Transcatheter aortic valve implantation: assessing the learning curve

Impact of proficiency in the transcatheter aortic valve implantation procedure on clinical outcomes: a single center retrospective study

BACKGROUND

We used transcatheter aortic valve implantation (TAVI) procedure time to investigate the association between surgical team maturity and outcome.

METHODS

Among patients who underwent TAVI between October 2015 and November 2019, those who had Sapien™ implanted with the transfemoral artery approach were included in the analysis. We used TAVI procedure time and surgery number to draw a learning curve. Then, we divided the patients into two groups before and after the number of cases where the sigmoid curve reaches a plateau. We compared the two groups regarding the surveyed factors and investigated the correlation between the TAVI procedure time and survey factors.

RESULTS

Ninety-nine of 149 patients were analysed. The sigmoid curve had an inflection point in 23.2 cases and reached a plateau in 43.0 cases. Patients in the Late group had a shorter operating time, less contrast media, less radiation exposure, and less myocardial escape enzymes than the Early group. Surgical procedure time showed the strongest correlation with the surgical case number.

CONCLUSION

The number of cases required for surgeon proficiency for isolated Sapien™ valve implantation was 43. This number may serve as a guideline for switching the anesthesia management of TAVI from general to local anesthesia.

2021 CSANZ and ANZSCTS Position Statement on the Operator and Institutional Requirements for a Transcatheter Aortic Valve Implantation (TAVI) Program in Australia

This document establishes the minimum standard for accreditation of institutions and operators as endorsed by the Cardiac Society of Australia and New Zealand (CSANZ) and the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS). The original Joint Society Position Statement was ratified in August 2014. This 2021 update replaces the original and serves as a consensus within which the Conjoint Committee for Trancatheter Aortic Valve Implantation (TAVI) Accreditation will function, as recommended by Medical Services Advisory Committee (MSAC) Determination for TAVI. This is not a Guideline Statement but takes into consideration regional, legislative, and health system factors important to establishing requirements for TAVI accreditation in Australia.

Establishing minimally invasive cardiac surgery in a low-volume mitral surgery centre

INTRODUCTION

Despite early enthusiasm, minimally invasive cardiac surgery has had a low uptake compared with novel techniques in interventional cardiology. Steep learning curves from high-volume centres have deterred smaller units from engaging, even though low-volume centres undertake a large proportion of surgical interventions worldwide. We sought to identify the safety and experience of learning minimally invasive cardiac surgery after undertaking a structured fellowship at Blackpool Victoria Hospital, a low-volume centre.

MATERIALS AND METHODS

A retrospective analysis of outcomes for all consecutive minimally invasive cardiac surgery procedures performed via a right mini-thoracotomy at our institution between 2007 and 2017 was undertaken. Clinical outcomes included death, conversion to sternotomy, stroke, renal failure and other organ support. Cardiopulmonary bypass, aortic cross-clamp times and learning cumulative sum sequential probability method curves were also assessed to determine how safely the procedure was adopted.

RESULTS

A total of 316 patients were operated on for mitral, tricuspid, atrial fibrillation, septal defects or other conditions. The mean logistic European System for Cardiac Operative Risk Evaluation score was 7.0 (± 8.5). Conversion to sternotomy occurred in 12 patients (3.8%) and in-hospital mortality was 7 (2.2%). None of the converted patients died. The learning curves showed an accelerated process of adoption, similar to reference figures from a high-volume German centre.

DISCUSSION

It is possible for low-volume cardiac surgical centres to undertake minimally invasive surgical programmes with good outcomes and short learning curves. Despite technical complexities, with a team approach, the learning curve can be navigated safely.

2019 Canadian Cardiovascular Society Position Statement for Transcatheter Aortic Valve Implantation

Transcatheter aortic valve implantation (TAVI) or replacement has rapidly changed the treatment of patients with severe symptomatic aortic stenosis. It is now the standard of care for patients believed to be inoperable or at high surgical risk, and a reasonable alternative to surgical aortic valve replacement for those at intermediate surgical risk. Recent clinical trial data have shown the benefits of this technology in patients at low surgical risk as well. This update of the 2012 Canadian Cardiovascular Society TAVI position statement incorporates clinical evidence to provide a practical framework for patient selection that does not rely on surgical risk scores but rather on individual patient evaluation of risk and benefit from either TAVI or surgical aortic valve replacement. In addition, this statement features new wait time categories and treatment time goals for patients accepted for TAVI. Institutional requirements and recommendations for operator training and maintenance of competency have also been revised to reflect current standards. Procedural considerations such as decision-making for concomitant coronary intervention, antiplatelet therapy after intervention, and follow-up guidelines are also discussed. Finally, we suggest that all patients with aortic stenosis might benefit from evaluation by the heart team to determine the optimal individualized treatment decision.

The role of a commercial radiation dose index monitoring system in establishing local dose reference levels for fluoroscopically guided invasive cardiac procedures

PURPOSE

The primary goal was to evaluate local dose level for fluoroscopically guided invasive cardiac procedures in a high-volume activity catheterization laboratory, using automatic data registration with minimal impact on operator workload. The secondary goal was to highlight the relationship between dose indices and acquisition parameters, in order to establish an effective strategy for protocols optimization.

METHODS

From September 2016 to December 2018, a dosimetric survey was conducted in the 2 rooms of the catheterization laboratory of our institution. Data collection burden was minimized using a commercial Radiation Dose Index Monitoring System (RDIMs) that analyzes dicom files automatically sent by the x-ray equipment. Data were combined with clinical information extracted from the HIS records reported by the interventional cardiologist. Local dose levels were established for different invasive cardiac procedures.

RESULTS

A total of 3029 procedures performed for 2615 patients were analyzed. Median KAP were 21 Gycm² for invasive coronary angiography (ICA) procedures, 61 Gycm² for percutaneous coronary intervention (PCI) procedures, 59 Gycm² for combined (ICA+PCI) procedures, 87 Gycm² for structural heart intervention (TAVI) procedures. A significant dose reduction (51% for ICA procedures and 58% for PCI procedures) was observed when noise reduction acquisition techniques were applied.

CONCLUSIONS

RDIMs are effective tools in the establishment of local dose level in interventional cardiology, as they mitigate the burden to collect and register extensive dosimetric data and exposure parameters. Systematic review of data support the multi-disciplinary team in the definition of an effective strategy for protocol management and dose optimization.

