Right Trigone Heart

The function of the heart is to circulate blood in closed circuit to the lungs, where blood is oxygenated, and out to the body, where oxygen provides fuel for cellular metabolism. To accomplish this task, blood is pumped by the right heart system from the body to the lungs. Once oxygenated in the lungs, blood is returned to the left heart, where it is then pumped out to the body. Although described as a biological pump, the heart is actually two biological pumps in series, composed of a right and left heart. Each unit of the heart is composed of an atrial and ventricular chamber; their synchronized contractions result in the forward flow of blood out of the heart. Crucial to the appropriate function of the heart are four valves (the mitral, aortic, tricuspid, and pulmonic) that function in concert to maintain forward flow of blood across the heart. Diseases affecting the heart valves result in either obstruction to forward flow (stenosis) or reversal of flow across an incompetent valve (regurgitation). In either case, significant morbidity and mortality will result if no treatment is offered to the patient.

This chapter was designed to provide a brief overview of the current treatment options for heart valve disease. Major topics of discussion are: (1) development of prosthetic valve replacements, (2) current issues with valve replacement, and (3) major valvular diseases that affect humans in the Western world (Fig. 1).

2. A NEW FRONTIER: VALVE REPLACEMENT

Before 1950, the ability to operate on the human heart safely and effectively was considered an insurmountable goal. Attempts to operate to correct valvular diseases without stopping the heart resulted in severe, often fatal, complications, including uncontrollable bleeding and the introduction of air emboli (1). The ability to maintain forward flow of blood while stopping the heart to allow the surgeon access to the valve would have to wait first for the development of cross-circulation and later for the perfection of cardiopulmonary bypass by Dr. C. Walton Lillehei, Richard L. Varco, and Dr. F. John Lewis at the University of Minnesota (Minneapolis, MN) (2). With this new approach, a new frontier in surgical options for the treatment of heart valve disease began to emerge (Figs. 2-4).

2.1. Mechanical Prosthetic Valves

By 1961, Dr. Albert Starr and Lowell Edwards had successfully implanted the world's first mechanical valve into a human to replace mitral valves deformed by rheumatic fever (3). Initially, this steel ball-and-cage design was successful in approx 50% of implantations. Major complications were soon recognized, including clot formation, resulting in embolic strokes; significant noise; red blood cell destruction; and healing tissue ingrowth causing valve obstruction.

A complete history of the development of currently used mechanical prostheses is beyond the scope of this text. However, it is important to mention two key aspects of any successful valve design: (1) improved valve hemodynamics and

Trigone Aorto Mitral

Fig. 1. Apical view of the four heart valves: aortic, mitral, pulmonic, and tricuspid.

Right fibrous trigone

Fig. 1. Apical view of the four heart valves: aortic, mitral, pulmonic, and tricuspid.

Lillehei HeartWalton Lillehei
Fig. 3. Dr. C. Walton Lillehei, the father of open heart surgery. Photo courtesy of the Lillehei Heart Institute.
Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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