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Endocarditis Prophylaxis
• The American College of Cardiology (ACC) and American Heart Association (AHA) currently suggest (class IIa recommendations) endocarditis prophylaxis for patients at the highest risk undergoing dental procedures involving gingival manipulation or perforation of the oral mucosa: (1) prosthetic cardiac valves or patients with prosthetic heart materials, (2) patients with a history of endocarditis, (3) patients with congenital heart disease that is either partially repaired or unrepaired, (4) patients with congenital heart disease with residual defects after repair, (5) patients with congenital heart disease completely repaired within 6 months of either catheter- or surgical-based repair, and (6) cardiac transplant patients with structurally abnormal valves.
• The ACC/AHA guidelines note that many patients and physicians expect and may give endocarditis prophylaxis in patients with valvular heart disease, aortic coarctation, and hypertrophic cardiomyopathy.
• The AHA notes that antibiotics should continue to be given where needed for prevention of wound infection.
• Endocarditis prophylaxis is not recommended for routine gastrointestinal or genitourinary procedures.
Risk Factors for Perioperative Myocardial Infarction
• Ischemic heart disease (known history of myocardial infarction, electrocardiographic [ECG] evidence, chest pain)
• Congestive heart failure (dyspnea, pulmonary edema on chest radiography, echocardiography findings)
• Cerebrovascular disease (stroke)
• High-risk surgery (vascular, thoracic, abdominal, orthopedic surgery)
• Preoperative insulin therapy
• Preoperative creatinine greater than 2 mg/dL
Noninvasive Stress Testing: AHA/ACC Guidelines
• Stress testing is only indicated if it would change patient management.
• Guidelines include noninvasive stress testing in patients scheduled for noncardiac surgery with active cardiac conditions (class I).
• Guidelines (class IIa) also suggest that there may be benefit of such testing in patients with three or more clinical risk factors and poor functional capacity.
• Noninvasive testing (class IIb) can be of some possible benefit in patients with one or two clinical risk factors undergoing intermediate-risk or vascular surgery.
• The AHA guidelines do not recommend the indiscriminate use of noninvasive cardiac testing for patients with no risk factors undergoing intermediate-risk surgery or patients undergoing low-risk surgery.
Testing for Cardiac Disease
• Holter monitor: Continuous ambulatory electrocardiographic (Holter) monitoring is useful in evaluating arrhythmias, antiarrhythmic drug therapy, and the severity and frequency of ischemic episodes.
• Exercise electrocardiography: Limited usefulness in patients with baseline ST-segment abnormalities and those who are unable to increase their heart rate (>85% of maximal predicted) because of fatigue, dyspnea, or drug therapy. For most ambulatory patients, exercise ECG testing is ideal because it estimates functional capacity and detects for myocardial ischemia.
• Myocardial perfusion scans: Myocardial perfusion imaging using thallium-201 or technetium-99m is used in evaluating patients who cannot exercise (e.g., peripheral vascular disease) or who have underlying ECG abnormalities that preclude interpretation during exercise (e.g., left bundle-branch block). If the patient cannot exercise, images are obtained before and after injection of an intravenous coronary dilator (e.g., dipyridamole or adenosine) to produce a hyperemic response similar to exercise.
• Echocardiography: This technique provides information about both regional and global ventricular function and may be carried out at rest, after exercise, or with administration of dobutamine.
• Coronary angiography: Gold standard in detecting coronary artery disease (CAD). In evaluating fixed stenotic lesions, occlusions greater than 50% to 75% are generally considered significant. Significant stenosis of the left main coronary artery is ominous because it affects almost the entire left ventricle.
Indications for Preoperative Coronary Revascularization
• The ACC/AHA guidelines note that only the subset of patients with CAD who would benefit from revascularization irrespective of their need for a nonemergent surgical procedure are likely to benefit from preoperative coronary interventions.
• The indications for testing of those patients as candidates for a coronary intervention is predicted by their general requirement for such evaluation as a part of the management of CAD irrespective of the planned surgery.
• General contraindications to surgery are an myocardial infarction (MI) less than 1 month before surgery with persistent ischemic risk by symptoms or noninvasive testing, uncompensated heart failure, and severe aortic or mitral stenosis.
