Kovács, Sándor J.
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01.08.2013; Blackwell Publishing Ltd
• Subjects: Calibration; Cardiovascular disease; Catheterization; Contraction; Coronary vessels; Datasets; diastolic function; Heart; Heart attacks; hemodynamics; Hypertension; Original Research; phase plane analysis; Physiology; Pressure; Ventricle; phase plane analysis; Catheterization; diastolic function; hemodynamics
• ISSN: 2051-817X; 2051-817X
• DOI: 10.1002/phy2.43

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. e00043 Normalization of pressure phase plane (dP/dt vs. P) loops generated by left ventricular (LV) hemodynamic pressure data reveals features that remain after normalization ‐and therefore are conserved during isovolumic relaxation. The method reveals load independent features of diastole – and provides mechanistic insight regarding maximal crossbridge uncoupling and calcium sequestration rates.