Bradycardia is associated with development of coronary collateral vessels in humans

Background The development of mature coronary collateral vessels in patient s with obstructive coronary artery disease (CAD) decreases the ischemic myo cardial burden. Chronic bradycardia has been shown to stimulate formation o f collateral vessels in experimental models, Objective To test our hypothesis that CAD patients with bradycardia would h ave 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 obstru ctive CAD. Methods Admission electrocardiograms and rhythm tracings obtained during an giography of all patients presenting to the cardiac catheterization laborat ory were screened from January to October 1997, Angiograms for patients wit h heart rates less than or equal to 50 beats/min were reviewed, An equivale nt 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 rate s less than or equal to 50 beats/min (group and A) controls with heart rate s 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 m ean collateral grades were 1.66 and 0.95 for subjects in groups A and B, re spectively (P < 0.001) CAD patients with bradycardia are more likely (odds ratio 24, 95% confidence interval 5-146) to have angiographic coronary coll aterals than are those with higher heart rates, Conclusion Results of this study demonstrate that there is an association b etween bradycardia and growth of collateral vessels in patients with obstru ctive CAD, Bradycardic agents may be useful for promoting development of co ronary collaterals in patients with atherosclerotic disease. Coron Artery D is 11:467-472 (C) 2000 Lippincott Williams & Wilkins.