1. Cardiac Veins: These are a network of veins that drain blood from the heart's muscle (myocardium) back into the right atrium. (1,3)
2. Coronary sinus
   1. Coronary sinus: The coronary sinus is the primary vein of the heart, where the larger veins draining the myocardium empty into. It is situated between the left atrial wall and the ventricular myocardium. It drains into the right atrium.(1,2)
   2. AR Figure 106 – Cardiac veins: Coronary sinus
      1. Great cardiac vein
         1. Great cardiac vein: The great cardiac vein is a major vein that runs within the left atrioventricular groove alongside the left circumflex artery, draining blood from the left ventricular apex, anterior interventricular septum, anterior portions of both ventricles, and part of the left atrium.. (4)
         2. Left marginal vein of heart
            1. Left marginal vein of heart: The left marginal vein drains the lateral and posterior/inferior wall of the left ventricle. (2,4)
         3. Anterior interventricular vein
            1. Anterior interventricular vein: The anterior interventricular vein travels in the anterior interventricular groove with the left anterior descending coronary artery (LAD), draining blood from the left ventricular apex, anterior interventricular septum, anterior portions of both ventricles.(4)
      2. AR Figure 107 – Cardiac veins: Anterior interventricular vein
         1. Oblique vein of left atrium
            1. Oblique vein of left atrium: The oblique vein of the left atrium is a small vessel that collects blood from the inferior wall of the left atrium and typically merges with either the great cardiac vein or the coronary sinus.(4)
      3. Inferior vein of left ventricle
         1. Inferior vein of left ventricle: The inferior vein of the left ventricle is a tributary that drains the inferior wall of the left ventricle. It usually joins the great cardiac vein or the coronary sinus.(1,2,4)
      4. Middle cardiac vein
         1. Middle cardiac vein: This vein ascends with the inferior interventricular artery and drains into the coronary sinus (1,2,4)
      5. Small cardiac vein
         1. Small cardiac vein: This runs alongside the right coronary artery in the right atrioventricular groove and typically drains into the coronary sinus. This vein primarily drains the inferior wall of the right ventricle. (1,2,3)
         2. Right marginal vein of heart
            1. Right marginal vein of heart: The right marginal vein is a vein that runs alongside the right marginal artery, following the lateral wall of the right ventricle. (4)
3. Anterior cardiac veins
   1. AR Figure 108 – Cardiac veins: Anterior cardiac veins
      1. Anterior cardiac veins
         1. Anterior cardiac veins: The anterior cardiac veins are a variable group of veins that drain a significant portion of the right ventricle, and they directly empty into the right atrium above the right atrioventricular groove. (4)