Coronary circulation

Coronary circulation

Coronary circulation is the blood supply of the heart. The left and right coronary arteries arise from the sinuses of Valsalva at the aortic root. The left main coronary artery (LMCA) divides soon after formation into left anterior descending (LAD) and left circumflex (LCx) coronary arteries. The LAD courses down in the anterior interventricular groove gives rises to multiple septal branches to the interventricular septum and diagonal branches to the lateral wall of the left ventricle. LCx runs in the atrioventricular groove and gives off obtuse marginal branches to the left ventricle. Right coronary artery (RCA) runs in the right part of the atrioventricular (AV) groove and gives off the sinus node artery and right ventricular branches. When it reaches the junction of the interatrial, atrioventricular and interventricular grooves (crux of the heart), it divides into the posterior descending artery (PDA) and posterior left ventricular (PLV) branches. PDA runs in the posterior interventricular groove and supplies the posterior one third of the interventricular septum. In this description, it is the RCA which crosses the crux of the heart and it is called the right dominant system. If it is the LCx which crosses to the opposite side, then it is called the left dominant system. PDA and PLV branches arise from the LCx in a left dominant system. In a co-dominant system, PLV comes from the LCx and PDA from the RCA. The atrioventricular nodal (AV node) artery usually arises from the right coronary artery.

The LAD can be three types depending on its distribution:

1. Type 1: Stops short of the apex
2. Type 2: Reaches up to the apex
3. Type 3: Wraps around the apex

It may be noted that in both left dominant system and right dominant system, major portion of the left ventricular myocardium is always supplied by the left coronary artery.

Important coronary veins are the lateral veins, great cardiac vein, anterior interventricular vein and oblique vein of left atrium (Marshall’s). Cardiac veins drain into the coronary sinus, which empties into the right atrium.

Left coronary angiogram showing its branches (see text for abbreviations).

Right  coronary angiogram showing its branches (see text for abbreviations).