A comparison of long-term mortality for off-pump and on-pump coronary artery bypass graft surgery

Mortality risk factors from converting off-pump coronary artery bypass to on-pump coronary artery bypass

Introduction:

A number of large-scale retrospective studies revealed that off-pump coronary artery bypass (OPCAB) was superior to on-pump coronary artery bypass (ONCAB). The aim of the study was to investigate risk factors for mortality when OPCAB is converted to ONCAB.

Methods:

Patients who underwent OPCAB conversion to ONCAB at the Beijing Anzhen Hospital between January 2003 and January 2013 were assigned to the non-survivor and survivor groups. Background demographics, illness history and preoperative, intraoperative and postoperative variables were compared.

Results:

Of the 247 cases, 15.4% of the patients died. Patients in the non-survivor group were older and more frequently had diabetes mellitus (DM), arrhythmia, myocardial infarction (MI) in the past 30 days (all p<0.05) and MI combined with mitral regurgitation (p<0.0001); they more frequently had bigger left ventricular end-diastolic dimension (p=0.0019), greater fall in blood pressure, ventricular fibrillation for longer periods, longer conversion time and bypass graft occlusion. All patients in the non-survivor group received intra-aortic balloon pump compared to 89.5% in the survivor group and extracorporeal membrane oxygenation was more common. Left main coronary artery disease (OR=4.431, 95%CI: 2.440-8.048, p<0.0001), blood pressure decline ⩽40 mmHg (OR=0.509, 95%CI: 0.447-0.580, p<0.0001) and time for conversion to ONCAB ⩾20 min were independently associated with mortality. Rates of postoperative complications, such as renal failure, cerebral infarction or hemorrhage, MI and redo sternotomy, were higher in the non-survivor group.

Conclusions:

Conversion from OPCAB to ONCAB is associated with high mortality. Risk factors include left main artery disease and duration of blood pressure decline >40 min.

The impact of off-pump surgery in end-organ function: practical end-points

Most surgeons perform coronary bypass surgery with the aid of cardiopulmonary bypass, which inflicts a massive systemic inflammatory response to the body leading to adverse clinical outcome. In an attempt to make CABG less invasive, interest have been diverted to the off pump technique.

The current review attempts to bring an insight onto the last ten years knowledge on the off-pump impact in end organ function, with an aim to draw some clear conclusions in order to allow practitioners to reflect on the subject.

Off-pump coronary surgery: current justifications

Although the literature has failed to project an overall superiority of off-pump vs. on-pump surgery, nevertheless, small randomized control trials and large meta-analysis studies have concluded that the incidence of a stroke is less than 1 % when anaortic off-pump techniques are advocated in patients with diseased ascending aorta. Furthermore, off-pump techniques or their combination with hybrid procedures may lead to a reduction of adverse outcome in the aged high-risk population with concomitant poor left ventricular function and co-morbidities. However, despite this, controversy still exists among the cardiac surgery community in terms of the benefit of this technique and its safety; hence, off-pump is becoming out of fashion. In this review paper, by looking at a "marginal group of patients" (elderly, high risks, atherosclerotic aortas) we attempt to re-establish and justify this technique and re-invent its usage.

The fate at mid-term follow-up of the on-pump vs. off-pump coronary artery bypass grafting surgery

AIMS

To evaluate the fate of on-pump coronary artery bypass grafting (ON-pump CABG) vs. off-pump coronary artery bypass grafting (OP-CABG) surgery at mid-term follow-up.

METHODS

From January 2008 to December 2010, 369 patients underwent surgical myocardial revascularization by means of OP-CABG techniques (n = 166) or with ON-pump CABG (n = 203). Data of the two groups of patients were retrospectively analyzed.

RESULTS

As compared with OP-CABG, in the ON-pump CABG patients, mean value of Logistic EuroSCORE (8.1 ± 7.8% vs. 6.2 ± 5.9%, P = 0.04), more extended coronary disease (2.7 ± 0.5 vs. 2.5 ± 0.7 diseased vessels/patient, P < 0.001) consequently requiring greater number of grafts/patient (2.9 ± 0.9 vs. 2.3 ± 0.9, P < 0.0001), and emergency surgery (12 vs. 6%, P = 0.03) were more frequently observed. Operative mortality was 1.9% in ON-pump CABG vs. 1.2% in OP-CABG (P = 0.6) and incidence of stroke 2.46 vs. 1.81% (P = 0.7). The incidence of stroke was reduced at 1.2% when OP-CABG PAS-Port 'clamp-less' technique was used.Intraoperatively, costs per patient were higher for OP-CABG vs. ON-pump CABG (1.930,00 +1.050,00 €, if PAS-port system was included, vs. 1.060,00 € for ON-pump surgery). ICU stay (1.9 ± 1.0 days vs. 1.4 ± 0.7 days) and total postoperative in-hospital stay (5.3 ± 3.3 days vs. 5.5 ± 3.5 days) were similar in both groups.At 4 years, survival (91 ± 13% in the ON-pump CABG vs. 84 ± 19% in the OP-CABG), freedom from major adverse cardiac events (composite end-point of all-cause death, myocardial infarction, and repeat coronary revascularization of the target lesion) (82 ± 9% vs. 76 ± 14%), and major adverse cardiac and cerebrovascular events (80 ± 11% vs. 72 ± 16%) were not significantly different. Freedom from late cardiac death was slightly significant higher after ON-pump CABG (98 ± 4% vs. 90 ± 10%, P = 0.05).

