Comparison of Outcomes After Transcatheter vs Surgical Aortic Valve Replacement Among Patients at Intermediate Operative Risk With a History of Coronary Artery Bypass Graft Surgery: A Post Hoc Analysis of the SURTAVI Randomized Clinical Trial | Valvular Heart Disease | JAMA Cardiology | JAMA Network
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Figure.  Exercise Capacity and Quality-of-Life Outcomes at 1 Year
Exercise Capacity and Quality-of-Life Outcomes at 1 Year

A, The mean difference in meters walked at 30 days and 1 year relative to baseline in patients receiving transcatheter aortic valve replacement (TAVR; 112 patients at 30 days and 103 at 1 year) and surgical aortic valve replacement (SAVR; 103 patients at 30 days and 90 at 1 year). B, Mean Kansas City Cardiomyopathy Questionnaire (KCCQ) overall summary score for patients receiving TAVR and SAVR. Data were available at baseline, 30 days, 6 months, and 1 year for 135, 133, 121, and 116 patients receiving TAVR, respectively, and for 133, 123, 120, and 106 patients receiving SAVR. The difference between groups was significant at 30 days.

aP < .001.

bP = .04.

Table 1.  Baseline Demographic Characteristics and Medical History
Baseline Demographic Characteristics and Medical History
Table 2.  30-Day and 1-Year Adjudicated Outcomesa
30-Day and 1-Year Adjudicated Outcomesa
1.
Biancari  F, Onorati  F, Mariscalco  G,  et al.  First-time, isolated surgical aortic valve replacement after prior coronary artery bypass surgery: results from the RECORD multicenter registry.  J Card Surg. 2014;29(4):450-454. doi:10.1111/jocs.12365PubMedGoogle ScholarCrossref
2.
Vohra  HA, Pousios  D, Whistance  RN,  et al.  Aortic valve replacement in patients with previous coronary artery bypass grafting: 10-year experience.  Eur J Cardiothorac Surg. 2012;41(3):e1-e6. doi:10.1093/ejcts/ezr212PubMedGoogle ScholarCrossref
3.
Khaladj  N, Shrestha  M, Peterss  S,  et al.  Isolated surgical aortic valve replacement after previous coronary artery bypass grafting with patent grafts: is this old-fashioned technique obsolete?  Eur J Cardiothorac Surg. 2009;35(2):260-264. doi:10.1016/j.ejcts.2008.09.051PubMedGoogle ScholarCrossref
4.
Odell  JA, Mullany  CJ, Schaff  HV, Orszulak  TA, Daly  RC, Morris  JJ.  Aortic valve replacement after previous coronary artery bypass grafting.  Ann Thorac Surg. 1996;62(5):1424-1430. doi:10.1016/0003-4975(96)00635-2PubMedGoogle ScholarCrossref
5.
Byrne  JG, Karavas  AN, Filsoufi  F,  et al.  Aortic valve surgery after previous coronary artery bypass grafting with functioning internal mammary artery grafts.  Ann Thorac Surg. 2002;73(3):779-784. doi:10.1016/S0003-4975(01)03456-7PubMedGoogle ScholarCrossref
6.
Reardon  MJ, Van Mieghem  NM, Popma  JJ,  et al; SURTAVI Investigators.  Surgical or transcatheter aortic-valve replacement in intermediate-risk patients.  N Engl J Med. 2017;376(14):1321-1331. doi:10.1056/NEJMoa1700456PubMedGoogle ScholarCrossref
7.
Kappetein  AP, Head  SJ, Généreux  P,  et al; Valve Academic Research Consortium-2.  Updated standardized endpoint definitions for transcatheter aortic valve implantation: the Valve Academic Research Consortium-2 consensus document.  J Thorac Cardiovasc Surg. 2013;145(1):6-23. doi:10.1016/j.jtcvs.2012.09.002PubMedGoogle ScholarCrossref
8.
Arnold  SV, Reynolds  MR, Wang  K,  et al; CoreValve US Pivotal Trial Investigators.  Health status after transcatheter or surgical aortic valve replacement in patients with severe aortic stenosis at increased surgical risk: results from the CoreValve US pivotal trial.  JACC Cardiovasc Interv. 2015;8(9):1207-1217. doi:10.1016/j.jcin.2015.04.018PubMedGoogle ScholarCrossref
9.
ATS Committee on Proficiency Standards for Clinical Pulmonary Function Laboratories.  ATS statement: guidelines for the six-minute walk test.  Am J Respir Crit Care Med. 2002;166(1):111-117. doi:10.1164/ajrccm.166.1.at1102PubMedGoogle ScholarCrossref
10.
Gupta  T, Khera  S, Kolte  D,  et al.  Transcatheter versus surgical aortic valve replacement in patients with prior coronary artery bypass grafting: trends in utilization and propensity-matched analysis of in-hospital outcomes.  Circ Cardiovasc Interv. 2018;11(4):e006179. doi:10.1161/CIRCINTERVENTIONS.117.006179PubMedGoogle ScholarCrossref
11.
Reinöhl  J, Kaier  K, Reinecke  H,  et al.  Transcatheter aortic valve replacement: the new standard in patients with previous coronary bypass grafting?  JACC Cardiovasc Interv. 2016;9(20):2137-2143. doi:10.1016/j.jcin.2016.07.035PubMedGoogle ScholarCrossref
12.
Greason  KL, Mathew  V, Suri  RM,  et al.  Transcatheter versus surgical aortic valve replacement in patients with prior coronary artery bypass graft operation: a PARTNER trial subgroup analysis.  Ann Thorac Surg. 2014;98(1):1-7. doi:10.1016/j.athoracsur.2014.02.079PubMedGoogle ScholarCrossref
13.
Conte  JV, Gleason  TG, Resar  JR,  et al.  Transcatheter or surgical aortic valve replacement in patients with prior coronary artery bypass grafting.  Ann Thorac Surg. 2016;101(1):72-79. doi:10.1016/j.athoracsur.2015.06.067PubMedGoogle ScholarCrossref
14.
Ando  T, Briasoulis  A, Holmes  AA, Afonso  L, Schreiber  T, Kondur  A.  Transcatheter aortic valve replacement versus surgical aortic valve replacement in patients with previous coronary artery bypass surgery: a systematic review and meta-analysis.  Int J Cardiol. 2016;215:14-19. doi:10.1016/j.ijcard.2016.04.033PubMedGoogle ScholarCrossref
Brief Report
June 19, 2019

