Materials and Methods
This is a retrospective cohort study of all adult patients (≥ 18 years
of age) who underwent isolated minimally invasive aortic valve
replacement at a single academic medical center between January 1, 2015
and June 5, 2020 (Robert Wood Johnson University Hospital, New
Brunswick, New Jersey). This center has an average annual surgical
volume of 15,000 cases performed out of twenty-two operating rooms;
approximately 1,600 are cardiac surgical procedures, with 1,400 open
cases and 200 transcatheter valves procedures per year. The data source
for the study is the cardiac surgery database of the academic center,
developed according to The Society of Thoracic Surgeons (STS) Adult
Cardiac Database version 2.81 definitions. The database contains patient
demographics, baseline clinical and perioperative characteristics,
in-hospital outcomes, and 30-day outcomes. This study was approved by
the Institutional Review Board at the academic center.
Minimally invasive aortic valve replacement (mini-AVR) patients included
those who underwent aortic valve replacement through partial sternotomy
or right minithoracotomy. Patients were selected for minimally invasive
valve surgery versus conventional full sternotomy based upon shared
decision-making between the surgeon and the patient. The study
population was stratified into three cohorts by patient BMI according to
the Centers for Disease Control and Prevention adult obesity
classifications: Class I (BMI 30.0 to < 35.0
kg/m2), Class II (BMI 35.0 to < 40.0
kg/m2), and Class III (BMI ≥ 40.0
kg/m2). Patients with a non-obese BMI (< 30
kg/m2) and those who underwent additional concomitant
procedures (e.g. , double valve replacement) were excluded from
the study.
Baseline patient demographic, clinical, and perioperative
characteristics were recorded and compared between cohorts. Primary
outcomes of postoperative length of stay, mortality within 30 days after
surgery, and total direct costs were evaluated. To contextualize 30-day
mortality, in-hospital mortality and 30-day readmission were analyzed as
secondary outcomes. Postoperative complications of atrial fibrillation,
acute renal failure, bleeding requiring transfusion, delayed extubation,
circulatory support with intra-aortic balloon pump, and stroke were
assessed as tertiary outcomes.
Continuous and categorical variables are presented as median and
interquartile range (IQR: 25th to
75th percentiles) and frequencies and percentages,
respectively, and compared using the Kruskal–Wallis one-way analysis of
variance test or Fishers exact test with the Freeman-Halton
extension.8 Statistical significance was accepted at ap value of less than 0.05.