Risk of Noncardiac Surgery with Aortic Stenosis
Abstract & Commentary
By Michael H. Crawford, MD Dr. Crawford is Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco and Editor of Clinical Cardiology Alert. Dr. Crawford is on the speaker's bureau for Pfizer.
Synopsis: Aortic stenosis increases the risk of MI, but not overall mortality with noncardiac surgery.
Source: Zahid M, et al. Perioperative Risk of Noncardiac Surgery Associated with Aortic Stenosis. Am J Cardiol. 2005;96:436-438.
Although the presence of aortic stenosis (as) is believed to increase the risk of noncardiac surgery, little contemporary data on this subject exist. Thus, Zahid and colleagues used the National Hospital Discharge Survey (NHDS) to find 5149 patients with AS who underwent noncardiac surgery between 1996 and 2002, and 10,284 age- and sex-matched controls. Also, matching included the surgical risk determined by an independent assessment of each type of surgery. Co-morbid conditions were noted. The primary outcome measure was all-cause mortality and myocardial infarction (MI). Baseline characteristics showed that the AS patients had more coronary artery disease and heart failure, and the controls had more hypertension and diabetes.
Results: AS patients had more MIs and a longer hospital stay on average, but mortality was not different between the 2 groups. Multivariate predictors of an adverse outcome were age > 65 years, congestive heart failure, and coronary artery disease. AS almost doubled the risk of MI (OR = 1.94, 95% CI 1.59-2.36, P < .001). Hypertension reduced the risk of MI. After correcting for these comorbid conditions, patients with AS has a 55% greater risk of a perioperative MI. Buxton et al concluded that AS increases the risk of MI, but not overall mortality with noncardiac surgery.
This study confirms the study done by Goldman in the 1970s, which showed that important AS increased the risk of serious complications. Unfortunately, this study does not provide information on the effect of the severity of AS, because it was not known to the investigators. The study was based upon the ICD-9-CM codes, procedure codes, and demographic/descriptive data from the NHDS, which is a random sample representing about 1% of all nonfederal hospital discharges. The fact that mortality was not different suggests that they were not operating on patients with severe or critical AS. The fact that coronary disease presence was adjusted suggests that perioperative MIs in AS patients can also be caused by increased demand or reduced supply due to factors such as hypotension and tachyarrhythmias, even with normal coronary arteries. As expected, AS patients represent a higher risk group at increased risk for MI, but not necessarily perioperative death. Thus, AS does not seem to be an absolute exclusion from necessary noncardiac surgery, but such patients need meticulous care in the perioperative period.