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Determinants of arrhythmic death during coronary artery reperfusion: effect of perfusion bed size
Insights
Larger ischemic areas increase the risk of reperfusion ventricular fibrillation (VF) after transient ischemia. Dogs with larger at-risk left ventricular regions (R/LV) were more likely to die from reperfusion VF.
Area of Science:
- Cardiovascular Science
- Ischemia-Reperfusion Injury
Background:
- Transient ischemia can lead to serious cardiac events.
- Ventricular fibrillation (VF) is a critical consequence of myocardial ischemia.
Purpose of the Study:
- To investigate the relationship between the size of the ischemic region and the incidence of reperfusion VF.
- To determine if the extent of myocardial damage influences VF occurrence post-ischemia.
Main Methods:
- Occlusion of the circumflex coronary artery (CFX) in 19 dogs for 20 minutes, followed by 10 minutes of reperfusion.
- Quantification of the left ventricle at risk (R/LV) using Evans blue and saline perfusion to delineate unstained (risk) and stained (normal) regions.
- Measurement of R/LV size by analyzing heart slices and calculating the mass of normal and risk regions.
Main Results:
- Dogs that died from reperfusion VF had a significantly larger R/LV (42.3 +/- 5.0%) compared to survivors (24.2 +/- 9.4%, p < 0.001).
- All dogs that died had an R/LV greater than 35%, while 12 out of 13 survivors had an R/LV less than 35% (p = 0.0005).
- The incidence of reperfusion VF is directly related to the size of the ischemic insult.
Conclusions:
- The size of the ischemic region is a critical determinant of reperfusion ventricular fibrillation.
- A larger extent of myocardial tissue at risk significantly elevates the likelihood of fatal reperfusion VF.
- Findings highlight the importance of infarct size in predicting outcomes after transient myocardial ischemia.
Abstract:
To further our understanding of the factors determining the consequences of transient episodes of ischemia, we studied the influence of the size of the ischemic bed on the incidence of ventricular fibrillation (VF). The circumflex coronary artery (CFX) was occluded at various locations in 19 dogs. After 20 minutes of occlusion followed by 10 minutes of reperfusion the dogs were killed. The portion of the left ventricle (LV) at risk of infarcting (R/LV) was defined as the region supplied by the occluded CFX and determined by simultaneous perfusion of the CFX with saline solution, just beyond the occlusion site, and of the aorta with Evan's blue. Bread loaf slices of the heart were photographed and projected, and the normal (blue) and risk regions (unstained) traced. The product of area and slice weight yielded mass of normal and risk regions. The R/LV of dogs that died of reperfusion VF (n = 6) was 42.3 +/- 5.0%, larger (p less than 0.001) than R/LV in all surviving dogs (n = 13), 24.2 +/- 9.4%. Twelve of the 13 survivors had R/LV less than 35%, whereas all dogs that died had R/LV greater than 35% (p = 0.0005). As is true for VF occurring during coronary artery occlusion, the incidence of reperfusion VF is related to the size of the ischemic insult.