The learning curve in transcatheter aortic valve implantation clinical studies: A systematic review

Background

Transcatheter aortic-valve implantation (TAVI) has become an essential alternative to surgical aortic-valve replacement in the treatment of symptomatic severe aortic stenosis, and this procedure requires technical expertise. The aim of this study was to identify prospective studies on TAVI from the past 10 years, and then to analyze the quality of information reported about the learning curve.

Materials and methods

A systematic review of articles published between 2007 and 2017 was performed using PubMed and the EMBASE database. Prospective studies regarding TAVI were included. The quality of information reported about the learning curve was evaluated using the following criteria: mention of the learning curve, the description of a roll-in phase, the involvement of a proctor, and the number of patients suggested to maintain skills.

Results

A total of sixty-eight studies met the selection criteria and were suitable for analysis. The learning curve was addressed in approximately half of the articles (n = 37, 54 percent). However, the roll-in period was mentioned by only eight studies (12 percent) and with very few details. Furthermore, a proctorship was disclosed in three articles (4 percent) whereas twenty-five studies (37 percent) included authors that were proctors for manufacturers of TAVI.

Conclusion

Many prospective studies on TAVI over the past 10 years mention learning curves as a core component of successful TAVI procedures. However, the quality of information reported about the learning curve is relatively poor, and uniform guidance on how to properly assess the learning curve is still missing.

Learning curve for transcatheter aortic valve replacement for native aortic regurgitation: Safety and technical performance study

Background

Transcatheter aortic valve replacement (TAVR) is a fundamentally new procedure for the treatment of native aortic regurgitation (AR). The number of cases needed to gain proficiency with the procedure is unknown.

Hypothesis

This study aimed to evaluate the learning curve for TAVR for native AR.

Methods

This study retrospectively reviewed a prospective database from 134 consecutive native AR patients who underwent the J‐valve TAVR system, which performed by a single team interventional cardiologist. The cumulative sum (CUSUM) method was used to analyze the learning curve. Patients were divided into two groups in chronological order, defined by the surgeon's early (group 1: the first 52 cases) and skilled (group 2: the next 82 cases) experience. Demographic data, intraoperative characteristics, and short‐term surgical outcomes were compared between the two groups.

Results

CUSUM plots revealed decreasing procedure time and fluoroscopy time after patients 52 and 43, respectively. The patient date consistently demonstrated that high‐risk scores and major perioperative parameters were comparable between the two groups. The use of contrast dye (group 1, 94.22 ± 30.07 mL; group 2, 70.43 ± 15.02 mL, P<.05), total procedure time (group 1, 84.96 ± 17.76 minutes; group 2, 59.95 ± 12.83 minutes, P<.05), and fluoroscopy time (group 1, 11.52 ± 3.81 minutes; group 2, 6.47 ± 1.53 minutes, P<.05) were significantly reduced in group 2. The overall device success rate in group 1 was 96.2% vs 96.3% in group 2 and remained high (P = 1.0). The overall 30‐day mortality was 3.8% in group 2 (group 1, 0 to group 2, 3.8%; P = .16). The complications rate, such as pulmonary hypertension, chronic kidney disease, and coronary artery disease were higher in group 2.

Conclusions

For a surgeon without previous TAVR experience, 52 cases of performance is the minimal requirement to gain the proficiency of TAVR for native AR. The skilled surgeons have been observed with reduced procedural time, fluoroscopy times, radiation exposure dose, and contrast volume usage. However, the overall prognosis was not significantly different between the two groups.

When the Complex Meets the High-Risk: Mechanical Cardiac Support Devices and Percutaneous Coronary Interventions in Severe Coronary Artery Disease

Coronary artery disease (CAD) remains a leading cause of mortality and morbidity worldwide. Few practice guidelines directly address the issue of revascularization in patients with CAD at higher risk of periprocedural complications. It remains a challenge to appropriately identify the subset of patients with CAD who will require short-term use of mechanical cardiocirculatory support devices (MCSDs) when high-risk (HR) percutaneous coronary intervention (PCI) is required. Issues of the complexity (coronary anatomy and high burden of comorbidities) and risk status (hemodynamic precarity or compromise) need to be considered when considering revascularization in patients. This review will focus on the evolving concept of protected PCI in patients with CAD, and how a balanced, integrated heart-team approach remains the path to optimal patient-centred care in the setting of HR-PCI supported with MCSD.

Developing process measures in value-based healthcare: the case of aortic valve disease

Background

As process measures can be means to change practices, this article presents process measures that impact on outcome measures for surgical aortic valve replacement (SAVR) and transcatheter aortic valve replacement (TAVR) within value-based healthcare.

Methods

Desk research and observations of patient trajectories were performed to map the processes involved in TAVR and SAVR. Semistructured interviews were conducted with healthcare professionals (n=8) and patients (n=2) to explore which processes were most important in relation to a standard set of outcome measures that was already monitored. Additionally, open interviews (n=2) were held to prioritise results. A focus group was performed for validation of the formulated process measures. Numerical data for these measures was not collected.

Results

Process maps of the full cycle of care of TAVR and SAVR treatments in theory and in practice were developed. 28 processes were found important by interview participants due to their expected impact on patient-relevant outcomes. Seven processes were prioritised to be most important and were formulated into 12 process measures for both TAVR and SAVR: ‘Number of times that deficient information provision to SAVR patients causes negative outcomes’, ‘Type of TAVR/SAVR prosthesis’, ‘Brand of TAVR prosthesis’, ‘Number of times the frailty score of a TAVR/SAVR patient >75 years is measured’, ‘Time between TAVR/SAVR surgery indication and surgery’, ‘Number of times that anticoagulants are stopped within 3 days before surgery’, ‘Time in hours between TAVR/SAVR surgery and permanent pacemaker implantation’ and ‘Percentage of standardised pain measurements’.

Conclusion

This study proposes an addition of select process measures to standard sets of outcome measures to improve healthcare quality. It illustrates a clear method for identifying process measures with impact on health outcomes in the future.

Association Between Hospital Volume and 30-Day Readmissions Following Transcatheter Aortic Valve Replacement

Importance

With the approval of transcatheter aortic valve replacement (TAVR) for patients with severe symptomatic aortic stenosis at intermediate surgical risk, TAVR volume is projected to increase exponentially in the United States. The 30-day readmission rate for TAVR was recently reported at 17.9%. The association between institutional TAVR volume and the 30-day readmission metric has not been examined.

Objective

To assess the association between hospital TAVR volume and 30-day readmission.

Design, Setting, and Participants

In this observational study, we used the 2014 Nationwide Readmissions Database to identify hospitals with established TAVR programs (performing at least 5 TAVRs in the first quarter of 2014). Based on annual TAVR volume, hospitals were classified as low (<50), medium (≥50 to <100), and high (≥100) volume. Rates, causes, and costs of 30-day readmissions were compared between low-, medium-, and high-volume hospitals. Data were analyzed from November to December 2016.

Exposure

Transcatheter aortic valve replacement.

Main Outcomes and Measures

Thirty-day readmissions.

Results

Of 129 hospitals included in this study, 20 (15.5%) were categorized as low volume, 47 (36.4%) as medium volume, and 62 (48.1%) as high volume. Of 16 252 index TAVR procedures, 663 (4.1%), 3067 (18.9%), and 12 522 (77.0%) were performed at low-, medium-, and high-volume hospitals, respectively. Thirty-day readmission rates were significantly lower in high-volume compared with medium-volume (adjusted odds ratio, 0.76; 95% CI, 0.68-0.85; P < .001) and low-volume (adjusted odds ratio, 0.75; 95% CI, 0.60-0.92; P = .007) hospitals. Noncardiac readmissions were more common in low-volume hospitals (65.6% vs 60.6% in high-volume hospitals), whereas cardiac readmissions were more common in high-volume hospitals (39.4% vs 34.4% in low-volume hospitals). There were no significant differences in length of stay and costs per readmission among the 3 groups (mean [SD], 5.5 [5.0] days vs 5.9 [7.5] days vs 6.0 [5.8] days; P = .74, and $13 886 [18 333] vs $14 135 [17 939] vs $13 432 [15 725]; P = .63, respectively).

Conclusions and Relevance

We report for the first time, to our knowledge, an inverse association between hospital TAVR volume and 30-day readmissions. Lower readmission at higher-volume hospitals was associated with significantly lower cost to the health care system.

TAVR Procedural Volumes and Patient Outcomes: Analysis of Recent Data

In less than 15 years, transcatheter aortic valve replacement (TAVR) has progressed from a procedure of last resort in patients at prohibitively high perioperative risk for major morbidity and mortality from surgical valve replacement to a viable alternative option to surgery in most patients with native (non-bicuspid) aortic valve stenosis. The number of medical centers offering TAVR has rapidly proliferated. There is mounting evidence that there are variations in patient outcomes associated with the yearly number of TAVR cases performed at each respective center. This review outlines the evolution of TAVR indications, common complications, the current literature addressing the association between procedural volumes and patient outcomes in TAVR, and offers a synopsis of risk factor assessment for patients considered for TAVR.

A retrospective study of conscious sedation versus general anaesthesia in patients scheduled for transfemoral aortic valve implantation: A single center experience

OBJECTIVES

The current 2017 ESC/EACTS guidelines recommend transcatheter aortic valve implantations (TAVIs) as the therapy of choice for inoperable patients with severe symptomatic aortic stenosis. Most of the TAVIs worldwide are performed under general anaesthesia (GA). Although conscious sedation (CS) concepts are increasingly applied in Europe, it is still a matter of debate which concept is associated with highest amount of safety for this high-risk patient population. The aim of this single center, before-and-after study was to investigate feasibility and safety of CS compared with GA with respect to peri-procedural complications and 30-day mortality in patients scheduled for transfemoral TAVI (TF-TAVI).

METHODS

From March 2012 until September 2014, patients scheduled for the TF-TAVI procedure were included in a prospective, observational manner. From the 200 patients finally included, 107 procedures were performed under GA, using either an endotracheal tube or a laryngeal mask, and balanced anaesthesia. CS was performed in 93 patients using low-dose propofol and remifentanil.

RESULTS

Conversion to GA was needed 4 times due to procedural-related complications (4.3%), in one patient due to ongoing agitation (1.1%). The CS-group showed significantly shorter key time courses: anaesthesia time (105 [95-120] minutes vs 115 [105-140] minutes, P-value = 0.009, Mann-Whitney-U-test) and length of stay in the intensive care unit (1.6 [1.0-1.5] d vs 2.1 [1.0-2.0] d, P-value = 0.002, Mann-Whitney-U-test). The lowest mean arterial pressure was significantly higher in the CS-group compared with the GA-group (74.3 mmHg vs 55.2 mmHg, P-value <0.0001, t-test). CS was associated with less requirements of norepinephrine (0.1 μg/kg vs 2.3 μg/kg, P-value <0.0001, Mann-Whitney-U-test).

CONCLUSIONS

Our single-center data demonstrate that CS is a feasible and safe alternative, especially with respect to a higher degree of intra-procedural haemodynamic stability, and a reduced length of stay in the intensive care unit.

Factors Associated with Discharge to a Skilled Nursing Facility after Transcatheter Aortic Valve Replacement Surgery

An assumption regarding transcatheter aortic valve replacement (TAVR), a minimally invasive procedure for treating aortic stenosis, is that patients remain at, or near baseline and soon return to their presurgical home to resume activities of daily living. However, this does not consistently occur. The purpose of this study was to identify preoperative factors that optimally predict discharge to a skilled nursing facility (SNF) after TAVR. Delineation of these conditions is an important step in developing a risk stratification model to assist in making informed decisions. Data was extracted from the American College of Cardiology (ACC) transcatheter valve therapy (TVT) registry and the Society of Thoracic Surgeons (STS) database on 285 patients discharged from 2012⁻2017 at a tertiary referral heart institute located in the southeastern region of the United States. An analysis of assessment, clinical and demographic variables was used to estimate relative risk (RR) of discharge to a SNF. The majority of participants were female (55%) and white (84%), with a median age of 82 years (interquartile range = 9). Approximately 27% (n = 77) were discharged to a SNF. Age > 75 years (RR = 2.3, p = 0.0026), female (RR = 1.6, p = 0.019), 5-meter walk test (5MWT) >7 s (RR = 2.0, p = 0.0002) and not using home oxygen (RR = 2.9, p = 0.0084) were identified as independent predictive factors for discharge to a SNF. We report a parsimonious risk-stratification model that estimates the probability of being discharged to a SNF following TAVR. Our findings will facilitate making informed treatment decisions regarding this older patient population.

