Functional adaptations in coronary reactivity following healthy pregnancy in swine.

This study tested the hypothesis that coronary artery adaptations during the postpartum period are related to underlying reductions in endothelium-dependent relaxation and/or augmented smooth muscle vasoconstrictor responsiveness. In vivo experiments were performed in control (nonpregnant) and postpartum swine 35-45 days post-delivery, with isometric tension experiments performed in isolated coronary arteries from those animals. Coronary artery rings demonstrated increases in active tension generation following incremental increases in passive stretch with no differences between groups.

Impaired balance between coronary blood flow and myocardial metabolism in postpartum swine.

Understanding of the mechanisms contributing to the increased maternal susceptibility for major adverse cardiovascular events in the postpartum period remains poor. Accordingly, this study tested the hypothesis that the balance between coronary blood flow and myocardial metabolism is compromised during the puerperium period (35-45 days post-delivery) in swine. Systemic and coronary hemodynamic responses were assessed in anesthetized, open-chest control (nonpregnant) and puerperium/postpartum swine at baseline and in response to intravenous infusion of dobutamine (1-30 μg/kg/min).

Integrated modeling and simulation of recruitment of myocardial perfusion and oxygen delivery in exercise.

While exercise-mediated vasoregulation in the myocardium is understood to be governed by autonomic, myogenic, and metabolic-mediated mechanisms, we do not yet understand the spatial heterogeneity of vasodilation or its effects on microvascular flow patterns and oxygen delivery. This study uses a simulation and modeling approach to explore the mechanisms underlying the recruitment of myocardial perfusion and oxygen delivery in exercise. The simulation approach integrates model components representing: whole-body cardiovascular hemodynamics, cardiac mechanics and myocardial work; myocardial perfusion; and myocardial oxygen transport.

Unraveling the Gordian knot of coronary pressure-flow autoregulation.

The coronary circulation has the inherent ability to maintain myocardial perfusion constant over a wide range of perfusion pressures. The phenomenon of pressure-flow autoregulation is crucial in response to flow-limiting atherosclerotic lesions which diminish coronary driving pressure and increase risk of myocardial ischemia and infarction. Despite well over half a century of devoted research, understanding of the mechanisms responsible for autoregulation remains one of the most fundamental and contested questions in the field today.

Oxygen-sensing pathways below autoregulatory threshold act to sustain myocardial oxygen delivery during reductions in perfusion pressure.

The coronary circulation has an innate ability to maintain constant blood flow over a wide range of perfusion pressures. However, the mechanisms responsible for coronary autoregulation remain a fundamental and highly contested question. This study interrogated the local metabolic hypothesis of autoregulation by testing the hypothesis that hypoxemia-induced exaggeration of the metabolic error signal improves the autoregulatory response.