Results
During the study period, 404 patients underwent isolated mini-AVR. There
were 222 patients with a non-obese BMI who were excluded from the study.
The final study population included 182 patients: 106 (58.2%) with
Class I obesity, 42 (23.1%) with Class II obesity, and 34 (18.7%) with
Class III obesity. The total study population had a median (IQR) BMI of
34.0 (31.7-37.4) kg/m2.
Baseline demographic and clinical characteristics amongst patient
cohorts are described in Table 1. The prevalence of diabetes mellitus
correlates with obesity class, with the proportion of diabetic patients
increasing from Class I to Class II and from Class II to Class III
(Class I 33.0% [n=35] vs. Class II 33.3% [n=14] vs. Class III
55.9% [n=19]; p=0.049). The Society of Thoracic Surgeons (STS)
predictive risk of mortality (PROM) score also increases with increasing
obesity class (Class I 1.03% [0.70-1.92%] vs. Class II 1.39%
[0.96-2.22%] vs. Class III 1.86% [1.22-2.41%]; p=0.028). The
proportion of patients with hypertension does not differ between cohorts
(p=0.687). Most patients were of Caucasian race, with all African
American and Asian patients falling into the Class I obesity cohort.
Patient race was not statistically different between obesity classes
(p=0.327).
Table 2 presents perioperative characteristics of the population
stratified by patient cohort. There was no difference amongst cohorts in
bypass or cross-clamp time (p=0.332 and p=0.784, respectively), ICU
length of stay (p=0.180), or intraoperative or postoperative transfusion
of blood products. Patients with Class II obesity demonstrated a less
frequent requirement for postoperative packed red blood cell
transfusions (Class I 12.3% [n=13] vs. Class II 0.0% [n=0] vs.
Class III 14.7% [n=5]; p=0.018), but with no different rates of
postoperative bleeding (Class I 0.94% [n=1] vs. Class II 0.0%
[n=0] vs. Class III 5.88% [n=2]; p=0.131).
The postoperative length of stay (Class I 4.0 [3.0-6.0] days vs.
Class II 4.5 [3.0-6.0] days vs. Class III 5.0 [4.0-6.0] days;
p=0.098) and total direct costs (Class I $24,487
[$20,199-$27.480] vs. Class II $22,921 [$20,433-$27,740]
vs. Class III $23,886 [$20,063-$33,800]; p=0.860) did not differ
between obesity class cohorts (Figure 1). Postoperative 30-day mortality
(Class I 2.83% [n=2] vs. Class II 0% [n=0] vs. Class III 0%
[n=0]; p=0.763) did not differ between patient cohorts and was
contextualized by in-hospital mortality and 30-day readmission rates
that also failed to show between-cohort differences. Aside from
postoperative atrial fibrillation, which was observed much more
frequently in patients with Class II and III obesity
(p<0.001), postoperative complication rates were comparable
between cohorts (Figure 2).