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Is the non-use of a saphenous vein graft the true question in coronary surgery?

Is the non-use of a saphenous vein graft the true question in coronary surgery? Arterial revascularization, Coronary artery bypass grafting, Coronary artery disease , Internal mammary artery, Propensity score analysis, Saphenous vein graft In this issue of the European Journal of Cardiothoracic Surgery, Royse et al. [1] present further analysis of total arterial revascularization (TAR) using the database of the Society of Cardiothoracic Surgeons of New Zealand and Australia. Specifically, the authors compared the long-term outcomes of coronary artery bypass grafting (CABG) based on the number of saphenous vein grafts (SVGs) and not according to the number of arterial grafts (AGs) or the specific arterial revascularization strategy used. The authors made extensive use of propensity matching techniques and concluded that any use of SVG, independently from all the other aspects of the grafting strategy, is associated with a significant reduction in long-term survival. In observational studies and meta-analyses, the use of 3 AGs and TAR has been associated with better long-term survival compared to the use of 2 or 1 AGs and saphenous veins [2, 3]. These earlier studies did encompass some of the patients also included in the cohort of the present analysis. However, it is, to our knowledge, the first time that the survival analysis is stratified by the number of SVGs, independently by the number of AGs and by any other surgical variables. The analysis has, however, some limitations: the authors did not match or perform hierarchal modelling for institutions or surgeons. It is conceivable that more experienced centres and operators used TAR more often, and this opens the door to a potential bias. Analysing the temporal trends, the use of TAR was higher in the initial part of the study period (Supplementary Table 3) [1], whereas the use of SVGs became more prominent later: from 2002 to 2013, the use of TAR increased by 50%, while the use of saphenous vein increased >500%. We are left with the question as to whether this is a true population level trend or simply due to different sampling (i.e. the practices of different institutions or surgeons). Of note, the authors did check for the influence of era in a subgroup analysis but did not match for the year of surgery. Also, the authors have not matched for the extent of coronary disease but only for the number of grafts performed. The 2 things are not necessarily categorically related, and, in the unadjusted analysis, the number of grafts is less in the all-arterial group, suggesting that TAR was used more for patients with less extensive disease. The major weakness of the analysis, however, is the use of retrospective observational data. Despite the considerable statistical effort of the authors, matching techniques can account only for measurable and accounted confounders. Databases capture only a minority of the variables that constitute the overall complexity of the individual patient. Factors such as frailty, socioeconomic status and psychological status are important determinants of long-term prognosis that are unlikely to be measured and matched even using very complex algorithms. In addition, target vessel quality and coronary anatomy are very important variables in the operating surgeon’s decision of which graft to use, and they are not measured and accounted for in any retrospective observational studies (and could not be matched in Royse’s analysis). We have recently shown how a treatment allocation bias exists even in more methodologically-solid retrospective studies comparing the use of single versus double internal thoracic arteries for CABG (with the healthier patients receiving bilateral AGs) [4]. The ‘eye balling’ of the operating surgeon, based on experience and clinical expertise/instinct, is probably the most powerful determinant of hidden bias in retrospective studies, which is very difficult (if not impossible) to neutralize using matching techniques. Randomization is the only method to avoid hidden confounders and to assure homogeneity between groups. This seems even more relevant when comparing surgical techniques with a different impact on the patient or different perceived long-term results. It must be noted the per-protocol use of a multiple arterial revascularization strategy has been shown to lead to detrimental consequences in terms of early clinical outcomes [5], so caution