Regional Variation in Utilization, In-hospital Mortality, and Health-Care Resource Use of Transcatheter Aortic Valve Implantation in the United States
We analyzed data from the National Inpatient Sample database covering the years 2012 to 2014 to identify all patients aged 18 years or older who underwent transcatheter aortic valve implantation (TAVI) in the United States. We assessed regional differences in the utilization of TAVI procedures, in-hospital mortality, and health-care resource use. A total of 41,025 TAVI procedures were recorded nationally during this period, with regional distributions as follows: 10,390 in the Northeast, 9,090 in the Midwest, 14,095 in the South, and 7,450 in the West. The national rate of TAVI procedures per million adults rose from 24.8 in 2012 to 63.2 in 2014. Utilization increased in all four census-defined geographic regions, with the highest number of implants per million adults in the Northeast, followed in descending order by the Midwest, South, and West.
The overall in-hospital mortality rate was 4.2%. After risk adjustment, in-hospital mortality was higher in the Midwest and the South compared to the Northeast, with no significant difference observed between the West and the Northeast. The Midwest showed an adjusted odds ratio (aOR) of 1.26 and the South an aOR of 1.61. The West had an aOR of 1.00, indicating similar mortality rates to the Northeast. The average length of hospital stay was shorter in all other regions compared to the Northeast. Among patients who survived to discharge, a larger proportion were discharged to skilled nursing facilities or received home health care in the Northeast, while the West had the highest rate of discharge to home. Hospital costs were highest in the West.
These findings reveal significant regional differences in TAVI-related care across the United States, suggesting variations in treatment practices, patient selection, post-procedure care, and associated costs. These disparities have implications for health policy and may guide further investigation into their underlying causes.
Background
Transcatheter aortic valve implantation is the preferred treatment for patients with severe aortic stenosis who are at high or prohibitive risk for perioperative mortality following surgical aortic valve replacement. As technological advances and clinical indications expand to include patients at intermediate surgical risk, the number of TAVI procedures performed in the U.S. is projected to increase. Despite this growth, regional differences in TAVI adoption, patient outcomes, and resource utilization have not been well studied. With a growing population eligible for TAVI, this information is critical for patients, clinicians, healthcare administrators, policy makers, and payers.
Methods
We used data from the 2012–2014 National Inpatient Sample database which is a comprehensive and publicly available dataset that includes a stratified 20% sample of inpatient discharges from U.S. community hospitals. The dataset covers over 96% of the U.S. population. Each patient record contains demographic information, primary and secondary diagnoses, procedures, hospital characteristics, expected payer, total charges, discharge disposition, length of stay, and comorbidity measures. Discharge weights were applied to generate national estimates. U.S. Census Bureau estimates were used to determine population data for rate calculations.
Patients aged 18 or older undergoing TAVI were identified using ICD-9-CM codes 35.05 and 35.06. Regional classification was based on hospital location including Northeast, Midwest, South, and West. Baseline characteristics included demographic factors such as age, gender, race, socioeconomic indicators like primary payer and household income by ZIP code, and clinical co-morbidities including cardiovascular diseases, diabetes, renal failure, pulmonary disease, and others. Hospital characteristics such as teaching status and bed size were also considered. TAVI access type either endovascular or transapical was recorded.
We analyzed yearly trends in TAVI utilization and the number of hospitals performing the procedure by region. The primary outcome was in-hospital mortality. Secondary outcomes included length of stay, discharge disposition among survivors, and total hospital costs adjusted for inflation to 2016 U.S. dollars. Cost data were missing for 1,735 records resulting in 39,290 patients included in the cost analysis. Discharge destinations were classified as home, short-term hospital, skilled nursing facility, or home health care.
Weighted data were used for all statistical analyses. We calculated the number of TAVI procedures and hospitals per million adults annually and by region. Categorical variables were compared using Pearson chi-square tests while continuous variables were compared using one-way ANOVA. Absolute standardized differences were also used to compare characteristics between regions using the Northeast as the reference. An absolute standardized difference greater than 10% was considered clinically meaningful.
