PREOPERATIVE INVESTIGATIONS

All patients undergoing valvular surgery should have a complete workup including clinical examination, chest x-ray, transthoracic echocardiography, and anesthesia consultation. In addition, laboratory tests are used to detect any biological or bacteriological anomalies. In diabetic patients, it is important to assess the effectiveness of blood glucose level control by measurement of hemoglobin A _1c . Patients with aortic root disease require computed tomography (CT) or magnetic resonance imaging. Coronary angiography is recommended in patients beyond the age of 45 or in younger patients with congenital malformations, depressed ventricular function, and/or atherosclerotic risk factors. Right and left heart catheterization should be additional tests ordered for patients with depressed ventricular function and/or congenital malformation. Because of the high risk of systemic embolization, patients with endocarditis should undergo head and abdominal computed tomography to detect asymptomatic focus of embolization or mycotic aneurysm. In the reoperative setting, chest computed tomography might be useful to assess the anatomical relationship between the ascending aorta, the right ventricle, and the posterior table of the sternum. Additional workup may be necessary in the presence of associated organ dysfunction such as respiratory insufficiency, gastrointestinal disorders, cerebrovascular disease, or renal failure. Finally, with the exception of emergency cases, a complete dental clearance should be obtained. Extensive dental extraction, commonly advised in the past, is no longer required provided that all decayed teeth are treated conservatively under proper antibiotic coverage.

Preoperative investigations allow determination of the risk factors for morbidity and mortality in each individual patient using one of the multiple scoring systems available.

The patient should always be carefully informed about his or her disease, the proposed operation in light of the surgeon’s experience, and the risk factors linked to the patient’s condition and this operation.

PREOPERATIVE CARE

Patients undergoing valvular surgery should continue their medications , including beta-blockers, diuretics, and drugs for associated diseases, until the night before the operation. There are a few exceptions, however. It is advisable to discontinue angiotensin-converting enzyme (ACE) inhibitors 48 hours before surgery to avoid intraoperative hypotension; a significant number of patients with previous percutaneous transluminal coronary angioplasty and stenting are referred for surgery while taking clopidogrel; in those patients it is advisable to discontinue clopidogrel 5 to 7 days before surgery whenever possible. In contrast, patients taking aspirin for coronary artery disease can undergo surgery without a significant increase of postoperative bleeding, although it is still preferable to discontinue this drug for a few days before surgery. Patients taking warfarin generally discontinue this medication 2 to 3 days before surgery. Patients at high risk for thromboembolic complications (such as low ejection fraction, atrial fibrillation, previously implanted mechanical valves) should be protected by use of an alternative anticoagulant strategy such as intravenous heparin or subcutaneous low molecular weight heparin.

Patients with mitral regurgitation and severe heart failure require hemodynamic optimization before surgery. This includes increased amounts of diuretics to address volume overload. In patients with low cardiac output or low mixed venous saturation, inotropic support may be necessary. In patients with severe decompensation from acute mitral regurgitation secondary to conditions such as papillary muscle rupture, intraaortic balloon counterpulsation is useful to improve hemodynamic conditions.

Patients with preoperatively elevated pulmonary artery systolic pressure (> 60 mm Hg), long-standing tricuspid regurgitation, or inferoposterior left ventricular infarction that may be associated with right ventricular infarction deserve careful consideration because of the possibility of right ventricular dysfunction. Patients with severe right ventricular dysfunction may benefit from inotropic support with vasodilating medications such as milrinone (0.5 mcg/kg/min), which, in addition to supplemental oxygen, may lower pulmonary vascular resistance and improve right ventricular performance. Other medications, such as intravenous nitrate or inhaled agents such as aerosolized prostacyclin and nitric oxide, can also lower pulmonary vascular resistance and improve perioperative right ventricular performance. Recombinant human B-type natriuretic peptide (BNP) is a promising new agent with pharmacological properties favorable for the treatment of right-sided heart failure. Its ability to markedly reduce pulmonary vascular resistance and central venous pressure without significant systemic vasodilatation may aid the management of selected patients.

POSTOPERATIVE MANAGEMENT

Based on years of experience, most patients benefiting from valve reconstruction have a very low operative mortality (<1%). However, appropriate postoperative care is critical to ensure the optimal success of the operation.

Patients with preserved ventricular function , good urine output, optimal arterial blood gases, and normal neurological status are extubated within hours following the completion of the cardiac procedure.

Patients with ventricular dysfunction should be weaned progressively from inotropic support. Afterload reduction with ACE inhibitors should be initiated when the patient is receiving minimal inotropic support with a systolic blood pressure >110 mm Hg. Most patients also require intravenous and then oral (PO or per os) diuretics at least for a few weeks.

Patients with persistent pulmonary artery hypertension can benefit from the administration of nitric oxide, nesiritide, and phosphodiesterase inhibitors in the intensive care unit followed by oral sildenafil citrate.

Strict glycemic control is important for all patients. Intensive insulin therapy with a target glucose level of 80 to 110 mg/dl should be instituted for both diabetic and nondiabetic patients. An intravenous insulin infusion is started intraoperatively and continued postoperatively. The intravenous insulin therapy is transitioned to subcutaneous therapy or oral antidiabetic therapy, or it is discontinued after 48 hours.

Anticoagulation is an important adjunct to valve surgery. Following valve reconstruction, patients are systematically anticoagulated with Coumadin with a goal International Normalized Ratio (INR) of 2 to 2.5 in about 2 months, the time necessary for the prosthetic ring to be covered by host tissue. Atrial fibrillation is present in about 20% of patients after reconstructive valve surgery. Beta-blockers should be given postoperatively to decrease the rate of new-onset atrial fibrillation. Most episodes of atrial fibrillation can be treated with a rate control strategy using beta-blockers or amiodarone and oral anticoagulation. In patients with atrial fibrillation, the use of intravenous heparin is controversial because of the risk-benefit ratio between mediastinal bleeding and thromboembolism. In those patients with atrial fibrillation persisting longer than 2 months, cardioversion should be attempted after the patients have received a full dose of amiodarone (400 mg/day for 1 week) and after transesophageal echocardiography has demonstrated the absence of atrial thrombus. In chronic atrial fibrillation, cardioversion is generally considered unnecessary because it is unsuccessful. Our experience, however, has shown that some patients with atrial fibrillation that has persisted up to 5 years can be converted into sinus rhythm by electrical shock. The chance of success is increased in younger patients with a moderately enlarged left atrium and a preserved thickness of the left atrial wall with no fibrotic transformation. In patients having had a successful Maze procedure, Coumadin should be continued for several months until durability of the sinus rhythm is demonstrated.

Predischarge echocardiography is recommended to assess both the valvular and the ventricular function and to serve as a reference for long-term follow-up.

As will become evident from this book, valve reconstructive surgery today can be performed with a very low operative mortality and low incidence of complications provided that normal valve function has been restored and perioperative management as outlined earlier has been carried out. The operative mortality in patients with rheumatic or degenerative valvular disease is 0.5% to 2%. In patients with ischemic or dilated cardiomyopathy, the operative mortality ranges between 4% and 6% (see Section V). In selected cases, the operative mortality should be less than 0.5%, which justifies considering an early operation in totally asymptomatic patients with severe mitral valve regurgitation.