2.2 Study population and outcomes
The NIS database was queried to identify the hospitalizations of the
following population: 1) adult patients age ≥ 18 years old and 2) those
with implantation of surgically implanted internal BiVADs (International
Classification of Disease 9th revision (ICD-9) code
37.52, which includes TAH) or surgically implanted external BiVADs
(ICD-9 code 37.60). The patients with orthotropic heart transplantations
(ICD-9 code 37.5, 37.51, and 33.6), temporary non-implantable external
systems (ICD-9 code 37.62), single ventricular devices (ICD-9 code 37.65
and 37.66), as well as percutaneous external devices (ICD-9 code 37.68)
were excluded. Of note, the use of two separate surgically implanted
VADs used for biventricular support fell ICD coding for “single
ventricular devices” and thus could not be isolated and captured in our
analysis. We also excluded the patients receiving intra-aortic balloon
pumps (IABPs, ICD-9 code 37.61 and 37.68) as well as implantable heart
systems (ICD-9 code 37.66). In total, 1,264 patients met these criteria,
representing 21,204 patients nationwide.
Primary outcomes of interest were utilization and in-hospital mortality.
Secondary outcomes included LOS, cost of hospitalization, and
complications: major bleeding requiring transfusion, gastrointestinal
(GI) bleed, hemoperitoneum, intracranial bleed, hemolytic anemia,
vascular complications, acute renal failure, mechanical complications,
systemic embolism, stroke or transient ischemic attack (TIA), and
infections. In addition to demographic information, other relevant
comorbidities (e.g., coronary artery disease (CAD), myocardial
infarction (MI), chronic pulmonary disease, anemia, coagulopathy,
diabetes, hypertension, renal failure, and peripheral vascular disease)
were queried. Information regarding the hospitalization – the region of
hospital, location and teaching status, volume, elective vs.
non-elective implantation, and insurance status – were included in the
analyses.