Diagnosis Related Group and Outcomes Following Transcatheter Aortic Valve Implantation

Abstract

BACKGROUND. The association between Medicare Severity-Diagnosis Related Group (DRG) and early and intermediate-term outcomes in patients undergoing transcatheter aortic valve implantation (TAVI) has not been well studied. We aimed to assess the relationship between DRG and 30-day and 1-year mortality in patients undergoing TAVI. METHODS. The study population included 289 patients with severe symptomatic AS who underwent TAVI from December 2015 to June 2018 at an academic tertiary care medical center. Patients were categorized as DRG 266 or DRG 267, specifying TAVI with or without major complication or comorbidities respectively. RESULTS. Of the 289 patients, 182 patients (63.0%) were classified under DRG 267 and 107 patients (37.0%) under DRG 266. The DRG 266 group had longer hospital lengths of stay and higher rates of discharge to a skilled nursing facility. While rates of in-hospital and 30-day mortality were similar in both DRG groups, the DRG 266 group had higher 1-year all-cause mortality (26.2% vs 8.8%, p<0.001). In multivariable analysis, serum creatinine (OR 1.42, 95%CI 1.05-1.93) was the only independent predictor of 1-year mortality in the DRG 266 group while atrial fibrillation (OR 3.04, 95%CI 1.03-8.92) was the only independent predictor of mortality in the DRG 267 group. CONCLUSIONS. In this prospective registry of patients undergoing TAVI, while rates of in-hospital and 30-day mortality were similar in both DRG 266 and 267 groups, the DRG 266 group had higher 1-year all-cause mortality. Distinct predictors of mortality in each DRG group exist.

INTRODUCTION

Transcatheter aortic valve implantation (TAVI) has become the mainstay therapy to treat older adults with severe symptomatic aortic stenosis (AS).^1-8 Reimbursement for TAVI in the United States is allocated to two possible Medicare Severity diagnosis-related groups (DRGs) - DRG 266 and DRG 267, which describe TAVI procedures associated with the presence or absence of a major complication or comorbidity (MCC) respectively. Common MCCs associated with the population undergoing TAVI have included acute heart failure, acute respiratory failure, acute tubular necrosis, shock, end stage renal disease, non-ST-elevation myocardial infarction, sepsis, and severe protein calorie malnutrition among others. Each DRG is associated with an assigned payment weight based upon the average resources utilized to treat Medicare patients within it. For instance, DRG 266 is associated with greater resources required to care for a patient with MCCs and hence has a higher level of reimbursement than DRG 267. Whether these two DRG codes are also associated with different clinical outcomes following TAVI is unknown. Accordingly, we aimed to evaluate the relationship between DRG code and 1-year mortality in patients undergoing TAVI.  

METHODS

A prospective observational study of adults undergoing TAVI at an academic tertiary medical center was conducted. Inclusion criteria were all adults (age > 18 years) with severe symptomatic AS or failure of a bioprosthetic aortic valve and undergoing TAVI at Stony Brook University Medical Center from December 2015 to June 2018. This cohort was classified into two DRG groups - DRG 266 versus DRG 267. DRG classification was determined by coders from hospital billing as well as clinical documentation integrity specialists who perform reviews of all TAVI procedures. Demographic and medical history extracted included age, sex, weight, height, body mass index, previous coronary artery bypass graft (CABG) surgery, previous myocardial infarction, previous surgical aortic valve replacement (AVR), previous balloon aortic valvuloplasty, previous mitral valve surgery, history of pacemaker or defibrillator, atrial fibrillation, chronic obstructive pulmonary disease, obstructive sleep apnea, previous transient ischemic attack or stroke, peripheral arterial disease, carotid artery disease, and diabetes mellitus. Imaging data extracted included echo data (e.g., aortic valve area (AVA) and index (AVAI), left ventricular ejection fraction (LVEF)), gated computed tomography angiography data (e.g., aortic annulus area and perimeter), and procedural data (e.g., conscious sedation, access type, transcatheter heart valve size and type, and presence of pre-dilatation and/or post-dilatation). Clinical outcomes included discharge location, length of stay (LOS) (admission to discharge, TAVI procedure to discharge), and in-hospital outcomes (all-cause mortality and disabling stroke). Post-discharge outcomes included 30-day all-cause mortality and disabling stroke, and 1-year all-cause mortality. This study was approved by our Institutional Review Board and a waiver of consent was obtained for all patients. 

