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Bradycardia is associated with development of coronary collateral vessels in humans
S R Patel1, J A Breall, D J Diver
1Institute for Cardiovascular Sciences and the Division of Cardiology, Georgetown University Medical Center, Washington, DC 20007-2197, USA.
Insights
Patients with coronary artery disease (CAD) and bradycardia (slow heart rate) show significantly better coronary collateral vessel development. This suggests bradycardic agents may aid in treating atherosclerotic disease.
Area of Science:
- Cardiology
- Vascular Biology
- Clinical Medicine
Background:
- Obstructive coronary artery disease (CAD) is associated with reduced blood flow to the heart muscle.
- Development of coronary collateral vessels can mitigate the effects of CAD by providing alternative blood supply.
- Chronic bradycardia, a slower than normal heart rate, has been experimentally linked to enhanced collateral vessel formation.
Purpose of the Study:
- To investigate the association between bradycardia and the development of coronary collateral circulation in patients with obstructive CAD.
- To compare collateral vessel formation in CAD patients with slow heart rates versus those with normal heart rates.
Main Methods:
- Retrospective analysis of angiograms and electrocardiograms from patients undergoing cardiac catheterization.
- Inclusion criteria: obstructive CAD (>=70% stenosis), sinus rhythm. Exclusion criteria: acute myocardial infarction, non-sinus rhythms.
- Comparison between a group with heart rates <= 50 beats/min and a control group with heart rates >= 60 beats/min.
Main Results:
- 61 patients were analyzed: 30 with bradycardia (Group A) and 31 controls (Group B).
- A significantly higher proportion of bradycardic patients (97%) had developed collaterals compared to controls (55%, P < 0.005).
- Mean collateral grade was significantly higher in Group A (1.66) than in Group B (0.95, P < 0.001). Bradycardia was associated with a 24-fold increased likelihood of having coronary collaterals.
Conclusions:
- Bradycardia is significantly associated with enhanced coronary collateral vessel development in patients with obstructive CAD.
- These findings suggest that bradycardic agents could be a therapeutic strategy to promote collateral growth in atherosclerotic disease.
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 < or = 50 beats/min were reviewed. An equivalent number of consecutive patients with heart rates > or = 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 < or = 50 beats/min (group A), and 31 controls with heart rates > or = 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.