and solid evidence are necessary before advocating the systematic use of TAR. The results of a recently published individual patient meta-analysis of randomized trials comparing the radial artery and the SVG as the second graft for CABG (where additional SVG conduits were used in both arms) contradict Royse’s findings, showing significant clinical advantages for the radial artery group despite the use of complementary venous grafts [6]. The largest randomized comparison of the use of single versus double internal thoracic artery [the Arterial Revascularization Trial (ART)] will publish its 10-year results later this year [7]. In the meantime, another large randomized trial on the use of single versus multiple AGs (the randomized comparison of the clinical outcome of single versus multiple arterial grafts—ROMA trial) is open to enrolment and has almost completed the pilot phase [8]. The latter has been designed taking into account the described potential biases of the observational studies and the lessons learned from a critical analysis of the ART. The primary outcome of this event-driven trial is a composite of major adverse cardiovascular event (death from any cause, any stroke, post-discharge myocardial infarction and/or repeat revascularization), and the study is powered to detect a 20% relative reduction in the primary outcome with 90% power. Royse’s Copernican revolution in the approach in defining the best revascularization strategy for CABG must be applauded for the ingenuity and the unconventionality. However, prospective randomized data are needed to correctly identify the best revascularization strategy for CABG patients. The 2014 guidelines on myocardial revascularization jointly developed by the European Society of Cardiology and the European Association for Cardio-Thoracic Surgery state that TAR should be considered in patients with reasonable life expectancy (class of recommendation IIa, level of evidence B) [9]. REFERENCES 1 Royse A , Pawanis Z , Cantly D , Ou-Young J , Eccleston D , Ajani A et al. The effect on survival from the use of saphenous vein graft during coronary bypass surgery: a large cohort study . Eur J Cardiothorac Surg 2018 ; doi:10.1093/ejcts/ezy213. 2 Gaudino M , Puskas JD , Di Franco A , Ohmes LB , Iannaccone M , Barbero U et al. Three arterial grafts improve late survival: a meta-analysis of propensity-matched studies . Circulation 2017 ; 135 : 1036 – 44 . Google Scholar CrossRef Search ADS PubMed 3 Yanagawa B , Verma S , Mazine A , Tam DY , Jüni P , Puskas JD et al. Impact of total arterial revascularization on long term survival: a systematic review and meta-analysis of 130, 305 patients . Int J Cardiol 2017 ; 233 : 29 – 36 . Google Scholar CrossRef Search ADS PubMed 4 Gaudino M , Di Franco A , Rahouma M , Tam DY , Iannaccone M , Deb S et al. Unmeasured confounders in observational studies comparing bilateral versus single internal thoracic artery for coronary artery bypass grafting: a meta-analysis . J Am Heart Assoc 2018 ; 7 : e008010 . Google Scholar CrossRef Search ADS PubMed 5 Gaudino M , Glieca F , Luciani N , Pragliola C , Tsiopoulos V , Bruno P et al. Systematic bilateral internal mammary artery grafting: lessons learned from the CATHolic University EXtensive BIMA Grafting Study . Eur J Cardiothorac Surg 2018 ; doi:10.1093/ejcts/ezy148. 6 Gaudino M , Benedetto U , Fremes S , Biondi-Zoccai G , Sedrakyan A , Puskas JD et al. Radial artery versus saphenous vein in coronary artery bypass surgery . N Engl J Med 2018 ; 378 : 2069 – 77 . Google Scholar CrossRef Search ADS PubMed 7 Taggart DP , Altman DG , Gray AM , Lees B , Gerry C , Benedetto U ; ART Investigators et al. Randomized trial of bilateral versus single internal-thoracic-artery grafts . N Engl J Med 2016 ; 375 : 2540 – 9 . Google Scholar CrossRef Search ADS PubMed 8 Gaudino M , Alexander JH , Bakaeen FG , Ballman K , Barili F , Calafiore AM et al. Randomized comparison of the clinical outcome of single versus multiple arterial grafts: the ROMA trial-rationale and study protocol . Eur J Cardiothorac Surg 2017 ; 52 : 1031 – 40 . Google Scholar CrossRef Search ADS PubMed 9 Kolh P , Windecker S , Alfonso F , Collet JP , Cremer J , Falk V et al. 2014 ESC/EACTS guidelines on myocardial revascularization: the task force on myocardial revascularization of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS) . Eur J Cardiothorac Surg 2014 ; 46 : 517 – 92 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png European Journal of Cardio-Thoracic Surgery Oxford University Press

