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Perioperative Management of Valvular Heart Disease
Preoperative Assessment
Valvular heart disease (VHD) is frequently observed in patients undergoing surgery. As the medical and minimally invasive management of coronary artery disease increases, the number of patients with untreated advanced valvular disease is likely to supersede the number of patients with advanced coronary disease. Similarly, the rapidly expanding use of percutaneous transcatheter aortic valve replacement for high- and intermediate-risk patients with aortic stenosis (AS), as well as the emergence of devices such as the Mitraclip for symptomatic management of high-risk patients with ischemic mitral regurgitation (MR), may increase the pool of patients with significant valvular disease undergoing noncardiac surgery. The association of VHD with other clinical predictors of increased perioperative cardiovascular risk is of prime importance, particularly as it relates to unstable coronary syndromes, decompensated heart failure with left ventricular (LV) dysfunction, and significant arrhythmias. For example, VHD has been reported to be a major predictor of increased perioperative cardiovascular risk, including myocardial infarction, heart failure, and cardiac death. In patients older than 65 years presenting for noncardiac or coronary artery surgery without concomitant valvular surgery, a history of VHD is predictive of lower LV ejection fraction (LVEF), and patients with preoperative symptomatic valvular disease have increased risk of congestive heart failure (CHF) after elective general surgical procedures. Similarly, significant aortic and mitral valvular dysfunction diagnosed by preoperative transthoracic echocardiography is an independent risk factor for perioperative myocardial infarction. Significant AS is one of the major factors adversely affecting the clinical outcome after noncardiac surgery, where it is found to increase the risk of both myocardial infarction and mortality. Thus, although it is important to preoperatively evaluate the presence, type, and severity of VHD, its natural history and relation to other disease states are key factors in determining the clinical management strategy for the perioperative period.
The physician must know the patient’s preoperative history and the results of the physical examination. If a cardiac murmur is present on preoperative evaluation, the anesthesiologist needs to decide whether it represents significant VHD (see later). Current American Heart Association/American College of Cardiology guidelines suggest that valvular intervention before elective noncardiac surgery is effective in reducing perioperative risks, so delaying elective noncardiac surgery if additional diagnostic interventions and treatment are needed is reasonable ( Fig. 14.1 ). Furthermore, while surgery not amenable to delays for definitive treatment can be performed, mapping the valvular lesion and its severity at minimum can usually be performed quickly. This can be helpful to facilitate discussion with the patient about the perioperative risks and to guide the anesthesiology team about anesthetic approaches, increased hemodynamic perioperative monitoring (including invasive hemodynamic catheters and echocardiography), and postoperative disposition of the patient to an appropriate setting (such as the intensive care unit). Patients with severe VHD may be more prone to hemodynamic instability during the operation, coupled with longer times for both anesthesia and surgery when compared with patients without VHD. High-risk surgical procedures (emergent major operations, aortic and peripheral vascular surgery, and prolonged surgical procedures associated with large fluid shifts or blood loss) pose a greater risk of hemodynamic instability and increased perioperative morbidity and mortality. Although no randomized trials have been performed to ascertain the best timing of surgical intervention, the indications for evaluation and treatment of valvular lesions prior to elective noncardiac surgery are the same as in the nonoperative setting. Thus, symptomatic stenotic lesions often require valve replacement or percutaneous valvotomy prior to noncardiac surgery to decrease cardiac risk, while it may be reasonable to perform elevated-risk elective noncardiac surgery in patients with asymptomatic severe stenotic lesions or with regurgitant lesions, as these may be more amenable to medical management in the perioperative setting. However, all of these patients have elevated risk for postoperative morbidity and mortality compared with patients free of VHD.
