CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 2, May/June 2023 AFRICA 95 significant proximal LAD stenosis is demonstrated in Table 3. The ROC curve for the LM–LAD angle had an area under the curve (AUC) of 0.747. The cut-off value of 42° of the LM–LAD angle had a sensitivity of 73%, specificity of 70%, positive predictive value of 70% and negative predictive value of 72.2% to predict significant proximal LAD stenosis. The ROC curve of the LAD–LCX angle had an AUC of 0.655. The cut-off value of 68° of the LAD–LCX angle had a sensitivity of 68%, specificity of 62%, positive predictive value of 64.3% and negative predictive value of 66% to predict significant proximal LAD stenosis (Fig. 3). The LM–LAD and LAD–LCX angles and other factors associated with development of significant proximal LAD stenosis [age, diabetes mellitus, left ventricular ejection fraction, LDL-C, total cholesterol and serum creatinine] were evaluated in a multivariate logistic regression analysis. The LM–LAD and LAD–LCX angles were independent factors for the development of significant proximal LAD stenosis. The odds ratio for the LM–LAD angle was 1.094 and 95% CI was 1.053–1.137, with p < 0.001. The odds ratio for the LAD–LCX angle was 0.951 and 95% CI was 0.924–0.978, with p = 0.001 (Table 4). Discussion Wide LM–LAD and LAD–LCX angles cause low wall shear stress, with subsequent progression of LAD atherosclerosis. As the bifurcation angle increased, the blood turbulence increased. Turbulence induced endothelial dysfunction, enhanced adhesion molecule expression, foam cell production and proliferation of smooth muscle cells. All these mechanisms contribute to the progression of coronary plaques in the area near to the bifurcation angle.16,17 The relationship between bifurcation angle and wall shear stress was previously investigated by multi-slice coronary computed tomography. Chaichana et al.18 reported a significant Fig. 2. Spider view of a 57-year-old patient with total occlusion of the proximal LAD (B). The LAD–LCX angle in the spider view was measured at 112.9°. LAD: left anterior descending, LCX: left circumflex artery. Table 1. Patients’ characteristics and laboratory data of the population studied Characteristics pLAD ≥ 50% (n = 100) pLAD < 50% (n = 100) Test of significance p-value Age, years 54.47 ± 11.68 47.30 ± 12.78 t = 4.142 < 0.001 Males, n, % 58 (58) 51 (51) χ2 = 0.988 0.320 Diabetes mellitus, n, % 37 (37) 21 (21) χ2 = 6.217 0.013 Hypertension, n, % 23 (23) 13 (13.0) χ2 = 3.388 0.066 Smoking, n, % 23 (23) 17 (17) χ2 = 1.125 0.289 Dyslipidaemia, n, % 34 (34) 28 (28) χ2 = 0.842 0.359 Creatinine, mg/dl 1.02 ± 0.26 0.89 ± 0.19 t = 3.915 < 0.001 Total cholesterol, mg/dl [mmol/l] 193.50 ± 31.1 [5.01 ± 0.81] 203.24 ± 34.34 [5.26 ± 0.89] t = 2.103 0.037 LDL-C, mg/dl [mmol/l] 127.24 ± 29.67 [3.30 ± 0.77] 136 ± 32.57 [3.52 ± 0.84] t = 1.988 0.048 HDL-C, mg/dl [mmol/l] 38.82 ± 6.91 [1.01 ± 0.18] 38.78 ± 7.89 [1.00 ± 0.20] t = 0.038 0.970 Triglycerides, mg/dl [mmol/l] 138.36 ± 49.45 [1.56 ± 0.56] 145.35 ± 58.69 [1.64 ± 0.66] U = 4476.5 0.201 LVEF, % 53.31 ± 8.83 59.63 ± 6.46 t = 5.777 < 0.001 pLAD: proximal left anterior descending artery, HDL-C: high-density lipoprotein cholesterol, LDL-C: low-density lipoprotein cholesterol, LVEF: left ventricular ejection fraction. Table 2. Bifurcating coronary angles in the two groups studied Angles pLAD ≥ 50% (n = 100) pLAD < 50% (n = 100) Test of significance p-value LM–LAD angle, ° 60.91 ± 25.93 38.91 ± 21.33 U = 2533.5 < 0.001 LAD–LCX angle, ° 84.55 ± 32.98 68.01 ± 28.12 U = 3453.5 < 0.001 Data are described as mean ± SD. LM: left main coronary artery, pLAD: proximal left anterior descending artery, LCX: left circumflex artery. A B Table 3. Validity (AUC, sensitivity, specificity) for the LM–LAD and LAD–LCX angles to predict significant coronary artery stenosis Angles AUC p-value 95% CI Cut off Sensitivity Specificity PPV NPV LM–LAD angle 0.747 < 0.001* 0.677–0.816 > 42 73.0 70.0 70.9 72.2 LAD–LCX angle 0.655 < 0.001* 0.578–0.731 > 68 68.0 62.0 64.3 66.0 AUC: area under a curve, CI: confidence interval, PPV: positive predictive value, NPV: negative predictive value. *Significant as p < 0.05
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