This review discusses the cardiac risks associated with aortic stenosis (AS) during noncardiac surgery. The following are 10 points to consider:

1. Based on studies published in the 1960s through the 1980s, AS was thought to be associated with a high risk of cardiac complications during noncardiac surgery. The current 2014 American College of Cardiology (ACC)/American Heart Association (AHA) guidelines on valvular heart disease recommend moderate-risk elective noncardiac surgery in patients with asymptomatic severe AS (Class IIa, Level of Evidence B); the guidelines also note that, in patients with moderate to severe AS, the 30-day mortality is higher for patients with AS (2.1%) compared with propensity score–matched controls (1%).
2. Published reports addressing the perioperative risk associated with AS include substantial ambiguity in terms of assessment of AS severity (mean gradient vs. peak gradient vs. not reported, aortic valve area vs. not reported), concomitant left ventricular (LV) systolic dysfunction, concomitant valve disease, and symptoms.
3. In studies that reported it, perioperative risk appears to have been higher among patients with symptoms of AS, concomitant LV systolic dysfunction, and/or concomitant valve disease (especially mitral regurgitation).
4. The authors discuss concerns regarding the hemodynamic assessment of AS severity using echocardiography/Doppler, including the impact of LV outflow tract cross-sectional shape on calculation of the effective orifice area; potential inconsistencies in data between peak velocity, mean gradient, and effective orifice area; and the difference between effective orifice area on echo/Doppler and the Gorlin valve area at heart catheterization.
5. Among patients with AS, adverse outcomes during noncardiac surgery can be attributed to the following interactions between AS, anesthesia, and surgical stress:
   • Anesthesia can result in a decrease in systemic vascular resistance; because of the fixed obstruction of AS, there is an inadequate compensatory increase in cardiac output, leading to hypotension.
   • Hypotension in turn can lead to reduced myocardial perfusion and myocardial ischemia, with resulting decreased LV contractility.
   • Anesthesia can result in reduced sinus node automaticity, arrhythmias, and direct myocardial depression.
6. In that definitions for severe AS typically were used to define progression to symptoms or generalized cardiac mortality risk, the authors note that the question of clinical pertinence is whether there are echo/Doppler parameters of AS that are associated with a high cardiac risk during noncardiac surgery.
7. The authors hypothesize that increased cardiac risk during noncardiac surgery is associated with an aortic valve area ≤0.7 cm² and mean gradient ≥50 mm Hg.
8. The cardiac risk during noncardiac surgery in patients with AS appears to have decreased compared to historical reports, perhaps due to an increased awareness of hemodynamic concerns and advances in anesthetic and surgical approaches.
9. The authors suggest that perioperative surgical risk in patients with AS might be assessed using exercise echocardiography, associating an increase in mean gradient of ≥18 mm Hg with increased risk. A study is cited that associated increase in gradients during exercise with outcomes among patients with AS who were not undergoing noncardiac surgery.
10. The authors note that there are little data that address risk during noncardiac surgery among patients with low-flow, low-gradient severe AS with normal LV ejection fraction; and that there are no data that address the efficacy of transcatheter aortic valve replacement among patients undergoing noncardiac surgery.

Keywords: Anesthesia, Aortic Valve Stenosis, Aortic Valve, Echocardiography, Doppler, Arrhythmias, Cardiac

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