August 1, 1993Circulation
Does preconditioning protect the coronary vasculature from subsequent ischemia/reperfusion injury?
Why the study?
Does ischemic preconditioning prevent low reflow and loss of coronary vasodilator reserve after sustained ischemia/reperfusion injury in a canine model?
Population
32 anesthetized open-chest dogs undergoing 1 hour of sustained left anterior descending coronary artery…
Comparison
Preconditioning vs Control group
Design
Preclinical, randomly assigned
Follow-up
4 hours of reperfusion
Authors
Discussion
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Implication
Preconditioning fails to protect coronary vasculature in this canine model; leaves open whether myocyte and microvascular protection can be decoupled or targeted separately.
Key Points
- To evaluate whether ischemic preconditioning attenuates post-ischemic low reflow and preserves coronary vasodilator reserve following sustained myocardial ischemia and reperfusion.
- Thirty-two anesthetized open-chest dogs subjected to 1 hour of sustained LAD occlusion and 4 hours of reperfusion were randomly assigned to preconditioning (four cycles of 5-minute LAD occlusion and reperfusion) or control.
- In Protocol 1 (n=14), vasodilator reserve was assessed via acetylcholine and nitroglycerin before occlusion and after reperfusion; in Protocol 2 (n=18), vasodilators were administered only during reperfusion.
- Myocardial blood flow and infarct size (triphenyltetrazolium staining) were measured across groups to assess low reflow and tissue necrosis.
- In Protocol 2, preconditioning significantly reduced infarct size relative to control (2 +/- 1% vs 11 +/- 3% of the risk region; P < .01).
- Coronary vasodilator response to acetylcholine deteriorated markedly by 4 hours of reflow in both preconditioned (from 23.6 +/- 5.3 to 15.6 +/- 3.5 mL/min; P < .01) and control groups (from 18.2 +/- 2.1 to 15.4 +/- 1.7 mL/min; P < .05), with no difference between groups (P = NS).
- Subendocardial blood flow deteriorated similarly from 30 minutes to 4 hours post-reperfusion in both preconditioned (0.74 +/- 0.08 to 0.50 +/- 0.06 mL min-1 g-1; P < .05) and control animals (1.84 +/- 0.50 to 0.55 +/- 0.11 mL min-1 g-1; P < .05).
Structured PICO
Does ischemic preconditioning prevent low reflow and loss of coronary vasodilator reserve after sustained ischemia/reperfusion injury in a canine model?
P
Population
32 anesthetized open-chest dogs undergoing 1 hour of sustained left anterior descending (LAD) coronary artery occlusion and 4 hours of reperfusion.
I
Intervention
Preconditioning (four episodes of 5 minutes of LAD occlusion plus 5 minutes of reperfusion before sustained ischemia)
C
Comparator
Control group (no intervention before sustained ischemia)
O
Outcome
Coronary vasodilator reserve (response to acetylcholine and nitroglycerin) and low reflow (regional myocardial blood flow) at 30 minutes and 4 hours after reflow, and infarct sizesurrogate
Ischemic preconditioning reduces myocardial infarct size but fails to protect the coronary vasculature from low reflow and loss of vasodilator reserve after ischemia/reperfusion injury.
Cite This Study
Bauer et al. (1993) studied this question.