Left (posterior) aortic sinus and left main stem
Aortic sinus
The sinus behind the left aortic cusp gives the left coronary ostium. The left main stem is only 1 to 2 cm long, passes behind the pulmonary trunk and bifurcates into the LAD and circumflex; in about a third it trifurcates with a ramus intermedius.
Detail
- Gives rise to
- Left main stem, then LAD and circumflex (plus ramus intermedius in ~1/3)
- Territory
- Roughly two-thirds of LV myocardium and most of the septum
- Length
- 1 to 2 cm before bifurcation
When it goes wrong
Acute left main occlusion
ST elevation in aVR greater than V1 with widespread ST depression, cardiogenic shock and very high mortality
Left main stenosis of 50% or more on angiography
Indication for revascularisation; CABG remains the default over PCI for complex disease
Practise this structure
1 question in the bank tagged Coronary Circulation.