Acute Coronary Syndrome

An active unstable coronary syndrome is, until proved otherwise, an ACS reflecting erosion or rupture of an atherosclerotic plaque. Patients with an ACS are at increased perioperative risk, and in such cases, surgery should be delayed when possible. Retrospective electrocardiogram analysis from the GUSTO-IIb (Global Use Of Strategies To Open occluded arteries in ACSs) study demonstrated that mortality rates rise for 20 to 30 days after presentation, after which mortality rates stabilize. As such, current guidelines identify 30 days as the cutoff for a “recent” ACS ; further delay in surgery would not be expected to alter risk, in the absence of other confounding issues.

Decompensated Congestive Heart Failure

Although treatments for congestive heart failure have advanced significantly in the past decade, survival benefits have been more prominent in patients with mild to moderate disease than in those with advanced heart failure. The annual mortality rate in randomized trials of Class III/IV heart failure ranges from 18.5% to 73%, whereas the Acute Decompensated Heart Failure National Registry (ADHERE) of decompensated heart failure admissions found an overall in-hospital mortality rate of 4%; subgroup mortality rates ranged from 2.1% to 21.9%. These rates, which exceed the expected cardiovascular event rates for the vast majority of elective surgical procedures, would almost certainly increase significantly with the hemodynamic and systemic stress of surgery. Early multivariate risk factor analyses confirmed that decompensated heart failure was associated with increased perioperative morbidity and mortality risk. As such, decompensated congestive heart failure must be treated before surgery.

Arrhythmia

In the perioperative context, “significant” arrhythmia refers to hemodynamically significant rhythm disturbances. However, ventricular arrhythmias are of sufficient threat that even hemodynamically tolerated sustained ventricular arrhythmias should delay anything but emergent surgery. There is no literature characterizing the level of risk that can be ascribed to a preoperative sustained ventricular arrhythmia; given the life-threatening nature of such arrhythmias, to seek to obtain such data would be unethical. In contrast, there is evidence that nonsustained ventricular arrhythmias do not preclude surgical procedures and do not increase perioperative cardiovascular risk.

Uncontrolled atrial arrhythmias (i.e., with ventricular response rates exceeding approximately 100 beats per minute) place patients at increased risk of demand ischemia. Accordingly, rate control should be established before surgery. Although rate-controlled atrial arrhythmias do not preclude surgery, they are associated with an unmodifiable increase in perioperative risk and identify a sicker cohort of patients. For patients undergoing CABG, preoperative atrial fibrillation (AF) increases the length of stay, rehospitalization rate, and long-term mortality rate but not the operative mortality rate. Preoperative AF is associated with an increased perioperative cardiovascular mortality rate (adjusted odds ratio, 4.0) in noncardiac surgery, but this may reflect unidentified comorbidities that increased both the prevalence of AF and cardiovascular risk or an inadequate perioperative rate control.

With atrial arrhythmias, there is the ancillary issue of anticoagulation. Rapid postoperative reinstatement of anticoagulation to minimize thromboembolic risk places patients at an increased risk of postoperative bleeding and may not provide significant benefit. Although patients with AF are, in general, at relatively low short-term risk of thromboembolic events, having age-dependent stroke rates of 1% to 5% per year, the potentially devastating nature of these events makes risk–benefit assessment challenging. In the current ACC/AHA guidelines, a Class IIb recommendation is given to “bridging” patients for whom oral anticoagulants must be held for more than a week, but notes that the efficacy of both unfractionated heparin and subcutaneous low-molecular-weight heparin in this setting is uncertain. Modern oral anticoagulants offer the benefit of predictable bioavailability and effect, relative to unfractionated heparin, and avoid the risk of heparin-induced thrombocytopenia. However, the inability to reverse these agents may limit their use in the perioperative setting.

Symptomatic bradycardia and high-grade atrioventricular conduction abnormalities are also considered significant arrhythmias in the context of preoperative risk assessment. For these rhythms, the primary consideration is whether temporary or permanent pacemaker implantation should be considered. The availability of reliable “semi-permanent” devices enables protection from bradycardia perioperatively without consigning the patient to a permanent device if the bradycardia is anticipated to resolve (e.g., Lyme carditis with heart block) or is by nature transient (e.g., vagal hypersensitivity).

Valvular Disease

Valvular disease is the best studied of the four “major” risk factors. In general, regurgitant lesions are not a contraindication to elective surgery because such lesions are relatively tolerant of perioperative fluid shifts and anesthetic induction. In contrast, symptomatic or severe stenotic lesions are sensitive to changes in both preloading and afterloading, increasing the risk of perioperative hemodynamic embarrassment.

Although the decreasing incidence of rheumatic heart disease has made mitral valve stenosis a rare clinical finding, aortic stenosis (AS) remains common. Some retrospective surgical series found no increase in perioperative cardiovascular event rates in patients with significant AS, but the majority of studies suggest that morbidity and mortality rates are higher in these patients. A recent retrospective case-control analysis supports this contention, in that stenosis severity predicted a sevenfold increase in cardiovascular events. Taken together, the available evidence supports the current standard of practice, in which clinically significant AS is addressed before an elective surgical procedure. Although percutaneous balloon valvuloplasty was historically used in patients needing surgery who were not candidates for aortic valve replacement, transcatheter aortic valve replacement may now allow a more durable intervention in such patients. This novel therapy is developing rapidly, but its use perioperatively remains to be determined.

Evidence for Perioperative Beta-Blockade

The role of so-called demand perioperative ischemia suggests that hemodynamic stress contributes to cardiovascular events. Periods of greatest risk include peri-induction and the immediate postoperative period, presumably as lightened sedation allows increasing sympathetic drive and resultant tachycardia. Sympatholytic therapy with beta-blockers should blunt this response, minimizing myocardial demand.

