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 cons umption (MVo(2)) during moderate RC hypotension preserve RV high-energ y phosphates. RC arteries of anesthetized dogs were cannulated and per fused with arterial blood supplied by a pressurized extracorporeal cir cuit. RC perfusion pressure (RCPP) was either kept constant at 100 mmH g or reduced to 60 or 30 mmHg for 20 min followed by a freeze-clamp bi opsy of RV. Left ventricular (LV) biopsy was also performed to compare energy metabolism between RV and LV. RCBF and MVo(2) significantly de creased when RCPP was reduced to 60 mmHg, but RV segment shortening (% SS) was unchanged; ATP, creatine phosphate (CrP) and phosphorylation s tate 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 1 00 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 phos phor ylation state during moderate RC hypotension. Furthermore, the RV myoc ardium maintains a much lower energy level than LV myocardium, commens urate with its lower energy requirements.