ABSTRACT & COMMENTARY
Risk of Non-Cardiac Surgery with Severe Aortic Stenosis
By Michael H. Crawford, MD
This article originally appeared in the November 2014 issue of Clinical Cardiology Alert. It was peer reviewed by Susan Zhao, MD. Dr. Crawford is Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco, and Dr. Zhao is Director, Adult Echocardiography Laboratory, Associate Chief, Division of Cardiology, Department of Medicine, Santa Clara Valley Medical Center. Dr. Crawford and Dr. Zhao report no financial relationships relevant to this field of study.
Tashiro T, et al. Perioperative risk of major non-cardiac surgery in patients with severe aortic stenosis: A reappraisal in contemporary practice. Eur Heart J 2014;35:2372-2381.
Ever since the first Goldman index, severe aortic stenosis (AS) has been known to be a risk factor for perioperative morbidity and mortality for non-cardiac surgery. Current guidelines recommend that elective non-cardiac surgery be postponed in symptomatic patients with severe AS until valve replacement can be performed, and performed in asymptomatic patients only if essential. However, more recent data suggest that severe AS may be less of a risk today. Thus, these investigators from the Mayo Clinic performed a retrospective observational study of severe AS patients undergoing intermediate or high-risk surgeries and compared them to matched controls undergoing the same surgery. Major adverse cardiovascular events (MACE) were death, myocardial infarction, stroke, ventricular tachyarrhythmia, or heart failure occurring in the first 30 days post-op.
In the 10-year database examined, there were 256 severe AS patients who had major non-cardiac surgery and they were matched (age, sex, year of surgery) with 256 controls who had the same procedures. Cardiac symptoms were present in 42% of the patients and 33% of the controls (P = 0.001). Patients also had more coronary disease and hypertension and lower ejection fractions. There was no significant difference in 30-day mortality between the patients and controls (5.9% vs. 3.1%, P = 0.13). The patients had more MACE (19% vs. 11%, P = 0.01), but mainly due to heart failure. Multivariate analysis showed that emergency surgery, atrial fibrillation, and creatinine > 2.0 mg/dL were predictors of cardiac death. Emergency surgery was the strongest predictor of 30-day mortality in both groups. Severe AS was associated with a higher 1-year mortality (19% vs. 8%, P < 0.001). The authors concluded that perioperative mortality in patients with severe AS undergoing noncardiac surgery is lower than previously reported and is no different than that observed in a matched control group without AS. However, severe AS is a strong predictor of postoperative heart failure.
COMMENTARY
This report builds on a smaller observational study from the Mayo Clinic published several years ago which showed that necessary surgery could be done safely in selected patients with severe AS. Although 30-day mortality was twice as high in the severe AS patients (6% vs. 3%), this difference was not statistically significant. Also, the most potent predictor of 30-day mortality was emergency surgery in both groups. There were no operative deaths in either group. The presence of severe AS did increase post-operative MACE, but only because of the development of heart failure (19% vs. 11%, P = 0.001). The incidences of myocardial infarction, stroke, and ventricular tachyarrhythmia were low (all < 2%) and not different between the groups.
The significance of the cardiac symptoms in this analysis was revealing. The presence of symptoms, which were common in all the patients, increased 30-day mortality in both groups. In the patients without symptoms, 30-day mortality and MACE were the same in both groups. This suggests that asymptomatic patients with severe AS can safely undergo essential intermediate- to high-risk surgery, especially if attention is paid to careful anesthetic and surgical care to avoid heart failure. The European Society of Cardiology guidelines state that low- to intermediate-risk surgery in asymptomatic patients is acceptable. The AHA/ACC guidelines state that in asymptomatic patients surgery should be postponed and the patient evaluated for aortic valve replacement. The latter recommendations should perhaps be liberalized based on this study.
Both the European and American guidelines recommend canceling non-cardiac surgery in symptomatic patients with severe AS until the patient can be further evaluated for possible aortic valve replacement. The effect of symptoms on outcomes in this study would support these recommendations. However, they would apply to all patients, including those without AS. Also, emergency surgery influenced the results. In those undergoing elective surgery (91% of the study population), 30-day mortality was < 5% in the severe AS and control patients. Thus, emergency surgery should be avoided in severe AS patients whenever possible.
There are limitations to this study. Retrospective observational studies can be influenced by selection biases. All the study patients had had an echocardiogram, so they probably had clinical indications for this study. Also, unmeasured confounders can influence the results. For example, within 30 days of non-cardiac surgery, six patients had aortic valve replacement. In addition, the study patients were collected between 2000-2010, before percutaneous aortic valve replacement came into widespread use. Finally, the study was done in a single tertiary care referred center.
In summary, any minor surgery is relatively safe in severe AS patients. Asymptomatic patients can have elective surgery with relatively low mortality and morbidity if care is taken to avoid the induction of heart failure. Symptomatic patients should only undergo essential non-cardiac surgery and should be evaluated for aortic valve replacement before or at least after non-cardiac surgery. Emergency surgery should be avoided if possible.
