Metabolic changes and mitochondrial dysfunction early following transthoracic countershock in dogs.
The mechanisms of myocardial injury and necrosis following transthoracic shocks from a direct current cardiac defibrillator were investigated in adult greyhounds. Myocardial lactate extraction became negative maximally at 1 minute, following two (mean -22% +/- SEM23) or five (-193% +/- 135) shocks and returned to baseline in 6-15 minutes. Myocardial necrosis assessed at 4 hours following the shock period was 0.05 g (+/- 0.03) after two shocks, 6.69 g (+/- 1.76) after five shocks and zero in controls. In further experiments, dogs received five or zero (dummy) shocks and mitochondria were isolated from their hearts following excision within 1 minute of receiving the final shock. Maximal oxygen consumption in right ventricular mitochondria was lower than the unshocked controls with both glutamate (66.9 +/- 9.4 nanoatoms of oxygen/mg per minute, n = 9 vs 86.6 +/- 13.6 nanoatoms/mg per minute, n = 7) and succinate (96.2 +/- 8.7 nanoatoms/mg per minute, n = 9 vs 119.5 +/- 14.4 nanoatoms/mg per minute, n = 7) as substrates. Using electron spin resonance spectroscopy, an increase in a peroxyl-free radical with g = 2.031 was detected in myocardial tissue after two internal shocks (50 joules stored energy, 0.5-minute intervals). We conclude that mitochondrial dysfunction and free-radical generation are likely contributors to cellular injury following multiple countershocks.
Trouton
T G
TG
Regional Medical Cardiology Centre, Royal Victoria Hospital, Belfast, Northern Ireland.
Allen
J D
JD
Yong
L K
LK
Rooney
J J
JJ
Adgey
A A
AA
D000818:Animals; D004285:Dogs; D004554:Electric Countershock / Q000009:adverse effects*; D004578:Electron Spin Resonance Spectroscopy; D005260:Female; D005609:Free Radicals; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D008297:Male; D008929:Mitochondria, Heart / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology*; D010101:Oxygen Consumption
D005609:Free Radicals; D007773:Lactates; D019344:Lactic Acid