Comparison of Outcomes After Transcatheter vs Surgical Aortic Valve Replacement Among Patients at Intermediate Operative Risk With a History of Coronary Artery Bypass Graft Surgery: A Post Hoc Analysis of the SURTAVI Randomized Clinical Trial

Author Affiliations
  • 1Houston Methodist DeBakey Heart and Vascular Center, Houston, Texas
  • 2St Antonius Hospital, Nieuwegein, the Netherlands
  • 3Erasmus University Medical Center, Rotterdam, the Netherlands
  • 4NYU Langone Medical Center, New York, New York
  • 5OhioHeath Riverside Methodist Hospital, Columbus, Ohio
  • 6The Johns Hopkins University, Baltimore, Maryland
  • 7Iowa Heart Center, Des Moines
  • 8St Francis Hospital, Roslyn, New York
  • 9Medtronic, Minneapolis, Minnesota
  • 10Beth Israel Deaconess Medical Center, Boston, Massachusetts
JAMA Cardiol. 2019;4(8):810-814. doi:10.1001/jamacardio.2019.1856
Key Points

Question  Is there evidence to guide the treatment decision between transcatheter or surgical aortic valve replacement for patients with aortic stenosis at intermediate operative risk and a history of coronary artery bypass graft (CABG) surgery?

Findings  In this post hoc analysis of 273 intermediate-risk patients with prior CABG surgery enrolled in a randomized clinical trial, both transcatheter and surgical aortic valve replacement were safe and provided symptom relief. The transcatheter approach provided more rapid improvement in quality of life and better exercise tolerance at 1-year follow-up.

Meaning  Transcatheter and surgical aortic valve replacement are appropriate treatments in patients with prior CABG surgery, and the less-invasive transcatheter approach may facilitate faster recovery.

Abstract

Importance  Surgical aortic valve replacement (SAVR) has increased risk for patients with aortic stenosis (AS) and a history of coronary artery bypass graft (CABG) surgery. Transcatheter aortic valve replacement (TAVR) may be an alternative.

Objective  To compare TAVR with SAVR outcomes in patients at intermediate operative risk with prior CABG surgery.

Design, Setting, and Participants  In this post hoc analysis of the Surgical Replacement and Transcatheter Aortic Valve Implantation (SURTAVI) noninferiority randomized clinical trial, patients with severe, symptomatic AS at intermediate operative risk were enrolled from 87 centers across the United States, Europe, and Canada from June 2012 to June 2016 and followed-up with up to July 2017. Those with a history of CABG surgery were considered for analysis. Data were analyzed from September to December 2017.

Interventions  A total of 1746 patients were enrolled and randomized 1:1 to self-expanding TAVR or SAVR. An implant was attempted in 1660 patients, of whom 273 had prior CABG surgery, including 136 who underwent attempted TAVR and 137 who underwent attempted SAVR.

Main Outcomes and Measures  The primary outcome was all-cause mortality or disabling stroke at 1-year follow-up. Efficacy outcomes included quality of life, measured using the Kansas City Cardiomyopathy Questionnaire at 30 days, 6 months, and 1 year, and distance walked in 6 minutes, measured using the 6-minute walk test at 30 days and 1 year.

Results  Of the 136 patients in the TAVR cohort, 111 (81.6%) were male, and the mean (SD) age was 76.9 (6.5) years; of the 137 in the SAVR cohort, 117 (85.4%) were male, and the mean (SD) age was 76.6 (6.5) years. The mean (SD) Society of Thoracic Surgeons Predicted Risk of Mortality score was 5.0% (1.6%) in the TAVR cohort and 5.2% (1.7%) in the SAVR cohort. All-cause mortality or disabling stroke at 1-year follow-up was 8.9% (95% CI, 5.2-15.2) in the TAVR cohort and 6.7% (95% CI, 3.5-12.8) in the SAVR cohort (log-rank P = .53). Compared with patients receiving SAVR, the mean (SD) Kansas City Cardiomyopathy Questionnaire summary score was significantly better among patients receiving TAVR at 30 days (81.4 [19.2] vs 69.7 [22.6]; P < .001); treatments were similar at 1 year (85.7 [14.6] vs 82.8 [18.4]; P = .19). Compared with patients in the SAVR cohort, those in the TAVR cohort showed greater mean (SD) improvement in distance walked at 1 year (48.3 [120.6] m vs 16.8 [88.7] m; P = .04).

Conclusions and Relevance  Both TAVR and SAVR were safe for intermediate-risk patients with AS and prior CABG surgery. The transcatheter approach facilitated faster improvement in quality of life and better exercise capacity at 1-year follow-up.

Trial Registration  ClinicalTrials.gov identifier: NCT01586910

Introduction

Coronary artery disease previously treated with coronary artery bypass graft (CABG) surgery is common in patients with severe, symptomatic aortic stenosis (AS) and increases the complexity of surgical aortic valve replacement (SAVR) owing to the risks of sternal re-entry with cardiac or graft injury.1-5 Transcatheter aortic valve replacement (TAVR) is a less invasive approach that may be particularly well-suited for these patients. The purpose of this study was to compare outcomes after TAVR using a self-expanding device with outcomes after SAVR in patients with AS at intermediate operative risk and a history of CABG surgery.

