Impact of surgical aortic valve and coronary intervention volume on transcatheter aortic valve replacement outcomes

Introduction

Background

Over the past 20 years, transcatheter aortic valve replacement (TAVR) has emerged as a minimally invasive procedure for treating aortic valve diseases (1-3). The successful execution of TAVR requires technical expertise derived from both interventional cardiology and cardiac surgery (4). As a result, procedural volume requirements for institutions performing TAVR, surgical aortic valve replacement (SAVR), and percutaneous coronary intervention (PCI) were highlighted in an expert consensus (5). Specifically, institutions must perform at least 40 SAVR and 300 PCI procedures in the year preceding the initiation of a TAVR program and at least 30 SAVR and 300 PCI procedures annually for existing TAVR programs. However, no evidence-based studies have been conducted to establish these standards.

Rationale and knowledge gap

Previous research has demonstrated that higher hospital TAVR volumes are associated with fewer postoperative complications and that increasing procedural experience results in lower TAVR-related mortality and morbidity rates (6). However, the relationship between hospital SAVR volume and TAVR outcomes remains unclear. Two similar studies using Centers for Medicare & Medicaid Services (CMS) databases produced conflicting results (7,8). Although PCI and TAVR are distinct procedures, we hypothesized that higher PCI volume may reflect institutional catheter-based experience and infrastructure that could influence TAVR outcomes. Furthermore, no studies have examined the association between hospital PCI volume and TAVR outcomes.

Objective

The first TAVR in China was performed in 2010. Since the approval of domestic transcatheter valves by the China National Medical Products Administration in 2017, the number of hospitals performing TAVR has increased. Given the significant clinical and policy implications, it is critical to establish qualification recommendations for new TAVR institutions to ensure patient safety. This study aimed to evaluate the relationship between annual hospital SAVR and PCI volume and the outcomes of early TAVR cases performed at each hospital. We present this article in accordance with the STROBE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-802/rc).

Methods

Study design

This was a retrospective study based on data extracted from the Hospital Quality Monitoring System (HQMS), a nationwide administrative database covering tertiary hospitals in China. We identified TAVR procedures performed between January 1, 2016 and December 31, 2021. The primary aim was to examine the association between institutional volumes of SAVR or PCI and early TAVR outcomes. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments.

Data source and study population

HQMS is a mandatory national patient-level database includes information from the front pages of in-hospital medical records from tertiary hospitals across China. All tertiary hospitals in China are required to submit standardized discharge records for inpatients to the HQMS (supplementary file available at https://cdn.amegroups.cn/static/public/jtd-2025-802-1.pdf). We identified TAVR procedures using the International Classification of Diseases, Ninth Revision (ICD-9) procedure codes (Table S1). To assess outcomes during the learning curve, we selected the first 125 TAVR cases at each hospital as the early procedures (6).

Variable definitions and outcomes

Baseline characteristics included demographics, possible risk factors, and comorbidities, such as hypertension, diabetes mellitus, coronary heart disease, unstable angina, atrial fibrillation, previous heart failure, peripheral vascular disease, stroke, renal failure, chronic obstructive pulmonary disease, and cancer. All covariates were defined based on previous studies, with the corresponding ICD diagnostic codes used to identify surrogates for these variables in the dataset (Table S2). The Charlson Comorbidity Index was also calculated for each patient.

The primary outcome was in-hospital death or discharge against medical advice (DAMA) (hereafter referred to as “death or DAMA”) after TAVR. In China, patients discharged against medical advice are often in terminal stages of life with poor prognosis. This is relatively common due to traditional customs, financial concerns, and lack of social support. The rates of in-hospital death and DAMA following cardiac surgery in China are similar and are often employed as a composite indicator of hospital quality by the government (9,10). Secondary outcomes included in-hospital stroke and permanent pacemaker implantation.

Classifications of high- and low-volume hospitals

The annual SAVR and PCI volumes between 2016 and 2021 were calculated and averaged for every hospital. To assess the validity of existing recommendations, hospitals were categorized into high SAVR (≥40 per year) and low SAVR (<40 per year), as well as high PCI (≥300 per year) and low PCI (<300 per year), based on the 2018 American Association for Thoracic Surgery/American College of Cardiology/Society for Cardiovascular Angiography and Interventions/Society of Thoracic Surgeons (AATS/ACC/SCAI/STS Expert Consensus on Operator and Institutional Recommendations and Requirements for TAVR). Furthermore, continuous volume cut-offs were applied for binary hospital classification to determine whether a more appropriate annual volume threshold existed. TAVR outcomes were then evaluated using these different volume thresholds for high- and low-volume hospitals.

