Table 2.

Study characteristics, strengths, limitations, and findings.

Reference	Country of Origin	Study Aim	Sample Size	Study Design	Strengths	Limitations	Key Findings
Chaichana et al. [11] (2011)	Australia	To investigate the haemodynamic effect of variable LAD-LCx angulation using realistic and simulated LAD-LCx models.	12 models	Descriptive	Realistic modelling derived from CCTA datasets of real patients Wall shear stress gradient (WSSG) analysed Relatively large sample size for CFD study Analysed several different angle sizes	Simulations assumed a rigid arterial wall Incorporated a Newtonian fluid model Did not account for pathological changes	Regions of low wall shear stress (WSS) corresponded to regions of low flow velocity Reduced wall pressure, WSS and flow velocity was observed at the bifurcation sites of all models Models with wide LAD-LCx angles demonstrated reduced WSS and WSSG at the bifurcation site compared to those with narrow angles Wall pressure in the LAD and LCx arteries was higher in models with a wider LAD-LCx angle, than those with a narrow angle
Cui et al. [8] (2017)	China	To evaluate the value of LAD-LCx angles and plaque characteristics as predictors of coronary stenosis by dual-source computed tomography.	106 patients	Causal-comparative	LAD-LCx angles were measured on CCTA Degree of coronary stenosis was determined by ICA Explored relationships between LAD-LCx angle and degree of coronary stenosis	Single-centre study Authors state “more participants are required to verify [their] results,” but do not discuss the extent to which their study was limited by their sample size Did not explore relationships between CAD risk factors and LAD-LCx angle, despite collecting this demographical data	Wide LAD-LCx angle was associated with significant left coronary stenosis and non-calcified plaques LAD-LCx angle was significantly wider in patients with ≥50% left coronary stenosis, than those with <50% left coronary stenosis LAD-LCx angle of 78° was calculated as a cut-off value for predicting significant left coronary stenosis
Juan et al. [7] (2017)	Taiwan	To understand the relationship between LAD-LCx angle and CAD in patients with normal, non-significantly and significantly stenosed left coronary arteries.	313 patients	Causal-comparative	LAD-LCx angles were measured on CCTA Explored relationships between LAD-LCx angle and several CAD risk factors Cross tabulated LAD-LCx with multiple variables via logistic regression Relatively large overall sample size Degree of coronary stenosis was determined by ICA	Study validity may have been affected by the small size of group III compared to groups I and II A proportion of the CCTA datasets were of lower quality than the remainder of the sample, which may have affected angle measurements	LAD-LCx angle was significantly wider in patients with ≥50% coronary stenosis than those with normal coronary arteries LAD-LCx angle of 80° was calculated as a cut-off value for predicting left coronary stenosis Males and patients with high body mass index (BMI) were significantly more likely to have a LAD-LCx angle > 80°, compared to females and patients with low BMI, respectively
Kamangar et al. [18] (2020)	Saudi Arabia, India and Oman	To compare the effect of bifurcation angle on haemodynamic parameters in the left coronary artery with 80% stenosis.	4 models	Descriptive	Analysed the haemodynamics of stenotic bifurcations Incorporated a non-Newtonian fluid model	Sample consisted of simulated models only Simulations assumed a rigid arterial wall Only investigated haemodynamics of 80% stenosed vessels Very few angles were studied	Wall pressure at the stenotic region was significantly reduced with wide LAD-LCx angle, compared to narrow LAD-LCx angle Flow velocity at the stenotic region increased with LAD-LCx angle WSS at the area of stenosis in models with wide LAD-LCx angle was higher than in those with narrow angles High WSS was observed at the stenotic region in all models
Liu et al. [9] (2019)	China	To investigate the effect of different bifurcation angles on the left coronary artery.	4 models	Descriptive	Used one realistic model derived from the CCTA dataset of a real patient	Simulations assumed a rigid arterial wall Incorporated a Newtonian fluid model Very few angles were studied	Models with wide LAD-LCx angles demonstrated reduced WSS at the bifurcation site compared to those with narrow angles The angle between the left main coronary artery and the LAD artery (LM-LAD angle) influences WSS Models with a narrow left main-LAD (LM-LAD) angle demonstrated greater WSS at the bifurcation site than those with wide LM-LAD angle
Moon et al. [15] (2018)	South Korea	To evaluate the associations between the left main-LAD and LAD-LCx angles, and LAD stenosis.	201 patients	Causal-comparative	LAD-LCx angles were measured on CCTA Relatively large sample size	Unclear whether group with ≤50% stenosis included patients without CAD Degree of coronary stenosis was measured on CCTA Calculated LAD-LCx cut-off value for predicting CAD lower than several other studies	LAD-LCx angle was significantly wider amongst patients with ≥50% stenosis, compared to those with ≤50% stenosis LAD-LCx angle of 60° was calculated as a cut-off value for predicting left coronary stenosis LM-LAD angle was significantly wider amongst patients with CAD, compared to those without CAD