Methods
Patients and Design

The Surgical Replacement and Transcatheter Aortic Valve Implantation (SURTAVI) trial (NCT01586910) enrolled patients across 87 sites in the United States, Europe, and Canada between June 2012 and June 2016.6 Aortic valve replacement was attempted in 1660 patients, of whom 864 had an attempted TAVR and 796 had an attempted SAVR. The trial complied with the Declaration of Helsinki, all local ethics committees approved the research protocol, and written informed consent was obtained from all patients. The trial protocol can be found in Supplement 1. A total of 136 patients who received TAVR and 137 who received SAVR underwent CABG surgery prior to enrollment in the trial and were included in this post hoc analysis (eFigure 1 in Supplement 2).

End Points

The primary end point was all-cause mortality or disabling stroke at 1-year follow-up, with disabling stroke defined according to the Valve Academic Research Consortium–2 (VARC-2).7 Other safety and efficacy end points were explored through 1-year follow-up, including symptom status defined by New York Heart Association (NYHA) class, quality of life assessed by the Kansas City Cardiomyopathy Questionnaire,8 and exercise capacity determined by the 6-minute walk test.9

Statistical Analysis

Categorical variables were compared using χ2 or Fisher exact tests. Continuous variables were presented as means with SDs and compared using the t test. Kaplan-Meier estimates were used to construct all-cause mortality or disabling stroke for the time-to-event analysis. The log-rank test was used to compare the time to events. All testing used a 2-sided α level less than .05. Cox proportional hazard modeling was used to test for an interaction between prior CABG surgery and no prior CABG surgery for any safety outcome at 30 days and 1 year. Statistical analyses were performed using SAS version 9.4 (SAS Institute).

Results
Patients

The baseline characteristics are presented in Table 1. Of the 136 patients in the TAVR cohort, 111 (81.6%) were male, and the mean (SD) age was 76.9 (6.5) years; of the 137 in the SAVR cohort, 117 (85.4%) were male, and the mean (SD) age was 76.6 (6.5) years. The mean (SD) Society of Thoracic Surgeons Predicted Risk of Mortality score was 5.0% (1.6%) in the TAVR cohort and 5.2% (1.7%) in the SAVR cohort.

Clinical Outcomes

Clinical outcomes are presented in Table 2. All-cause mortality or disabling stroke at 1-year follow-up did not differ between treatments (TAVR: 8.9%; 95% CI, 5.2-15.2; SAVR: 6.7%; 95% CI, 3.5-12.8; P = .53) (eFigure 2 in Supplement 2). There was no significant difference in all-cause mortality or all stroke at 30 days.

Several adverse events were more common at 30 days following SAVR compared with TAVR, including stage 2 or 3 acute kidney injury, requirement for blood transfusion, and new or worsening atrial fibrillation. A new permanent pacemaker was required more often following TAVR than SAVR. There was no interaction between prior CABG surgery and no prior CABG surgery status for any outcome at 30 days or 1 year (eTable 1 in Supplement 2).

Aftercare and Symptom Status

Compared with patients undergoing SAVR, patients undergoing TAVR had a shorter index hospital stay (mean [SD] duration, 5.1 [3.8] days vs 9.0 [5.7] days; P < .001). More patients in the TAVR cohort were discharged directly home rather than to another care facility compared with those in the SAVR cohort (125 of 136 [91.9%] vs 99 of 137 [72.3%]; P < .001) (eTable 2 in Supplement 2). At 30 days, 98 of 131 patients receiving TAVR (74.8%) and 70 of 125 patients receiving SAVR (56.0%) were in NYHA class I (P = .002). At 1-year follow-up, there was no difference between groups, with 91 of 125 patients in the TAVR cohort (72.8%) and 80 of 111 in the SAVR cohort (72.1%) in NYHA class I (P = .94) (eFigure 3 in Supplement 2).

