Intramyocardial ST-segment elevation correlates closely with increased carbon dioxide tension during ischemia, whereas epicardial electrograms are less sensitive for detecting regional myocardial ischemia.
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Hypothesis-generating in animal models; leaves open whether intramyocardial recordings improve clinical ischemia detection.
Ischemic changes in the left ventricular wall were investigated during graded coronary constriction in 9 dogs. Epicardial and intramyocardial electrograms were recorded and changes in ST-segment voltage were correlated with the changes in intramyocardial gas tensions in outer and inner layers of the myocardium measured using a mass spectrometer. Electrographic and metabolic changes appeared first in inner layer and proceeded to outer layer with increasing severity of coronary constriction. In both layers intramyocardial ST-segment elevation was closely related with the increase in carbon dioxide tension (r = 0.78 in inner layer and r = 0.67 in outer layer). Epicardial electrogram, however, reflected the regional ischemia less sensitively than intramyocardial electrograms and has a limited function to detect myocardial ischemia.
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Maekawa et al. (1980) studied this question.
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