Valvular Heart Disease
Regardless of the lesion or its cause, preoperative evaluation should be primarily concerned with determining the identity and severity of the lesion and its hemodynamic significance, residual ven-tricular function, and the presence of any secondary effects on pulmonary, renal, and hepatic function.
Concomitant CAD should not be overlooked, par-ticularly in older patients and those with known risk factors (see above). Myocardial ischemia may also occur in the absence of significant coronary occlusion in patients with severe aortic stenosis or regurgitation.
The preanesthesia history should focus on symptoms related to decreased ventricular function. Symptoms and signs should be correlated with laboratory data. Questions should evaluate exercise tolerance, fatiga-bility, and pedal edema and shortness of breath in general (dyspnea), when lying flat (orthopnea), or at night (paroxysmal nocturnal dyspnea). The New York Heart Association functional classification of heart disease (Table 21–13) is useful for grading the severity of heart failure symptoms and estimating prognosis. Patients should also be questioned about chest pains and neurological symptoms. Some val-vular lesions are associated with thromboembolic phenomena. Prior procedures, such as valvotomy or valve replacement and their effects, should also be well documented.
A review of medications should evaluate effi-cacy and exclude serious side effects. Commonly used agents include diuretics, vasodilators, ACE inhibitors, β-blockers, antiarrhythmics, and anti-coagulants. Preoperative vasodilator therapy may be used to decrease preload, afterload, or both. Excessive vasodilatation worsens exercise tolerance and is often first manifested as postural (orthostatic) hypotension.
The most important signs to identify on physical examination are those of congestive heart failure. Left-sided (S3 gallop or pulmonary rales) and right-sided (jugular venous distention, hepatojugular reflux, hepatosplenomegaly, or pedal edema) signs may be present. Auscultatory findings may confirm the valvular dysfunction ( Figure 21–7), but echocar-diographic studies are more reliable. Neurological deficits, usually secondary to embolic phenomena, should be documented.
In addition to the laboratory studies discussed for patients with hypertension and CAD, liver function tests may be useful in assessing hepatic dysfunction caused by passive hepatic congestion in patients with severe or chronic right-sided failure. Arterial blood gases can be measured in patients with significant pulmonary symptoms. Reversal of warfarin or hepa-rin should be documented with a prothrombin time and international normalized ratio (INR) or partial thromboplastin time, respectively, prior to surgery.
Electrocardiographic findings are generally nonspecific. The chest radiograph is useful to assess cardiac size and pulmonary vascular congestion.
Echocardiography, imaging studies, and cardiac catheterization provide important diagnostic and prognostic information about valvular lesions, but should only be obtained if the results will change therapy or outcomes. More than one valvular lesion is often found. In many instances, noninvasive stud-ies obviate the need for cardiac catheterization, unless there are concerns about CAD. Information from these studies is best reviewed with a cardiolo-gist. The following questions must be answered:
· Which valvular abnormality is most important hemodynamically?
· What is the severity of an identified lesion?
· What degree of ventricular impairment is present?
· What is the hemodynamic significance of other identified abnormalities?
· Is there any evidence of CAD?
The ACC/AHA have prepared detailed guide-lines to assist in the management of the patient with valvular heart disease. Although the evaluation of the patient with a heart murmur generally rests with the cardiologist, anesthesia providers will on occa-sion discover the presence of a previously undetected murmur on preanesthetic examination. In particu-lar, anesthetists are concerned that undiagnosed, critical aortic stenosis might be present, which could potentially lead to hemodynamic collapse with either regional or general anesthesia. In the past, most val-vular heart diseases were a consequence of rheumatic heart disease; however, with an aging surgical popu-lation, increasing numbers of patients have degener-ative valve problems. More than one in eight patients older than age 75 years may manifest at least one form of moderate to severe valvular heart disease.
A study conducted in the Netherlands reported that the prevalence of aortic stenosis was 2.4% in patients older than age 60 years who were scheduled for elective surgery. Underdiagnosed valvular disease is particularly prevalent in elderly females.
According to the ACC/AHA guidelines, auscul-tation of the heart is the most widely used method to detect valvular heart disease. Murmurs occur as a consequence of the accelerated blood flow through narrowed openings in stenotic and regurgitant lesions. Although systolic murmurs may be related to increased blood flow velocity, the ACC/AHA guide-lines note that all diastolic and continuous murmurs reflect pathology. Other than murmurs that are thought to be innocent, such as mid-systolic flow murmurs (grade 2 or softer), the ACC/AHA guide-lines recommend echocardiographic evaluation.
When new murmurs are detected in a preoperative evaluation, consultation with the patient’s personal physician is helpful to determine the need for echo-cardiographic evaluation. In many centers, immedi-ate echocardiographic evaluation can be performed in the preoperative area.