Myocardial perfusion and function during acute right ventricular systolic hypertension.

This research studied the effects of sudden high blood pressure in the right ventricle of the heart on blood flow and heart function in ponies. The findings suggest the heart can adapt to such stress by adjusting its blood flow, particularly by vasodilation in the right ventricle and septum.

Objective of the Research

• The primary objective of this study was to understand the mechanics and response of the heart (specifically the right ventricle) under conditions of acute right ventricular systolic hypertension (RVSH). The term “acute” is indicative of a sudden or rapid increase in right ventricular pressure.

Methodology Used

• Six ponies were anesthetized and their hemodynamics, myocardial function, and regional myocardial blood flow (MBF) were measured under normal conditions (control).
• Then, the ponies were subjected to RVSH, raising the systolic pressure in the right ventricle to 90 mmHg, and measurements were taken again.
• Both normoxic (normal oxygen levels) and isocapnic hypoxic (lowered oxygen levels without change in carbon dioxide concentration) conditions were used for this experiment.

Key Findings and Conclusions

• Upon creating RVSH, significant changes were noticed in the pattern of ventricular MBG distribution, favoring the right ventricle. Both the inner (endocardium) and outer (epicardium) layers of the right ventricle received proportionate blood supply, indicating that the natural regulation of blood flow in the heart vessels was not disrupted even under the stress of increased pressure and hypoxic conditions.
• The research noted a substantial increase in MBF to the right side of the heart’s septum (the wall dividing left and right heart chambers) during RVSH. This finding implies that when the right ventricle contracts under high pressure, the right portion of the septum aids in supporting this action.
• Despite the reduced driving pressure in right ventricular coronary arteries, these increments in MBF were seen, indicating a compensatory mechanism of coronary vasodilation.
• The authors also speculated that the pony’s slower heart rate, in combination with a large vasodilatory reserve, facilitated these changes despite decreased coronary driving pressure.