Volume-outcome relationship in transcatheter aortic valve implantations in Germany 2008-2014: a secondary data analysis of electronic health records

OBJECTIVES

We examine the volume-outcome relationship in isolated transcatheter aortic valve implantations (TAVI). Our interest was whether the volume-outcome relationship for TAVI exists on the centre level, whether it occurs equally for different outcomes and how it develops over time.

DESIGN

Secondary data analysis of electronic health records. The comprehensive German Federal Bureau of Statistics Diagnosis Related Groups database was queried for data on all isolated TAVI procedures performed in Germany between 2008 and 2014. Logistic and linear regression analyses were carried out. Risk adjustment was applied using a predefined set of patient characteristics to account for differences in the risk factor composition of the patient populations between centres and over time. Centres performing TAVI were stratified into groups performing <50, 50-99 and ≥100 procedures per year.

SETTING

Germany 2008-2014.

PARTICIPANTS

All patients undergoing isolated TAVI in the observation period.

INTERVENTIONS

None.

PRIMARY AND SECONDARY OUTCOME MEASURES

In-hospital mortality, bleeding, stroke, probability of ventilation >48 hours, length of hospital stay and reimbursement.

RESULTS

Between 2008 and 2014, a total of 43 996 TAVI procedures were performed in 113 different centres in Germany with a total of 2532 cases of in-hospital mortality. Risk-adjusted in-hospital mortality decreases over the years and is lower the higher the annual procedure volume at the centre is. The magnitude of the latter effect declines over the observation period. Our results indicate a ceiling effect in the volume-outcome relationship: the volume-outcome relationship is eminent in circumstances of relatively unfavourable outcomes. Alongside improving outcomes, however, the volume-outcome relationship decreases. Also, a volume-outcome relationship seems to be absent in circumstances of constantly low event rates.

CONCLUSIONS

The hypothesised volume-outcome relationship for TAVI exists but diminishes and may disappear over time. This should be taken into account when considering mandatory minimum thresholds.

Regional Variation in Utilization, In-hospital Mortality, and Health-Care Resource Use of Transcatheter Aortic Valve Implantation in the United States

We queried the National Inpatient Sample database from 2012 to 2014 to identify all patients aged ≥18 years undergoing transcatheter aortic valve implantation (TAVI) in the United States. Regional differences in TAVI utilization, in-hospital mortality, and health-care resource use were analyzed. 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 TAVI implants per million adults increased from 24.8 in 2012 to 63.2 in 2014. The utilization of TAVI increased during the study period in all 4 geographic regions, with the number of implants per million adults being highest in the Northeast, followed by the Midwest, South, and West, respectively. Overall in-hospital mortality was 4.2%. Compared with the Northeast, risk-adjusted in-hospital mortality was higher in the Midwest (adjusted odds ratio [aOR] 1.26 [1.07 to 1.48]) and the South (aOR 1.61 [1.40 to 1.85]) and similar in the West (aOR 1.00 [0.84 to 1.18]). Average length of stay was shorter in all other regions compared with the Northeast. Among patients surviving to discharge, disposition to a skilled nursing facility or home health care was most common in the Northeast, whereas home discharge was most common in the West. Average hospital costs were highest in the West. In conclusion, we observed significant regional differences in TAVI utilization, in-hospital mortality, and health-care resource use in the United States. The findings of our study may have important policy implications and should provide an impetus to understand the source of this regional variation.

Learning Curves Among All Patients Undergoing Transcatheter Aortic Valve Implantation in Germany: A Retrospective Observational Study

BACKGROUND

Transcatheter aortic valve implantation (TAVI) is a rapidly evolving technique for therapy of aortic stenosis. Previous studies report learning curves with respect to in-hospital mortality and clinical complications. We aim to determine whether observed improvements of in-hospital outcomes after TAVI are the result of improvements in procedures or due to a change in the patient population, and whether improvements differ between the transfemoral (TF) and the transapical (TA) approach.

METHODS

Data was analyzed using risk-adjusted regression analyses in order to track the development of clinical outcomes of all isolated TAVI procedures performed in Germany from 2008 to 2013 (N=32.436) in all German hospitals performing TAVI. Measurements include in-hospital mortality, stroke, bleeding, and mechanical ventilation.

RESULTS

Unadjusted mortality rates decrease over time for both TA-TAVI and TF-TAVI. Reductions in mortality were smaller for TA-TAVI than for TF-TAVI. These trends could also be observed for risk-adjusted (standardized) mortality rates, indicating that time trends and differences between TA-TAVI (around 7% in 2013) and TF-TAVI (around 4% in 2013) cannot be explained by changes in the risk factor composition of the patient populations. Bleeding complications decreased for both access routes. Both unadjusted and standardized bleeding rates were substantially higher for TA-TAVI. In addition, TA-TAVI procedures were associated with an increased likelihood of requiring >48h of mechanical ventilation.

CONCLUSIONS

Observed improvements in TAVI-related in-hospital mortality are not due to a change in patient population. The results indicate the superiority of a TF-first approach.

Use of extracorporeal membrane oxygenation in complicated transcatheter aortic valve replacement

OBJECTIVES

Although transcatheter aortic valve replacement (TAVR) is an excellent alternative procedure for high-risk patients with severe symptomatic aortic stenosis, it is often associated with life-threatening complications. We report on the emergency or elective use of veno-arterial extracorporeal membrane oxygenation (ECMO) to manage these complications.

METHODS

Between December 2013 and February 2016, 46 patients underwent TAVR at our institution. Of these, 4 patients required emergency ECMO support and another 3 patients were electively placed on ECMO support at the start of the procedure. The mean age of the ECMO patients was 87.3 ± 3.6 years and all were female. The Society of Thoracic Surgeons-predicted risk of mortality score in these patients was 12.2 ± 6.2%.

RESULTS

TAVR with ECMO was completed through the transapical approach in 6 patients, and the transfemoral approach in 1 patient. The arterial access route for ECMO was the femoral artery in 5, the external iliac artery in 1, and the subclavian artery in 1. Indications for the use of emergency ECMO were hemodynamic instability in 2, cardiogenic shock in 2, while indications for elective ECMO were severe pulmonary hypertension, impaired left ventricular function and a combination of these. There was no 30-day mortality, and the 1-year survival rate was 83.3% with no significant difference compared to patients without ECMO support.

