Bradycardia is associated with development of coronary collateral vessels in humans

Background The development of mature coronary collateral vessels in patients with obstructive coronary artery disease (CAD) decreases the ischemic myocardial burden. Chronic bradycardia has been shown to stimulate formation of collateral vessels in experimental models, Objective To test our hypothesis that CAD patients with bradycardia would have better developed collateral circulation than would members of a control group, Design A retrospective study examining the relationship between bradycardia and the development of coronary collateral vessels in patients with obstructive CAD. Methods Admission electrocardiograms and rhythm tracings obtained during angiography of all patients presenting to the cardiac catheterization laboratory were screened from January to October 1997, Angiograms for patients with heart rates less than or equal to 50 beats/min were reviewed, An equivalent number of consecutive patients with heart rates greater than or equal to 60 beats/min served as controls. Patients with acute myocardial infarction, with rhythms other than sinus, and without high grade obstructive CAD (< 70% stenosis) were excluded from the study. Results The study population consisted of 61 patients, 30 having heart rates less than or equal to 50 beats/min (group and A) controls with heart rates greater than or equal to 60 beats/min (group B), A significantly greater proportion of patients in group A than of matched controls was demonstrated to have developed collaterals (97 versus 55% in group B, P < 0.005), The mean collateral grades were 1.66 and 0.95 for subjects in groups A and B, respectively (P < 0.001) CAD patients with bradycardia are more likely (odds ratio 24, 95% confidence interval 5-146) to have angiographic coronary collaterals than are those with higher heart rates, Conclusion Results of this study demonstrate that there is an association between bradycardia and growth of collateral vessels in patients with obstructive CAD, Bradycardic agents may be useful for promoting development of coronary collaterals in patients with atherosclerotic disease. Coron Artery Dis 11:467-472 (C) 2000 Lippincott Williams & Wilkins.