Materials and Methods
Data Source Patients for this study were drawn from the Northern New England Cardiovascular Disease Study Group (NNECDSG) Cardiac Surgery Registry. Data in the NNECDSG registry are validated against billing data from each hospital every 2 years to ensure complete capture of cases and accurate vital status at discharge. The institutional review boards at all but one of the seven hospitals have designated the NNECDSG a quality improvement registry, and, for this reason, patient consent is waived. The last hospital obtains patient consent. For information about patient survival beyond hospital discharge, the NNECDSG data were linked to the National Death Index (through 2001) and the Social Security Administration Master Death File with complete data through the end of 2010. In 2012, the NNECDSG became a certified user of the Social Security Administration data and, as such, receives monthly updates of death data as well as death data from the departments of vital statistics of Maine, New Hampshire, and Vermont.
Patient Groups and Operative Details
We compared 262 patients who underwent sutureless aortic valve (SLV) implantation with 394 patients who underwent standard sutured aortic valves (SAVR). These operations occurred between August 2015 and December 2018 and were performed by three surgeons who use both valve types at a single institution. Patients with mechanical valves or homografts and those with endocarditis, aortic dissection or emergency presentation were excluded. Hospital cost data (including the valve cost) were reviewed.
Study End Points
The primary end point of this study was all-cause mortality among patients undergoing aortic valve replacement. In addition, we examined whether mortality outcomes differed based on type of operation and type of valve used for the operation. Other outcomes studied included operative times, postoperative morbidity (reoperation for bleeding, perioperative stroke, acute kidney injury, mediastinitis or sternal dehiscence, pneumonia, and prolonged ventilation), and length of hospitalization.
Statistical Analysis
Baseline characteristics between groups were compared by using the c2 test for categorical variables and the Wilcoxon rank-sum test for continuous variables. To account for differences between groups, a non-parsimonious, multivariable propensity model was used. The model included surgical procedure, age, sex, body surface area, preoperative white blood cell count, prior percutaneous coronary intervention, vascular disease, diabetes, chronic obstructive pulmonary disease, congestive heart failure, preoperative dialysis or creatinine of 2 mg/dL or more, New York Heart Association class 4, prior stroke, ejection fraction, left main stenosis 50% or greater, three-vessel coronary disease, recent myocardial infarction (within 7 days), acuity at time of operation, and hospital where operation was performed. Standardized differences (std dif) of means are reported for the comparison between the two groups in the unadjusted and inverse probability weighting adjusted data. Hazard ratios (HRs) and 95% confidence limits were generated by using Cox proportional hazard regression models. All data were analyzed with Stata statistical software, version 14.1 (Stata Corp, College Station, TX).