Coronary sinus
Venous return
A 2 to 3 cm wide vein in the posterior atrioventricular groove that receives most of the venous drainage of the heart and opens into the right atrium between the inferior vena cava orifice and the tricuspid valve, guarded by the Thebesian valve.
Traced from the start
- Left (posterior) aortic sinus and left main stem
- Left anterior descending (anterior interventricular) artery
- Diagonal branches of the LAD
- Septal perforating branches of the LAD
- Left circumflex artery
- Obtuse marginal branches of the circumflex
- Anterior left ventricular wall and apexAnterior two-thirds of the interventricular septumLateral left ventricular wall
- Right (anterior) aortic sinus
- Right coronary artery
- Posterior descending (posterior interventricular) artery
- Inferior (diaphragmatic) left ventricular wall and posterior third of the septumPosterior (inferobasal) left ventricular wall
- Right (acute) marginal artery
- Right ventricular free wall
- Great cardiac veinMiddle cardiac veinSmall cardiac vein
- Coronary sinus
Detail
- Tributaries
- Great, middle and small cardiac veins, posterior vein of the left ventricle, oblique vein of Marshall
- Opens into
- Right atrium between the IVC opening and the tricuspid orifice (Thebesian valve)
- Oxygen content
- Lowest venous saturation in the body (about 30%): the myocardium extracts 70 to 80% of delivered oxygen at rest
- Consequence
- Extra oxygen demand can be met only by increasing flow (coronary vasodilation, mainly adenosine), not by extracting more
When it goes wrong
Cannulating the coronary sinus from the right atrium
Route for the left ventricular lead in cardiac resynchronisation therapy and for retrograde cardioplegia during bypass surgery
Fixed coronary stenosis with already maximal oxygen extraction
Any rise in demand (exercise, tachycardia, anaemia) causes ischaemia because flow cannot rise and extraction cannot increase
Practise this structure
1 question in the bank tagged Myocardial Oxygen Supply.