Key result
Regional myocardial stretch causes ST-segment elevation in normal hearts independent of ischemia.
Why the study?
The role of regional myocardial stretch in inducing ST-segment elevation without myocardial ischemia was unclear.
Stretch-induced ST elevation without ischemia cautions against assuming all ST changes reflect ischemia; leaves open human relevance.
The purpose of this study was to evaluate ST-segment elevation induced by regional myocardial stretch without myocardial ischemia in canine hearts. A strain gauge arch (TH-601T) was sutured to the left ventricular epicardium, parallel to the short axis, to shorten the end-diastolic length of the myocardium beneath the arch (stretch zone; SZ) and to produce regional myocardial stretch in each of 6 dogs. An increase in preload caused by altering the height of a saline-filled reservoir affected prolongation or shortening of the myocardium both in the SZ and outside the arch (normal zone; NZ) to increase myocardial stretch. An epicardial electrocardiogram was recorded in both the SZ and the NZ. After suture of the strain gauge arch, the ST segment was elevated in the SZ. An increase in preload augmented stretch during systole in the SZ, resulting in additional ST-segment elevation. These results suggest that regional myocardial stretch itself plays an important role in ST-segment elevation.
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Shimada et al. (1997) studied Normal canine hearts (n=6). Regional myocardial stretch vs. Normal zone (outside the arch) was evaluated on ST-segment elevation. Regional myocardial stretch induced by a strain gauge arch and increased preload caused ST-segment elevation in normal canine hearts without myocardial ischemia.
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