CONCLUSION

The use of ECMO in very high-risk patients undergoing TAVR may increase safety and contribute to excellent outcomes. Although ECMO support is rarely needed in TAVR, a well-prepared treatment strategy by the heart team is mandatory.

Learning effect and diffusion of innovative medical devices: the case of transcatheter aortic valve implantation in Italy

AIM

We investigated the diffusion of transcatheter aortic valve implantation (TAVI) since its introduction into the Italian market aimed at identifying the potential drivers of uptake and diffusion at hospital and regional levels.

MATERIALS & METHODS

We estimated the determinants of TAVI diffusion in Italy from 2007 to 2015 with a regression analysis based on registry data.

RESULTS

Since 2007, TAVI has shown significant diffusion rates in Italy. The diffusion is positively correlated with implanting centers' experience and with the presence of key opinion leaders. Regional recommendations on the use of TAVI negatively influence the diffusion. Reimbursement policies do not exert a relevant impact.

CONCLUSION

Learning effect seems to be the major driver of TAVI diffusion in Italy.

Avoiding the Learning Curve for Transcatheter Aortic Valve Replacement

Objectives. To evaluate whether collaboration between existing and new transcatheter aortic valve replacement (TAVR) programs could help reduce the number of cases needed to achieve optimal efficiency. Background. There is a well-documented learning curve for achieving procedural efficiency and safety in TAVR procedures. Methods. A multidisciplinary collaboration was established between the Minneapolis VA Medical Center (new program) and the University of Minnesota (established program since 2012, n = 219) 1 year prior to launching the new program. Results. 269 patients treated with TAVR (50 treated in the first year at the new program). Mean age was 76 (±18) years and STS score was 6.8 (±6). Access included transfemoral (n = 35, 70%), transapical (n = 8, 16%), transaortic (n = 2, 4%), and subclavian (n = 5, 10%) types. Procedural efficiency (procedural time 158 ± 59 versus 148 ± 62, p = 0.27), device success (96% versus 87%, p = 0.08), length of stay (5 ± 3 versus 6 ± 7 days, p = 0.10), and safety (in hospital mortality 4% versus 6%, p = 0.75) were similar between programs. We found no difference in outcome measures between the first and last 25 patients treated during the first year of the new program. Conclusions. Establishing a partnership with an established program can help mitigate the learning curve associated with these complex procedures.

Neurological Injury in Intermediate-Risk Transcatheter Aortic Valve Implantation

BACKGROUND

The application of transcatheter aortic valve implantation (TAVI) to intermediate-risk patients is a controversial issue. Of concern, neurological injury in this group remains poorly defined. Among high-risk and inoperable patients, subclinical injury is reported on average in 75% undergoing the procedure. Although this attendant risk may be acceptable in higher-risk patients, it may not be so in those of lower risk.

METHODS AND RESULTS

Forty patients undergoing TAVI with the Edwards SAPIEN-XT™ prosthesis were prospectively studied. Patients were of intermediate surgical risk, with a mean±standard deviation Society of Thoracic Surgeons score of 5.1±2.5% and a EuroSCORE II of 4.8±2.4%; participant age was 82±7 years. Clinically apparent injury was assessed by serial National Institutes of Health Stroke Scale assessments, Montreal Cognitive Assessments (MoCA), and with the Confusion Assessment Method. These identified 1 (2.5%) minor stroke, 1 (2.5%) episode of postoperative delirium, and 2 patients (5%) with significant postoperative cognitive dysfunction. Subclinical neurological injury was assessed using brain magnetic resonance imaging, including diffusion-weighted imaging (DWI) sequences preprocedure and at 3±1 days postprocedure. This identified 68 new DWI lesions present in 60% of participants, with a median±interquartile range of 1±3 lesions/patient and volumes of infarction of 24±19 μL/lesion and 89±218 μL/patient. DWI lesions were associated with a statistically significant reduction in early cognition (mean ΔMoCA -3.5±1.7) without effect on cognition, quality of life, or functional capacity at 6 months.

CONCLUSIONS

Objectively measured subclinical neurological injuries remain a concern in intermediate-risk patients undergoing TAVI and are likely to manifest with early neurocognitive changes.

CLINICAL TRIAL REGISTRATION

URL: http://www.anzctr.org.au. Australian & New Zealand Clinical Trials Registry: ACTRN12613000083796.

Clinical outcomes of transcatheter aortic valve implantation: from learning curve to proficiency

Objective

The use of transcatheter aortic valve implantation (TAVI) is growing rapidly in countries with a predominantly elderly population, posing a huge challenge to healthcare systems worldwide. The increment of human and economic resource consumption imposes a careful monitoring of clinical outcomes and cost-benefit balance, and this article is aimed at analysing clinical outcomes related to the TAVI learning curve.

Methods

Outcomes of 177 consecutive transfemoral TAVI procedures performed in 5 years by a single team were analysed by the Cumulative Sum of failures method (CUSUM) according to the clinical events comprised in the Valve Academic Research Consortium (VARC-2) safety end point and the VARC-2 definition of device success. Margins for events acceptance were extrapolated from landmark trials that tested both balloon or self-expandable percutaneous valves.

Results

30-day and 1-year survival rates were 97.2% and 89.9%, respectively. Achievement of the primary end point (number of cases needed to provide the acceptable margin of the composite end point of any death, stroke, myocardial infarction, life-threatening bleeding, major vascular complications, stage 2–3 acute kidney injury and valve-related dysfunction requiring a repeat procedure) required the performance of 54 cases, while the learning curve to achieve ‘device success’ identified 32 cases to reach the expected proficiency. In this experience, the baseline clinical risk as assessed by the Society of Thoracic Surgeons (STS) score determined the long-term survival rather than the adverse events related to the learning curve.

Conclusions

A relatively large number of cases are required to achieve clinical outcomes comparable to those reported in high-volume centres and controlled trials. According to our national workload standards, this represents more than 2 years of continuous activity.

Effect of Clinical Trial Experience on Transcatheter Aortic Valve Replacement Outcomes

BACKGROUND

Transcatheter aortic valve replacement (TAVR) was approved by the Food and Drug Administration (FDA) in November 2011 after a collaborative technology development process involving professional medical societies, the medical device industry, and the FDA. After FDA approval, TAVR was adopted by numerous hospitals that had not participated in TAVR clinical trials. It is uncertain if outcomes at these hospitals were comparable with those at clinical trial hospitals.

