How Accurate Is Vasodilator Myocardial Imaging In Assessing Perioperative Cardiac Risk?

Most patients, even those undergoing major vascular surgery who have underlying CAD, have no perioperative cardiac complications. Therefore, preoperative cardiac risk tests will have low specificity and low positive predictive value. Many studies have a high sensitivity ( 90%) in this procedure but lower specificity. Positive predictive value is generally low.

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Even selective testing does little to improve these percentages.

Dipyridamole-Thallium-201 Scintigraphy (DTS) and Perioperative Myocardial Infarction or Death in Vascular Surgery Patients.

From Granieri, R, Macpherson DS: Perioperative care of the vascular surgery patient: The perspective of the internist. J Gen Intern Med 7:102-113, 1992, with permission.

How is a patient with a prosthetic valve managed perioperatively?

If cardiac function is relatively normal, there are two major risks to which patients with prosthetic valves are exposed: infective endocarditis and thromboembolism. Infective endocarditis in patients with prosthetic valves is associated with significant morbidity and mortality. Regardless of the risk of individual procedures for blood contamination, most patients should be given endocarditis prophylaxis perioperatively.

For thromboembolism most patients can be safely managed by discontinuing warfarin therapy 3-4 days before the procedure and then restarting it when adequate hemostasis has been achieved postoperatively, usually in the evening after surgery. In high-risk patients (e.g. the patient with a prosthetic mitral valve in atrial fibrillation), this regimen may not afford adequate protection against thromboembolism, and so it may be appropriate to hospitalize the patient and switch to continuous intravenous heparin 3 days before surgery. The infusion can be stopped approximately 6 hours before the procedure. The infusion is started again, along with warfarin, when adequate hemostasis is assured postoperatively and is continued for 3 days, at which time oral anticoagulation alone should be adequate.

AHA Recommendations for the Prevention of Bacterial Endocarditis in At-Risk Patients (including Prosthetic Heart Valves)

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