Dynamic myocardial contractile parameters from left ventricular pressure-volume measurements

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Cardiac Mechanics

Background:

• Understanding left ventricular (LV) pressure-volume dynamics is crucial for assessing cardiac function.
• Existing models often simplify the complex interplay between chamber dynamics and myocardial mechanics.
• Accurate estimation of myocardial contractile parameters in a beating heart remains a challenge.

Purpose of the Study:

• To develop and validate a dynamic model linking LV pressure-volume dynamics with cardiac muscle force-length dynamics.
• To assess the impact of model residual errors on the estimation of myocardial contractile parameters.
• To establish a method for deriving dynamic myocardial contractile behavior from beating heart data.

Main Methods:

• Developed a mathematical model integrating chamber pressure-volume and cardiac muscle force-length dynamics.
• Applied the dynamic LV model to pressure-volume data from an isolated, isovolumically beating rat heart.
• Validated estimated myocardial parameters against direct measurements from isolated muscle fibers.

Main Results:

• The dynamic LV model explained over 80% of pressure variation due to volume perturbations.
• Good agreement was found between model-derived and directly measured myocardial contractile parameters (magnitude and kinetics).
• Small systematic residual errors did not impede accurate parameter estimation.

Conclusions:

• The dynamic LV model reliably estimates myocardial contractile parameters from beating heart pressure-volume signals.
• This model provides a crucial link between cardiac muscle and whole-heart function dynamics.
• Enables in vivo investigation of myofilament behavior's relevance to cardiovascular system function.