Spatial organization of acute myocardial ischemia

J Electrocardiol. May-Jun 2016;49(3):323-36. doi: 10.1016/j.jelectrocard.2016.02.014. Epub 2016 Feb 20.

Abstract

Introduction: 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.

Methods: 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.

Results: 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).

Conclusions: 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.

Keywords: Acute myocardial ischemia; Spatial organization; Subendocardium; Subepicardium.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Acute Disease
  • Animals
  • Body Surface Potential Mapping / methods*
  • Diagnosis, Computer-Assisted / methods
  • Dogs
  • Heart Conduction System / physiopathology*
  • Humans
  • Myocardial Ischemia / diagnosis*
  • Myocardial Ischemia / physiopathology*
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Spatio-Temporal Analysis
  • Species Specificity
  • Swine
  • Swine, Miniature