Severe aortic stenosis (AS) is a known predictor of cardiac risk during noncardiac surgery. However, for patients with asymptomatic AS, it is unclear whether aortic valve surgery should precede noncardiac surgery. We studied 30 patients with asymptomatic, severe AS with a mean age of 78 ± 9 years, an aortic valve area of 0.77 ± 0.16 cm 2 , a mean gradient of 50.1 ± 9.5 mm Hg, and a peak gradient of 84 ± 22 mm Hg. They were compared to 60 age-matched (within 2 years) and gender-matched (ratio of 1:2) patients with mild-to-moderate AS (controls). The primary end point of the study was a composite of death, myocardial infarction, heart failure, ventricular arrhythmias before dismissal, and intraoperative hypotension requiring vasopressor administration. Most patients (>75%) and controls underwent intermediate-risk surgical procedures that were similar with respect to the nature of the surgery, type of anesthesia used, and preoperative risk assessment. Combined postoperative events were more common for the patients (n = 10; 33%) than for the controls (n = 14; 23%), but the difference was not statistically significant (p = 0.06). Intraoperative hypotension requiring vasopressor use was more likely for the patients (n = 9; 30%) than for the controls (n = 10; 17%; odds ratio 2.5; p = 0.11). The perioperative myocardial infarction rates were similar for both groups (3%; p = 0.74). No deaths, heart failure events, or ventricular arrhythmias occurred in the patients and 1 death and 1 ventricular arrhythmia episode occurred in the controls. In conclusion, intermediate-to-low–risk noncardiac surgery for patients with severe, asymptomatic AS can be performed relatively safely. Intraoperative hypotension was frequent and required prompt and aggressive treatment.
Severe aortic stenosis (AS) is a known risk factor for noncardiac surgery. Surgical stress and anesthesia can result in unexpected hypotension, which can lead to decreased coronary perfusion and death for some patients with severe AS. For patients with severe, symptomatic AS, the most recent guidelines from the American College of Cardiology and the American Heart Association have recommended aortic valve replacement before noncardiac surgery. However, for patients with asymptomatic, severe AS identified before noncardiac surgery, the optimal care management has been unclear. Previous studies of symptomatic and asymptomatic patients with severe AS have reported conflicting results. Some studies showed no increase in mortality risk and others have suggested increased risk. Hence, it is unclear whether these patients should first undergo aortic valve surgery or proceed directly to noncardiac surgery. The purpose of the present study was to evaluate the postoperative outcomes of patients with asymptomatic, severe AS who underwent noncardiac surgery.
Methods
The Mayo Clinic Institutional Review Board approved the present study. Eligible patients had asymptomatic AS, had undergone noncardiac surgery at Mayo Clinic (Scottsdale, Arizona) from January 1, 1998, through December 31, 2007, and had transthoracic echocardiograms available from ≥6 months before the noncardiac surgery. Of the 602 patients identified, 30 consecutive patients with severe, asymptomatic AS were compared to 60 age-matched (within 2 years) and gender-matched (ratio of 1:2) patients with mild-to-moderate AS (controls).
The data were collected by manually reviewing the medical charts to determine any preoperative history of syncope, presyncope, angina, or dyspnea related to AS. The anesthesia records were reviewed to extract information regarding the American Society of Anesthesiologists score, duration of surgery, type of anesthesia used, and intraoperative complications. The postoperative records, including the laboratory and electrocardiographic data, were reviewed to ascertain the occurrence of myocardial infarction (MI), heart failure, and ventricular arrhythmia. Cardiac risk stratification was based on the current American College of Cardiology/American Heart Association guidelines, which have classified surgical procedures into low-, moderate-, and high-risk categories. Hypertension was defined as a documented diagnosis of hypertension or the use of antihypertensive medications. Diabetes mellitus was defined as a documented diagnosis of diabetes mellitus or treatment with oral hypoglycemic agents or insulin. Hyperlipidemia was defined as a documented diagnosis of hyperlipidemia or treatment with antilipid therapy. Chronic obstructive pulmonary disease was defined as a documented diagnosis of the disease, a cerebrovascular event as a documented history of stroke, and coronary artery disease as a documented history of MI, a previous positive stress test with a repaired defect, a history of percutaneous coronary intervention (with a balloon or stent), or previous coronary artery bypass grafting.
All patients underwent a comprehensive 2-dimensional and Doppler echocardiographic evaluation before surgery. The left ventricular ejection fraction (EF) was determined using both the modified Quinones method and visual assessment. A nonimaging probe from multiple windows was used to obtain the maximal aortic jet velocity and time velocity integral. The maximal instantaneous and mean pressure gradients were calculated using a modified Bernoulli equation. The aortic valve area (AVA) was calculated using the continuity method by determining the left ventricular outflow tract diameter and velocity. The severity of AS was classified on the basis of the most recent American College of Cardiology/American Heart Association guidelines. Specifically, patients with an AVA <1.0 cm 2 and a mean pressure gradient >40 mm Hg were considered to have severe AS; patients with an AVA of 1.0 to 1.5 cm 2 and a mean pressure gradient of 25 to 40 mm Hg were considered to have moderate AS; and patients with an AVA >1.5 cm 2 and a mean pressure gradient <25 mm Hg were considered to have mild AS.
Patients were excluded from the study if they had a moderate or greater degree of aortic regurgitation, as assessed by color flow Doppler criteria combined with quantitative Doppler echocardiography. Patients were also excluded if they had symptomatic AS.
The primary end point of the study was a composite of death, MI, heart failure, ventricular arrhythmias before dismissal, and intraoperative hypotension requiring vasopressor administration. Any deaths that occurred before dismissal were considered related to noncardiac surgery. MI was defined as chest pain or electrocardiographic changes associated with positive cardiac biomarkers, or both. Any ventricular tachycardia before dismissal was considered ventricular arrhythmia.
Continuous variables are expressed as the mean ± SD and categorical variables as frequency (percentage). Baseline variables were compared among the patients and controls using conditional logistic regression analysis for 1:2 matching. A multivariate logistic regression analysis was used to predict the occurrence of perioperative events in the patients versus controls. The analysis adjusted for the baseline variables of age, cardiac risk stratification, and American Society of Anesthesiologists score. The odds ratios and corresponding 95% confidence intervals are reported. p Values <0.05 were considered statistically significant. All analyses were performed with Statistical Analysis Systems software, version 9.1.3 (SAS Institute, Cary, North Carolina).
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