Categorical variables were presented as percentages and compared with the chi-squared test or Fisher’s exact test, if applicable. Continuous variables were presented as means ± standard deviation (SD) and compared using student’s t test. Multivariable logistic regression was utilized to determine the independent predictors of 1-year mortality for DRG 266 and 267. Predictors for the logistic regression were selected based on statistical significance in the univariate analysis (P<.1). SPSS version 29.0 (IBM Inc.) was used for data analysis and a two-tailed P-value of .05 was regarded as statistically significant.

RESULTS

Of the 289 patients, 182 patients (63.0%) were classified under DRG 267 and 107 patients (37.0%) under DRG 266.  While no differences in age and sex were noted in both groups, the DRG 266 group had lower body mass index and higher serum creatinine (Table 1). Procedural characteristics of TAVI were similar in both DRG 266 and 267 groups (Table 2).

Discharge location, hospital length of stay, and clinical outcomes are highlighted in Table 3. The DRG 266 group was more likely to be discharged to a skilled nursing facility (29.5% vs 10.4%, P<.001) and had longer mean hospital lengths of stay. While no significant differences in in-hospital or 30-day outcomes were noted between the DRG groups, 1-year all-cause mortality was significantly higher in the DRG 266 group (26.2% vs 8.8%, P<.001) (Figure 1). In multivariable analysis, serum creatinine (OR 1.42, 95%CI 1.05-1.93) was the only independent predictor of 1-year mortality in the DRG 266 group while atrial fibrillation (OR 3.04, 95%CI 1.03-8.92) was the only predictor of mortality in the DRG 267 group (Table 4).

DISCUSSION

Several notable findings stem from this study. First, approximately 38% of patients undergoing TAVI in our registry were billed under DRG 266, i.e., with presence of major comorbidities. Second, 1-year mortality rates are nearly three-fold higher in the presence of DRG 266 compared to DRG 267. Finally, distinct predictors of mortality exist in each DRG group. To our knowledge, this is the first study to assess the prevalence of DRG 266 and DRG 267 in patients undergoing TAVI at an academic medical center and their association with post-TAVI outcomes.

Presence of major comorbidities (e.g., heart failure, atrial fibrillation, peripheral arterial disease, anemia, liver disease, cancer, diabetes mellitus, and dialysis-dependent end stage renal disease) in patients undergoing TAVI have been associated with significantly higher hospital costs.^9,10 Higher hospital cost burden has been attributed to higher Society of Thoracic Surgeons predicted risk of mortality, baseline warfarin use, transapical access, operating room use and time, higher post-procedural complication rates (i.e., acute respiratory failure requiring mechanical ventilation, acute kidney injury, cardiogenic shock, bleeding, conduction abnormalities requiring pacemaker), and longer hospital and intensive care unit length of stay.^9-18 Machine learning algorithms have been utilized to predict costs in patients undergoing transfemoral TAVI.¹⁹ While cost- and outcomes-related DRG data has been studied in patients undergoing thoracic or abdominal aortic aneurysm repair^20-22 and transcatheter edge-to-edge repair,²³ no previous data to our knowledge exists regarding DRG-related outcomes in post-TAVI patients.

Our study had a number of limitations. First, observational data in this study was internally validated, but not centrally adjudicated. Second, DRG classification may differ from institution to institution as large university medical centers receive higher reimbursement due to encounter of patients with more advanced comorbidities.²⁴ Third, DRG misclassification²⁵ may occur given the absence of uniformity of DRG coding across institutions. Fourth, given that the study period occurred prior to the commercial approval of TAVI devices for low surgical risk patients, the current population undergoing TAVI may be younger with less comorbidities. Finally, nearly all TAVI cases in our study were via transfemoral approach with predominance of balloon-expandable valve use. Despite these limitations, our study is the first to our knowledge to address both the prevalence of each DRG and their association with outcomes in adults undergoing TAVI.

Conclusions

In conclusion, in this observational prospective registry of patients undergoing TAVI, while rates of in-hospital and 30-day mortality were similar in both DRG 266 and 267 groups, the DRG 266 group had higher 1-year all-cause mortality. Distinct predictors of mortality in each DRG group exist.

References

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Affiliations and Disclosures

From the ¹Division of Cardiovascular Medicine, ²Division of Cardiothoracic Surgery, Department of Medicine, State University of New York at Stony Brook, Stony Brook, New York.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

The authors report that patient consent was provided for publication of the images used herein.

Manuscript accepted June 13, 2023.

Address for correspondence: Puja B. Parikh, MD, MPH, FACC, FAHA, FSCAI, Director, Transcatheter Aortic Valve Replacement Program, Associate Professor of Medicine, Division of Cardiology, Stony Brook University Medical Center, Health Sciences Center, T16-080, Stony Brook, NY 11794-8160. Email: puja.parikh@stonybrookmedicine.edu