Since the 1950s more than 80 models of prosthetic heart valves have been developed and used. More than 60,000 valve replacements are performed annually in the United States. Prosthetic heart valves may be mechanical or bioprosthetic. Mechanical valves, which are composed primarily of metal or carbon alloys, are classified according to their structure as caged-ball, single-tilting-disk, or bileaflet-tilting-disk valves. Bioprostheses may be heterografts, which are composed of porcine or bovine tissue (pericardial or valvular) mounted on a metal support, or homografts, which are preserved human aortic valves. The most commonly used prosthetic valves are listed in Table 1 and illustrated in Figure 1. . . .

Prosthetic heart valves

• The history and physical examination most accurately predict the risks of anesthesia and the likelihood of required changes in monitoring or therapy. • For diabetic patients, end-organ dysfunction and the degree of glucose control in the perioperative and periprocedural periods are the critical issues with regard to risk. • The keys to managing blood glucose levels in diabetic patients perioperatively are to set clear goals and then monitor blood glucose levels frequently enough to adjust therapy to achieve these goals. • Obesity is associated with multiple comorbid conditions, including diabetes, hyperlipidemia, and cholelithiasis, but the primary concern is derangements of the cardiopulmonary system. • Obstructive sleep apnea is important to recognize because of the increased sensitivity to and the consequence of the depressing effects of hypnotics and opioids on airway muscle tone and respiration, as well as the difficulty with laryngoscopy and mask ventilation. • Although no controlled, randomized prospective clinical studies have been performed to evaluate the use of adrenergic receptor blocking drugs in patients undergoing resection of pheochromocytoma, the preoperative use of such drugs is generally recommended. • For patients with hypertension, the routine administration of all drugs preoperatively is recommended, except angiotensin-converting enzyme inhibitors and angiotensin II antagonists. • Evaluation of a patient with cardiovascular disease depends on clinical risk factors, the extent of surgery, and exercise tolerance. • In patients with pulmonary disease, the following should be assessed: dyspnea, coughing and the production of sputum, recent respiratory infection, hemoptysis, wheezing, previous pulmonary complications, smoking history, and physical findings. • In patients with pulmonary disease, several strategies have been suggested, including cessation of smoking 8 weeks or more preoperatively. • Risk factors for perioperative renal dysfunction include advanced age, congestive heart failure, previous myocardial revascularization, diabetes, and increased baseline blood creatinine concentration. • One of the primary objectives for a patient with renal disease is ensuring that the renal dysfunction is not augmented and thereby increasing the chance for renal failure, coma, and death. • Mild perioperative anemia may be clinically significant only in patients with ischemic heart disease. • Careful management of long-term drug administration should include questions about the effects and side effects of alternative as well as prescription drugs. Acknowledgment: The editors and the publisher would like to thank Dr. Michael F. Roizen, who was a contributing author to this topic in the prior edition of this work. It has served as the foundation for the current chapter.

Anesthetic Implications of Concurrent Diseases

The role of surgery before the completion of a standard course of antibiotics in endocarditis continues to evolve. The most commonly cited indications for surgery include heart failure, repeated emboli, resistant infection, large vegetations seen by echocardiography, and deep tissue involvement. It has also been suggested that any prosthetic valve infected with a nonstreptococcal pathogen should be considered for early replacement. We discuss the rationale behind surgical intervention, critically review the pertinent literature, and propose guidelines for the clinical management of these patients.

Surgery in active endocarditis.

For most of this century, the stethoscope has served as a critical diagnostic tool in cardiovascular evaluation. With the advent of numerous new diagnostic modalities, however, especially ultrasonic imaging and Doppler techniques, cardiac auscultation is receiving less emphasis in teaching and practice.1 To compound this problem further, phonocardiography, ie, the graphic recording of heart sounds, which had served as a valuable means for teaching and documenting auscultation, has been largely discarded in this country. Although medical training directors and their students generally believe that cardiac auscultation is a skill that physicians should master,1 there appears to be a widespread belief that this skill is of secondary importance because the same information is readily obtainable through newer technological means. Possibly as a result of this attitude, there is no structured teaching of cardiac auscultation in three fourths of American internal medicine programs and two thirds of cardiology programs.1 This will inevitably lead to poor practice and teaching of this technique at all levels of training. Although not as well documented, the same process of attrition is probably affecting the other cognitive skills of history taking and bedside examination.2 3 4 

Conventional wisdom dictates that auscultation not only provides important clinical information in itself but also is a cost-effective means to select additional tests.5 To support these assumptions, however, we must evaluate contemporary information concerning not only how auscultation can be used for additional test selection but also how it might, in comparison with other testing methods, provide a source of information of independent clinical value. For this reason, we shall examine a few specific examples in which auscultation can be used to achieve these ends. To maximize information gained through auscultation, however, we must attempt to identify sources of inaccuracy and suggest methods to correct these …

Cardiac Auscultation A Glorious Past—But Does It Have a Future?

Exercise testing: uses and limitations considering recent studies.

Before prosthetic function can be adequately assessed, physicians must be acquainted with the normal acoustic events associated with these devices. The auscultatory findings of the most commonly used devices--ball, disk, porcine, and bileaflet valves--are reviewed. The mechanisms of sound production and their timing are discussed.

Auscultation of the Normally Functioning Prosthetic Valve

Directional variability in the R wave response during serial exercise testing in patients with coronary artery disease

Phonocardiographic Characteristics of the St. Jude Prosthesis in the Aortic Position

The phonocardiographic characteristics of the porcine bioprosthesis in the aortic position were evaluated in 24 asymptomatic patients. A medium to high frequency early systolic sound (AO) was present in 16 of 24 patients; abrupt "halting" of the stiff cusps of the porcine bioprosthesis during early left ventricular ejection seems to be the likely mechanism for the genesis of this sound. An unusually high amplitude aortic closing sound (AC) was present in all patients. A high frequency crescendo-decrescendo systolic murmur in early to mid systole was present in 22 patients. Possible mechanisms for the systolic murmur include: 1) altered resonating properties of the cusps, 2) functional bioprosthetic stenosis, and 3) the presence of a flexible stent. An early systolic opening sound preceding a short systolic murmur and a loud closing sound are common phonocardiographic findings of an uncomplicated porcine bioprosthesis in the aortic position. Therefore, absence of the aortic opening sound, alterations in the amplitude of the aortic closing sound, or an increase in the length of the systolic murmur may suggest bioprosthetic malfunction.

Neale D. Smith

Papers

Auscultation of the Normally Functioning Prosthetic Valve

Directional variability in the R wave response during serial exercise testing in patients with coronary artery disease

Phonocardiographic Characteristics of the St. Jude Prosthesis in the Aortic Position

Phonocardiographic profile of the porcine bioprosthesis in the aortic position.