The first large-scale study of perioperative beta-blockade randomly assigned patients undergoing intermediate- to high-risk surgery to placebo versus atenolol (target heart rate, 65 beats per minute), reducing postoperative mortality rate from 8% to 0% by 3 months after surgery. Three years later, the Dutch Echocardiographic Cardiac Risk Evaluation Applying Stress Echocardiography (DECREASE) study group randomly assigned high-risk vascular surgery patients with positive preoperative dobutamine echocardiography to perioperative bisoprolol versus placebo, with a reduction in cardiac death rates from 17% to 3.4% and nonfatal myocardial infarction (MI) rates from 17% to 0%. Subsequent work by the same group demonstrated that maximal beta-blockade dose and heart rate control optimized the perioperative protective benefit.

The role, if any, of beta-blockade in low-risk patients remains unclear. In a retrospective analysis of a multicenter cohort (the Premier’s Perspective database) undergoing major noncardiac surgery, the perioperative mortality rate was lower with beta-blocker use in intermediate- and high-risk patients but showed a trend toward increased mortality rates in low-risk patients. These data are difficult to interpret because beta-blocker use in these patients may serve as a marker for a negative perioperative event that led to, rather than resulted from, beta-blockade. Although some studies have gone so far as to suggest that beta-blockade is not beneficial in intermediate-risk patients or even high-risk patients, these results likely reflect methodologic limitations, including underdosing and inadequate duration of beta-blockade, abrupt initiation of a relative high dose of long-acting beta-blockade without preceding dose titration, and dilution with low-risk procedures or patients.

The DECREASE-2 study randomly assigned a relatively homogenous population of 770 intermediate-risk vascular surgery patients to preoperative stress testing versus no testing; patients with significant stress-induced ischemia could have preoperative revascularization at the discretion of their care team. In this population, of which 8.8% had extensive ischemia (35% of whom underwent revascularization [50% partial, 50% complete] before vascular surgery), there were no significant differences in death or MI rates. In contrast, heart rate control was significantly correlated with morbidity and mortality rates: the event rate was 1.7% in patients with a heart rate below 50 beats per minute versus 16.5% in patients with a heart rate exceeding 65 beats per minute. These results suggest that, if adequate beta-blockade can be achieved, preoperative cardiac stress testing has no role in intermediate-risk patients. The weight of evidence supporting perioperative beta-blocker therapy prompted a focused update to the ACC/AHA perioperative guidelines, which advised perioperative beta-blockade in high-risk patients (Class I recommendation for vascular surgery, Class IIa for intermediate- to high-risk surgery); beta-blockade in low-risk patients receiving a Class IIb recommendation. In the subsequent full revision of the ACC/AHA guidelines, these recommendations were broadened to a Class IIa indication encompassing all patients with at least one clinical risk factor and/or with known CAD who are scheduled for intermediate- or high-risk procedures.

Evidence for Other Perioperative Medical Interventions

Invasive monitoring (e.g., pulmonary artery catheters [PACs] and arterial lines), cardiac telemetry, and an intensive care unit (ICU) setting have all been proposed to decrease perioperative morbidity. Although there are no randomized controlled trial data examining their role in perioperative cardiovascular risk reduction, cardiac telemetry and ICU admission are widely accepted as cost-effective and beneficial in at least a subset of patients, particularly high-risk patients, as well as those requiring invasive monitoring or frequent titration of hemodynamically active medications. In contrast, the perioperative role of the PAC has decreased in recent years. Observational studies suggest that PAC use increases morbidity and mortality rates. Although prospective studies of PACs in the perioperative setting have a number of methodologic limitations, the largest randomized controlled study suggests that PACs have insufficient benefit. The PAC has no role in current routine perioperative care, although we cannot exclude the possibility that there does exist a specific subpopulation for which use of the device may be beneficial.

A number of pharmacologic agents, including alpha agonists, nitroglycerin, and diltiazem, have been studied but have shown only limited evidence of perioperative benefit. More recently, 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors (“statins”), drugs with recognized pleiotropic therapeutic effects on the cardiovascular system, have been examined. Observational retrospective studies suggest that perioperative statin use is protective, and a growing body of evidence supports statin use in vascular surgery patients and patients undergoing abdominal surgery. In the current ACC/AHA guidelines, statin initiation receives a Class IIa recommendation for patients undergoing vascular surgery and a Class IIb recommendation for patients with at least one clinical risk factor scheduled to undergo an intermediate risk procedure; patients already taking a statin should continue the medication perioperatively (Class I).

A medication of ongoing consideration is aspirin. Although antiplatelet agents were traditionally discontinued perioperatively to minimize bleeding, observational trials demonstrated decreased morbidity and mortality rates in cardiac surgery patients who received perioperative aspirin. Limited evidence in noncardiac surgery suggests aspirin may be beneficial in this setting, although other researchers have found no clinical benefit. The need to continue antiplatelet therapy after drug-eluting stent (DES) placement is an additional driver for continuing aspirin: data suggest that the risks of antiplatelet-associated bleeding are less than the risks associated with antiplatelet withdrawal after stenting. Research into intravenous “bridge” therapies is ongoing, but to date, the clinical benefits of such a strategy are unclear. Given the continuing evolution of available agents for and considerations inherent in antiplatelet therapy management after stenting, a cardiologist should be consulted before discontinuation of antiplatelet therapy for any procedure in a patient with a coronary artery stent. Consensus guidelines from the European Society for Cardiology underscore the need for multidisciplinary consultation and care of these patients.