Transthoracic echocardiography usually provides the most thorough assessment of the significance of a cardiac murmur, although preoperative electrocardiography and chest radiography can provide clues to the severity of VHD and associated cardiac conditions. Echocardiography is an important tool for assessing the significance of cardiac murmurs by imaging cardiac structure, function, and the direction and velocity of blood flow through cardiac valves and chambers. Current guidelines recommend performing preoperative echocardiography for patients with clinically suspected moderate or greater degrees of valvular stenosis or regurgitation, provided there is no echocardiography exam available in the year prior to the procedure. Furthermore, a repeat examination is indicated for patients with a significant change in either clinical status or physical examination since last echocardiography. If the results of transthoracic echocardiography are inconclusive in defining the diagnosis, other tests, including transesophageal echocardiography (TEE) and cardiac catheterization, should be considered. It is important to glean from the echocardiography report not only the severity of the most significant valvular lesion but also other indices of cardiac function, including presence of dilated atriae, the size and thickness of the left and right ventricles, evidence of elevated right ventricular pressures, and presence and severity of diastolic dysfunction. Preoperative knowledge of those parameters is very helpful in the perioperative management of patients with VHD. In determining whether symptoms are present, exercise testing may be helpful, as many patients tend to limit their daily activity.
Finally, the specific type of surgery and urgency of the operation are important factors in stratifying perioperative risk for VHD surgical patients. High-risk surgical procedures, including emergent major operations, aortic and peripheral vascular surgery, and prolonged surgical procedures associated with large fluid shifts or blood loss, pose a greater threat of hemodynamic instability and portend an increase in perioperative morbidity and mortality.
Preoperative Preparation
Antimicrobial Prophylaxis
Surgical procedures may induce bacteremia and thus expose patients to the risk of acquiring infective endocarditis, a potentially lethal disease if not aggressively treated. Valvular abnormalities, particularly those that result in high-velocity jets, can damage the endothelial lining, lead to platelet aggregation and fibrin deposition at those sites, and create a higher risk for bacterial colonization. To date, the efficacy of prophylactic antibiotics is based on laboratory animal models and small-scale clinical studies using primarily surrogate markers of infective endocarditis. Current clinical strategies in endocarditis prevention are based on recommendations from the American Heart Association in 2007 and are outlined in Box 14.1 and Table 14.1 . These recommendations are substantially different from earlier guidelines from 1997. Current guidelines suggest that antibiotic prophylaxis solely for prevention of infective endocarditis is reasonable only for a small subset of patients with valvular disease at a high risk of adverse outcome from endocarditis. These patients include surgical patients with prosthetic valves, patients with previous history of endocarditis, unrepaired cyanotic congenital heart disease, or completely repaired congenital heart defect with prosthetic material or device within 6 months of the procedure. Furthermore, cardiac transplant patients with secondary valvulopathies are at a high risk of endocarditis. Antibiotic prophylaxis for these high-risk patients (see Box 14.1 ) is considered reasonable for dental and oral procedures involving manipulation of gingival tissue, the periapical region of teeth, or perforation of the oral mucosa. In addition, prophylaxis is reasonable for surgical procedures involving the respiratory tract or infected skin, skin structures, or musculoskeletal tissue. In contrast, prophylaxis is not routinely recommended for infective endocarditis prevention in patients undergoing genitourinary or gastrointestinal procedures. In terms of administration, the initial dose of antimicrobials should begin within 1 hour prior to surgical incision.
Box 14.1
Reproduced with permission from Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective endocarditis: guidelines from the American Heart Association: a guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Reprinted with permission Circulation . 2007;116:1736–54. © 2007 American Heart Association, Inc.
Endocarditis prophylaxis for cardiac conditions.
Endocarditis prophylaxis recommended
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High-risk category
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Prosthetic cardiac valve or prosthetic material used for cardiac valve repair
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Previous infective endocarditis
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Congenital heart disease (CHD)
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Unrepaired cyanotic CHD, including palliative shunts and conduits
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Completely repaired congenital heart defect with prosthetic material or device, whether placed by surgery or by catheter intervention, during the first 6 months after the procedure
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Repaired CHD with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device (which inhibit endothelialization)
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Cardiac transplant recipients who develop cardiac valvulopathies
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Table 14.1
Prophylactic regimens for individuals at high risk for endocarditis.
Reproduced with permission from Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective endocarditis: guidelines from the American Heart Association: a guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Reprinted with permission Circulation . 2007;116:1736–54.
| Regimen: single dose 30 to 60 min before procedure |
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|---|---|---|---|
| Situation | Agent | Adults | Children |
|
|
|
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IM, Intramuscular; IV, intravenous.
a Or other first- or second-generation oral cephalosporin in equivalent adult or pediatric dosage.
b Cephalosporins should not be used in an individual with a history of anaphylaxis, angioedema, or urticaria with penicillins or ampicillin.
