Coronary collateral circulation

Comparison of coronary collateral circulation in diabetic and nondiabetic patients suffering from coronary artery disease

BACKGROUND AND HYPOTHESIS

Although it is well established that diabetes mellitus (DM) induces more severe coronary artery disease (CAD), it is not known whether it contributes to the development of coronary collateral circulation. The present study examines coronary collateral circulation in diabetic and nondiabetic patients with angiographically verified CAD.

METHODS

The study group consisted of 463 diabetic patients (382 men, 81 women) with a mean age of 60.3 +/- 8.8 years, and 227 nondiabetic subjects (159 men, 68 women) with a mean age of 59.2 +/- 9 years. The extension and functional capacity of coronary collateral circulation was assessed according to the Cohen and Rentrop grading system of 0 to III.

RESULTS

We found that diabetic patients had grade III collateral circulation more frequently than nondiabetic subjects (13.2 vs. 8.5%, p < 0.01). This finding was even more pronounced in diabetic men aged < 55 years compared with both nondiabetic men (20 vs. 3.4%, p < 0.001) and diabetic women (20 vs. 2.2%, p < 0.001). Grade III collateral circulation was found to develop mainly at the left anterior descending (LAD) coronary artery and the right coronary artery (RCA), where complete occlusions of coronary arteries usually occur.

CONCLUSIONS

Diabetic patients with CAD develop more extensive coronary collateral circulation than nondiabetic subjects, especially men aged < 55 years. The collateral circulation mainly develops at the LAD and RCA.

Effects of intra-aortic balloon counterpulsation on coronary pressure in patients with stenotic coronary arteries

BACKGROUND

The benefits of intra-aortic balloon pumping (IABP) usage reportedly occur through systolic unloading of the left ventricle and the augmentation of diastolic coronary flow. The aim of this study was to assess the change in intracoronary pressure distal to the coronary stenosis after the IABP by using an intracoronary pressure wire.

METHODS

Hemodynamic variables and intracoronary pressure data were measured in 16 patients requiring IABP for clinical indication (11 vessels with coronary stenosis and 5 normal vessels were enrolled). Coronary pressure was measured directly in each vessel with and without IABP support.

RESULTS

The diastolic aortic pressure during IABP increased compared with that without the IABP (97.9 +/- 11.7 vs 80.3 +/- 10.7 mm Hg, P < .01). The systolic aortic and intracoronary pressure during the IABP decreased (aortic pressure: 83.8 +/- 10.4 vs 95.9 +/- 11.3 mm Hg, P < .01, intracoronary pressure: 67.6 +/- 16.5 vs 76.2 +/- 20.4 mm Hg, P < .01). The diastolic distal coronary pressure (Pd) increased during the IABP in healthy coronary arteries (87.3 +/- 4.8 vs 72.1 +/- 10.3 mm Hg, P < .05). However, Pd in stenotic coronary arteries with the IABP did not increase statistically compared with those without the IABP (44.0 +/- 21.3 vs 42.8 +/- 17.9 mm Hg). There was a significant correlation between the change in Pd after IABP insertion and percent diameter stenosis calculated by quantitative coronary angiography (r2 = 0.51, P < .001).

CONCLUSIONS

In the presence of a critical coronary stenosis, the IABP does not increase the diastolic coronary pressure distal to the stenosis. Thus, the major effect of IABP on high-risk patients with severe coronary stenosis may relate to the reduction of oxygen demand by systolic unloading more than diastolic augmentation of the coronary flow.

The Relationship of Chronic Angiotensin Converting Enzyme Inhibitor Use and Coronary Collateral Vessel Development

BACKGROUND

Angiotensin II induces various growth factors such as vascular endothelial growth factor, platelet-derived growth factor, and fibroblast growth factor, and recent studies suggest that the expression of these growth factors promotes collateral growth. We hypothesized that the blockage of angiotensin II production by ACE inhibitors might interfere with collateral development in patients with coronary occlusion.

METHODS

The study group consisted of 187 patients (114 males, mean ages, 62 +/- 11 years) who had chronic (> 1 month) coronary occlusion (TIMI flow grade < or = 1) in one of 3 epicardial coronary arteries. Collaterals were graded using the Rentrop classification, and the patients were divided into 2 groups according to having good (grade 2 and 3) or poor (grade 0 and 1) collaterals (n = 127 and 60, respectively). Clinical and angiographic characteristics were compared in the 2 groups.

RESULTS

ACE inhibitor use (52% versus 35%, P = 0.04) and the prevalence of diabetes mellitus (DM) (43% versus 27%, P = 0.02) was higher in patients with poor collaterals. Patients with poor collaterals had a higher frequency of circumflex artery (Cx) occlusion, worse wall motion, and lower ejection fraction. In multivariate analysis, ACE inhibitor use (OR: 2.4; 95% CI = 1.23-4.68, P = 0.01) and the occlusion of Cx (OR: 3.3, 95% CI; 1.33-8.12, P = 0.01) were found to be independent predictors for poor collateral development, whereas there was a trend for DM as a predictor for poor collaterals (OR: 1.9, 95% CI = 0.97-3.8, P = 0.06).

CONCLUSION

The findings suggest that ACE inhibitor therapy may contribute to poor collateral development in patients with coronary occlusion.

