Do cardiac risk stratification indexes accurately estimate perioperative risk in noncardiac surgery patients?
PATIENTS WITH SEVERE AORTIC STENOSIS
Neither index lists severe aortic stenosis as a risk factor. The RCRI derivation and validation studies had only 5 patients with severe aortic stenosis, and the NSQIP validation study did not include any patients with aortic stenosis. Nevertheless, severe aortic stenosis increases the risk of cardiac complications in the perioperative period,7 making it important to consider in these patients.
Although patients with severe symptomatic aortic stenosis need valvular intervention before the surgery, patients who have asymptomatic severe aortic stenosis without associated cardiac dysfunction do not. Close hemodynamic monitoring during surgery is reasonable in the latter group.5,7
PATIENTS WITH RECENT STROKE
What would be the cardiac risk for a patient scheduled for elective hip surgery who has had a stroke within the last 3 months? If one applies both indexes, the cardiac risk comes to less than 1% (low risk) in both cases. However, this could be deceiving. A large study8 published in 2014 showed an elevated risk of cardiac complications in patients undergoing noncardiac surgery who had had an ischemic stroke within the previous 6 months; in the first 3 months, the odds ratio of developing a major adverse cardiovascular event was 14.23.This clearly overrides the traditional expert opinion-based evidence, which is that a time lapse of only 1 month after an ischemic stroke is safe for surgery.
PATIENTS WITH DIASTOLIC DYSFUNCTION
A 2016 meta-analysis and systematic review found that preoperative diastolic dysfunction was associated with higher rates of postoperative mortality and major adverse cardiac events, regardless of the left ventricular ejection fraction.9 However, the studies investigated included mostly patients undergoing cardiovascular surgeries. This raises the question of whether asymptomatic patients need echocardiography before surgery.
In a patient who has diastolic dysfunction, one should maintain adequate blood pressure control and euvolemia before the surgery and avoid hypertensive spikes in the immediate perioperative period, as hypertension is the worst enemy of those with diastolic dysfunction. Patients with atrial fibrillation may need more stringent heart rate control.
In a prospective study involving 1,005 consecutive vascular surgery patients, the 30-day cardiovascular event rate was highest in patients with symptomatic heart failure (49%), followed by those with asymptomatic systolic left ventricular dysfunction (23%), asymptomatic diastolic left ventricular dysfunction (18%), and normal left ventricular function (10%).10
Further studies are needed to determine whether the data obtained from the assessment of ventricular function in patients without signs or symptoms are significant enough to require updates to the criteria.
WHAT ABOUT THE ROLE OF BNP?
In a meta-analysis of 15 noncardiac surgery studies in 850 patients, preoperative B-type natriuretic peptide (BNP) levels independently predicted major adverse cardiac events, with levels greater than 372 pg/mL having a 36.7% incidence of major adverse cardiac events.11
A recent publication by the Canadian Cardiovascular Society12 strongly recommended measuring N-terminal-proBNP or BNP before noncardiac surgery to enhance perioperative cardiac risk estimation in patients who are age 65 or older, patients who are age 45 to 64 with significant cardiovascular disease, or patients who have an RCRI score of 1 or higher.
Further prospective randomized studies are needed to assess the utility of measuring BNP for preoperative cardiac risk evaluation.
PATIENTS WITH OBSTRUCTIVE SLEEP APNEA
Patients with obstructive sleep apnea scheduled for surgery under anesthesia have a higher risk of perioperative complications than patients without the disease, including higher rates of cardiac complications and atrial fibrillation. However, the evidence is insufficient to support canceling or delaying surgery in patients with suspected obstructive sleep apnea.
After comorbid conditions are optimally treated, patients with obstructive sleep apnea can proceed to surgery, provided strategies for mitigating complications are implemented.13
