Whether a second arterial conduit improves outcomes in patients undergoing myocardial revascularization surgery is and will remain unclear until the 10-year results of the ART (Arterial Revascularization Trial) are published. Consequently, arterial conduits other than the left internal thoracic artery are seldom used in daily practice.

Using a database including 126 non-federal hospitals in California, researchers compared all-cause mortality and rates of stroke, acute myocardial infarction, repeat revascularization, and wound infection between propensity score-matched cohorts between 2006 and 2011. Populations had undergone coronary artery bypass grafting with the left internal thoracic artery plus a second arterial conduit (right internal thoracic artery or radial artery, n = 5866) or a venous conduit (n = 53,566).

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Propensity score matching using 34 preoperative variables yielded 5813 matched sets for the final analysis. Additionally, a sub-group analysis compared outcomes between recipients of a right internal thoracic artery conduit (n = 1576) or a radial artery conduit (n = 4290).

Receipt of a second arterial conduit was associated with lower mortality at 7 years (13.1% vs. 10.6%; hazard ratio [HR]: 0.79; 95% confidence interval [CI]: 0.72-0.87), lower rates of acute myocardial infarction (HR: 0.78; 95% CI: 0.70-0.87) and lower rates of repeat revascularization (HR: 0.82; 95% CI: 0.76-0.88).

Despite this significant improvement as regards events, second arterial conduit use decreased from 10.7% in 2006 to 9.1% in 2011 (p ≤ 0.001).

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Right internal thoracic artery grafts were associated with similar mortality rates (10.3% vs. 10.7%) and similar rates of combined adverse cardiovascular events. However, the risk of sternal wound infection was significantly higher when compared with a second arterial conduit from the radial artery.

Conclusion

Second arterial conduit use is low and declining over time, despite plenty of evidence associating arterial grafts with lower mortality and fewer combined events. A right internal thoracic artery graft offers no benefit over that of a radial artery, but does increase the risk of sternal wound infection.

Editorial

This is a topic on which speculation will continue until the final 10-year follow-up ART trial results are published. So far, we have 5-year interim results showing that second right internal thoracic artery grafts did not offer any benefit and contributed with an increase in sternal wound infections. We must be patient. Upon randomization, we knew that whatever advantages there might be, if any, they would be revealed in the long term. A post-hoc 5-year ART analysis did show that radial artery graft use was beneficial as regards combined events, particularly significantly lower rates of revascularization compared with venous grafts (4.4% vs. 7.6%).

Whenever we refer to randomized clinical studies involving patients with multivessel disease while in the process of choosing between angioplasty or surgery for a particular case, we usually review trials such as the SYNTAX, for example, in which almost 30% of all patients received two internal thoracic artery grafts (which is quite far from daily practice as regards most surgeons).

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However, this cited study is not the only one reporting that the use of multiple arterial conduits is below 10%. The Society of Thoracic Surgeons (STS) reported that, between 2011 and 2012, the use of two internal thoracic artery grafts was below 5% and the use of a radial artery graft was also below 5%. Nowadays, there is evidence that the use of angioplasty in daily practice is higher than what SYNTAX suggests (with plenty of examples: SYNTAX II, EXCEL, NOBLE, FAME III coming soon, etc.). We can state that angioplasty has improved compared to SYNTAX outcomes by simply taking into account the fact that the rates of definite/probable thrombosis for first-generation drug-eluting stents (DES, such as the TAXUS stent used in SYNTAX) were around 2.3% at two years vs. 0.7% for second-generation DES in the same time period (Kedhi E et al., EuroIntervention 2012).

Surgeons cannot argue the same while using, despite all evidence, three times less arterial conduits in daily practice than in randomized studies.

Original title: Second Arterial Versus Venous Conduits for Multi-Vessel Coronary Artery Bypass Surgery in California.

Reference: Andrew B. Goldstone et al. Circulation. 2017 Dec 14. [Epub ahead of print].

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