A network meta-analysis, published in the Journal of the American College of Cardiology, indicates that an off-pump coronary artery bypass grafting (CABG) technique that avoids all manipulation of the ascending aorta—anaortic or “no-touch” off-pump CABG—significantly reduces the risk of postoperative stroke and short-term mortality compared with standard CABG. Another off-pump CABG technique that used the Heartstring clampless system was also found to reduce the risk of stroke compared with standard CABG.
According to authors Dong Fang Zhao (Sydney Medical School, The University of Sydney, Sydney, Australia) and others, the risk of stroke after CABG “remains a major disadvantage” for surgical revascularisation compared with percutaneous coronary intervention. They add: “A number of mechanisms may cause stroke or subtle neurological injury after CABG, including embolisation of air, debris, or clot from the cardiopulmonary bypass circuit, hypoperfusion, or hyperperfusion, a systemic inflammatory response or dislodgement of atherosclerotic plaque during manipulation of crossclamping of the ascending aorta. Therefore, elimination of aortic manipulation and cardiopulmonary bypass may reduce the rate of postoperative stoke.”
In this network-meta-analysis, Zhao et al reviewed data for four different CABG techniques—no-touch CABG, off-pump CABG with a partial clamp, off-pump CABG with a clampless device (Heartstring, Maquet), and standard CABG—to determine the effect of varying degrees of aortic manipulation on postoperative outcomes after CABG. The primary outcome was the rate of postoperative stroke and secondary outcomes included postoperative mortality, myocardial infarction and renal failure among others.
Of 37, 720 patients in the study, from 13 studies, 7,098 underwent no touch CABG, 12,512 underwent off-pump CABG with partial clamp, 2,997 underwent off-pump CABG with the Heartstring system, and 15,113 underwent standard CABG.
In a pairwise meta-analysis, no touch CABG was associated with a significant reduction in stroke compared with both standard CABG (0.4% vs. 1.8%, respectively; p<0.00001) and with off-pump CABG with a partial clamp (0.4% vs. 1.3%; p<0.0001). The authors report that the superiority of the no-touch CABG technique compared with off-pump CABG with partial clamp “may explain the inability of the randomised trials to detect a difference in stroke between off-pump CABG,” explaining that these off-pump techniques “eliminate cardiopulmonary bypass but not aortic manipulation”.
The pairwise meta-analysis also showed that off-pump CABG with the Heartstring system significantly reduced postoperative stroke compared with standard CABG: 0.96% vs. 2.2%, respectively; p=0.009. Furthermore, it found that no-touch CABG was associated with a significant reduction in 30-day mortality compared with standard CABG: 1% vs. 2.2% respectively, p<0.0001.
Zhao et al comment that previous studies have also shown no touch CABG to reduce the rate of stoke, but note their network meta-analysis “included all possible comparisons” between no touch CABG, CABG with partial clamp, CABG with the Heartstring system, and standard CABG in a Bayesian network. “By ranking treatments according to their comparative effectiveness for reducing stroke, the model demonstrated that anaortic off-pump CABG was the superior CABG technique, followed by off-pump CABG with the Heartstring system, then off-pump CABG with the partial clamp, and finally on-pump CABG,” they state and conclude: “Further randomised studies utilising a true anaortic technique are still needed to confirm these results.”
Study author Michael Vallely (Sydney Medical School, The University of Sydney, Sydney, Australia) told Cardiovascular News: “From the CORONARY trial, we know that there’s equivalent freedom from MACCE when off-pump CABG is compared with standard CABG, suggesting off-pump CABG—performed by experienced surgeons—provides equivalent potency outcomes. Unfortunately this trial did not specify the off-pump technique that should be used, so only a small (unpublished) number of the off-pump patients were done “no-touch” or anaortic. We have known for many years that the use of bilateral mammary arteries and total arterial grafting confers a long term survival benefit over a single mammary artery and vein grafts. Aortic no-touch tends to use a higher number of total arterial grafting strategies when compared to on-pump CABG. Therefore, theoretically, if the grafts are equivalent but there’s a higher proportion of patients having two internal mammary arteries and total-arterial grafting, then anaortic should have better long term outcomes thant traditional on-pump CABG with left internal mammary artery and vein.”