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Dependency of location of salvageable myocardium on type of intervention
Insights
Drug interventions and reperfusion salvage different myocardial tissue zones in ischemic hearts. Reperfusion primarily salvages subepicardial tissue, while drugs like ibuprofen salvage subepicardial and lateral border zones.
Area of Science:
- Cardiovascular Science
- Pharmacology
- Myocardial Ischemia Research
Background:
- Understanding salvageable myocardium is crucial for treating myocardial infarction.
- The location of salvaged tissue can differ based on the intervention method.
Purpose of the Study:
- To determine the location of salvageable border zone tissue in relation to the ischemic coronary bed.
- To investigate if salvaged tissue location varies with the mechanism of salvage (drug vs. reperfusion) and intervention type.
Main Methods:
- Forty-four dogs underwent left anterior descending coronary artery occlusion (6 hours) or occlusion followed by reperfusion (4 hours occlusion, 2 hours reperfusion).
- Groups received saline, ibuprofen, flurbiprofen, or L-hydroxyphenylglycine intravenously at specific time points.
- Infarct size and location of salvaged tissue were analyzed.
Main Results:
- Drug interventions (ibuprofen, flurbiprofen, L-hydroxyphenylglycine) and reperfusion salvaged 17-42% of at-risk myocardium, compared to 6% with saline.
- Reperfusion (Group V) primarily salvaged subepicardial tissue (ratio 14.8:1 subepicardium:subendocardium).
- Drug interventions salvaged both subepicardial and lateral border zones (ratios 3.3:1 to 2.0:1).
Conclusions:
- Drug-induced infarct size reduction is associated with salvage in lateral and subepicardial zones.
- Reperfusion-mediated tissue salvage is predominantly located in the subepicardium.
- These findings clarify the distinct spatial patterns of myocardial salvage by drugs versus reperfusion.
Abstract:
The purpose of this study were (1) to determine the location of the salvageable border zone in relation to the ischemic coronary bed, and (2) to determine whether the location of salvaged tissue differs depending on the mechanism of salvage and the type of intervention. Forty-four open chest dogs were subjected to either 6 hours of occlusion of the left anterior descending coronary artery or 4 hours of occlusion of this artery followed by 2 hours of reperfusion. Dogs with 6 hours of occlusion received either saline solution (Group I, n = 9), ibuprofen, 12.5 mg/kg body weight, (Group II, n = 7), flurbiprofen, 1 mg/kg (Group III, n = 10), or L-hydroxyphenylglycine, 10 mg/kg (Group IV, n = 8) intravenously 30 minutes and 3 hours after coronary occlusion. Dogs in Group V (n = 10) were subjected to 4 hours of coronary occlusion followed by 2 hours of reperfusion, but received no drugs. Although from 17 to 42 percent of the myocardium at risk did not become infarcted in Groups II through V compared with only 6 percent in Group I, the location of salvaged tissue was different in dogs receiving reperfusion (Group V) from that of dogs receiving drug interactions (Groups II, III and IV). In Group V, the salvaged tissue was primarily subepicardial with virtually no lateral zone of salvaged tissue (ratio of salvaged subepicardium to salvaged subendocardium 14.8 +/- 1.9 to 1). In Groups II, III and IV, there was a portion of the myocardium at risk at both lateral margins that did not become infarcted, as well as a portion of subepicardial tissue (ratio of subepicardium to subendocardium salvaged 3.3 +/- 0.4 in Group II, 2.5 +/- 0.1 in Group III and 2.0 +/- 0.2 in Group IV). Thus, infarct size reduction by ibuprofen, flurbiprofen and L-hydroxyphenylglycine is accompanied by lateral and subepicardial zones of salvage, whereas tissue salvaged by reperfusion is located primarily in the subepicardium. These observations should help to resolve the controversy regarding the existence and location of the various zones of ischemic myocardium that can be salvaged by drugs or reperfusion.