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Spatial organization of acute myocardial ischemia
#MMPMID26947437
Aras K
; Burton B
; Swenson D
; MacLeod R
J Electrocardiol
2016[May]; 49
(3
): 323-36
PMID26947437
show ga
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.
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