Flow requirements in ventricular fibrillation: An in vivo nuclear magnetic resonance analysis of the left ventricular high-energy phosphate pool.
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 alpha-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.


CONCLUSIONS
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
M G
MG
Department of Emergency Medicine, The Ohio State University, Columbus, OH 43210, USA. angelos.1@osu.edu
Rath
D P
DP
Zhu
H
H
Beckley
P D
PD
Robitaille
P M
PM
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001783:Blood Flow Velocity; D006352:Heart Ventricles / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D010725:Phosphocreatine / Q000378:metabolism*; D012039:Regional Blood Flow; D013552:Swine; D014693:Ventricular Fibrillation / Q000503:physiopathology*; D016276:Ventricular Function; D016277:Ventricular Function, Left / Q000502:physiology
D010725:Phosphocreatine; D000255:Adenosine Triphosphate