Clinical trials have shown an increase in survival in patients with beta blockers after infarction. In addition, the majority of patients undergoing myocardial revascularization are also treated preoperatively with beta blockers. It is commonly thought that beta blockers exert their protective effect primarily by decreasing heart rate and subsequent myocardial work. The present study was designed to determine whether beta blockade has any primary protective metabolic effects on globally ischemic myocardium. Thirty-four anesthetized dogs underwent total myocardial ischemia at 37°C. High-energy nucleotide and lactate levels in left ventricular tissue samples were determined at control and at 15 minute intervals as well as at the onset of ischemic contracture in 24 dogs. Seventeen dogs were treated with propranolol before ischemia. The time to ischemic contracture in control dogs was 63.3 ± 1.4 minutes compared with 75.9 ± 2.2 minutes in the propranolol-treated group (p < 0.01). In addition to significantly delaying the onset of ischemic contracture, propranolol also decreased the rate of anaerobic glycolysis during ischemia. Ischemic contracture occurred in the control group with an average adenosine triphosphate level of 1.26 ± 0.08 μmol compared to 0.91 ± 0.08 μmol/gm wet weight for the beta blocked group (p < 0.0025). These are the first data suggesting that the protective effects of beta blockade may be related to a beneficial effect on ischemic myocardial metabolism allowing myocardium to survive with lower levels of adenosine triphosphate.
|Original language||English (US)|
|Number of pages||9|
|Journal||Journal of Thoracic and Cardiovascular Surgery|
|Issue number||3 I|
|State||Published - 1986|
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine