Objectives: The aim of this study was to evaluate myocardial blood flow regulation in collateral-dependent myocardium of patients with coronary artery disease. Background: Despite great clinical relevance, perfusion correlates of collateral circulation in humans have rarely been estimated by quantitative methods at rest and during stress. Methods: Nineteen patients with angina and isolated occlusion of the left anterior descending (n = 14) or left circumflex (n = 5) coronary artery were evaluated. Using positron emission tomography and nitrogen-13 ammonia, we obtained flow measurements at baseline, during atrial pacing-induced tachycardia and after intravenous administration of dipyridamole (0.56 mg/kg body weight over 4 min). Flow values in collateral-dependent and remote areas were compared with values in 13 normal subjects. Results: Flow at rest was similar in collateralized and remote myocardium (0.61 ± 0.11 vs. 0.63 ± 0.17 ml/min per g, mean ± 1 SD), and both values were lower than normal (1.00 ± 0.20 ml/min per g, p <0.01). During pacing, blood flow increased to 0.83 ± 0.25 and 1.11 ± 0.39 ml/min per g in collateraldependent and remote areas, respectively (p <0.05 vs. baseline); both values were lower than normal (1.86 ± 0.61 ml/min per g, p <0.01). Dipyridamole induced a further increase in perfusion in remote areas (1.36 ± 0.57 ml/min per g, p <0.01 vs. pacing) but not in collateral-dependent regions (0.93 ± 0.37 ml/min per g, p = NS vs. pacing); again, both values were lower (p <0.01) than normal (3.46 ± 0.78 ml/min per g). Dipyridamole flow in collateral-dependent myocardium was slightly lower in patients with poorly developed than in those with well developed collateral channels (0.75 ± 0.29 vs. 1.06 ± 0.38 ml/min per g, respectively, p = 0.06); however, the former showed higher flow inhomogeneity (collateral/control flow ratio 0.58 ± 0.10 vs. 0.81 ± 0.22, respectively, p <0.02). A linear direct correlation was observed between flow reserve of collateral-dependent and remote regions (r = 0.83, p <0.01). Conclusions: Despite rest hypoperfusion, collateral-dependent myocardium maintains a vasodilator reserve that is almost fully utilized during increases in oxygen consumption. A global microvascular disorder might hamper adaptation to chronic coronary occlusion.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine