Chapter 23

INTRODUCTION

Historically, the cardiac venous system has received less attention than its companion, the arterial system. The recent increase in the performance of sophisticated electrophysiologic and interventional cardiac procedures using the cardiac veins has renewed interest in the cardiac venous system.

This chapter provides a general overview of important facets of the cardiac venous system related to its embryologic development, anatomy, physiology, pathophysiology, and clinical significance. Although nomenclature for the cardiac venous system varies slightly across reviews and journal articles,1,2 the more commonly accepted nomenclature has been used in this chapter.

EMBRYOLOGIC DEVELOPMENT

Vessels develop by a process called vasculogenesis, which involves the coalescence of angioblasts into primary vessels. Subsequent branching and growth occur by angiogenesis, a process guided by cues from vascular endothelial and other growth factors.3 The coronary arteries and veins arise from an extensive mesenchymal cell–derived subepicardial capillary plexus in the embryonic heart. This plexus spreads along the anterior interventricular sulcus (AIVS), the atrioventricular sulcus (AVS), and the posterior interventricular sulcus (PIVS); around the bulbous cordis; and finally into the myocardium. Various molecular factors play a role in the differentiation of vessels into arteries and veins.4,5,6,7 The venous side of the subepicardial capillary plexus subsequently grows toward and into the wall of the sinus venosus. The portions of the venous capillary plexus that persist during fetal growth develop into the great cardiac vein (GCV) in the AIVS, the middle cardiac vein (MCV) in the PIVS, and the right and left marginal veins (LMVs) running along the right and left cardiac margins toward the coronary sulcus. The venous side of the capillary plexus appears to form connections with the luminal circulation earlier than the arterial side.8,9,10,11,12

In the fourth week of embryonic life, the heart tube forms a cardiac loop that brings the sinus venosus, a conduit between the veins and atrial cavity, posterior to the atrial cavity (Figure 23-1A). The sinus venosus receives venous blood from the right and left sinus horns and empties into a common atrial cavity through a wide sinuatrial orifice. The sinus horn on each side, in turn, receives venous blood from the vitelline, umbilical, and common cardinal veins (see Figure 23-1A). By the fifth week, the left-sided vitelline and umbilical veins obliterate, reducing the left sinus horn dimensions. The wide sinuatrial orifice shifts rightward from its central position, displacing the sinuatrial orifice toward the developing right atrium (Figure 23-1B). The right sinus horn and its veins enlarge as a result of blood shunting from left to right. The right and left atria also become more distinct. At this stage, the sinus venosus, represented predominantly by the right sinus horn, is the only venous system communication with the right atrium. The sinus venosus subsequently is ...

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