Rodriguez-Granillo et al. [17] (2007)	Argentina	To explore plaque burden at different segments of the left main bifurcation and its relationship with bifurcation angle using high-resolution multislice CT coronary angiography.	50 patients	Causal-comparative	LAD-LCx angles were measured on CCTA	Relatively small sample size Degree of coronary stenosis was not considered	Wide LAD-LCx angle was closely related to the presence of plaques within the left coronary artery bifurcation
Sun [16] (2013)	Australia	To investigate the relationship between intraluminal appearances of coronary plaques and left coronary bifurcation angle and plaque components using coronary CT virtual intravascular endoscopy (VIE).	50 patients	Causal-comparative	LAD-LCx angles were measured on CCTA Explored possible relationships between LAD-LCx angle and intraluminal appearances	Degree of coronary stenosis was not considered CCTA datasets were acquired on three different CT machines with three different imaging protocols Relatively small sample size	LAD-LCx angle was significantly wider amongst patients with left CAD, compared to those with a normal left coronary artery The mean diameters of LAD and LCx in patients with left coronary disease and a LAD-LCx angle > 80° were significantly larger than those with left coronary disease and a LAD-LCx angle < 80°
Sun & Cao [6] (2011)	Australia	To investigate the relationship between left coronary bifurcation and dimensional changes and development of CAD using CT angiography.	30 patients	Causal-comparative	LAD-LCx angles were measured on CCTA Findings are supported by several other studies Valid statistical tests were conducted	Degree of coronary stenosis was not considered Relatively small sample size	LAD-LCx angle was significantly wider amongst patients with left CAD, compared to those without left CAD 89% of patients with both LAD and LCx disease had a bifurcation angle > 90%
Sun & Chaichana [10] (2017)	Australia	To investigate the correlation between LAD-LCx angle and coronary stenosis, as assessed via CCTA-generated CFD analysis.	30 models	Descriptive	Realistic modelling derived from CCTA datasets of real patients Degree of coronary stenosis was determined by ICA Relatively large sample size for a CFD study	Simulations assumed a rigid arterial wall Incorporated a Newtonian fluid model Authors do not provide their definition for ‘significant coronary stenosis’ Number of cases with significant coronary stenosis was small Study focused on calcified plaques	Increased WSS was observed in the LAD and LCx arteries of models with significant coronary stenosis and a LAD-LCx angle > 80° Wall pressure decreased at stenotic regions in patients with wide LAD-LCx angles Flow velocity increased at post-stenotic regions in the LAD and LCx arteries with significant stenosis LAD-LCx angle of 80° was calculated as a cut-off value for predicting significant left coronary stenosis
Temov & Sun [4] (2016)	Australia	To explore the association between LAD-LCx angle and common atherosclerotic risk factors with regard to CAD development using CCTA.	196 patients	Causal-comparative	LAD-LCx angles were measured on CCTA Relatively large sample size Explored relationships between LAD-LCx angle and several CAD risk factors	Degree of coronary stenosis was not considered Multivariate analysis was not conducted	Males were significantly more likely to have a LAD-LCx angle > 80°, compared to females Patients with a BMI > 25 kg/m2 were significantly more likely to have a LAD-LCx angle > 80°, compared to those with a BMI < 25 kg/m2
Zhang et al. [12] (2016)	China	To determine whether there is a relationship between bifurcated arterial geometry and haemodynamics.	7 models	Descriptive	Wall pressure gradient (WPG) was analysed in addition to WSS	The sample consisted of simulated models only Simulations assumed a rigid arterial wall Incorporated a Newtonian fluid model	Models with wide LAD-LCx angle had larger low WSS regions, compared to those with narrow LAD-LCx angle Models with wide LAD-LCx angle demonstrated smaller regions of low WPG at the bifurcation site, compared to models with narrow LAD-LCx angle
Ziyrek et al. [19] (2020)	Turkey	To analyse the effect of coronary bifurcation angle and left main coronary artery length on atherosclerotic lesion localisation.	467 patients	Causal-comparative Correlational	LAD-LCx angles were measured on ICA Relatively large sample size Degree of coronary stenosis was determined by ICA Performed correlational analysis	Number of patients with significant ≥50% coronary stenosis was small Focused only on plaques located in close proximity to the LCA bifurcation site	LAD-LCx angle of 80.5° was calculated as a cut-off value for predicting atherosclerotic lesion/s located ≤5 mm from the bifurcation site Wide LAD-LCx angle was strongly correlated with lesions located closer to the LCA bifurcation site LAD-LCx angle was significantly wider amongst males, compared to females

BMI—body mass index, CAD—coronary artery disease, CCTA—coronary computed tomography angiography, CFD—computational fluid dynamics, ICA—invasive coronary angiography, LAD—left anterior descending, LCA-left coronary artery, LCx—left circumflex, WSS—wall shear stress, WSG—wall pressure gradient.