Anticoagulation
Some patients with VHD receive chronic anticoagulation therapy. It is important to understand the indication for anticoagulation to determine the risks associated with holding anticoagulation in the perioperative period as well as options for anticoagulation bridging. In general, anticoagulation should not be held for procedures that do not have elevated bleeding risk. Patients with mechanical valves are currently all chronically anticoagulated with warfarin, as novel oral anticoagulation agents (NOACs) have not been tested or found to have excess risk. Per current guidelines, patients with mechanical mitral valves, mechanical caged-ball or tilting-disc aortic valves, or patients with mechanical valves and recent stroke/transient ischemic attack are considered at high risk for thrombotic complications, and periprocedural bridging is recommended for procedures with elevated bleeding risk. Bridging can either be performed by unfractionated heparin (UFH) infusion or subcutaneous low-molecular-weight heparin. Patients with bileaflet mechanical aortic valves but without atrial fibrillation and other stroke risk factors are considered to be at low risk for thrombotic complications, so no bridging is recommended. Patients with bileaflet mechanical aortic valves and either atrial fibrillation or risk factors for stroke (prior stroke or transient ischemic attack, hypertension, diabetes, CHF, or age over 75 years) are considered at moderate risk for thrombotic complications, so the risk of thrombosis must be weighed carefully against the risk of increased bleeding during the perioperative period. Patients with VHD who have not undergone a surgical replacement but require anticoagulation for atrial fibrillation are generally either considered to be at low or moderate risk of thrombotic complication, with the exception of patients with stroke or transient ischemic attack less than 3 months ago, a high burden of stroke risk factors (indicated by CHADS 2 score of 5 or higher), or rheumatic heart disease. Most of these patients will therefore not require an anticoagulation bridge from warfarin. Furthermore, many of these will be chronically anticoagulated with NOACs that allow patients to relatively quickly reverse anticoagulation by stopping the medication secondary to their short half-life compared with warfarin.
With regard to pregnancy, the American College of Chest Physicians concluded that it is reasonable to use one of the following three regimens to manage anticoagulation during pregnancy: (1) either LMWH or UFH between 6 and 12 weeks of gestation and close to term, with warfarin administered at all other times; (2) aggressive dose-adjusted UFH throughout pregnancy; or (3) aggressive dose-adjusted LMWH throughout pregnancy. In general, anticoagulation should be resumed postoperatively as quickly as possible from a procedural bleeding standpoint.
Chronic Medications
Patients with severe VHD are often treated with antiarrhythmic, inotropic, or diuretic therapy (or more than one of these), and it is extremely important that these drugs be continued during the perioperative period. An inability to administer postoperative oral medications in a timely fashion to heart failure patients could be one reason for the occurrence of postoperative CHF. Similarly, cessation of antiarrhythmic drugs may pose a serious risk for the patient with severe AS in whom cardiac output and hemodynamic stability critically depend on normal sinus rhythm. Finally, therapy aimed at minimizing the perioperative cardiac risk has to be considered. Perioperative beta-blockade has been shown to reduce the risk of cardiac events in patients with a risk of myocardial ischemia undergoing noncardiac surgery. Withholding beta-blockers has shown to be a strong risk factor for postoperative atrial fibrillation after coronary bypass surgery, and continuation of beta-blockers after noncardiac surgery is associated with lower operative mortality and lower incidence of myocardial infarction. However, initiating beta-blockade in all-comers in the perioperative setting has been shown to increase mortality and elevate risk of strokes. Thus, the safety and efficacy of beta-blockers in heart failure patients undergoing noncardiac surgery is uncertain and should be evaluated on a case-by-case basis. The benefit has to be balanced against the risk of compromising cardiac inotropic function in unstable VHD patients or those with limited contractile reserve. Furthermore, recent data have cast some doubt on the efficacy of perioperative beta-blocker therapy in patients with intermediate risk factors. There is also growing evidence that alpha-2-agonists and statins reduce the risk of adverse cardiac events in surgical patients ; however, additional large-scale trials are still needed to further delineate the role of these agents. Finally, although an active inflammatory process contributing to calcific AS has been recognized, a prospective randomized clinical trial concluded that intensive lipid-lowering therapy with statin drugs did not halt the progression of stenosis or induce its regression.
Intraoperative Management
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