title: Contraction-relaxation coupling mechanism characterization in the thermodynamic phase plane: normal vs. impaired left ventricular ejection fraction.
abstract: Using simultaneous pressure-volume measurements obtained during cardiac catheterization, we employ the thermodynamic phase-plane (TPP) method to characterize global contraction-relaxation coupling (CRC) between normal and impaired left ventricular (LV) ejection fraction (LVEF) groups. The cardiac cycle inscribes a closed loop in the TPP defined by the coordinates "potential" power [V(dP/dt), ergs/s] and "kinetic" power [P(dV/dt), ergs/s]. The TPP-derived indexes kappa and rho define the chamber's contractile and CRC attributes, respectively. Data from 33 subjects dichotomized as normal control (n = 22, >50% LVEF) and impaired LVEF (n = 11, <50% LVEF) were analyzed. The results were as follows: kappa = 3.0 +/- 1.1 and rho = -0.38 +/- 0.21 for controls and kappa = 5.4 +/- 1.6 and rho = -1.14 +/- 0.47 for the impaired LVEF group; kappa and rho are significantly higher for impaired LVEF than for control (P < 0.001 for both). As kappa increased, rho decreased (r = -0.69) for all subjects. Hence, ventricles with impaired LVEF are thermodynamically less efficient because they require more potential power per unit of delivered kinetic power than controls. We conclude that TPP-derived indexes of CRC facilitate assessment of chamber efficiency in thermodynamic terms and elucidate the dominant differentiating features in terms of CRC indexes.
authors.affiliation: Cardiovascular Biophysics Laboratory, Washington Univ. Medical Center, St. Louis, MO 63110, USA.
authors.forename: Yue
authors.initials: Y
authors.lastname: Wu
authors.forename: Yingbo
authors.initials: Y
authors.lastname: Yu
authors.forename: Sándor J
authors.initials: SJ
authors.lastname: Kovács
mesh_terms: D000818:Animals; D003198:Computer Simulation; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D013318:Stroke Volume; D013816:Thermodynamics; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000503:physiopathology*