Multivariable logistic regression models were developed to assess differences in in-hospital mortality across regions adjusting for demographic, clinical, and hospital variables as well as TAVI access type. Generalized estimating equations accounted for clustering within hospitals. Missing data on payer, income, and race were addressed by substituting the most common category for payer and income while creating a separate category for missing race data. This approach is supported by previous studies.
To evaluate regional differences in length of stay and hospital costs multivariable linear regression models were used with log transformation of both outcomes due to skewed distributions. All statistical analyses were performed using IBM SPSS Statistics 21.0. Significance was defined as a two-sided p-value less than 0.05. Results from regression models are presented as odds ratios with 95% confidence intervals.
Results
Of 41,025 TAVI procedures in the United States between 2012 and 2014 10,390 were performed in the Northeast 9,090 in the Midwest 14,095 in the South and 7,450 in the West. Overall the number of TAVIs per million population aged ≥18 years increased from 24.8 in 2012 to 63.2 in 2014. The utilization of TAVI increased during the study period in each of the four census regions with the number of implants per million adult population being highest in the Northeast followed by the Midwest South and the West respectively. The number of TAVIs per million population aged ≥75 years also increased during the study period in each of the four census regions with utilization being highest in the Northeast. The number of hospitals performing TAVI each year also increased during the study period in all four regions with growth in the number of TAVI hospitals per million population aged ≥18 years in all four regions with the magnitude of the increase being highest in the Northeast and lowest in the West.
The mean age of the overall cohort was 81.1 ± 8.5 years. Baseline characteristics of patients undergoing TAVI in the four regions showed significant variation in demographic and clinical factors across regions. In-hospital mortality rates showed overall compared with the Northeast risk-adjusted in-hospital mortality was higher in the Midwest and the South and similar in the West. The higher risk-adjusted mortality in the Midwest compared with the Northeast was observed only in 2012 whereas this difference was no longer significant in 2013 and 2014. In-hospital mortality difference between South versus the Northeast narrowed but persisted throughout the study period. Average LOS of the TAVI hospitalization was shorter in all other regions compared with the Northeast. In contrast average hospital costs were highest in the West and lowest in the Midwest. Risk-adjusted differences in average hospital costs although statistically significant were numerically very small. Among patients surviving to discharge disposition to a skilled nursing facility or home health care was most common in the Northeast while home discharge was most common in the West.
Discussion
This study analyzed an unselected cohort of patients undergoing TAVI in the United States to examine regional variation in TAVI utilization, in-hospital mortality, and healthcare resource use. The key findings show substantial variation in the utilization of TAVI among the four US geographic regions. There was a temporal increase in the number of TAVI hospitals and TAVI procedures performed across all regions. Compared with the Northeast, the risk-adjusted in-hospital mortality was higher in the Midwest and the South. Average length of stay after TAVI was highest in the Northeast, where more patients were discharged to a skilled nursing facility or with home health care. Hospital costs were highest in the West.
The number of TAVI procedures per million population aged ≥18 years was highest in the Northeast followed by the Midwest, the South, and the West, respectively. These findings could be partly explained by variations in the number of eligible TAVI recipients among the four regions. The number of potential TAVI candidates is likely related to the proportion of the elderly population in each region. According to U.S. Census Bureau estimates, the proportion of the population aged ≥75 years is highest in the Northeast, followed by the Midwest, the South, and the West. However, utilization of TAVI per million population aged ≥75 years was also higher in the Northeast compared with other regions, suggesting additional factors beyond age distribution contribute to regional variation in utilization. Socioeconomic characteristics of the population may also play a role. Cardiac procedures are less likely to be utilized by patients from lower socioeconomic strata. Nine of the lowest 15 median household income states are located in the South, compared with the highest median household income states in the Northeast, consistent with the lowest TAVI utilization in the South and highest in the Northeast. Adoption and uptake of new medical technologies depend on several factors including access to trained personnel, procedure reimbursement, and cost-effectiveness of establishing a TAVI program in a hospital-based system.
