Ganesh Athappan MD Ashley Davidoff MD
The nomenclature of the cardiac veins is confounding and it probably stems from the lack of sufficient attention to the anatomy of the cardiac veins in the past. Knowledge of the anatomy of the cardiac veins have become extremely important in recent years since it is imperative in the accurate and safe placement of pacing leads.Additional sources of confusion include the tendency to call the veins of the heart the coronary veins. “Coronary veins” is infrequently used as a general term for the veins of the heart, but none of the veins is specifically named a coronary vein ie there is no such vein as the “left coronary vein”for example. The use of the term “coronary veins” for the heart is therefore discouraged, except for the use of coronary sinus which is universally accepted.
The coronary vein aka the left gastric vein, has also been a source of confusion since it has nothing to do with the heart and is named as such because it is shaped like a crown.
The coronary sinus is the final common pathway of the veins of the heart, It empties into the right atrium at the entrance of the IVC into the heart.
The coronary sinus is formed by three major veins of the heart, the great, middle and small cardiac veins. It is approximately 2.5 cms in length and lies in the atrioventricular groove on the inferior wall of the heart, anterior to the atria, and posterior to the ventricles. It is formed behind the left atrium as a continuation of the great cardiac vein and proceeds right ward to enter the right atrium, covered by muscular fibers of the left atrium.
The coronary sinus enters the right atrium, anterior to the IVC, and just above and posterior to the septal leaflet of the tricuspid valve. Both the coronary sinus, a vein, and the circumflex coronary artery travel in the same direction in the AV groove – a somewhat rare instance in the body.
Courtesy Ashley Davidoff TheCommonVein.net
The Thebesian valve is a fenestrated membrane that is often present at the entrance of the coronary sinus into the right atrium
Tributaries of the Coronary Sinus
The three major tributaries of the coronary sinus are;
a) great cardiac vein that follows the course of the LAD and circumflex territory
b) middle cardiac vein which follows the course of the PDA and its territory
c) small cardiac vein which drains the remaining portions of the RCA territory
The left sided arterial system has two main vessels (LAD and circumflex) and the right has only one named vessel – the right coronary artery. Oddly in the venous system, the left only has one named major vessel – the great cardiac vein and the right has two – middle and small cardiac vein. Additionally bothte left and right systems drain into one common vein – the coronary sinus
Left Sided Venous System of the Heart
The main left sided vein is the great cardiac vein which travels in the atrioventricular groove and it is formed by the anterior interventricular vein which travels with the LAD, and the left marginal vein which travels with the obtuse marginal vein (s)
Great Cardiac Vein
The great cardiac vein begins at the cardiac apex and ascends along the anterior interventricular groove progressing to the base of the ventricles as the anterior inter ventricular vein. At the coronary groove it turns to the left to form the base of the triangle of “Brocq and Mouchet “with the two branches of the left coronary artery; the left anterior descending and the left circumflex arteries. The triangle is traversed by the diagonal branch of the LAD. The great cardiac vein runs along the coronary grove with the left circumflex to reach the posterior surface of the heart where it terminates by opening into the left extremity of the coronary sinus . (This is a rare occurrence of arterial and venous flow in the same direction – in the coronary groove). The opening of the great cardiac vein is guarded by the valve of Vieussens.
The Right Sided Cardiac Veins
The right cardiac venous system drains into the coronary sinus via two major tributaries; the middle cardiac vein and the small cardiac vein. The middle cardiac vein drains the posterior interventricular system (PDA territory) and also the posterior left ventricular veins. The small cardiac vein drains the conal veins, anterior veins of the RV and the right marginal vein. Smaller tributaries of both the right ventricle and right atrium drain directly via Thebesian veins into the RA and RV cavity
Middle cardiac Vein (Posterior interventricular vein)
The middle cardiac vein begins at the cardiac apex and runs upwards in the posterior interventricular groove to reach the right extremity of the coronary sinus. The great cardiac vein and the middle cardiac vein are the two most consistent tributaries of the coronary sinus.
Small Cardiac Vein
The small cardiac vein runs in the coronary groove between the right atrium and ventricle. It drains the posterior surface of the right atrium and ventricle and opens into the right extremity of the coronary sinus. The middle cardiac and small cardiac vein drains most of the RCA territory. The right marginal vein ascends along the right margin of the heart and joins the small cardiac vein in the coronary sulcus, or opens directly into the right atrium.
The endocardium and innermost myocardium are drained by the least cardiac (Thebesian) veins which drain directly into the left atrium and left ventricle. Schuenke
Other Smaller Veins
‘The Posterior Vein of the Left Ventricle courses along the diaphragmatic surface of the left ventricle to the coronary sinus, but may end in the great cardiac vein.
Anterior cardiac veins begin over the anterior surface of the right ventricle cross the coronary groove and end directly in the right atrium or by joining the small cardiac vein.
Smallest cardiac veins or The Thebesian veins are minute vessels that begin in capillary beds of the myocardium and open directly into the chambers of the heart .
The oblique vein of the left atrium (Marshall’s vein) descends obliquely on the back of the left atrium joins the coronary sinus at its left extremity. The vein represents the embryonic remnants of the left SVC.
Clinical considerations :
The coronary sinus enlarges with elevation of the right sided pressures and also with a persistent left sided superior vena cava which enters into the coronary sinus via a patent vein of Marshall
It has as mentioned significance to eletrophysiologists since it the rout that is used to place left ventricular epicardial leads for cardiac resynchronization therapy.
The coronary sinus (CS) has also been used in electrophysiological studies for ablation of the postero-septal and left-sided accessory pathways.
Clinical considerations :
coronary sinus is the site for left ventricular (LV) epicardial lead placement for cardiac resynchronization therapy.
The coronary sinus (CS) has been used in electrophysiological studies for ablation of the postero-septal and left-sided accessory pathways.
Dilatation of the MVA primarily affects its postero-lateral aspect, which is related to the coronary sinus.
The coronary venous anatomy as described has a high degree of variability which makes it unsuitable for electrophysiologists, mandating a segmental approach to coronary venous classification which will be subsequently described in later sections of the heart module .
“Initially described in 1706 by Vieussens and further elaborated by Thebesius in 1708, thebesian veins are small, valveless venous channels that provide direct connections between the coronary arteries or the coronary venous system and the chambers of the heart. They are thought to be more prevalent in the right atrium and the right ventricle. It has been proposed that thebesian veins provide an alternative channel of nutrition to the myocytes under certain conditions.”
Maasarany SE, Ferret CG, Ferth A, Sheppard M, Henein MY. The coronary sinus conduit function . anatomical study . Europace 2005 7(5):475-481
Singh JP, Houser H, Heist EK, Ruskin JN. The Coronary Venous Anatomy A Segmental Approach to Aid Cardiac Resynchronization Therapy. JACC 2005;46(1):68-74