Impact of Simulated Vascular Aging and Heart Rate on Myocardial Efficiency: A Tale of Two Paradigms from In Silico Modelling.

INTRODUCTION

Vascular aging is associated with a loss of aortic compliance (C), which results in increased left ventricular pressure-volume area (PVA), stroke work (SW) and myocardial oxygen consumption (MVO). Myocardial efficiency (MyoEff) is derived from the PVA and MVO construct, which includes potential energy (PE). However, the SW/MVO ratio does not include PE and provides a more accurate physiologic measure.

METHODS

We used a modified computational model (CM) to assess PVA and SW and calculate MVO using a pressure-work index (e MVO), to derive MyoEff-PVA and MyoEff-SW metrics. Phase I evaluated five levels of human C from normal (N) to stiff (S) at 80 bpm, and Phase II evaluated two levels of C (N and S) at three heart rates (60, 100, and 140 bpm).

RESULTS

During Phase I, MyoEff-PVA increased from 20.7 to 31.2%, and MyoEff-SW increased from 14.8 to 18.9%. In Phase II, during the N setting coupled with increases in the heart rate, the MyoEff-PVA decreased from 29.4 to 14.8 to 9.5%; the MyoEff-SW also decreased from 22.5 to 10.3 to 5.9%. As expected, during the S setting, MyoEff-PVA decreased from 45.5 to 22.9 to 14.8; a similar effect occurred with the MyoEff-SW, demonstrating a decrease from 29.9 to 13.9 to 7.9%, respectively.

CONCLUSIONS

The CM provided insights into a simple and clinically relevant calculation for assessing MyoEff. The agreement on the CM metrics aligns with studies conducted previously in the clinical setting.