Mechano-chronotropic Unloading During the Acute Phase of Myocardial Infarction Markedly Reduces Infarct Size via the Suppression of Myocardial Oxygen Consumption.

The oxygen supply-demand imbalance is the fundamental pathophysiology of myocardial infarction (MI). Reducing myocardial oxygen consumption (MVO2) in acute MI (AMI) reduces infarct size. Since left ventricular (LV) mechanical work and heart rate are major determinants of MVO2, we hypothesized that the combination of LV mechanical unloading and chronotropic unloading during AMI can reduce infarct size via synergistic suppression of MVO2. In a dog model of ischemia-reperfusion, as we predicted, the combination of mechanical unloading by Impella and bradycardic agent, ivabradine (IVA), synergistically reduced MVO2. This was translated into the striking reduction of infarct size with Impella + IVA administered 60 min after the onset of ischemia compared to no treatment (control) and Impella groups (control 56.3 ± 6.5, Impella 39.9 ± 7.4 and Impella + IVA 23.7 ± 10.6%, p < 0.001). In conclusion, Impella + IVA during AMI reduced infarct size via marked suppression of MVO2. The mechano-chronotropic unloading may serve as a powerful therapeutic option for AMI.