METHODS AND RESULTS

All patients with Medicare physician claims for TAVR between January 1, 2011, and November 30, 2012, were identified, and postoperative mortality was assessed using Medicare enrollment data. Risk-adjusted mortality was calculated via a multivariable model that adjusted for demographics and comorbidities. We identified 5009 patients who underwent TAVR, with 3617 TAVRs performed at 68 hospitals that had participated in clinical trials and 1392 TAVRs performed at 140 nontrial hospitals. The preoperative characteristics of patients at trial versus nontrial hospitals were similar. There were no significant differences in risk-adjusted 30-day mortality (5.9% versus 5.6%, odds ratio, 0.88; 95% confidence interval, 0.66-1.15; P=0.34) or 180-day mortality (16.5% versus 15.8%, odds ratio, 0.99; 95% confidence interval, 0.75-1.3; P=0.94).

CONCLUSIONS

Patients undergoing TAVR at nontrial hospitals had comparable clinical outcomes to patients undergoing TAVR at clinical trial hospitals. This finding contrasts with several other cardiovascular devices and procedures for which higher mortality was observed at hospitals that did not participate in clinical trials. The unique policy and regulatory environment governing TAVR adoption by hospitals may have contributed to better outcomes during the technology diffusion process.

Learning curves for transapical transcatheter aortic valve replacement in the PARTNER-I trial: Technical performance, success, and safety

OBJECTIVES

Introduction of hybrid techniques, such as transapical transcatheter aortic valve replacement (TA-TAVR), requires skills that a heart team must master to achieve technical efficiency: the technical performance learning curve. To date, the learning curve for TA-TAVR remains unknown. We therefore evaluated the rate at which technical performance improved, assessed change in occurrence of adverse events in relation to technical performance, and determined whether adverse events after TA-TAVR were linked to acquiring technical performance efficiency (the learning curve).

METHODS

From April 2007 to February 2012, 1100 patients, average age 85.0 ± 6.4 years, underwent TA-TAVR in the PARTNER-I trial. Learning curves were defined by institution-specific patient sequence number using nonlinear mixed modeling.

RESULTS

Mean procedure time decreased from 131 to 116 minutes within 30 cases (P = .06) and device success increased to 90% by case 45 (P = .0007). Within 30 days, 354 patients experienced a major adverse event (stroke in 29, death in 96), with possibly decreased complications over time (P ∼ .08). Although longer procedure time was associated with more adverse events (P < .0001), these events were associated with change in patient risk profile, not the technical performance learning curve (P = .8).

CONCLUSIONS

The learning curve for TA-TAVR was 30 to 45 procedures performed, and technical efficiency was achieved without compromising patient safety. Although fewer patients are now undergoing TAVR via nontransfemoral access, understanding TA-TAVR learning curves and their relationship with outcomes is important as the field moves toward next-generation devices, such as those to replace the mitral valve, delivered via the left ventricular apex.

Using simulation for teaching femoral arterial access: A multicentric collaboration

OBJECTIVE

To assess the impact of simulation training on complications associated with femoral arterial access obtained by first year cardiology fellows.

BACKGROUND

Prior studies demonstrate a higher incidence of arterial access related complications among patients undergoing invasive cardiac procedures.

METHODS

First year cardiology fellows at four teaching hospitals in Michigan tracked their femoral access experience and any associated complications between July 2011 and June 2013. Fellows starting their academic training in July 2012 were first trained on a specially developed simulator before starting their rotation in the catheterization laboratory. The primary outcome was access proficiency, defined as five successful femoral access attempts without any complication or need to seek help from a more experienced team member.

RESULTS

A total of 1,278 femoral access attempts were made by 21 fellows in 2011-2012 compared with 869 femoral access attempts made by 21 fellows in 2012-2013. There was a lower rate of access related complications in patients undergoing access attempts by first year fellows in year 2 compared with year 1 (2.1% versus 4.5%, P = 0.003). The number of procedures to achieve procedural proficiency was significantly higher in year 1 compared with year 2 (median 20 versus 10, P = 0.007).

CONCLUSIONS

Incorporation of simulation in the training of first year fellows was associated with an improvement in proficiency and a clinically meaningful reduction in vascular complications.

Predictors of Permanent Pacemaker Implantation After Transcatheter Aortic Valve Replacement

OBJECTIVE

Determine predictors of permanent pacemaker (PPM) implantation after transcatheter aortic valve replacement (TAVR).

DESIGN

A retrospective chart review of patients undergoing TAVR at the authors' institution. Extracted data included patient demographics, electrocardiogram, procedural, and echocardiographic data. Multivariate regression was performed to identify associations with PPM implantation.

SETTING

Single-center academic hospital.

PARTICIPANTS

Patients undergoing TAVR.

INTERVENTIONS

This study was retrospective. No interventions were performed on patients.

MEASUREMENTS AND MAIN RESULTS

Baseline electrocardiogram, Society of Thoracic Surgeons score, age, and echocardiographic parameters were not predictors of PPM implantation. However, multiple deployments was a risk factor, and degree of paravalvular leak trended toward significance. Ten patients required placement of a 2nd valve, or valve-in-valve (VIV). Of the 10 patients with VIV, 5 (50%) required a PPM, compared with 8 (14%) of 56 patients with a single valve (OR 6.0, p = 0.02). PPM implantation occurred in 5 (42%) patients with no leak, 8 (19%) patients with trace leak, and no patients with mild or moderate leak (p = 0.085). In patients with no or trace leak, VIV increased the likelihood of PPM from 17.4% to 62.5% (OR 7.9, p = 0.006). For the 42 patients with trace leak, VIV increased the likelihood of PPM from 11.4% to 57.1% (OR 10.33, p = 0.005).

CONCLUSIONS

The authors found VIV placement, and likely degree of paravalvular leak, to be predictors of PPM placement. VIV and the degree of leak may be useful markers for postoperative prophylactic pacemaker placement.

Influence of experience and the surgical learning curve on long-term patient outcomes in cardiac surgery

OBJECTIVE

We hypothesized that increased postgraduate surgical experience correlates with improved operative efficiency and long-term survival in standard cardiac surgery procedures.

