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Spatial organization of acute myocardial ischemia.

ABSTRACT: Myocardial ischemia is a pathological condition initiated by supply and demand imbalance of the blood to the heart. Previous studies suggest that ischemia originates in the subendocardium, i.e., that nontransmural ischemia is limited to the subendocardium. By contrast, we hypothesized that acute myocardial ischemia is not limited to the subendocardium and sought to document its spatial distribution in an animal preparation. The goal of these experiments was to investigate the spatial organization of ischemia and its relationship to the resulting shifts in ST segment potentials during short episodes of acute ischemia.We conducted acute ischemia studies in open-chest canines (N=19) and swines (N=10), which entailed creating carefully controlled ischemia using demand, supply or complete occlusion ischemia protocols and recording intramyocardial and epicardial potentials. Elevation of the potentials at 40% of the ST segment between the J-point and the peak of the T-wave (ST40%) provided the metric for local ischemia. The threshold for ischemic ST segment elevations was defined as two standard deviations away from the baseline values.The relative frequency of occurrence of acute ischemia was higher in the subendocardium (78% for canines and 94% for swines) and the mid-wall (87% for canines and 97% for swines) in comparison with the subepicardium (30% for canines and 22% for swines). In addition, acute ischemia was seen arising throughout the myocardium (distributed pattern) in 87% of the canine and 94% of the swine episodes. Alternately, acute ischemia was seen originating only in the subendocardium (subendocardial pattern) in 13% of the canine episodes and 6% of the swine episodes (p<0.05).Our findings suggest that the spatial distribution of acute ischemia is a complex phenomenon arising throughout the myocardial wall and is not limited to the subendocardium.

SUBMITTER: Aras K

PROVIDER: S-EPMC4853261 | biostudies-literature | 2016 May-Jun

REPOSITORIES: biostudies-literature

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Spatial organization of acute myocardial ischemia.

Aras Kedar K Burton Brett B Swenson Darrell D MacLeod Rob R

Journal of electrocardiology 20160220 3

<h4>Introduction</h4>Myocardial ischemia is a pathological condition initiated by supply and demand imbalance of the blood to the heart. Previous studies suggest that ischemia originates in the subendocardium, i.e., that nontransmural ischemia is limited to the subendocardium. By contrast, we hypothesized that acute myocardial ischemia is not limited to the subendocardium and sought to document its spatial distribution in an animal preparation. The goal of these experiments was to investigate th ...[more]

PMID: 26947437

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Project description:ObjectiveHumanin (HN), an endogenous antiapoptotic peptide, has previously been shown to protect against Alzheimer's disease and a variety of cellular insults. We evaluated the effects of a potent analog of HN (HNG) in an in vivo murine model of myocardial ischemia and reperfusion.Methods and resultsMale C57BL6/J mice (8 to 10 week old) were subjected to 45 minutes of left coronary artery occlusion followed by a 24-hour reperfusion. HNG or vehicle was administered IP 1 hour prior or at the time of reperfusion. The extent of myocardial infarction per area-at-risk was evaluated at 24 hours using Evans Blue dye and 2-3-5-triphenyl tetrazolium chloride staining. Left ventricular function was evaluated at 1 week after ischemia using high-resolution, 2D echocardiography (VisualSonics Vevo 770). Myocardial cell signaling pathways and apoptotic markers were assessed at various time points (0 to 24 hours) following reperfusion. Cardiomyocyte survival and apoptosis in response to HNG were assessed in vitro. HNG reduced infarct size relative to the area-at-risk in a dose-dependent fashion, with a maximal reduction at the dose of 2 mg/kg. HNG therapy enhanced left ventricular ejection fraction and preserved postischemic left ventricular dimensions (end-diastolic and end-systolic), resulting in improved cardiac function. Treatment with HNG significantly increased phosphorylation of AMPK and phosphorylation of endothelial nitric oxide synthase in the heart and attenuated Bcl-2-associated X protein and B-cell lymphoma-2 levels following myocardial ischemia and reperfusion. HNG improved cardiomyocyte survival and decreased apoptosis in response to daunorubicin in vitro.ConclusionsThese data show that HNG provides cardioprotection in a mouse model of myocardial ischemia and reperfusion potentially through activation of AMPK-endothelial nitric oxide synthase-mediated signaling and regulation of apoptotic factors. HNG may represent a novel agent for the treatment of acute myocardial infarction.

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Spatial organization of acute myocardial ischemia.

Publications

Spatial organization of acute myocardial ischemia.

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