Exercise Capacity and Quality of Life

Patients receiving TAVR walked significantly farther in 6 minutes than patients receiving SAVR at 30 days and 1 year (Figure, A). The Kansas City Cardiomyopathy Questionnaire overall summary score demonstrated clinically meaningful improvement in quality of life over time for patients in both treatment arms (Figure, B). Patients in the TAVR cohort showed a larger improvement at 30 days compared with those in the SAVR cohort, but by 1 year, the degree of improvement was similar between groups.

Echocardiographic Findings

At each time point after the procedure, the mean aortic valve gradient was lower (mean [SD] gradient at 1-year follow-up: TAVR, 8.2 [3.5] mm Hg; SAVR, 11.6 [5.1] mm Hg; P < .001). Additionally, the aortic valve area was larger for patients receiving TAVR compared with those receiving SAVR (mean [SD] aortic valve area at 1-year follow-up: TAVR, 2.2 [0.6] cm2; SAVR, 1.8 [0.6] cm2; P < .001) (eFigure 4 in Supplement 2).

Discussion

This post hoc analysis from the SURTAVI trial6 suggests that for intermediate-risk patients with symptomatic, severe AS and prior CABG surgery, TAVR using the self-expanding valve and SAVR are both safe. The rate of all-cause mortality and disabling stroke as well as the individual components of this primary end point were similar at 30 days and 1 year. Complications of the procedures differed, with those receiving SAVR having more transfusions, acute kidney injury, and atrial fibrillation. Transcatheter aortic valve replacement led to a higher pacemaker rate but also to significantly better aortic valve area and mean gradient and a more rapid improvement in symptoms, exercise capacity, and quality of life.

Reoperation in patients with prior CABG surgery carries increased risk both because these patients tend to be older and have more comorbidities and because of the risk of cardiac or graft injury during sternal re-entry.1-5 Real-world clinical practice is steering away from repeated surgery in favor of TAVR. A 2018 analysis from the National Inpatient Sample database between 2012 and 201410 showed that for patients with prior CABG surgery, the number of TAVRs increased from 1615 in 2012 to 4400 in 2014, while the number of SAVRs decreased from 2285 to 1895 during this period. In Germany, TAVR was the preferred therapy in nearly 90% of patients with prior CABG in 2013.11 The available clinical evidence generally supports this trend. Outcomes of the Placement of Aortic Transcatheter Valves IA randomized clinical trial favored SAVR,12 while those in the CoreValve Pivotal Trial favored TAVR.13 A 2016 review and meta-analysis14 found that patients with previous CABG surgery treated with TAVR or SAVR had similar short-term and long-term survival, but TAVR resulted in a shorter hospital stay and a greater need for postprocedure pacemakers.

It is interesting that although quality-of-life improvement for SAVR caught up to that for TAVR by 1 year, the exercise capacity was better for TAVR throughout follow-up. There are at least 2 potential reasons for this. Some patients may believe themselves to be disabled even if they are objectively doing well. Also, TAVR’s superior hemodynamics may have facilitated increased transvalvular flow needed for exercise.

Limitations

This study has limitations. The cohort in this post hoc analysis represents 16.4% of the total SURTAVI trial population with an attempted implant. Firm conclusions cannot be drawn because of the limited statistical power.

Conclusions

Our study suggests that both SAVR and TAVR are safe for patients with prior CABG surgery at intermediate operative risk. Treatment modality influenced the postoperative course, with TAVR facilitating faster improvement in quality of life and more robust exercise tolerance, which persisted at 1-year follow-up.

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Article Information

Accepted for Publication: April 24, 2019.

Corresponding Author: Michael J. Reardon, MD, Houston Methodist DeBakey Heart and Vascular Center, 6550 Fannin St, Ste 1401, Houston, TX 77030 (mreardon@houstonmethodist.org).

Published Online: June 19, 2019. doi:10.1001/jamacardio.2019.1856

Author Contributions: Dr Reardon had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Reardon, Heijmen, Van Mieghem, Williams, Watson, Conte, Kappetein, Popma.

