Patients with mechanical heart valves usually tolerate surgery well (206). These patients should receive antibiotic prophylaxis (Table 22.8). If the patient is taking aspirin therapy, it should be discontinued 1 week before the procedure and restarted as soon as it is considered safe by the
Table 22.18 Signs and Symptoms of Valvular Heart Disease 1.
Systolic murmur at right sternal border, which radiates into carotids 2.
3.
4.
Chest radiograph with calcified aortic ring, left ventricular enlargement 5.
Electrocardiogram with high R waves, depressed T waves in lead I, and precordial leads Mitral stenosis 1.
2.
3.
4.
5.
Chest radiograph with left atrial dilation 6.
Electrocardiogram with large P waves and right axis deviation surgeon. Patients with a bileaﬂet aortic valve with no risk factors (atrial fibrillation, previous thromboembolism, left ventricular dysfunction, a hypercoagulable state, older generation thrombogenic valve) generally do not require anticoagulation bridging. Warfarin should be stopped 72 hours prior to the procedure and resumed 24 hours after the procedure. In contrast, patients with a mechanical aortic valve and any above mentioned risk factor, or a mechanical mitral valve, should be bridged with intravenous unfractionated heparin when the INR falls below 2. The heparin drip should be stopped approximately 6 to 8 hours before the procedure and restarted as soon as possible after surgery when the patient is deemed stable from postoperative bleeding risk. The heparin bridge can be stopped when the INR reaches therapeutic levels (207).
In the postoperative period, patients with mitral stenosis should be carefully monitored for pulmonary edema because they may not be able to compensate for the amount of intravenous ﬂuid administered during surgery. Prevention of tachycardia is important, as it may lead to pulmonary edema. Patients with mitral stenosis frequently have pulmonary hypertension and decreased airway compliance. They may require more pulmonary support and therapy postoperatively, including prolonged mechanical ventilation.
For patients with significant aortic stenosis, it is imperative that a sinus rhythm be maintained during the postoperative period. Even sinus tachycardia can be deleterious because it shortens the diastolic time. Bradycardia less than 45 beats per minute should be treated with atropine. Supraventricular dysrhythmias may be controlled with verapamil or direct-current cardioversion. Particular attention should be provided to the maintenance of proper ﬂuid status, digoxin levels, electrolyte levels, and blood replacement.
Hypertension Patients with controlled essential hypertension have no increased risk of perioperative cardiac morbidity or mortality (208). Patients with concomitant heart disease are at elevated risk and should be completely evaluated by a cardiologist preoperatively. Laboratory studies should include an ECG, chest radiography, blood count, urinalysis, and serum electrolytes and creatinine measurement. Antihypertensive medications should be continued perioperatively. Beta-blockers should be continued, parenterally if necessary, to avoid rebound tachycardia, hypercontractility, and hypertension. Clonidine may cause significant rebound hypertension if withdrawn acutely. Angiotensin converting enzyme inhibitor agents and angiotensin II receptor antagonists are associated with increased intraoperative hypotension and perioperative renal dysfunction possibly resulting from a hypovolumic state. It may be prudent to withhold these agents on the morning of surgery and resume them postoperatively when good renal function and euvolumia is confirmed (155).