The thermodynamics of diastole: kinematic modeling-based derivation of the P-V loop to transmitral flow energy relation with in vivo validation

• Published in: American journal of physiology. Heart and circulatory physiology 2011-02, Vol.300 (2), p.H514-H521
• Main Authors: Mossahebi, Sina, Shmuylovich, Leonid, Kovács, Sándor J
• Format: Article
• Language: English
• Subjects: Aged; Algorithms; Biomechanical Phenomena; Blood Pressure - physiology; Data Interpretation, Statistical; Diastole - physiology; Echocardiography, Doppler; Elasticity; Energy Transfer - physiology; Female; Genotype & phenotype; Hemodynamics - physiology; Humans; Kinematics; Linear Models; Male; Middle Aged; Mitral Valve - physiology; Models, Biological; Regression analysis; Reproducibility of Results; Stroke Volume - physiology; Thermodynamics; Ultrasonic imaging; Ventricular Function, Left - physiology; Viscoelasticity
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00814.2010

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.