Acute Colloid Administration Increases Ischemia in the Myocardium Supplied by a Stenotic Coronary Artery

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Abstract
The effect of acute colloid administration was evaluated in the pig heart in which an external coronary artery stenosis was applied. Seven pigs received thiopentone and halothane anesthesia. Ultrasonic crystals were inserted in the myocardium supplied by the left anterior descending (LAD) and circumflex coronary arteries. Left ventricular pressure was measured and regional myocardial function was quantified with the pressure-length loop and the endsystolic pressure-length ratio. A significant stenosis was applied to the LAD artery, after which the animal received fixed colloids to increase the left ventricular end-diastolic pressure. Regional myocardial ischemia was defined with reference to postsystolic shortening and lactate production from the region supplied by the LAD artery. The application of the stenosis caused an increase in postsystolic shortening from 9.62% ± 4.24% to 26.12% ± 5.81% (mean ± SEM; P < 0.05), and lactate extraction changed from 15.88% ± 2.38% to −9.56% ± 5.32% (P < 0.05). Acute colloid administration increased the left ventricular enddiastolic pressure from 9.71 ± 1.77 to 15.93 ± 2.07 mm Hg (P < 0.05), and lactate extraction further decreased to −76.63% ± 19.19% (P < 0.05). Postsystolic shortening increased to 36.22% ± 5.10% (P < 0.05). The oxygen tension in the venous blood draining the LAD region decreased from 36.74 ± 9.37 to 17.34 ± 1.23 mm Hg (P < 0.05). We conclude that in the acute pig model, augmentation of the preload worsens regional myocardial ischemia in an area supplied by a stenotic coronary artery.

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