Risk-adjusted in-hospital mortality was higher in the Midwest compared with the Northeast, driven by higher in-hospital mortality only in 2012. In that year, the number of TAVI procedures per million population aged ≥18 years in the Midwest was lower than in the Northeast, with a similar number of TAVI hospitals per million adult population. This translates to a lower average hospital TAVI volume in the Midwest compared with the Northeast. Higher procedural volume has been associated with better in-hospital outcomes of TAVI, which might partly explain these results. The prevalence of comorbidities among TAVI recipients was also higher in the Midwest compared with the Northeast. Although accounted for in multivariable risk adjustment, residual confounding might have played a role. Risk-adjusted in-hospital mortality was higher in the South compared with the Northeast, narrowing but persisting throughout the study period. Differences in baseline patient characteristics between the two regions were unlikely to contribute to this difference as TAVI recipients in the South were younger and had similar comorbidity prevalence compared with the Northeast. Racial and socioeconomic differences, such as a higher proportion of Hispanics and more patients from lower-income strata, could be partly responsible since these factors have been linked to worse cardiovascular outcomes. Differences in hospital TAVI volumes could also contribute. Although both the number of TAVI procedures and hospitals per million population aged ≥18 years were lower in the South compared with the Northeast, the absolute difference in procedures was larger, resulting in lower average hospital TAVI volumes in the South. A higher proportion of patients undergoing TAVI in small-sized, nonteaching hospitals in the South compared with the Northeast might also explain some of the variation. A “learning-curve” effect has been described for TAVI, with increasing procedural proficiency correlating with greater hospital experience. Regional differences in the timing of new TAVI hospital establishments during the study period could also have contributed to observed variations in risk-adjusted in-hospital mortality.
The average length of stay for TAVI hospitalization was shorter in the Midwest, the South, and the West compared with the Northeast. Discharge to a skilled nursing facility or with home health care was more frequent, while home discharge was less frequent in the Northeast compared with other regions. These differences can potentially be explained by practice-level variations across regions, including differences in TAVI in-hospital patient management protocols emphasizing “fast track” or “minimalist” approaches focused on early extubation, fewer days in the intensive care unit, and early ambulation. Longer lengths of stay and lower rates of home discharge in the Northeast could also be partly related to lower risk-adjusted in-hospital mortality, indicating sicker patients surviving hospitalization and requiring skilled nursing services at discharge. Regional differences in average costs, although statistically significant, were too small to be meaningful after multivariable risk adjustment.
These findings suggest professional societies like the American College of Cardiology and Society of Thoracic Surgeons, along with hospitals offering structural heart programs, should implement best practices and expert consensus decision pathway guidelines for TAVI to streamline patient care and improve outcomes nationwide.
Our study has certain limitations. TAVI utilization was examined per million population aged ≥18 or ≥75 years since the regional prevalence of severe symptomatic aortic stenosis could not be determined. Our study years reflect the early phase of the US commercial TAVI experience; therefore, many hospitals began performing TAVIs mid-study period. Annual hospital TAVI volume data could not be analyzed. Operator experience data were unavailable. AM 095 The National Inpatient Sample is administrative data without information on Society of Thoracic Surgeons scores, valve type and size, medication use, or echocardiographic variables such as paravalvular leak. Data on cause of death or long-term mortality were not available. Lastly, due to the observational design, residual measured or unmeasured confounding might account for some findings.
Disclosures: Dr. Bortnick reports funding from the Empire Clinical Research Investigator Program and NIH/National Center for Advancing Translational Science (NCATS) Einstein-Montefiore CTSA Grant Number UL1TR001073. Dr. Abbott consults for Pfizer and Recor. Dr. Fonarow consults for Medtronic and Abbott/St Jude Medical. Dr. Deepak L. Bhatt discloses relationships with various organizations including advisory boards, board memberships, honoraria, research funding, royalties, site co-investigator roles, trustee positions, and unfunded research. All other authors declare no relevant conflicts of interest.