The physiologic basis of dobutamine as compared with dipyridamole stress interventions in the assessment of critical coronary stenosis.

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Abstract
Noninvasive cardiac imaging with echocardiography or thallium-201 scintigraphy utilizing pharmacologic agents as alternatives to exercise is gaining popularity. We investigated the physiologic rationale underlying the optimal choice of pharmacologic stress for functional versus perfusion imaging. With the use of an open-chest dog model, a critical stenosis of the left circumflex coronary artery was produced with total ablation of hyperemic response to a 15 sec period of complete occlusion. Regional left ventricular wall thickening was assessed by quantitative two-dimensional echocardiography. Regional myocardial blood flow was determined by microspheres in both the flow-restricted left circumflex area and the control area supplied by the left anterior descending artery. Eight dogs received 15 micrograms/kg/min dobutamine intravenously for 10 min, and nine dogs received 0.14 mg/kg/min dipyridamole intravenously for 4 min. Dobutamine induced wall thickening abnormalities in all dogs while dipyridamole induced dysfunction in only 55% of the animals studied (p less than .01). Subendocardial blood flow to the left circumflex area was unchanged after both dobutamine and dipyridamole when compared with baseline blood flow. However, subendocardial blood flow increased markedly after dipyridamole in the control area. Regional subendocardial blood flow ratio (left anterior descending/left circumflex) was 3.74 +/- 0.09 (mean +/- SEM) after dipyridamole versus 1.27 +/- 0.09 after dobutamine (p less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)