Evaluation of Isovolumic Relaxation Phase in the Process of Ventricular Remodeling following Myocardial Infarction

The course of cardiac remodeling after an acute cardiac MI, might affect the orientation of the cardiac muscle fibers as well as their contraction behavior. This may result in alteration of the untwisting during isovolumic relaxation phase, which might have effects on rapid early filling phase. In the present article, the variation of the time constant of isovolumic pressure drop (τ) has been studied during the course of cardiac remodeling after different types of induced myocardial infarction (MI) in sheep. The results for each group show different patterns of change in τ. The normalized τ curve in all three groups of anteroapical, anterobasal and posterobasal MI group show a rise 30 minutes after infarction. Two weeks later, the pressure drop constants decline to a lower level than baseline and by eight weeks after infarction, the time constant reached around the baseline level.