Flow Requirements in Ventricular Fibrillation: An In Vivo Nuclear Magnetic Resonance Analysis of the Left Ventricular High-Energy Phosphate Pool, , ,

Study objective: We sought to determine whether flow rates of approximately 60% of normal values are sufficient to preserve the left ventricular myocardial high-energy phosphate pool during ventricular fibrillation (VF). Methods: Mixed-breed swine (weight 22.4±2.5 kg) were anesthetized with α-chloralose, placed in a state of VF, and perfused with extracorporeal circulation at a target flow of 50 mL·kg–1·min–1. In vivo whole-wall (average of left ventricular wall) and spatially localized phosphorous-31 nuclear magnetic resonance (NMR) spectra were acquired at baseline and during VF. Results: Mean flow during VF was 58±20 mL·kg–1·min–1 (±SD; 95% confidence interval, 44 to 71) or about 60% of baseline cardiac output (n=13). Whole-wall adenosine triphosphate (ATP) decreased during perfused VF (P <.05), whereas creatine phosphate (CP) remained unchanged from baseline. With spatially localized NMR, the ratios of CP/ATP were similar at baseline in all layers (endocardium → epicardium) of the left ventricular wall. However, during perfused VF, subepicardial CP/ATP ratios increased by 14% to 40% compared with baseline values, whereas subendocardial CP/ATP ratios remained unchanged (1% to 3% increase). An additional 4 animals perfused at 72±10 mL·kg–1·min–1 (±SD; 95% confidence interval, 56 to 92) during VF had preservation of CP and ATP levels. Conclusion: Flow levels equivalent to 60% of baseline cardiac output were insufficient to maintain normal high-energy phosphate levels in the in vivo fibrillating myocardium. At this level of flow, myocardial high-energy phosphate loss is nonhomogeneous within the left ventricular wall. [Angelos MG, Rath DP, Zhu H, Beckley PD, Robitaille P-ML: Flow requirements in ventricular fibrillation: An in vivo nuclear magnetic resonance analysis of the left ventricular high-energy phosphate pool. Ann Emerg Med November 1999;34:583-588.]