METHODS

Utilizing a prospectively collected retrospective database, we identified patients who underwent isolated coronary artery bypass grafting (CABG) (n = 3726), aortic valve replacement (AVR) (n = 1626), mitral valve repair (n = 731), mitral valve replacement (MVR) (n = 324), and MVR + AVR (n = 184) from January 2002 through June 2012. After adjusting for patient risk and surgeon variability, we evaluated the influence of surgeon experience on cardiopulmonary bypass and crossclamp times, and long-term survival.

RESULTS

Mean surgeon experience after fellowship graduation was 16.0 ± 11.7 years (range, 1.0-35.2 years). After adjusting for patient risk and surgeon-level fixed effects, learning curve analyses demonstrated improvements in cardiopulmonary bypass and crossclamp times with increased surgeon experience. There was marginal improvement in the predictability (R(2) value) of cardiopulmonary bypass and crossclamp time for CABG with the addition of surgeon experience; however, all other procedures had marked increases in the R(2) following addition of surgeon experience. Cox proportional hazard models revealed that increased surgeon experience was associated with improved long-term survival in AVR (hazard ratio [HR], 0.85; P < .0001), mitral valve repair (HR, 0.73; P < .0001), and MVR + AVR (HR, 0.95; P = .006) but not in CABG (HR, 0.80; P = .15), and a trend toward significance in MVR (HR, 0.87; P = .09).

CONCLUSIONS

In cardiac surgery, not including CABG, surgeon experience is an important determinant of operative efficiency and of long-term survival.

5-year outcomes of transcatheter aortic valve replacement or surgical aortic valve replacement for high surgical risk patients with aortic stenosis (PARTNER 1): a randomised controlled trial

BACKGROUND

The Placement of Aortic Transcatheter Valves (PARTNER) trial showed that mortality at 1 year, 2 years, and 3 years is much the same with transcatheter aortic valve replacement (TAVR) or surgical aortic valve replacement (SAVR) for high-risk patients with aortic stenosis. We report here the 5-year outcomes.

METHODS

We did this randomised controlled trial at 25 hospitals, in Canada (two), Germany (one), and the USA (23). We used a computer-generated randomisation sequence to randomly assign high-risk patients with severe aortic stenosis to either SAVR or TAVR with a balloon-expandable bovine pericardial tissue valve by either a transfemoral or transapical approach. Patients and their treating physicians were not masked to treatment allocation. The primary outcome of the trial was all-cause mortality in the intention-to-treat population at 1 year, we present here predefined outcomes at 5 years. The study is registered with ClinicalTrials.gov, number NCT00530894.

FINDINGS

We screened 3105 patients, of whom 699 were enrolled (348 assigned to TAVR, 351 assigned to SAVR). Overall mean Society of Thoracic Surgeons Predicted Risk of Mortality score was 11·7%. At 5 years, risk of death was 67·8% in the TAVR group compared with 62·4% in the SAVR group (hazard ratio 1·04, 95% CI 0·86-1·24; p=0·76). We recorded no structural valve deterioration requiring surgical valve replacement in either group. Moderate or severe aortic regurgitation occurred in 40 (14%) of 280 patients in the TAVR group and two (1%) of 228 in the SAVR group (p<0·0001), and was associated with increased 5-year risk of mortality in the TAVR group (72·4% for moderate or severe aortic regurgitation vs 56·6% for those with mild aortic regurgitation or less; p=0·003).

INTERPRETATION

Our findings show that TAVR as an alternative to surgery for patients with high surgical risk results in similar clinical outcomes.

FUNDING

Edwards Lifesciences.

Temporal Trends in Quality of Life Outcomes After Transapical Transcatheter Aortic Valve Replacement: A Placement of AoRTic TraNscathetER Valve (PARTNER) Trial Substudy

BACKGROUND

In the Placement of AoRTic TraNscathetER Valve (PARTNER) randomized controlled trial (RCT), which represented the first exposure to transapical transcatheter aortic valve replacement (TA-TAVR) for many clinical sites, high-risk patients undergoing TA-TAVR derived similar health-related quality of life (HRQoL) outcomes when compared with surgical aortic valve replacement (SAVR). With increasing experience, it is possible that HRQoL outcomes of TA-TAVR may have improved.

METHODS AND RESULTS

We evaluated HRQoL outcomes at 1-, 6-, and 12-month follow-ups among 875 patients undergoing TA-TAVR in the PARTNER nonrandomized continued access (NRCA) registry and compared these outcomes with those of the TA-TAVR and SAVR patients in the PARTNER RCT. HRQoL was assessed with the Kansas City Cardiomyopathy Questionnaire (KCCQ), the Medical Outcomes Study Short-Form 12, and the EuroQoL-5D, with the KCCQ overall summary score serving as the primary end point. The NRCA TA-TAVR and RCT TA-TAVR and SAVR groups were generally similar. The primary outcome, the KCCQ summary score, did not differ between the NRCA TA-TAVR and the RCT TA-TAVR group at any follow-up timepoints, although there were small differences in favor of the NRCA cohort on several KCCQ subscales at 1 month. There were no significant differences in follow-up HRQOL between the NRCA-TAVR and the RCT SAVR cohorts on the KCCQ overall summary scale or any of the disease-specific or generic subscales.

CONCLUSIONS

Despite greater experience with TA-TAVR in the NRCA registry, HRQoL outcomes remained similar to those of TA-TAVR in the original RCT cohort and no better than those with SAVR. These findings have important implications for patient selection for TAVR when transfemoral access is not an option.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00530894.

Dynamics of device innovation: implications for assessing value

BACKGROUND

In recent years, there has been growing interest in evaluating the health and economic impact of medical devices. Payers increasingly rely on cost-effectiveness analyses in making their coverage decisions, and are adopting value-based purchasing initiatives. These analytic approaches, however, have been shaped heavily by their use in the pharmaceutical realm, and are ill-adapted to the medical device context.

METHODS

This study focuses on the development and evaluation of left ventricular assist devices (LVADs) to highlight the unique challenges involved in the design and conduct of device trials compared with pharmaceuticals.

RESULTS

Devices are moving targets characterized by a much higher degree of post-introduction innovation and "learning by using" than pharmaceuticals. The cost effectiveness ratio of left ventricular assist devices for destination therapy, for example, decreased from around $600,000 per life year saved based on results from the pivotal trial to around $100,000 within a relatively short time period.

