A thorough knowledge of the anatomy of the heart is a prerequisite for the successful completion of the myriad procedures performed by the cardiothoracic surgeon. This chapter describes the normal anatomy of the heart, including its position and relationship to other thoracic organs. It also describes the incisions used to expose the heart for various operations and discusses in detail the cardiac chambers and valves, coronary arteries and veins, and the important but surgically invisible conduction tissues.
Location of the Heart Relative to Surrounding Structures
The overall shape of the heart is that of a three-sided pyramid located in the middle mediastinum (Fig. 2-1). When viewed from the heart’s apex, the three sides of the ventricular mass are readily apparent (Fig. 2-2). Two of the edges are named. The acute margin lies inferiorly and describes a sharp angle between the sternocostal and diaphragmatic surfaces. The obtuse margin lies superiorly and is much more diffuse. The posterior margin is unnamed but is also diffuse in its transition.
This diagram shows the heart within the middle mediastinum with the patient supine on the operating table. The long axis lies parallel to the interventricular septum, whereas the short axis is perpendicular to the long axis at the level of the atrioventricular valves.
This diagram shows the surfaces and margins of the heart as viewed anteriorly with the patient supine on the operating table (left) and as viewed from the cardiac apex (right).
One-third of the cardiac mass lies to the right of the midline and two-thirds to the left. The long axis of the heart is oriented from the left epigastrium to the right shoulder. The short axis, which corresponds to the plane of the atrioventricular groove, is oblique and is oriented closer to the vertical than the horizontal plane (see Fig. 2-1).
Anteriorly, the heart is covered by the sternum and the costal cartilages of the third, fourth, and fifth ribs. The lungs contact the lateral surfaces of the heart, whereas the heart abuts onto the pulmonary hila posteriorly. The right lung overlies the right surface of the heart and reaches to the midline. In contrast, the left lung retracts from the midline in the area of the cardiac notch. The heart has an extensive diaphragmatic surface inferiorly. Posteriorly, the heart lies on the esophagus and the tracheal bifurcation and bronchi that extend into the lung. The sternum lies anteriorly and provides rigid protection to the heart during blunt trauma and is aided by the cushioning effects of the lungs.
The Pericardium and Its Reflections