Using the radial artery instead of the saphenous vein for patients undergoing coronary artery bypass graft (CABG) surgery leads to lower mortality and better cardiac outcomes, according to research presented at the American College of Cardiology’s Virtual Scientific Session Together with World Congress of Cardiology (ACC.20/WCC Virtual).
Mario Gaudino (professor of cardiothoracic surgery at Weill Cornell Medicine, New York, USA), principal investigator for the RADIAL study, presented the findings to the virtual conference via a video link. It showed that after 10 years of follow-up, using the radial artery rather than the saphenous vein was associated with a statistically significant decrease in the combined rate of death, myocardial infarction and repeat revascularisation procedures. There was also a significantly lower incidence of the combined endpoint of death and myocardial infarction and a survival benefit in the radial group (although this was a post-hoc analysis).
CABG is the most frequently performed heart operation in adults, accounting for about 60% of all heart surgeries performed annually in adults in the USA.
Gaudino told the online audience: “Observational studies have suggested that coronary artery bypass graft patients who receive the radial artery instead of the saphenous vein as the second conduit have better long-term outcomes. However, observational studies are open to confounders and bias, and in this case in particular, to treatment allocation bias, with surgeons using the conduit that is known to have the better patency rate in a patient with the longest life expectancy. The Radial Artery Database International Alliance (RADIAL) is an individual patient pooled database from five trials that have compared the patency rate of the radial artery and the saphenous vein.”
The trials were performed in Australia, Korea, Italy, Serbia and the UK; they enrolled a combined total of 1,036 patients, with average age at surgery of 67 years, and 70% were men. Patients receiving bypass surgery were randomly assigned to a second bypass from either the radial artery or the saphenous vein.
Five-year findings were published in the New England Journal of Medicine in 2018. Gaudino and colleagues found that patients who received radial artery bypass surgery had significantly fewer heart attacks and repeat revascularisation procedures than those who received a saphenous vein bypass. The mortality rate was similar in the two groups. Outlining the earlier findings, Gaudino clarified: “The composite outcome was clearly driven by repeat revascularisation. It was unclear to what extent the use of per-protocol angiography by the majority of the trials included in the analysis may have inflated the rate of repeat revascularisation.”
The current study includes an additional five years of follow-up from patients enrolled in the original trials. Most of the trials used telephone follow-up but two of them also used linkage to national databases.
As in the five-year analysis, the primary outcome in the extended study was a composite of death, myocardial infarction and repeat revascularisation. A secondary outcome of major adverse clinical events included death and myocardial infarction.
More than 90% of the patients had 10-years follow-up data available. There was no statistically significant difference in the baseline characteristics between the two groups.
Gaudino outlined: “The use of a radial artery was associated with a statistically significant reduction in the composite outcome of death, MI, and repeat revascularisation, with a hazard ratio of 0.73 [95% confidence interval {CI} 0.61–0.88]. Similar results were found for the secondary outcome. There was a statistically significant reduction in the composite of major cardiac events including only death and myocardial infarction, with a hazard ratio of 0.77 [95% CI 0.63–0.94].”
He added: “Death was not a prespecified outcome and was analysed post hoc. However, there was a statistically significant survival advantage for patients who received a radial artery graft, with a hazard ratio of 0.73”.
On the individual components of the composite outcome, incidence of myocardial infarction was lower in the radial artery group than in the patients who received a saphenous vein graft, but the difference did not reach statistical significance, “and there was a clear and high statistically significant difference in repeat revascularisations, again in favour of the radial artery group”.
In a subgroup analysis the only significant treatment effect modifier was gender, with women showing the largest benefit from the use of a radial artery. In addition, time segmented analysis of the association between the use of per-protocol angiography in the first five years of follow-up and repeat revascularisation and the primary composite outcome found a clear association with the difference in repeat revascularisation but no association with the difference in primary composite outcome.
Limitations of the study are that the results are from a pooled analysis of several small trials rather than one large trial, and the number of patients was relatively small. As a result, conceded Gaudiono, “even at 10 years … some of the comparisons may be underpowered.”
But, he said: “Of note, this is the first report of a survival benefit for bypass surgery using multiple arterial grafts that is based on randomised data.”