Acquisition, analysis, or interpretation of data: Reardon, Van Mieghem, Williams, Yakubov, Kleiman, Conte, Chawla, Hockmuth, Petrossian, Robinson, Kappetein, Li, Popma.

Drafting of the manuscript: Reardon, Popma.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Li.

Administrative, technical, or material support: Conte.

Study supervision: Reardon, Heijmen, Van Mieghem, Williams, Yakubov, Watson, Kleiman, Kappetein.

Conflict of Interest Disclosures: Dr Reardon serves on an advisory board for Medtronic. Dr Heijmen serves as a consultant for Medtronic and Terumo Aortic. Dr Van Mieghem has received research grants from Boston Scientific, Medtronic, Edwards Lifesciences, and Abbott Vascular and serves on the advisory boards of Ancora Heart and PulseCath BV. Dr Williams serves as a consultant for Edwards Lifesciences and Medtronic, has received speaker fees from Abbott Laboratories, and has received research grants from Medtronic. Dr Yakubov has received research grants from Medtronic and Boston Scientific, serves on advisory boards for Medtronic and Boston Scientific, and is a principal investigator, steering committee member, and screening committee member for the CoreValve clinical trials. Dr Watson serves on the speakers’ bureau and is a proctor for Boston Scientific, Edwards Lifesciences, Medtronic, and LivaNova. Dr Kleiman has received fees for providing educational services from Medtronic. Dr Chawla has served as a proctor for Medtronic. Dr Petrossian has received research support from Medtronic. Dr Kappetein is an employee and shareholder of Medtronic. Dr Li is an employee and shareholder of Medtronic. Dr Popma has received grants from Medtronic, Boston Scientific, Edwards Lifesciences, Abbott Vascular, and Direct Flow Medical; personal fees from Boston Scientific and Edwards Lifesciences; and serves on the medical advisory board of Boston Scientific and Cordis. No other disclosures were reported.

Funding/Support: The Surgical Replacement and Transcatheter Aortic Valve Implantation trial was funded by Medtronic.

Role of the Funder/Sponsor: The study sponsor was responsible for the design of the study, selection of the clinical sites, monitoring of the data, management of the case report forms, and statistical analysis but had no role in the conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Meeting Presentation: Portions of this article were presented at the 2018 EuroPCR Conference; May 22, 2018; Paris, France.

Additional Contributions: Molly Schiltgen, MS (Medtronic, Minneapolis, Minnesota), drafted the Methods and Results sections, created all tables and figures, and ensured the accuracy of the trial information. Mike Boulware, PhD, Erin McDowell, BS, Maarten Hollander, MSc, Stephanie Geerts, MSc, and Sonia Diaz de Leon, MS (Medtronic, Minneapolis, Minnesota), provided study management. None of the contributors were compensated for their work aside from their salary.