Statistical analysis

Bivariate analysis was performed to compare patient characteristics and outcomes between the high/low SAVR and high/low PCI groups. Continuous variables were expressed as mean ± standard deviation, while categorical variables were reported as frequencies and percentages. The Mann-Whitney U test was used to assess the significance of continuous variables, and the Chi-squared test was applied for categorical variables.

To examine the relationship between TAVR procedure outcomes and volume, a mixed penalized quadratic spline model (11) was applied, using the 20th, 40th, 60th, and 80th quantiles of TAVR volume as knots, with hospitals as random effects. Adjustments were made for potential confounders, such as age, sex, risk factors, and comorbidities. The 95% confidence interval (CI) for the predicted probability of adverse events was generated through 1,000 bootstrap resamplings with replacements. A mixed logistic model was employed to assess the effect of high/low SAVR and high/low PCI on adverse events during hospitalization, with hospitals treated as random effects and adjustments made for potential confounders. Statistical significance was set at two-tailed P<0.05, and all statistical analyses were performed using SAS software version 9.4 (SAS Institute, Cary, NC, USA).

Results

Between 2016 and 2021, a total of 12,823 TAVR procedures were performed at 461 hospitals and recorded in the HQMS (Figure S1). After excluding patients under 18 years of age to ensure consistency in the adult cohort, and excluding those beyond the 125th TAVR case at each site, a total of 8,314 cases were included in the analysis. (Figure S2). Hospitals classified as high-SAVR-volume centers, based on a threshold of 40 SAVRs per year, performed 5,936 TAVR procedures; in contrast, low SAVR-volume hospitals performed 2,378 procedures. Additionally, high-PCI-volume hospitals, defined by a threshold of 300 PCIs per year, accounted for 8,090 TAVR procedures; in contrast, low-PCI-volume hospitals performed 224 TAVR procedures.

Patient characteristics of early TAVR cases

Table 1 presents the baseline characteristics of the four groups. Notably, most differences between the paired groups were not statistically significant, except for age, which was higher in the high-volume group compared with the low-volume group. There was also no statistically significant difference in Charlson scores between the high- and low-volume groups.

TAVR case sequence and clinical outcomes

The unadjusted clinical outcomes of TAVR included death or DAMA (4.7%), permanent pacemaker implantation (8.4%), and stroke (1.1%). The association between case-sequence volume and risk-adjusted outcomes, which were adjusted for patient age, sex, and other risk factors and comorbidities, is shown in Figure 1. In the overall population, a significant linear association was observed between increasing TAVR volume and decreasing death or DAMA rates after adjusting for baseline patient characteristics. The modelled death or DAMA rates for the first case versus the 125th case were 5.82% (95% CI: 4.88–7.26%) and 3.17% (95% CI: 1.03–4.68%), respectively. Approximately every 10 additional TAVR operations led to a 5% decrease in death or DAMA [odds ratio (OR), 0.95; 95% CI: 0.92–0.99; P=0.01]. However, patient in-hospital stroke and permanent pacemaker implantation were not associated with the TAVR sequence (P=0.89 and 0.71, respectively).

Figure 1 Volume-outcome association for outcomes. These plots depict the continuous case sequence approach, comparing the volume of early TAVR cases with the rate of adverse outcomes. The adjusted frequencies are shown for death or DAMA (A), permanent pacemaker implantation (B), and stroke (C). A significant relationship was found between volume and death or DAMA, as indicated by the colored bands representing 95% confidence intervals. DAMA, discharge against medical advice; TAVR, transcatheter aortic valve replacement.

Additionally, a decrease in death or DAMA rates was observed with increasing TAVR volume in hospitals with both high and low SAVR volumes after grouping based on the hospital’s annual SAVR volume (Figure S3). The modelled death or DAMA rate was lower in hospitals with high SAVR volumes compared with those with low SAVR volumes. However, no statistically significant decline in death or DAMA rates was observed with every 10 additional TAVR operations in the high- and low-SAVR groups (OR, 0.97; 95% CI: 0.93–1.01; P=0.17 and OR, 0.93; 95% CI: 0.83–1.05; P=0.26).