• Patients with stable angina and significant left main, stable angina and three-vessel disease, stable angina and two-vessel disease with an ejection fraction below 50%, unstable angina, non–ST-segment elevation MI, and acute ST segment elevation MI benefit from revascularization before noncardiac surgery (class I).
• Conversely, revascularization is not indicated in patients with stable angina (class III).
• Moreover, elective noncardiac surgery is not recommended within 4 to 6 weeks after bare metal stent placement or within 12 months of placement of a drug-eluting stent if antiplatelet therapy needs to be discontinued.
• Anesthesia staff should never of their own volition discontinue antiplatelet or antithrombotic agents perioperatively but should work in collaboration with the patient’s surgeons and cardiologists.
Guidelines for Perioperative Blood Pressure
• Intraoperative blood pressure (BP) should generally be kept within 10% to 20% of preoperative levels.
• In treating hypertension, an angiotensin-converting enzyme (ACE) inhibitor is considered an optimal first-line choice for patients with left ventricular dysfunction or heart failure, but an ACE inhibitor or angiotensin receptor blocker is not considered an optimal initial single agent in the setting of hyperlipidemia, chronic kidney disease, or diabetes (particularly with nephropathy). A β-adrenergic blocker or, less commonly, a calcium channel blocker is used as a first-line agent for patients with CAD.
• Treatment guidelines recommend a diuretic with or without β-adrenergic blockade or a calcium channel blocker alone for elderly patients.
• Elective surgical procedures on patients with sustained preoperative diastolic BP higher than 110 mm Hg—particularly those with evidence of end-organ damage despite attempts to correct the BP with intravenous agents—should be delayed until BP is better controlled over the course of several days.
• Patients who present with elevated BP the morning of surgery are at high likelihood for hypotension with induction and then exaggerated hypertension with intubation.
• Direct intraarterial pressure monitoring is needed for patients with wide swings in BP and for major surgeries associated with large changes in cardiac preload or afterload.
• Malignant hypertension is a true medical emergency characterized by severe hypertension (>210/120 mm Hg) associated with papilledema and, frequently, encephalopathy and requires vasodilator infusions and inpatient admission.
Perioperative Myocardial Ischemia
• Common causes include severe hypertension or tachycardia (particularly in the presence of ventricular hypertrophy); coronary artery vasospasm or anatomic obstruction; severe hypotension, hypoxemia, or anemia; and severe aortic stenosis or regurgitation. Sudden withdrawal of antianginal medication perioperatively—particularly β-blockers—can precipitate a sudden increase in ischemic episodes (rebound hypertension, tachycardia, or both).
• Symptom history, such as chest pain, dyspnea, poor exercise tolerance, syncope, or near syncope, includes important indicators of ischemia.
• Unstable angina is defined as (1) an abrupt increase in the severity, frequency (more than three episodes per day), or duration of anginal attacks (crescendo angina); (2) angina at rest; or (3) new onset of angina (within the past 2 months) with severe or frequent episodes (more than three per day). It usually reflects severe underlying coronary disease and frequently precedes MI. Critical stenosis is present in more than 80% of patients, and they should be evaluated for coronary angiography and revascularization. Laboratory evaluation for patients who have a history compatible with recent unstable angina and are undergoing emergency procedures should also include serum cardiac enzymes.
• Chronic stable angina symptoms are generally absent until the atherosclerotic lesions cause 50% to 75% occlusions in the coronary circulation. When a stenotic segment reaches 70% occlusion, maximum compensatory dilatation is usually present distally; blood flow is generally adequate at rest but becomes inadequate with increased metabolic demand. Chronic stable (mild to moderate) angina does not appear to increase perioperative risk substantially.
Treatment of Ischemic Heart Disease
• Correction of risk factors in the hope of slowing disease progression
• Modification of the patient’s lifestyle to reduce stress and improve exercise tolerance
• Correction of complicating medical conditions that can exacerbate ischemia, such as hypertension, anemia, hypoxemia, hyperthyroidism, fever, infection, or adverse drug effects
• Pharmacologic manipulation of the myocardial oxygen supply–demand relationship
• Correction of coronary lesions by percutaneous coronary intervention (angioplasty with or without stenting, or atherectomy) or coronary artery bypass surgery
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