Anatomic assessment of the left main bifurcation and dynamic bifurcation angles using computed tomography angiography

An understanding of the left main coronary artery (LMCA) anatomy is important for accurate diagnosis and therapy. We aimed to investigate LMCA anatomy via 128-multisliced coronary computed-tomography-angiography (CCTA) in patients with normal LMCA.

A total of 201 CCTA studies were included in this study. Anatomical features of LMCA including cross-sectional areas of the LMCA ostial, LMCA distal, left anterior descending artery (LAD) ostial and left circumflex artery (LCX) ostial, and degree of tapering and LMCA bifurcation angles (BA) in the form of LMCA-LCX BA, LMCA-LAD BA, LAD-LCX BA at end-diastole and end-systole.

The mean age was 55 ± 11; 55.7% of patients were males. Right coronary artery was dominant in 173 (86.1%) patients. Mean LMCA length was 10.0 ± 4.5 mm. The mean values of LMCA ostial, LMCA distal, LAD ostial and LCX ostial areas were 18.2 ± 5.1 mm², 13.2 ± 4.0 mm², 9.0 ± 3.2 mm² and 7.6 ± ± 2.8 mm², respectively. LMCA ostial-distal area, LMCA distal-LAD ostial area and LMCA distal-LCX ostial area ratios were ≥ 1.44 - < 1.69 in 47 (23.4%), 53 (26.4%), 47 (23.4%) patients, respectively, and were ≥ 1.69 - < 1.96 in 19 (9.5%), 24 (11.9%), 40 (19.9%) patients respectively. Systolic motion modifies LMCA BAs; systolic motion begets an increment of LMCA-LAD angle in 72.6% of patients and decrement of LAD-LCX angle in 75.6% of patients. Patients with T-shaped LAD-LCX BA was shown to have significantly longer LMCA, larger LAD ostial area, larger LCX ostial area and higher diastolic-to-systolic range (DSR) of LAD-LCX BA compared to patients with Y-shaped LAD-LCX BA.

LMCA with T-shaped distal BA was found to have significantly longer LMCA, larger LAD ostial area, larger LCX ostial area and higher DSR of distal BA compared to patients with Y-shaped distal BA. These findings may provide useful information for LMCA bifurcation stenting or designing dedicated stents for LMCA.