Updated guidelines on cardiovascular evaluation before noncardiac surgery: A view from the trenches

TESTING FOR LEFT VENTRICULAR DYSFUNCTION OR ISCHEMIA

In patients with dyspnea of unexplained cause or worsening dyspnea, assessment of left ventricular function is reasonable, but this is not part of a routine preoperative evaluation.

Pharmacologic stress testing is reasonable for patients at elevated risk with poor functional capacity if the results will change their management, but it is not useful for patients undergoing low-risk surgery. Although dobutamine stress echocardiography may be slightly superior to pharmacologic myocardial perfusion imaging, there are no head-to-head randomized controlled trials, and the guidelines suggest considering local expertise in deciding which test to use.

The presence of moderate to large areas of ischemia (reversible perfusion defects or new wall-motion abnormalities) is associated with risk of perioperative myocardial infarction or death, whereas evidence of an old infarction is associated with long-term but not short-term risk. The negative predictive value of these tests in predicting postoperative cardiac events is high (> 90%), but the positive predictive value is low.

CORONARY REVASCULARIZATION

Coronary artery bypass grafting and percutaneous coronary intervention

The guidelines recommend coronary revascularization before noncardiac surgery only when it is indicated anyway, on the basis of existing clinical practice guidelines.

Whether performing percutaneous coronary intervention before surgery will reduce perioperative cardiac complications is uncertain, and coronary revascularization should not be routinely performed solely to reduce perioperative cardiac events. The only two randomized controlled trials, Coronary Artery Revascularization Prophylaxis (CARP)²⁰ and DECREASE V²¹ evaluating prophylactic coronary revascularization before noncardiac surgery found no difference in either short-term or long-term outcomes, although subgroup analysis found a survival benefit in patients with left main disease who underwent bypass grafting. Preoperative percutaneous coronary intervention should be limited to patients with left main disease in whom comorbidities preclude bypass surgery and those with unstable coronary disease who may benefit from early invasive management.

The urgency and timing of the noncardiac surgery needs to be taken into account if percutaneous coronary intervention is being considered because of the need for antiplatelet therapy after the procedure, and the potential risks of bleeding and stent thrombosis. If the planned surgery is deemed time-sensitive, then balloon angioplasty or bare-metal stenting is preferred over placement of a drug-eluting stent.

The new guidelines continue to recommend that elective noncardiac surgery be delayed at least 14 days after balloon angioplasty, 30 days after bare-metal stent implantation, and ideally 365 days after drug-eluting stent placement, and reiterate that it is potentially harmful to perform elective surgery within these time frames without any antiplatelet therapy. However, a new class IIb recommendation (benefit ≥ risk) states that "elective noncardiac surgery after [drug-eluting stent] implantation may be considered after 180 days if the risk of further delay is greater than the expected risks of ischemia and stent thrombosis."

This is an important addition to the guidelines because we are often faced with patients needing to undergo surgery in the 6 to 12 months after placement of a drug-eluting stent. Based on previous guidelines, whether it was safe to proceed in this setting created controversy among the perioperative team caring for the patient, and surgery was often delayed unnecessarily. Recent studies^22,23 suggest that the newer drug-eluting stents may require a shorter duration of dual antiplatelet therapy, at least in the nonsurgical setting.

MEDICAL THERAPY

Antiplatelet therapy: Stop or continue?

The risk of perioperative bleeding if antiplatelet drugs are continued must be weighed against the risk of stent thrombosis and ischemia if they are stopped before the recommended duration of therapy. Ideally, some antiplatelet therapy should be continued perioperatively in these situations, but the guidelines recommend that a consensus decision among the treating physicians should be made regarding the relative risks of surgery and discontinuation or continuation of antiplatelet therapy. Whenever possible, aspirin should be continued in these patients.

Although the Perioperative Ischemic Evaluation (POISE)-2 trial²⁴ found that perioperative aspirin use was not associated with lower rates of postoperative myocardial infarction or death, it increased bleeding. Patients with stents who had not completed the recommended duration of antiplatelet therapy were excluded from the trial. Additionally, only 5% of the study patients had undergone percutaneous coronary intervention.

According to the guidelines and package inserts, if antiplatelet agents need to be discontinued before surgery, aspirin can be stopped 3 to 7 days before, clopidogrel and ticagrelor 5 days before, and prasugrel 7 days before. In patients without stents, it may be reasonable to continue aspirin perioperatively if the risk of cardiac events outweighs the risk of bleeding, but starting aspirin is not beneficial for patients undergoing elective noncardiac noncarotid surgery unless the risk of ischemic events outweighs the risk of bleeding.

Beta-blockers

In view of the issue of scientific integrity of the DECREASE trials, a separately commissioned systematic review² of perioperative beta-blocker therapy was performed. This review suggested that giving beta-blockers before surgery was associated with fewer postoperative cardiac events, primarily ischemia and nonfatal myocardial infarction, but few data supported their use to reduce postoperative mortality. Beta-blocker use was associated with adverse outcomes that included bradycardia and stroke. These findings were similar with the inclusion or exclusion of the DECREASE trials in question or of the POISE trial.²⁵

In addition to recommending continuing beta-blockers in patients already on them (class I—the highest recommendation), the guidelines say that it may be reasonable to start them in patients with intermediate- or high-risk ischemia on stress tests as well as in patients with three or more RCRI risk factors (class IIb). In the absence of these indications, initiating beta-blockers preoperatively to reduce risk even in patients with long-term indications is of uncertain benefit. They also recommended starting beta-blockers more than 1 day preoperatively, preferably at least 2 to 7 days before, and note that it was harmful to start them on the day of surgery, particularly at high doses, and with long-acting formulations.

