Cardiovascular clinics最新文献

As patients survive to advanced age, they commonly develop degenerative valvular heart disease as well as degenerative diseases of other organ systems. In addition, a reservoir of patients with other forms of valvular heart disease develop progressive symptomatology with advancing age. These patients often present a challenge to the cardiologist in both diagnosis and management. Inasmuch as these patients tolerate cardiovascular surgery less well than their younger counterparts, criteria for surgical intervention may often need modification. Chronologic age must be recognized as but one of many factors affecting physiologic function. Knowledge of aging-related alterations in function must be employed in both diagnostic and therapeutic algorithms. At times, input from other health-care providers who specialize in the care of the elderly may assist in the assessment of these patients. Surgery should be reserved for higher-risk patients who are severely symptomatic or for those in whom severe symptoms are likely to soon develop based on the natural history of the disease process involved. Those less symptomatic elderly patients with otherwise preserved physiologic functions also may be offered valvular surgery. The availability of nonsurgical, albeit at times palliative, techniques to relieve aortic or mitral stenosis provides an alternative therapeutic option to cardiothoracic surgery. Advances in understanding the pathophysiology and medical therapy of heart failure will continue to contribute to an improved quality of life for those for whom only medical options exist.

The four mechanical valve prostheses currently available on the U.S. market have evolved from a field of more than 50 valves produced for human implantation since the early 1950s (Tables 11-1 to 11-4). This literature establishes that good results can be achieved with a number of cardiac prostheses if properly used and monitored after implant. The current generation of valves have demonstrated ease of implantation, improved durability, good hemodynamic performance, and reduced thromboembolism and thrombosis with proper anticoagulation. The cost and complexity of completing PMA by the FDA, concern over product liability, and patent rights on design and raw materials have narrowed the choice of devices for surgeons in the United States and slowed the pace of new market entries. The evolution of mechanical valves has been reviewed and modes of valve failure reviewed when pertinent. Clinical expectations for earlier generation devices and present valves also are reviewed. Prostheses under evaluation are discussed along with considerations for valve implantation, surveillance, and anticoagulation. We have employed the SJM valve since about 1985. The proven good hemodynamic performance in small sizes and low profile have made its application well suited to the pediatric population and for smaller aortic roots. The well-guarded hinge mechanism and low probability for disc entrapment have facilitated its use in chordal sparing mitral replacements in our experience. Application in the tricuspid position also has been successful but requires close attention to anticoagulation.

All four cardiac valves can be imaged using MRI. Gradient-echo imaging is the preferred mode of imaging. Valvular regurgitation seen as an area of signal loss in the more proximal chamber can be diagnosed with a high degree of accuracy when compared with 2-D Doppler echocardiography and catheterization angiography. Aortic and mitral stenosis can be semiquantitatively diagnosed, but no method for determining valve areas is currently available. Cardiac prosthetic valves can be imaged but appear only as localized signal loss. Prosthetic valve regurgitation can be diagnosed in the same way as native valve regurgitation. At present, MRI, though not a widely used modality, can contribute significantly to the diagnosis of cardiac valve disorders. With the addition of fast magnetic resonance scanning, which can eliminate the need for electrocardiographic gating, it will be possible for patients with cardiac rhythm irregularities to be scanned, thus broadening the base of patients with valve disease who can be diagnosed.

Although Doppler echocardiography plays an important role in evaluating patients with suspected valvular heart disease, it should not replace a careful history, a meticulous physical examination, an electrocardiogram, and well-performed posteroanterior and lateral chest x-rays. Two-dimensional echocardiography can reliably evaluate anatomic valvular lesions, estimate left and right ventricular function, and exclude associated pericardial disease. Doppler echocardiography provides accurate hemodynamic parameters of the severity of aortic and mitral stenosis and the degree of pulmonary hypertension. In addition, color-flow Doppler is helpful in providing semiquantitative information with regard to the degree of MR, AR, or TR. Doppler echocardiography is very useful in evaluating patients before and after valvuloplasty but may be inaccurate when compared with cardiac catheterization immediately following mitral balloon valvuloplasty. However, in the long-term followup, after valvuloplasty, Doppler echocardiography is ideally suited to predict restenosis. A properly performed echo-Doppler study may allow the clinician to send a young patient for surgery when warranted by the clinical symptoms. However, in older patients, especially those with suspected coronary artery disease, and in multivalvular disease, cardiac catheterization may still be required.

During the first half of this century rheumatic fever was a common disease with significant morbidity and mortality in the United States. In the 1980s, when many clinicians were hoping this disease was a disease of the past, anxieties were renewed when outbreaks were reported in several areas around the country. Although the etiology still eludes us, insight has been gained. Environmental and genetic factors are believed to play a role in the epidemiology of this disease. Additionally, the implicated organism, the group A streptococcus, has many strains, and differences in its many proteins may determine their potential for rheumatic fever. The mechanisms leading to disease are not clear, but the streptococcus has been implicated as a source of antigens with cross-reactivity with human tissues and has been shown to modify immune mechanisms. Clinical aspects are briefly reviewed and physicians are reminded to consider rheumatic fever as a diagnostic possibility in the appropriate settings.