Association of hospital SAVR/PCI volume with TAVR outcomes

We observed a relationship between SAVR volume and outcomes after TAVR (Table 2). The incidence of death or DAMA following TAVR was significantly higher in hospitals with low SAVR volumes compared with those with high SAVR volumes (6.4% vs. 4.0%, P<0.001). However, no significant difference in death or DAMA rates was observed between hospitals with low and high PCI volumes (6.3% vs. 4.7%, P=0.27). In-hospital stroke and permanent pacemaker implantation were not associated with SAVR or PCI volume designations. After adjusting for relevant patient characteristics, including TAVR volume, TAVR procedures performed at hospitals with low SAVR volume were associated with increased odds of death or DAMA (OR, 1.45; 95% CI: 1.07–1.96; P=0.02). There was no significant increase in death or DAMA rates in hospitals with low PCI volumes (OR, 1.36; 95% CI: 0.77–2.40; P=0.29).

Furthermore, we applied continuous volume thresholds for the binary classification of hospitals. The adjusted ORs fluctuated as the volume cut-offs changed (Figure 2). Low SAVR status was associated with significantly increased odds of death or DAMA when the cut-off ranged from 15.5 to 107 SAVR procedures per year, with the OR peaking at 1.64 (95% CI: 1.21–2.21) at a cut-off value of 26 SAVR/year. In contrast, low PCI status was not associated with increased odds of death or DAMA across different cut-off values.

Figure 2 Relationship between low annual SAVR (A)/PCI (B) volume and death or DAMA of TAVR. The figure illustrates the odds ratio for death or DAMA based on low vs. high annual SAVR/PCI status, using continuous cut-offs, with a 95% confidence band. A low SAVR status was significantly associated with increased odds of death or DAMA when the cutoff ranged from 15.5 to 107 SAVRs/year. The rug plot along the horizontal axis displays the annual SAVR/PCI volume distribution for each hospital. DAMA, discharge against medical advice; PCI, percutaneous coronary intervention; SAVR, surgical aortic valve replacement; TAVR, transcatheter aortic valve replacement.

Discussion

Key findings

In the present study, we used the HQMS, an administrative database covering nearly all tertiary hospitals capable of performing cardiac surgeries in China. We included almost the entire Chinese TAVR population from 2016 to 2021. The in-hospital mortality and DAMA rates recorded in the HQMS were remarkably similar to the in-hospital and short-term mortality rates reported in smaller-scale TAVR registries in China (12,13), highlighting the wide coverage and high data quality of this administrative database. We observed a significant decline in the risk of death or DAMA as TAVR procedural experience increased during the first 125 cases. Additionally, TAVR procedures performed in hospitals with high SAVR volumes were associated with lower death or DAMA rates. However, this inverse association was not observed between higher PCI volumes and lower death or DAMA rates for TAVR.

Strengths and limitations

First, the HQMS is an administrative database based on discharge records and lacks detailed clinical data, including echocardiographic parameters, anatomical complexity, and standardized risk scores (e.g., STS, EuroSCORE). These unmeasured confounders may influence TAVR outcomes. To partially address this limitation, we adjusted for baseline comorbidities using the Charlson Comorbidity Index to reduce variation from institutional experience and case selection. Additionally, bleeding, vascular complications and paravalvular leakage are important adverse events in TAVR, but such data were not reliably available in the HQMS database due to its administrative nature. These events are often underreported or incompletely coded in discharge summaries. As such, we excluded these variables to avoid potential misclassification bias. Information on TAVR operators, whose experience might have influenced the outcomes, was also unavailable. However, our analyses and conclusions are based on hospital-level data.

Comparison with similar research and explanations of findings

Over the past 20 years, the use of TAVR has increased rapidly and has become the dominant form of aortic valve replacement in some developed countries, surpassing SAVR (14,15). However, TAVR is still in the training stage in China, with most hospitals remaining within their learning curve (16). Previous studies have demonstrated a volume-outcome relationship during the early learning period and the mature stage after the learning curve of TAVR (7,17,18). Our results are consistent with these findings, with early mortality rates dropping from 5.82% to 3.17% in China, comparable to the U.S., where early case mortality decreased from 5.9% to 3.8% (19).