Clinical contribution of the collateral circulation to myocardial protection

This section describes the clinical evidence for benefit from coronary collateral channels. There is data to suggest the presence of a protective effect in patients sustaining myocardial infarction regardless of whether they receive reperfusion therapy, and whether the collaterals were preformed. The role of pre-infarction angina in stimulating collateral development remains a contentious issue.

Mechanism of Myocardial Microvessel Formation in Cyanotic Congenital Heart Disease

BACKGROUND

Patients with cyanotic congenital heart disease (C-CHD) usually have myocardial thickening and fibrosis, both of which can affect the course of surgical management. Hypoxia and ischemia may stimulate microvessel formation in the myocardium, which may accelerate the myocardial thickening and fibrosis. Whether hyperplasia of microvessels occurs in the myocardium of C-CHD was investigated in this report.

METHODS AND RESULTS

The patients were divided into 2 groups; the C-CHD group (n = 22), and the acyanotic congenital heart disease (A-CHD) group (n = 24). The microvessels and vascular endothelial growth factor (VEGF) mRNA of the myocardium were detected by immunohistochemical staining assay and real-time quantitative reverse transcriptase polymeric chain reaction, respectively. The serum VEGF levels were measured by using enzyme-linked immunosorbent assay. The results were that: (1) the number of microvessels in the myocardium were more in the C-CHD group than in A-CHD group; (2) the serum VEGF levels in the C-CHD group vs the A-CHD group were higher in the preoperative period (p < 0.001), but there was no difference after operation; and (3) VEGF protein and the expression of VEGF mRNA in the myocardium were higher in the C-CHD group than in the A-CHD group (p < 0.01).

CONCLUSIONS

Myocardial microvessels formed in the myocardium of patients with C-CHD, possibly mediated by increasing VEGF levels (for this group of patients).

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 < 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.

Early infarct artery collateral flow does not improve long-term survival following thrombolytic therapy for acute myocardial infarction

It is known that acutely developed collaterals can prevent the onset of acute myocardial infarction (AMI) in the presence of a total coronary occlusion. However, there still is controversy concerning long-term follow-up of coronary collateral circulation to the infarct-related artery. In this study we analyze the prognostic role of collateral flow (degrees 0 to 3) as well as anterograde flow (degrees 0 to 3) in patients with AMI treated with thrombolytic therapy. Four hundred twenty-two patients (median age 57 years, 355 men) with AMI were treated with intravenous streptokinase and followed prospectively for up to 8 years. At the end of the study period, patients with collateral coronary flow 3 (n = 30) and those with flow <3 (n = 392) at in-hospital coronary arteriography had survival rates of 66% and 85%, respectively (p <0.12). Meanwhile, patients with coronary anterograde flow 3 (n = 189) and those with flow <3 (n = 233) had survival rates of 89% and 80%, respectively (p <0.04). By censored regression analysis, a negative correlation was found between coronary collateral flow degree and survival (p = 0.0498) and, inversely, a positive correlation was found between coronary anterograde flow degree and survival (p = 0.0053). By Cox multivariate analysis, the following variables showed significant correlations with long-term survival: global left ventricular ejection fraction (p = 0.0003), anterograde flow degree (p = 0.0006), collateral flow degree (negative correlation, p = 0.0179), and medical treatment (negative correlation, p = 0.0464). Thus, patients treated with intravenous streptokinase during AMI and with adequate coronary collateral circulation had a worse prognosis than those who developed adequate anterograde flow, probably because of residual myocardial ischemia. Such patients may benefit from coronary revascularization (angioplasty or surgery) to restore anterograde blood flow and minimize myocardium at risk.

Impact of intensive physical exercise and low-fat diet on collateral vessel formation in stable angina pectoris and angiographically confirmed coronary artery disease

This randomized study was performed to assess the effects of > 3 hours of physical exercise per week and low-fat diet on collateral formation in nonselected patients with coronary artery disease (intervention group, n = 56). Results were compared with those of patients in a control group (n = 57), who received usual care by their private physicians. Coronary lesions were assessed by quantitative coronary angiography at the beginning and after 1 year of study (n = 92). As previously reported, after 1 year there was a significant retardation of progression of coronary artery disease in the intervention group as compared with the control group. In this study, evaluation of collateral formation revealed no significant difference between both groups, and changes in hemodynamic and metabolic variables or leisure time physical activity were not related to changes in collateral formation. Although progression of the disease was significantly related to an increase in collateral formation, regression was significantly related to a decrease in collateral formation (p < 0.00001). Because patients in the intervention group exercised for > 3 hours/week, and patients with regression of coronary artery disease even dedicated 5 to 6 hours to leisure time physical activity per week, these findings question whether an exercise program within the safety tolerance of patients will be able to induce coronary collateralization in the presence of regression of coronary artery disease.

Interventional physiology. Part XVIII: Influence of intra-aortic balloon counterpulsation and collateral flow reversal during multivessel angioplasty

Flow velocity changes during multivessel angioplasty suggests that collateral flow has an important role in determining safety and ischemic threshold during these procedures. The physiology of collateral flow with and without intra-aortic balloon pumping has been demonstrated in this individual and provides insight into the mechanisms of reduced ischemia during high-risk coronary interventions.