Methods
We queried the National Inpatient Sample (NIS) (2007 to 2014) a nationally weighted data of all hospital discharges in the United States to describe the frequency of various complications in AIS patients with TTS and also to determine the predictors of all-cause in-hospital mortality. The NIS is a part of the Healthcare Cost and Utilization Project (HCUP) funded by the Agency for Healthcare Research and Quality (AHRQ) [11]. This data consists of a sample from 20% of total hospitalizations from nonfederal US community hospitals representing 95% of the general population in the US. The NIS contains de-identified data; hence, our study was exempt from an institutional review board authorization.
We used International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) to identify primary admissions for AIS (433.01, 433.11, 433.21, 433.31, 433.81, 433.91, 434.01, 434.11, 434.91 and 436) and then using ICD-9 CM code 429.83 admissions with TTS as a secondary discharge diagnoses were filtered.
The primary outcome of our study was to assess the prevalence, trends and all-cause inpatient mortality in AIS cohort with TTS vs. without TTS. Secondary outcomes included frequency of in-hospital complications such as cardiogenic shock, venous thromboembolism, respiratory failure, need for mechanical ventilation and healthcare resource utilization [discharge disposition, mean length of stay (LOS) and hospital charges] among AIS-TTS cohort as compared to AIS- non-TTS cohort.
We utilized designated weight values to produce nationally representative estimates and survey multivariable logistic regression models were performed after adjusting patients and hospital-level confounders to estimate the odds and 95% confidence intervals (CI) of in-hospital mortality and other complications in AIS cohort with TTS as compared to without TTS. We used SPSS v22 (IBM Corp., Armonk, NY) to perform all statistical analyses.