Is the non-use of a saphenous vein graft the true question in coronary surgery?

European Journal of Cardio-Thoracic Surgery , Volume Advance Article – Aug 9, 2018
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Publisher
Oxford University Press
Copyright
© The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
ISSN
1010-7940
eISSN
1873-734X
DOI
10.1093/ejcts/ezy281
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Abstract

Arterial revascularization, Coronary artery bypass grafting, Coronary artery disease , Internal mammary artery, Propensity score analysis, Saphenous vein graft In this issue of the European Journal of Cardiothoracic Surgery, Royse et al. [1] present further analysis of total arterial revascularization (TAR) using the database of the Society of Cardiothoracic Surgeons of New Zealand and Australia. Specifically, the authors compared the long-term outcomes of coronary artery bypass grafting (CABG) based on the number of saphenous vein grafts (SVGs) and not according to the number of arterial grafts (AGs) or the specific arterial revascularization strategy used. The authors made extensive use of propensity matching techniques and concluded that any use of SVG, independently from all the other aspects of the grafting strategy, is associated with a significant reduction in long-term survival. In observational studies and meta-analyses, the use of 3 AGs and TAR has been associated with better long-term survival compared to the use of 2 or 1 AGs and saphenous veins [2, 3]. These earlier studies did encompass some of the patients also included in the cohort of the present analysis. However, it is, to our knowledge, the first time that the survival analysis is stratified by the number of SVGs, independently by the number of AGs and by any other surgical variables. The analysis has, however, some limitations: the authors did not match or perform hierarchal modelling for institutions or surgeons. It is conceivable that more experienced centres and operators used TAR more often, and this opens the door to a potential bias. Analysing the temporal trends, the use of TAR was higher in the initial part of the study period (Supplementary Table 3) [1], whereas the use of SVGs became more prominent later: from 2002 to 2013, the use of TAR increased by 50%, while the use of saphenous vein increased >500%. We are left with the question as to whether this is a true population level trend or simply due to different sampling (i.e. the practices of different institutions or surgeons). Of note, the authors did check for the influence of era in a subgroup analysis but did not match for the year of surgery. Also, the authors have not matched for the extent of coronary disease but only for the number of grafts performed. The 2 things are not necessarily categorically related, and, in the unadjusted analysis, the number of grafts is less in the all-arterial group, suggesting that TAR was used more for patients with less extensive disease. The major weakness of the analysis, however, is the use of retrospective observational data. Despite the considerable statistical effort of the authors, matching techniques can account only for measurable and accounted confounders. Databases capture only a minority of the variables that constitute the overall complexity of the individual patient. Factors such as frailty, socioeconomic status and psychological status are important determinants of long-term prognosis that are unlikely to be measured and matched even using very complex algorithms. In addition, target vessel quality and coronary anatomy are very important variables in the operating surgeon’s decision of which graft to use, and they are not measured and accounted for in any retrospective observational studies (and could not be matched in Royse’s analysis). We have recently shown how a treatment allocation bias exists even in more methodologically-solid retrospective studies comparing the use of single versus double internal thoracic arteries for CABG (with the healthier patients receiving bilateral AGs) [4]. The ‘eye balling’ of the operating surgeon, based on experience and clinical expertise/instinct, is probably the most powerful determinant of hidden bias in retrospective studies, which is very difficult (if not impossible) to neutralize using matching techniques. Randomization is the only method to avoid hidden confounders and to assure homogeneity between groups. This seems even more relevant when comparing surgical techniques with a different impact on the patient or different perceived long-term results. It must be noted the per-protocol use of a multiple arterial revascularization strategy has been shown to lead to