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Effect of reduction in myocardial edema on myocardial blood flow and ventricular function after coronary reperfusion
R E Carlson1, A M Aisen, A J Buda
1Department of Medicine, Tulane University School of Medicine, New Orleans, Louisiana 70112.
Insights
Hypertonic mannitol reduced myocardial edema but did not improve blood flow, left ventricular function, or infarct size after reperfusion in dogs. Other mechanisms likely cause no-reflow and dysfunction.
Area of Science:
- Cardiovascular Research
- Myocardial Infarction
- Ischemia-Reperfusion Injury
Background:
- The role of myocardial edema in no-reflow, impaired left ventricular function, and infarct size following coronary occlusion and reperfusion remains unclear.
- Understanding these contributions is crucial for developing effective therapeutic strategies.
Purpose of the Study:
- To investigate the impact of reducing myocardial edema using hypertonic mannitol on the no-reflow phenomenon, left ventricular functional recovery, and infarct size.
- To determine if mitigating edema improves outcomes after myocardial ischemia and reperfusion.
Main Methods:
- Twenty-six open-chest dogs underwent coronary occlusion and reperfusion.
- Hypertonic mannitol was administered to 12 dogs 30 minutes before reperfusion to induce hyperosmolality.
- Proton nuclear magnetic resonance relaxation spectroscopy analyzed myocardial tissue biopsies to quantify edema content.
Main Results:
- Hypertonic mannitol significantly decreased ischemic myocardial tissue T1 relaxation times, indicating reduced edema.
- No significant differences were observed in subendocardial blood flow or left ventricular wall thickening between mannitol and control groups after 4-hour reperfusion.
- Infarct size was not significantly altered by hypertonic mannitol administration compared to the control group.
Conclusions:
- Reducing myocardial edema with hypertonic mannitol before reperfusion does not improve reperfusion blood flow or functional recovery.
- Mechanisms other than myocardial edema are likely responsible for the no-reflow phenomenon and contractile dysfunction post-reperfusion.
- Hypertonic mannitol administered prior to reperfusion does not reduce infarct size in this model.
Abstract:
The contribution of myocardial edema to the no-reflow phenomenon, left ventricular functional recovery, and infarct size after coronary occlusion and reperfusion is uncertain. To examine this, we studied 26 open-chest dogs after coronary occlusion and reperfusion. Twelve dogs received hypertonic mannitol 30 min before reperfusion, which increased serum osmolality (P less than 0.01 vs. control). Fourteen control dogs received a similar volume of saline that had no effect on serum osmolality. Tissue biopsies of central ischemic and normal myocardial areas were analyzed by proton nuclear magnetic resonance relaxation spectroscopy to assess edema content. Hypertonic mannitol resulted in a significant decrease in ischemic tissue T1 (767.0 +/- 16.3 vs. 818.6 +/- 19.0 ms, P less than 0.05) compared with the control group. Despite this, no significant differences were found between the mannitol and control groups in 4-h reperfusion subendocardial blood flow or left ventricular wall thickening. In addition, mannitol administered before reperfusion did not modify infarct size compared with the control group (infarct/risk area, 41.0 +/- 1.4 vs. 37.9 +/- 1.9%, P not significant). In conclusion, no benefit is produced in reperfusion blood flow or functional recovery by reducing edema in postischemic myocardial tissue. This suggests that mechanisms other than myocardial edema are responsible for myocardial no reflow and contractile dysfunction after coronary reperfusion. Furthermore, hypertonic mannitol administered before reperfusion does not reduce infarct size.