Our study demonstrated a significant association between hospital SAVR volume and TAVR outcomes. While this relationship has been observed in a few studies, its validity remains controversial. Similarly, the relationship between PCI volume and TAVR outcomes is still unclear. A study using CMS claims data found that hospital SAVR volume was correlated with 30-day and 1-year mortality rates after TAVR (8). However, another CMS data-based study failed to confirm this cross-volume effect when center-level TAVR volumes were incorporated into regression models (7). A more recent study using a similar methodology found that the effect of SAVR volume on TAVR outcomes varied over time (20).

Our findings highlight a strong association between institutional SAVR volume and improved TAVR outcomes, particularly when procedural experience is limited. This volume-outcome relationship may be mediated by several underlying mechanisms. First, high SAVR volume reflects greater surgical experience with aortic valve pathology and complex cardiac anatomy, which contributes to more accurate risk stratification and patient selection. In such institutions, heart team surgeons are better equipped to recognize high-risk features and guide treatment decisions, especially during early TAVR adoption. Second, high-volume SAVR centers are more likely to have well-established multidisciplinary heart teams, including experienced cardiac anesthesiologists, intensivists, perfusionists, and nursing staff. These teams, through their familiarity with open-heart procedures and postoperative care pathways, can deliver more effective perioperative management for TAVR patients. Third, institutional infrastructure tends to be more advanced in high SAVR centers, with access to hybrid operating rooms, extracorporeal life support, and emergency surgical backup. These resources are crucial for managing rare but catastrophic complications, such as device embolization, annular rupture, or tamponade. As previously reported, the need for conversion to open surgery during TAVR, while uncommon (0.3–0.7%), requires high-level surgical preparedness (21,22).

In contrast, PCI volume showed no significant association with TAVR outcomes. PCI expertise contributes to safe vascular access and coronary protection. PCI proficiency is now widespread in China, with over 0.9 million procedures performed annually (23), reducing inter-hospital variability. In our cohort, low PCI-volume hospitals represented 25% of institutions but performed only 2.7% of TAVR cases. The absence of a clear association between PCI volume and early TAVR outcomes may reflect the widespread standardization and technical proficiency of PCI procedures in contemporary practice.

Implications and actions needed

Despite the rapid growth of TAVR, China has not yet formulated specific policy guidelines for the TAVR program. Our findings emphasize the importance of maintaining open-heart surgical capacity within heart teams to improve TAVR outcomes, which has policy implications for setting minimum SAVR volume thresholds for new TAVR programs. These findings may not be generalizable to other healthcare systems with differing infrastructure and referral models. However, in developing countries, many hospitals are still within the TAVR learning curve. In this study, we found that the volume-outcome relationship between SAVR and TAVR was evident when hospital SAVR volume thresholds ranged from 15.5 to 107 procedures per year. The OR peaked at 26 SAVR procedures per year, this cutoff was derived empirically from statistical modeling and should not be interpreted as an absolute clinical inflection point. Although this metric does not represent an exact cut-off for minimal SAVR volume requirements, it provides critical information for physicians and policymakers. Therefore, greater attention should be given to quality control and the improvement of new TAVR programs, particularly in hospitals with low SAVR volumes.

Conclusions

A high hospital SAVR volume was associated with better outcomes in early TAVR cases. However, the accumulation of hospital PCI volumes was not linked to lower mortality rates following early TAVR. Our findings underscore the importance of an institution’s SAVR experience in implementing a TAVR program. Therefore, setting minimum SAVR volume thresholds and enhancing medical care quality should be considered to optimize TAVR performance in hospitals with low SAVR volumes.

Acknowledgments

The authors thank the National Health Commission of the People’s Republic of China and China Standard Medical Information Research Center for the support of this study. Our abstract has been accepted for presentation at the 103rd Annual Meeting of the American Association for Thoracic Surgery (AATS), held in Los Angeles, CA, USA, from May 6–9, 2023.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-802/rc

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-802/prf

Funding: This work was supported by grants from Capital’s Funds for Health Improvement and Research (No. 2022-1-4031) and the National High-Level Hospital Clinical Research Funding (Nos. 2023-GSP-RC-14 and 2023-GSP-QN-27).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-802/coif). All authors report that this work was supported by grants from Capital’s Funds for Health Improvement and Research (No. 2022-1-4031) and the National High-Level Hospital Clinical Research Funding (Nos. 2023-GSP-RC-14 and 2023-GSP-QN-27). The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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