References
1.
Biancari  F, Onorati  F, Mariscalco  G,  et al.  First-time, isolated surgical aortic valve replacement after prior coronary artery bypass surgery: results from the RECORD multicenter registry.  J Card Surg. 2014;29(4):450-454. doi:10.1111/jocs.12365PubMedGoogle ScholarCrossref
2.
Vohra  HA, Pousios  D, Whistance  RN,  et al.  Aortic valve replacement in patients with previous coronary artery bypass grafting: 10-year experience.  Eur J Cardiothorac Surg. 2012;41(3):e1-e6. doi:10.1093/ejcts/ezr212PubMedGoogle ScholarCrossref
3.
Khaladj  N, Shrestha  M, Peterss  S,  et al.  Isolated surgical aortic valve replacement after previous coronary artery bypass grafting with patent grafts: is this old-fashioned technique obsolete?  Eur J Cardiothorac Surg. 2009;35(2):260-264. doi:10.1016/j.ejcts.2008.09.051PubMedGoogle ScholarCrossref
4.
Odell  JA, Mullany  CJ, Schaff  HV, Orszulak  TA, Daly  RC, Morris  JJ.  Aortic valve replacement after previous coronary artery bypass grafting.  Ann Thorac Surg. 1996;62(5):1424-1430. doi:10.1016/0003-4975(96)00635-2PubMedGoogle ScholarCrossref
5.
Byrne  JG, Karavas  AN, Filsoufi  F,  et al.  Aortic valve surgery after previous coronary artery bypass grafting with functioning internal mammary artery grafts.  Ann Thorac Surg. 2002;73(3):779-784. doi:10.1016/S0003-4975(01)03456-7PubMedGoogle ScholarCrossref
6.
Reardon  MJ, Van Mieghem  NM, Popma  JJ,  et al; SURTAVI Investigators.  Surgical or transcatheter aortic-valve replacement in intermediate-risk patients.  N Engl J Med. 2017;376(14):1321-1331. doi:10.1056/NEJMoa1700456PubMedGoogle ScholarCrossref
7.
Kappetein  AP, Head  SJ, Généreux  P,  et al; Valve Academic Research Consortium-2.  Updated standardized endpoint definitions for transcatheter aortic valve implantation: the Valve Academic Research Consortium-2 consensus document.  J Thorac Cardiovasc Surg. 2013;145(1):6-23. doi:10.1016/j.jtcvs.2012.09.002PubMedGoogle ScholarCrossref
8.
Arnold  SV, Reynolds  MR, Wang  K,  et al; CoreValve US Pivotal Trial Investigators.  Health status after transcatheter or surgical aortic valve replacement in patients with severe aortic stenosis at increased surgical risk: results from the CoreValve US pivotal trial.  JACC Cardiovasc Interv. 2015;8(9):1207-1217. doi:10.1016/j.jcin.2015.04.018PubMedGoogle ScholarCrossref
9.
ATS Committee on Proficiency Standards for Clinical Pulmonary Function Laboratories.  ATS statement: guidelines for the six-minute walk test.  Am J Respir Crit Care Med. 2002;166(1):111-117. doi:10.1164/ajrccm.166.1.at1102PubMedGoogle ScholarCrossref
10.
Gupta  T, Khera  S, Kolte  D,  et al.  Transcatheter versus surgical aortic valve replacement in patients with prior coronary artery bypass grafting: trends in utilization and propensity-matched analysis of in-hospital outcomes.  Circ Cardiovasc Interv. 2018;11(4):e006179. doi:10.1161/CIRCINTERVENTIONS.117.006179PubMedGoogle ScholarCrossref
11.
Reinöhl  J, Kaier  K, Reinecke  H,  et al.  Transcatheter aortic valve replacement: the new standard in patients with previous coronary bypass grafting?  JACC Cardiovasc Interv. 2016;9(20):2137-2143. doi:10.1016/j.jcin.2016.07.035PubMedGoogle ScholarCrossref
12.
Greason  KL, Mathew  V, Suri  RM,  et al.  Transcatheter versus surgical aortic valve replacement in patients with prior coronary artery bypass graft operation: a PARTNER trial subgroup analysis.  Ann Thorac Surg. 2014;98(1):1-7. doi:10.1016/j.athoracsur.2014.02.079PubMedGoogle ScholarCrossref
13.
Conte  JV, Gleason  TG, Resar  JR,  et al.  Transcatheter or surgical aortic valve replacement in patients with prior coronary artery bypass grafting.  Ann Thorac Surg. 2016;101(1):72-79. doi:10.1016/j.athoracsur.2015.06.067PubMedGoogle ScholarCrossref
14.
Ando  T, Briasoulis  A, Holmes  AA, Afonso  L, Schreiber  T, Kondur  A.  Transcatheter aortic valve replacement versus surgical aortic valve replacement in patients with previous coronary artery bypass surgery: a systematic review and meta-analysis.  Int J Cardiol. 2016;215:14-19. doi:10.1016/j.ijcard.2016.04.033PubMedGoogle ScholarCrossref
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