CONCLUSIONS

These dynamics pose fundamental challenges to the evaluation enterprise as well as the policy-making world, which this paper addresses.

Predictors and incidence of access site complications in transcatheter aortic valve implantation with the use of new delivery systems

Objectives:

The aim of this single-center study was to assess the incidence and predictors of in-hospital access site complications related to transcatheter aortic valve implantation (TAVI) performed with new delivery systems in our hospital which has the largest case series in Turkey.

Materials and method:

We performed successful TAVI with the Edwards Sapien XT valve to 127 (46 male) patients via a transfemoral (121), trans-subclavian (5) and transapical (1) approach. Access site complications were defined according to the Valve Academic Research Consortium (VARC) end-point definitions.

Results:

Vascular complications occurred in 10.1% of patients. There was negative correlation between vascular complications and diameter of the common femoral artery (r = − 0.301, p=0.004), external iliac artery (r = − 0.327, p=0.004) and common iliac artery (r = − 0.324, p=0.004), but positive correlation between diabetes (r =0.240, p=0.008), sheath to femoral artery ratio (SFAR), sheath to external iliac artery ratio (SEIAR), procedure time, discharge time and the Society of Thoracic Surgeons (STS) score (respectively; r=0.339, 0.001, 0.527, 0.361, 0.289, p=0.003, 0.001, 0.001, 0.001, 0.002). The incidence of vascular complications was significantly higher in patients with diabetes and a high STS score. VARC bleeding complications occurred in 11.7 % of patients. The learning curve pointing out the importance of experience was significantly important in decreasing both bleeding and vascular complications.

Conclusions:

In this study, we demonstrated that major vascular complications related to TAVI decrease with the use of smaller delivery systems and experience and increase with high-risk scores (STS) and the presence of diabetes. In addition, VARC major vascular complications, observed mostly in patients with diabete mellitus (DM) and high STS scores, were associated with vascular diameters. These results further underline the importance of experience and a multidisciplinary team in patient selection and management for TAVI.

Learning curves for cardiothoracic and vascular surgical procedures--a systematic review

OBJECTIVES

The aim of this systematic review is to evaluate the learning curve (LC) literature and identify the LC of cardiothoracic and vascular surgical procedures.

SUMMARY AND BACKGROUND

The LC describes an observation that a learner's performance improves over time during acquisition of new motor skills. Measuring the LC of surgical procedures has important implications for surgical innovation, education, and patient safety. Numerous studies have investigated LCs of isolated operations in cardiothoracic and vascular surgeries, but a lack of uniformity in the methods and variables used to measure LCs has led to a lack of systematic reviews.

METHODS

The MEDLINE®, EMBASE™, and PsycINFO® databases were systematically searched until July 2013. Articles describing LCs for cardiothoracic and vascular procedures were included. The type of procedure, statistical analysis, number of participants, procedure setting, level of participants, outcomes, and LCs were reviewed.

RESULTS

A total of 48 studies investigated LCs in cardiothoracic and vascular surgeries. Based on operating time, the LC for coronary artery bypass surgery ranged between 15 and 100 cases; for endoscopic vessel harvesting and other cardiac vessel surgery between 7 and 35 cases; for valvular surgery, which included repair and replacement, between 20 and 135 cases; for video-assisted thoracoscopic surgery, between 15 and 35 cases; for vascular neurosurgical procedures between 100 and 500 cases, based on complications; for endovascular vessel repairs between 5 and 40 cases; and for ablation procedures between 25 and 60 cases. However there was a distinct lack of standardization in the variables/outcome measures used, case selection, prior experience, and supervision of participating surgeons and a range of statistical analyses to compute LCs was noted.

CONCLUSION

LCs in cardiothoracic and vascular procedures are hugely variable depending on the procedure type, outcome measures, level of prior experience, and methods/statistics used. Uniformity in methods, variables, and statistical analysis is needed to derive meaningful comparisons of LCs. Acknowledgment and application of learning processes other than those reliant on volume-outcomes relationship will benefit LC research and training of surgeons.

Health-related quality of life after transcatheter or surgical aortic valve replacement in high-risk patients with severe aortic stenosis: an updated review of literature

Recent trials have highlighted the comparable mortality benefits and durability of the results for patients with severe aortic stenosis (AS) and high surgical risk managed with either transcatheter aortic valve replacement (TAVR) or surgical aortic valve replacement (AVR). Various national guidelines and international regulatory bodies have approved TAVR, thereby leading to potential wide usage and dissemination of this technique worldwide. Quality-of-life outcomes, in spite of being an important measure of success and acceptability of the procedure, have not been publicized as extensively. For high risk patients with severe AS, implementation of TAVR has resulted in comparable survival, but different and novel adverse events compared with AVR. We present an updated review focusing on the quality-of-life outcomes and issues with this new and important procedural approach.

Multidisciplinary team approach for identifying potential candidate for transcatheter aortic valve implantation

PURPOSE

We sought to evaluate the clinical usefulness of decision making by a multidisciplinary heart team for identifying potential candidates for transcatheter aortic valve implantation (TAVI) in patients with symptomatic severe aortic stenosis.

MATERIALS AND METHODS

The multidisciplinary team consisted of two interventional cardiologists, two cardiovascular surgeons, one cardiac imaging specialist, and two cardiac anesthesiologists.

RESULTS

Out of 60 patients who were screened as potential TAVI candidates, 31 patients were initially recommended as appropriate for TAVI, and 20 of these 31 eventually underwent TAVI. Twenty-two patients underwent surgical aortic valve replacement (AVR), and 17 patients received only medical treatment. Patients who underwent TAVI and medical therapy were older than those who underwent surgical AVR (p<0.001). The logistic Euroscore was significantly highest in the TAVI group and lowest in the surgical AVR group (p=0.012). Most patients in the TAVI group (90%) and the surgical AVR group (91%) had severe cardiac symptoms, but only 47% in the medical therapy group had severe symptoms. The cumulative percentages of survival without re-hospitalization or all-cause death at 6 months for the surgical AVR, TAVI, and medical therapy groups were 84%, 75%, and 28%, respectively (p=0.007, by log-rank).

CONCLUSION

TAVI was recommended in half of the potential candidates following a multidisciplinary team approach and was eventually performed in one-third of these patients. One-third of the patients who were initially considered potential candidates received surgical AVR with favorable clinical outcomes.