title: The thermodynamics of diastole: kinematic modeling-based derivation of the P-V loop to transmitral flow energy relation with in vivo validation.
abstract: Pressure-volume (P-V) loop-based analysis facilitates thermodynamic assessment of left ventricular function in terms of work and energy. Typically these quantities are calculated for a cardiac cycle using the entire P-V loop, although thermodynamic analysis may be applied to a selected phase of the cardiac cycle, specifically, diastole. Diastolic function is routinely quantified by analysis of transmitral Doppler E-wave contours. The first law of thermodynamics requires that energy (ε) computed from the Doppler E-wave (εE-wave) and the same portion of the P-V loop (εP-V E-wave) be equivalent. These energies have not been previously derived nor have their predicted equivalence been experimentally validated. To test the hypothesis that εP-V E-wave and εE-wave are equivalent, we used a validated kinematic model of filling to derive εE-wave in terms of chamber stiffness, relaxation/viscoelasticity, and load. For validation, simultaneous (conductance catheter) P-V and echocadiographic data from 12 subjects (205 total cardiac cycles) having a range of diastolic function were analyzed. For each E-wave, εE-wave was compared with εP-V E-wave calculated from simultaneous P-V data. Linear regression yielded the following: εP-V E-wave=αεE-wave+b (R2=0.67), where α=0.95 and b=6e(-5). We conclude that E-wave-derived energy for suction-initiated early rapid filling εE-wave, quantitated via kinematic modeling, is equivalent to invasive P-V-defined filling energy. Hence, the thermodynamics of diastole via εE-wave generate a novel mechanism-based index of diastolic function suitable for in vivo phenotypic characterization.
authors.affiliation: Cardiovascular Biophysics Laboratory, School of Medicine, Department of Physics, College of Arts and Sciences, Washington University Medical Center, 660 S. Euclid Ave., Box 8086, St. Louis, MO. 63110, USA.
authors.forename: Sina
authors.initials: S
authors.lastname: Mossahebi
authors.forename: Leonid
authors.initials: L
authors.lastname: Shmuylovich
authors.forename: Sándor J
authors.initials: SJ
authors.lastname: Kovács
mesh_terms: D000368:Aged; D000465:Algorithms; D001696:Biomechanical Phenomena; D001794:Blood Pressure / Q000502:physiology*; D003627:Data Interpretation, Statistical; D003971:Diastole / Q000502:physiology*; D015150:Echocardiography, Doppler; D004548:Elasticity; D004735:Energy Transfer / Q000502:physiology*; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000502:physiology*; D008954:Models, Biological; D015203:Reproducibility of Results; D013318:Stroke Volume / Q000502:physiology*; D013816:Thermodynamics; D016277:Ventricular Function, Left / Q000502:physiology*