Functional Anatomy Of The Heart

Authors: Joseph F. Malouf, William D. Edwards, A. Jamil Tajik, James B. Seward BACKGROUND

The study of the heart and great vessels has come a long way since the days of Andreas Vesalius, the great 16th-century anatomist who recognized the impact of anatomy on the practice of medicine.! During the European Renaissance, the tomographic approach to the study of cardiac anatomy became popular because of its artistic-based correlations. This is vividly depicted in the drawings of Leonardo da Vinci2 (Fig. 2-1), who was called the first comparative anatomist since Aristotle. During the ensuing nearly four hundred years, however, interest in cardiac anatomy was very sporadic and limited to a few zealous and pioneering physicians, anatomists, and artists.

Anatomy The Heart Has Four Chambers
Figure 2-1: Four-chamber tomographic section of the heart as illustrated by Leonardo da Vinci. Note the thin-walled right ventricle and thick-walled left ventricle and detailed anatomic

connections. (From O'Malley and Saunders,2 with permission.)

The 19th century ushered in the era of anatomic dissection for the study of physiologic and pathophysiologic processes. Virchow in 1885 described the inñow-outñowmethod of cardiac dissection that followed the direction of blood flow.3 It was quick and simple and became the dissection method of choice. The works of Virchow and Osler paved the way to understanding the pathophysiologic basis of such diseases as pulmonary embolism, endocarditis, and heart failure.4 Renewed interest in the study of cardiac anatomy and pathology was facilitated by the rise in autopsy rates in Europe and North America during the first half of the 20th century.5 Herrick described the clinical features of coronary thrombosis.5 Later, Blumgart, Schlesinger, and Zoll advanced our understanding of coronary artery disease through elegant clinicopathologic correlations.5

These achievements notwithstanding, however, they were limited to postmortem examinations. The advent of cardiac surgery in the 1950s, followed by coronary angiography, was a major impetus for promoting the study of in vivo clinicopathologic anatomic correlations. While cardiac surgeons were quick to appreciate the importance of having a detailed understanding of cardiac anatomy, clinical cardiologists were more interested in pathophysiology. However, with the introduction of noninvasive imaging techniques [echocardiography, computed tomography (CT), magnetic resonance imaging (MRI), and single-photon-emission computed tomography (SPECT)] over the past two decades, the perception of cardiac anatomy and pathophysiology radically changed for all of medicine in general and cardiology in particular.

With increasing use of tomographic techniques in the diagnosis and management of cardiovascular diseases, there has been a corresponding decrease in the use of autopsy for anatomic correlations. The reasons for this decrease are complex and controversial and include an increased confidence in technology, lack of reimbursement for the cost of autopsy, and rescinding the mandate for autopsies for hospital accreditation.4 Nonetheless, autopsy still uncovers unexpected processes in about 15 percent of cases and is an invaluable tool for quality assurance programs.

Today, at the beginning of the 21st century, there is a resurgence in the clinicopathologic correlative approach to cardiovascular morphology. In particular, the tomographic presentation of cardiac structure, which had remained dormant for over a century, has become relevant because the diagnostic techniques used today are tomographic in nature.6 The specialties associated with cardiovascular diseases have been quick to embrace these newer anatomic presentations. Echocardiography was brought into the operating room, and with the advent of transesophageal echocardiography, the cardiologist became an indispensable member of the surgical team.7,8 Because of increasingly more sophisticated cardiac surgical techniques, coupled with closer interaction between the cardiac surgeon and the noninvasive cardiologist, there has been a growing demand for precise diagnostic tools with greater spatial and temporal resolution to guide the planning of surgical procedures and, therefore, to ensure their success.7,8

The interest in cardiac anatomy among cardiologists is by no means limited to those involved in imaging the heart. Over the past few years, there has been an explosion of interest in anatomically guided electrophysiologic mapping and ablation techniques, which are increasingly guided by intracardiac ultrasound.9-13 It has thus become feasible to accurately pinpoint the anatomic location of the source of many arrhythmias9-13 (Figs. 2-2 and 2-3). By providing the electrophysiologist with a real-time visual "road map," the "search and destroy" mission during an ablation procedure will be made much easier and results, as well as complications, recognized immediately.9-13 By providing a new window to the heart, real-time anatomic-electrophysiologic correlations also may help to enhance our understanding of the mechanisms of propagation of various arrhythmias.

Right Atrium Anatomy Echocardiography

Figure 2-2: Anatomic considerations in the treatment of supraventricular arrhythmias. AV, atrioventricular; Ao, ascending aorta; IVC, inferior vena cava; LV, left ventricle; PT, pulmonary trunk; RA, right atrium; RV, right ventricle; SVC, superior vena cava. (Courtesy of Dr. Douglas L Packer, Mayo Clinic, Rochester, Minnesota.)

Figure 2-2: Anatomic considerations in the treatment of supraventricular arrhythmias. AV, atrioventricular; Ao, ascending aorta; IVC, inferior vena cava; LV, left ventricle; PT, pulmonary trunk; RA, right atrium; RV, right ventricle; SVC, superior vena cava. (Courtesy of Dr. Douglas L Packer, Mayo Clinic, Rochester, Minnesota.)

Inferior Coronary Artery

Figure 2-3: Anatomic considerations in the treatment of ventricular arrhythmias. LV, left ventricle; LA, left atrium; MI, myocardial infarction; VT, ventricular tachycardia; VF, ventricular fibrillation; other abbreviations as in Fig 2-2. (Courtesy of Dr. Douglas L Packer, Mayo Clinic, Rochester, Minnesota.)

Figure 2-3: Anatomic considerations in the treatment of ventricular arrhythmias. LV, left ventricle; LA, left atrium; MI, myocardial infarction; VT, ventricular tachycardia; VF, ventricular fibrillation; other abbreviations as in Fig 2-2. (Courtesy of Dr. Douglas L Packer, Mayo Clinic, Rochester, Minnesota.)

In this technologically driven era, a new appreciation of cardiac anatomy has emerged as the cornerstone for clinical cardiology. The purpose of this chapter is to describe the anatomy of the heart by principally using the tomographic format prevalent in current CT, MRI, and echocardiography, with special emphasis and focus on clinically relevant anatomic details. We will make only a passing note of the next generation of imaging techniques. The intent is to emphasize the important anatomic features of various cardiovascular disease processes relative to diagnosis and management. Orientation of the Heart Within the Thorax

The body may be viewed in three standard anatomic planes: (1) frontal (coronal), (2) horizontal (transverse), and (3) sagittal that are orthogonal to one another.6,7 However, the three primary planes of the heart [short axis (transverse), four-chamber (frontal), and long-axis (sagittal)] do not correspond to the standard anatomic planes of the body6,7 (Fig. 2-4, Plate 1). Incorrect photographic or artistic orientation of surgical or autopsy specimens ofthe heart, presented out of context, can result in the display oftwo-dimensional images in nonanatomic positions and actually contribute to misconceptions regarding the position ofthe heart within the thorax6 Fig. 2-5, Plate 2).

Antomical Heart Position

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