Additionally, there is evidence of differences in outcome within the class of beta-blockers, with the more cardioselective drugs bisoprolol and atenolol being associated with more favorable outcomes than metoprolol in observational studies.

Statins

Multiple observational trials have reported that statins are associated with decreased perioperative morbidity and mortality. Limited evidence from three randomized controlled trials (including two from the discredited DECREASE group) suggests that there is a benefit in patients undergoing vascular surgery, but it is unclear for nonvascular surgery.^26–30

The ACC/AHA guidelines again give a class I recommendation to continue statin therapy perioperatively in patients already taking statins and undergoing noncardiac surgery, as there is some evidence that statin withdrawal is associated with increased risk. The guidelines comment that starting statin therapy perioperatively is reasonable for patients undergoing vascular surgery (class IIa) and may be considered in patients with other clinical guideline indications who are undergoing elevated-risk surgery (class IIb).

The mechanism of this benefit is unclear and may relate to the pleotropic as well as the lipid-lowering effects of the statins. Statins may also have beneficial effects in reducing the incidence of acute kidney injury and postoperative atrial fibrillation.

Whether a particular statin, dose, or time of initiation before surgery affects risk is also unknown at this time. The European guidelines⁶ recommend starting a longer-acting statin ideally at least 2 weeks before surgery for maximal plaque-stabilizing effects.

The risk of statin-induced myopathy, rhabdomyolysis, and hepatic injury appears to be minimal.

Other medications

Of note, the new guidelines do not recommend starting alpha-2 agonists for preventing cardiac events in patients undergoing noncardiac surgery. Despite previous evidence from smaller studies suggesting a benefit, the POISE-2 trial³¹ demonstrated that perioperative use of clonidine did not reduce cardiac events and was associated with a significant increase in hypotension and nonfatal cardiac arrest. However, clonidine should be continued in patients already taking it.

A somewhat surprising recommendation is that it is reasonable to continue angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs), and if they are held before surgery, to restart them as soon as possible postoperatively (class IIa). The guidelines note reports of increased hypotension associated with induction of anesthesia in patients taking these drugs but also note that there was no change in important postoperative cardiac and other outcomes. Although evidence of harm if these drugs are temporarily discontinued before surgery is sparse, the guidelines advocate continuing them in patients with heart failure or hypertension.

ANESTHESIA AND INTRAOPERATIVE MANAGEMENT

The classes of anesthesia include local, regional (nerve block or neuraxial), monitored anesthesia care (ie, intravenous sedation), and general (volatile agent, total intravenous, or a combination). The guideline committee found no evidence to support the use of neuraxial over general anesthesia, volatile over total intravenous anesthesia, or monitored anesthesia care over general anesthesia. Neuraxial anesthesia for postoperative pain relief in patients undergoing abdominal aortic surgery did reduce the incidence of myocardial infarction.

Heart failure is at least equal to coronary artery disease in terms of risk

The guidelines do not recommend routinely using intraoperative transesophageal echocardiography during noncardiac surgery to screen for cardiac abnormalities or to monitor for myocardial ischemia in patients without risk factors or procedural risks for significant hemodynamic, pulmonary, or neurologic compromise. Only in emergency settings do they deem perioperative transesophageal echocardiography reasonable to determine the cause of hemodynamic instability when it persists despite attempted corrective therapy.

Maintenance of normothermia is reasonable, as studies evaluating hypothermia or use of warmed air did not find a lower rate of cardiac events.^32,33

POSTOPERATIVE SURVEILLANCE

In observational studies, elevated troponin levels, and even detectable levels within the normal range, have been associated with adverse outcomes and predict mortality after noncardiac surgery—the higher the level, the higher the mortality rate.³⁴ Elevated troponins have many potential causes, both cardiac and noncardiac.

An entity termed myocardial injury after noncardiac surgery (MINS)³⁵ was described as prognostically relevant myocardial injury with a troponin T level higher than 0.03 ng/mL in the absence of a nonischemic etiology but not requiring the presence of ischemic features. Patients who had MINS had a higher 30-day mortality rate (9.8% vs 1.1%) and were also at higher risk of nonfatal cardiac arrest, heart failure, and stroke compared with patients who did not.

The guidelines recommend obtaining an electrocardiogram and troponin levels if there are signs or symptoms suggesting myocardial ischemia or infarction. However, despite the association between troponin and mortality, the guidelines state that "the usefulness of postoperative screening with troponin levels (and electrocardiograms) in patients at high risk for perioperative myocardial infarction, but without signs or symptoms suggestive of myocardial ischemia or infarction, is uncertain in the absence of established risks and benefits of a defined management strategy." They also recommend against routinely measuring postoperative troponins in unselected patients without signs or symptoms suggestive of myocardial ischemia or infarction, stating it is not useful for guiding perioperative management.

Although there was a suggestion that patients in the POISE trial³⁶ who suffered postoperative myocardial infarction had better outcomes if they had received aspirin and statins, and another study³⁷ showed that intensification of cardiac therapy in patients with elevated postoperative troponin levels after vascular surgery led to better 1-year outcomes, there are no randomized controlled trials at this time to support any specific plan or intervention.