detrimental consequences in terms of early clinical outcomes [5], so caution and solid evidence are necessary before advocating the systematic use of TAR. The results of a recently published individual patient meta-analysis of randomized trials comparing the radial artery and the SVG as the second graft for CABG (where additional SVG conduits were used in both arms) contradict Royse’s findings, showing significant clinical advantages for the radial artery group despite the use of complementary venous grafts [6]. The largest randomized comparison of the use of single versus double internal thoracic artery [the Arterial Revascularization Trial (ART)] will publish its 10-year results later this year [7]. In the meantime, another large randomized trial on the use of single versus multiple AGs (the randomized comparison of the clinical outcome of single versus multiple arterial grafts—ROMA trial) is open to enrolment and has almost completed the pilot phase [8]. The latter has been designed taking into account the described potential biases of the observational studies and the lessons learned from a critical analysis of the ART. The primary outcome of this event-driven trial is a composite of major adverse cardiovascular event (death from any cause, any stroke, post-discharge myocardial infarction and/or repeat revascularization), and the study is powered to detect a 20% relative reduction in the primary outcome with 90% power. Royse’s Copernican revolution in the approach in defining the best revascularization strategy for CABG must be applauded for the ingenuity and the unconventionality. However, prospective randomized data are needed to correctly identify the best revascularization strategy for CABG patients. The 2014 guidelines on myocardial revascularization jointly developed by the European Society of Cardiology and the European Association for Cardio-Thoracic Surgery state that TAR should be considered in patients with reasonable life expectancy (class of recommendation IIa, level of evidence B) [9]. REFERENCES 1 Royse A , Pawanis Z , Cantly D , Ou-Young J , Eccleston D , Ajani A et al. The effect on survival from the use of saphenous vein graft during coronary bypass surgery: a large cohort study . Eur J Cardiothorac Surg 2018 ; doi:10.1093/ejcts/ezy213. 2 Gaudino M , Puskas JD , Di Franco A , Ohmes LB , Iannaccone M , Barbero U et al. Three arterial grafts improve late survival: a meta-analysis of propensity-matched studies . Circulation 2017 ; 135 : 1036 – 44 . Google Scholar CrossRef Search ADS PubMed 3 Yanagawa B , Verma S , Mazine A , Tam DY , Jüni P , Puskas JD et al. Impact of total arterial revascularization on long term survival: a systematic review and meta-analysis of 130, 305 patients . Int J Cardiol 2017 ; 233 : 29 – 36 . Google Scholar CrossRef Search ADS PubMed 4 Gaudino M , Di Franco A , Rahouma M , Tam DY , Iannaccone M , Deb S et al. Unmeasured confounders in observational studies comparing bilateral versus single internal thoracic artery for coronary artery bypass grafting: a meta-analysis . J Am Heart Assoc 2018 ; 7 : e008010 . Google Scholar CrossRef Search ADS PubMed 5 Gaudino M , Glieca F , Luciani N , Pragliola C , Tsiopoulos V , Bruno P et al. Systematic bilateral internal mammary artery grafting: lessons learned from the CATHolic University EXtensive BIMA Grafting Study . Eur J Cardiothorac Surg 2018 ; doi:10.1093/ejcts/ezy148. 6 Gaudino M , Benedetto U , Fremes S , Biondi-Zoccai G , Sedrakyan A , Puskas JD et al. Radial artery versus saphenous vein in coronary artery bypass surgery . N Engl J Med 2018 ; 378 : 2069 – 77 . Google Scholar CrossRef Search ADS PubMed 7 Taggart DP , Altman DG , Gray AM , Lees B , Gerry C , Benedetto U ; ART Investigators et al. Randomized trial of bilateral versus single internal-thoracic-artery grafts . N Engl J Med 2016 ; 375 : 2540 – 9 . Google Scholar CrossRef Search ADS PubMed 8 Gaudino M , Alexander JH , Bakaeen FG , Ballman K , Barili F , Calafiore AM et al. Randomized comparison of the clinical outcome of single versus multiple arterial grafts: the ROMA trial-rationale and study protocol . Eur J Cardiothorac Surg 2017 ; 52 : 1031 – 40 . Google Scholar CrossRef Search ADS PubMed 9 Kolh P , Windecker S , Alfonso F , Collet JP , Cremer J , Falk V et al. 2014 ESC/EACTS guidelines on myocardial revascularization: the task force on myocardial revascularization of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS) . Eur J Cardiothorac Surg 2014 ; 46 : 517 – 92 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

Journal

European Journal of Cardio-Thoracic Surgery – Oxford University Press

Published: Aug 9, 2018

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