Long-term Survival Edge for On-Pump vs Off-Pump Coronary Bypass Surgery in Meta-Analysis

March 02, 2018

Mortality was slightly lower at least 4 years after coronary bypass surgery performed "on-pump," that is, with cardiopulmonary bypass (CPB) support, compared with beating-heart "off-pump" bypass surgery in a new meta-analysis.

The traditional procedure's advantage was only marginally significant and thin in absolute terms. The rates of death from any cause were 12.3% for on-pump surgery and 13.9% for the off-pump procedure (P = .03).

"The statistics are saying this is a significant difference and suggesting that 'on-pump' is superior," senior author, Nicola King, PhD, University of Plymouth, United Kingdom, told theheart.org | Medscape Cardiology. But that has to be weighed against the question of whether the difference is clinically important, "in which case, it comes down to the surgeon as to which method to use."

Whether coronary bypass surgery is performed off-pump generally depends on operator and institutional preference, but it requires special training, and its success is well known to depend on operator experience. Advocates of the off-pump strategy say it avoids the systemic inflammatory response and perhaps even the risk for stroke associated with CPB support.

But one message of the current analysis is that on-pump bypass surgery is at least not inferior to the off-pump procedure, King said. That applies even to stroke, undercutting an alleged advantage of the newer strategy, she observed.

The analysis showed no significant difference in stroke rate between the strategies or in rates of myocardial infarction, angina, or repeat revascularization.

"I think the practical application of our paper is, if you are in any way uncertain as to whether to do on-pump or off-pump, do on-pump as it may carry a small statistically significant long-term survival benefit," King said.

The meta-analysis was published online February 26 in the Journal of the American College of Cardiology with lead author Neil A Smart, PhD, University of New England, Armidale, Australia.

It was inspired, King said, by the previous shortage of solid, comparative long-term data for the two procedures, followed by recent publications of 5-year follow-up outcomes from two large randomized trials.

In both the ROOBY Follow-up Study (ROOBY-FS), with 2203 patients, and the CORONARY trial, with 4752 patients, mortality was about the same for off-pump and on-pump bypass surgery.

"On the whole, those two particular trials tended to show no difference at 5 years between any of the clinical outcomes. It was only when we put all of the trials together that we then found this difference in mortality," she said.

"Given the equivalent short-term safety of both approaches and the superior long-term outcomes now reported, an on-pump approach to coronary surgical revascularization continues to stand the test of time," according to David H Adams, MD, and Joanna Chikwe, MD (Icahn School of Medicine at Mount Sinai, New York City).

"It is time for the debate to move on," they write in an accompanying editorial. "The discussion needs to be reframed in terms of which patients may benefit more from one approach or the other."

On the basis of observational data, those might include "patients with severe atheromatous aortic disease, in which a 'no-touch' aortic technique can be safely used to minimize the risk of embolic stroke," and those with "very severe lung disease" to lower the risk for postoperative respiratory failure using the off-pump strategy.

"In the absence of these characteristics, patients will benefit most from referral to a surgeon with experience and documented excellent outcomes, rather than a targeted on- or off-pump technique preference," write Adams and Chikwe.

The meta-analysis included six randomized trials that enrolled both men and women and compare the two operative strategies with follow-up data reported to at least 4 years. They encompassed 4069 patients who received on-pump coronary bypass surgery and 4076 who had the procedure off pump.

Table. Odds Ratios for Outcomes, Off-Pump vs On-Pump CABG, in Meta-Analysis

Endpoints Odds Ratio (95% CI) P Value
All-cause mortality 1.16 (1.02 - 1.32) .03
Myocardial infarction 1.06 (0.91 - 1.25) .45
Angina 1.09 (0.75 - 1.57) .65
Need for revascularization 1.15 (0.95 - 1.40) .16
Stroke 0.78 (0.56 - 1.10) .16
CABG = coronary artery bypass grafting.

Although mortality and stroke may be the outcomes of most interest in comparing the two techniques, according to King, revascularization may also be important.

That's because of concerns that the graft's distal anastomosis is more difficult to complete during off-pump, beating-heart surgery, raising the risk for repeat revascularization, she observed.

But the meta-analysis found no significant difference for that outcome, a tilt in favor of the off-pump approach because it may lessen one of its alleged downsides.

King and the other authors report that they have no relevant disclosures. A dams reports that his institution "receives royalty payments from Edwards Lifesciences for intellectual property related to the development of two mitral valve repair rings, and from Medtronic for intellectual property related to the development of a tricuspid valve repair ring." Chikwe reports that she has no relevant relationships to disclose.

J Am Coll Cardiol. 2018;71:983-991, 992-993.   Abstract, Editorial 

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