Anatomic and functional significance of the coronary collateral pathways in coronary arterial obstruction.

Abstract

Coronary artery disease is a major cause of morbidity and mortality globally, and it is becoming an epidemic in developed as well as developing countries. In South Africa and the rest of sub-Saharan Africa, cardiovascular disease is an increasing cause of death and disability. An important cause of morbidity and mortality is the formation and rupture of atherosclerotic plaque with resultant occlusion of large and medium size arteries. In severe obstructive coronary artery disease, coronary collateral arteries serve as alternative conduits for blood flow to the myocardial tissue supplied by the obstructed vessel(s). The confirmation of the presence of coronary collateral circulation has left several questions such as the distribution, histology and anatomy of these vessels unanswered. Hence, there is still much to understand in respect of the development, potential for manipulation and the haemodynamic effects of the collateral pathways. The most extensive description of the pathways of the coronary collateral arteries to date was reported by Levin in 1974 who recorded 22 pathways. Since this compilation, it is apparent that there has been no additional study elucidating the pathways of coronary collateral arteries in severe obstruction of the major coronary arteries. Currently, the classification of the coronary collateral arterial vasculature is based on several methods and has led to difficulty in scientific communication, as well as the assessment of their structure and function. Therefore, there is the need for a standardized systematic classification of the coronary collateral pathways.

In routine coronary angiographic reports, the precise location of atherosclerotic lesions and the presence or absence of coronary collaterals is not usually indicated. The aim of this study was to document and classify the coronary collateral pathways using angiographic imaging techniques in the presence of total obstruction of the coronary arteries; and to evaluate the importance of coronary collaterals on left ventricular function. The study group was selected from the reviewed angiographic records of 2029 consecutive patients that had coronary catheterization performed by interventional Cardiologists for symptoms suggestive of coronary artery disease. The coronary angiograms of 286 patients (mean age: 59 ± 11 years) that met the inclusion criteria were selected for analysis from the angiograms reviewed. The sex distribution of these patients was 21.7% (62/286) females and 78.3% (224/286) males. The angiograms were obtained from the cardiac catheterization laboratories of hospitals within the private sector in the eThekwini Municipality region of KwaZulu-Natal, South Africa. Ethical approval (Ethics number BE 196/13) for the study was obtained from the University of KwaZulu- Natal Biomedical Research Ethics Committee. A total of 329 coronary arterial total obstructions were recorded in the angiograms analyzed, and these obstructions were found in the main coronary arteries as follows: anterior interventricular branch -76 obstructions, circumflex branch -87 obstructions and right coronary artery (RCA) -166 obstructions. In the obstruction of the different segments of the main coronary arteries, a total of 115 different collateral pathways were observed as follows: anterior interventricular branch - 32, circumflex branch – 46 and RCA- 37. An algorithm is proposed in the present study for identifying and labelling the coronary collateral pathways.

The richest collateral supply was to the RCA and the least was to the circumflex branch. The present study found no significant association between patients’ age and sex and the development of excellent or well-functioning collaterals. There was a significant association between the development of excellent collaterals and the proximal location of lesion in the RCA. In addition, a significant association was found between right coronary arterial dominant pattern and the development of excellent coronary collaterals in circumflex branch and RCA obstructions. There was a significant difference (p < 0.001) in the mean ejection fraction (EF) calculated for the different grades of coronary collaterals. Thus, the development of excellent collaterals has a significant supportive effect on the preservation of left ventricular function as compared to patients with absent or poor collateralization. There was also a significant positive correlation between coronary collateral grades and mean EF calculated for the different collateral grades. Consequently, left ventricular myocardial perfusion was greater in patients with well-developed coronary collaterals and resulted in a better recovery of left ventricular function in the presence of myocardial ischemia or infarction. The presence of well-developed collaterals may influence decision making in the management of patients with coronary arterial obstruction. In the presence of an adequately preserved left ventricular function by coronary collaterals in asymptomatic patients, there may be no need for coronary angioplasty, stent insertion or surgical intervention.