Stability of high-energy phosphates in right ventricle: Myocardial energetics during right coronary hypotension

This study was conducted to determine if mechanisms that reduce right coronary (RC) blood flow (RCBF) and right ventricular (RV) oxygen consumption (MV̇O₂) during moderate RC hypotension preserve RV high-energy phosphates. RC arteries of anesthetized dogs were cannulated and perfused with arterial blood supplied by a pressurized extracorporeal circuit. RC perfusion pressure (RCPP) was either kept constant at 100 mmHg or reduced to 60 or 30 mmHg for 20 min followed by a freeze-clamp biopsy of RV. Left ventricular (LV) biopsy was also performed to compare energy metabolism between RV and LV. RCBF and MV̇O₂ significantly decreased when RCPP was reduced to 60 mmHg, but RV segment shortening (%SS) was unchanged; ATP, creatine phosphate (CrP) and phosphorylation state of CrP ([CrP]/[Cr][P_i]) did not differ from control values. RV %SS, CrP, and phosphorylation state fell markedly at 30 mmHg RCPP. At 100 mmHg RCPP, CrP phosphorylation state in RV was only 35% of that in LV. These results indicate that RV increases its energetic efficiency without significant changes in high-energy phosphates or CrP phosphorylation state during moderate RC hypotension. Furthermore, the RV myocardium maintains a much lower energy level than LV myocardium, commensurate with its lower energy requirements.