The heart is supplied significantly with the LCA, and its pathogenesis strongly predicts mortality in patients with atherosclerosis. 23,24 Kalbfleisch and Hort, 25 who led an investigation on the region supplied by the coronary arteries using postmortem angiography, revealed that the LCA irrigated 68.8% of the cardiac muscle mass and 79% of the left ventricular cardiac muscle mass. As a result, ischemic disease of LCA may limit the coronary flow to a substantial area of the ventricular myocardium, making atherosclerotic disease of LCA more harmful than that of RCA. 8 The morphology of LCA varies markedly in terms of length, diameter, and the number of branches from its main stem, resulting in significant differences in values among authors in the literature (Table 3).
The length of the LMCA is significant in cardiac revascularization procedures and coronariographies because catheter placement becomes more challenging when the LMCA length is decreased. 2,20,26 The length of the LMCA trunk is typically about 5–15 mm, while data published by numerous authors reveals considerable variability in results depending on the approach used. Short and long LMCA trunks were thus categorized as length variants.
Banchi 27 found that the length of the LMCA trunk was < 5 mm in 2% of specimens. Reig et al. 26 reported that the LMCA trunk in 7.4% of their cases was ≤ 5 mm in length. Candir et al. 23 observed that the length of the LMCA trunk was < 5 mm in 6.5% of the cases, while Mamatha Hosapatna et al. 28 reported that 10% of their specimens had an LMCA trunk length of < 5 mm. 9.06% of specimens had a short LMCA trunk (< 5 mm) in Deepa Diwan's study, 1 whereas 0.Pereira da costa et al. 2 found 15.8% of the specimens with short LMCA i.e. (< 5 mm). Only 10.7% of the cases in our research were presented with the LMCA trunk length < 5 mm (Table 1, 3).
A short LMCA trunk has been considered a risk factor for the development of coronary artery disease. 29 This is because during systole, a certain degree of bending or kinking of the terminal branches, which increases the mechanical strain exerted on its walls, causes more arteriosclerotic deterioration. A short main trunk is also assumed to be a risk factor in coronary perfusion during surgical procedures like aortic valve replacement. 1,22 In this situation, the catheter might be placed into one of the terminal branches, causing ischemia in the terminal branch, which may result in ventricular arrhythmia, myocardial infarction, or both. Moreover, a short trunk length may make coronary angiography more challenging because when the catheter is inserted into one of the terminal branches, the other branch is not opacified, resulting in an incomplete view of the coronary tree. 28 Lewis et al. discovered a short common trunk as the cause of obstruction in the bundle of His' left branch11. Gazetopoulos et al. 30 performed a post-mortem examination to investigate the relationship between the length of the main coronary artery and the degree of atherosclerosis in its branches. They found that in cases with a short LMCA, atherosclerotic plaques in the LAD and LCx branches emerged sooner, developed rapidly at greater levels of severity, and led to myocardial infarction more commonly than in cases with a long LMCA. 29
A long LMCA indirectly preserves the first segment of the LAD artery against atherosclerosis by reducing its flexible part and hence its tendency to bend during systole. 30 We found 8.9% of cases of LMCA in our study, which is comparable to the observation found in earlier studies that showed a long common trunk is present in between 3.3% and 42.8% of cases (Table 3). There is no documented relationship between a long LMCA and pathologies or complications in cardiac surgery.
The knowledge of the prevalence of LCA and its branches is substantial for accurately estimating the precise extent of an infarct in ischemic heart disease, hemodynamic and surgical manipulation afterward, as well as for the accurate assessment of angiographic data. 31
The most common branching pattern is the bifurcation of LMCA into the LAD and LCx. The MA, on the other hand, can appear and cause trifurcation, quadrifurcation, and pentafurcation. 2,6,8 A median artery commences at the vertex of the angle created by the primary terminal arteries of the left coronary artery, has a substantial caliber, and extends halfway down the free wall of the left ventricle.1 In atherosclerosis, occlusion of the median artery can be just as hazardous as occlusion of the LAD or LCx. Identification of this atypical branching pattern is critical because it has the potential to supply a considerable region of the myocardium; and because it can provide a major source of collateral circulation in the event of obstruction of the LAD or LCX. 32
The branching pattern of LMCA has been well-documented in the literature. Banchi described the termination of LMCA with the most common (64%) being bifurcation. The possibility of the LMCA trunk dividing into three or four branches (31% and 5%, respectively) was also noted in the study. 33 Reig et al. observed that in 62% of the specimens, LMCA was divided into 2 branches as bifurcation, while 38% of the specimens had trifurcation. 8 Mamatha Hosapatna reported 93.3% of cases with bifurcation, whereas 6.7% had trifurcation. 28 Deepa Diwan et al. observed 84% of specimens with bifurcation and 6% with trifurcation. 1 A study by O.Pereira da Costa et al. found that 39.6% of specimens had bifurcation, 52.2% with the trifurcation, and 7.94% had tetrafurcation. 2
In the present study, about 71.1% of the cases had a bifurcation of the LMCA trunk, while the remaining 25.1%, 2.7%, and 0.4% were found to have trifurcation, tetrafurcation, and pentafurcation, respectively (Table 3).
With regard to the lumen diameter of the LMCA trunk, it has been suggested that the lumen diameter alongside the length of a vessel plays an essential role in describing the coronary vascular network quantitatively.34 The average diameter of left main coronary artery in our study was observed to be 4.69 ± 0.74 mm. This measurement was not significantly different between males and females (Table 1). J.Theodore et al. and Reig et al. investigated the main trunk of LMCA with average lumen diameters of 4.6 ± 0.5mm and 4.86 ± 0.80mm, respectively. 8,35
Concerning the dominance pattern of the heart which is demarcated by the posterior interventricular artery has an essential clinical significance. Left dominance was shown to have a considerably higher fatality rate than right dominance and co-dominance. 36 Dominance also contributed to LAD artery stenosis. A left-dominant heart would benefit more from LAD lesions therapeutically than a right-dominant one. 37 In the current study, there was right cardiac dominance in 89.3%, left in 5.2%, and co-dominance in 5.5% of the cases (Table 1). Multiple authors have also documented the dominance ratios as 83–85% right, 6–8% left, and 5–7% cases as co-dominant. 38–41
The published data from many researches reveals some discrepancies in outcomes. This might be due to differences in technique and case numbers (most studies were conducted on a few cases of cadavers), or it could be related to geographical or genetic variances. In the present study, the sample data was huge that were examined using 3D images derived from multi-detector CT, hence providing an excellent anatomic characterization of the course and variability of the coronary vessels.
However, we could not find any significant association between the length of LMCA and coronary dominance in our study. As well, the other variables of interest like age, sex, and the diameter of LMCA were also found to have no significant association with the length of LMCA. This study has shown that there is a substantial correlation between the LMCA trunk length and its branching pattern. The percentage of bifurcation declined as the length of LMCA grew, but the ratio of trifurcation, tetrafurcation, and pentafurcation rose, P < 0.05 (Table 2).
One possible limitation of this study was that the subjects were selected from patients who had some prevalence of coronary artery disease or stent placements and were referred to our hospital rather than healthy volunteers. As a result, the observers may have been biased in spotting deformities.