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High spinal anesthesia does not alter experimental myocardial infarction size or ischemic preconditioning
R Haessler1, R A Wolff, G L Chien
1Department of Anesthesiology, Oregon Health Sciences University, Portland, USA.
Journal of Cardiothoracic and Vascular Anesthesia
|February 1, 1997
Summary
Ischemic preconditioning limits myocardial infarction and delays ventricular fibrillation, but its protective effects on arrhythmias are abolished by central nervous system blockade. This suggests sympathetic nerve activation is not essential for preconditioning benefits.
Area of Science:
- Cardiovascular Physiology
- Neuroscience
- Cardiac Electrophysiology
Background:
- Ischemic preconditioning (IP) is a phenomenon where brief episodes of ischemia protect the myocardium against subsequent longer ischemic insults.
- The role of the central nervous system (CNS) in mediating these protective effects, particularly concerning ventricular arrhythmias, remains incompletely understood.
Purpose of the Study:
- To investigate the influence of the CNS on myocardial infarction (MI) and ventricular fibrillation (VF) development in both virgin and ischemically preconditioned myocardium.
- To determine if efferent sympathetic nerve activation is necessary for the anti-arrhythmic effects of IP.
Main Methods:
- New Zealand white rabbits underwent regional ischemia-reperfusion. Groups included preconditioned/non-preconditioned with intact or blocked CNS (total spinal anesthesia).
- Infarct size was assessed using tetrazolium staining, and ventricular arrhythmias were monitored.
- Statistical analysis included ANOVA for infarct size and Kruskal-Wallis for fibrillation.
Main Results:
- Ischemic preconditioning significantly reduced infarct size (8% vs. 43%) and delayed the onset of ventricular fibrillation (15.5 vs. 11 minutes).
- CNS blockade did not alter infarct size in non-preconditioned hearts but abolished the delay in fibrillation onset caused by preconditioning.
- Spinal blockade increased the incidence and duration of ventricular fibrillation in preconditioned animals, indicating a pro-arrhythmic effect.
Conclusions:
- Efferent sympathetic nerve activation is not required for the infarct-limiting and anti-arrhythmic effects of ischemic preconditioning.
- Ischemic preconditioning effectively delays the onset of ventricular arrhythmias.
- Central nervous system blockade exacerbates ischemia-reperfusion-induced ventricular arrhythmias, highlighting its critical role in cardiac protection.