Diseases of the cardiovascular system frequently confront the physician involved in the day-to-day care of patients. Knowledge of the underlying pathophysiologic processes associated with diseases of the heart and blood vessels provides a critical framework for patient management. This chapter deals with diseases of the heart, with the following chapter focusing on diseases of the blood vessels. Normal cardiac structure and function are summarized here, and pathophysiologic mechanisms for commonly encountered cardiac problems are then discussed, with emphasis on arrhythmias, heart failure, valvular heart disease, coronary artery disease, and pericardial disease.
NORMAL STRUCTURE & FUNCTION OF THE HEART
The heart is a complex organ whose primary function is to pump blood through the pulmonary and systemic circulations. It is composed of four muscular chambers: the main pumping chambers, the left and right ventricles, and the left and right atria, which act like “priming pumps” responsible for the final 20–30% of ventricular filling (Figure 10–1A). Peripheral venous return from the inferior and superior venae cavae fills the right atrium and ventricle (through the open tricuspid valve) (Figure 10–1B). With atrial contraction, additional blood flows through the tricuspid valve and completes the filling of the right ventricle. Unoxygenated blood is then pumped to the pulmonary artery and lung by the right ventricle through the pulmonary valve (Figure 10–1C). Oxygenated blood returns from the lung to the left atrium via four pulmonary veins (Figure 10–1D). Sequential left atrial and ventricular contraction pumps blood back to the peripheral tissues. The mitral valve separates the left atrium and ventricle, and the aortic valve separates the left ventricle from the aorta (Figures 10–1D and 10–1E).
Anatomy of the heart. A: Anterior view of the heart. B: View of the right heart with the right atrial wall reflected to show the right atrium. C: Anterior view of the heart with the anterior wall removed to show the right ventricular cavity. D: View of the left heart with the left ventricular wall turned back to show the mitral valve. E: View of the left heart from the left side with the left ventricular free wall and mitral valve cut away to reveal the aortic valve. (Redrawn, with permission, from Cheitlin MD et al, eds. Clinical Cardiology, 6th ed. Originally published by Appleton & Lange. Copyright © 1993 by The McGraw-Hill Companies, Inc.)
The heart lies free in the pericardial sac, attached to mediastinal structures only ...