Anatomic and functional significance of the coronary collateral pathways in coronary arterial obstruction.
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Date
2014
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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.
Description
Doctor degree. University of KwaZulu-Natal, Durban.