CONCLUSION

Mid-term freedom from composite end-points is similar after ON-pump CABG and OP-CABG. Freedom from cardiac death appears to be better after ON-pump CABG. OP-CABG needs for more expensive surgical technique. OP-CABG performed by an experienced surgical team using 'clamp-less' techniques can be an effective strategy in reducing postoperative stroke.

Does off-pump coronary artery bypass graft surgery have a beneficial effect on long-term mortality and morbidity compared with on-pump coronary artery bypass graft surgery?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether off-pump coronary artery bypass grafting (CABG) surgery offered superior long-term outcomes compared with on-pump CABG surgery. Best evidence papers were considered to be those that had a follow-up period of ≥5 years, had >50 patients in either cohort, did not utilize concomitant interventions nor comprised low-risk, high-risk or sub-population groups. Where potential duplicate data sets from the same institution were likely, the more credible and recently published study was included. Two hundred and fifty-six papers were found as a result of the reported search, of which 16 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. The 16 studies comprised 4 prospective randomized controlled trials (RCTs), with the remaining 12 retrospective, of which 8 were propensity-score matched. All 4 RCTs contained fewer than 450 participants. Two studies concluded with a survival advantage towards on-pump CABG: one, a large registry-based study, the Veterans Affairs, with >25 000 patients, and another, a propensity-matched retrospective study involving almost 8000 patients. The remaining 14 studies all provided evidence to suggest comparable long-term survival. In addition, all other long-term outcomes mentioned within these studies including angina recurrence, myocardial infarction heart failure, need for revascularization, stroke, graft patency, cognitive and quality of life showed similar results between the two groups. We conclude that off-pump CABG surgery may have similar or slightly reduced long-term survival compared with on-pump CABG surgery. Other long-term indicators such as cardiovascular or cerebrovascular events or neuro-psychological outcomes were similar between the two groups. Despite these conclusions, the evidence is limited by substantial variability in patient selection and study methods. The CORONARY (coronary artery bypass surgery off- or on-pump revascularization study) trial recently presented results, which showed no significant differences in composite outcomes at 1 year; it will be interesting to observe whether these comparable outcomes are maintained for a much longer time frame.

Performing coronary artery bypass grafting off-pump may compromise long-term survival in a veteran population

BACKGROUND

There are ample data regarding the short-term outcomes of on-pump and off-pump coronary artery bypass grafting (CABG), but little is known about the long-term survival associated with these approaches.

METHODS

Using the Veterans Affairs (VA) Continuous Improvement in Cardiac Surgery Program, we identified all VA patients (n = 65,097) who underwent primary isolated CABG from October 1997 to April 2011. The primary outcome measure was all-cause mortality. Age, 17 preoperative risk factors, and year of operation were used to calculate propensity scores for each patient. A greedy-match algorithm using the propensity scores matched 8,911 off-pump with 26,733 on-pump patients. Survival functions were estimated by the Kaplan-Meier method and compared by using the log-rank test.

RESULTS

In the complete cohort, off-pump was used in 11,629 of 65,097 (17.9%) operations. For the matched cohort, the median follow-up was 6.7 years (interquartile range, 3.72 to 9.35 years). Risk-adjusted mortality did not differ significantly between the off-pump and on-pump groups at 1 year (4.67% vs 4.78%; risk ratio [RR], 0.98; 95% confidence interval [CI], 0.88 to 1.09) or 3 years (9.21% vs 8.89%; RR, 1.04; 95% CI, 0.96 to 1.12). However, risk-adjusted mortality was higher in the off-pump group at 5 years (14.47% vs 13.45%; RR, 1.08; 95% CI 1.02 to 1.15) and 10 years (25.18% vs 23.57%; RR, 1.07; 95% CI, 1.03 to 1.12). Overall, the hazard ratio for off-pump vs on-pump was 1.06 (95% CI, 1.00 to 1.13; p = 0.04).

CONCLUSIONS

Off-pump CABG may be associated with decreased long-term survival. Further studies are needed to identify the reasons behind this finding.

Off-pump coronary artery bypass grafting--the current state

The optimal strategy for coronary revascularization remains controversial. Currently, most surgical revascularizations are performed with the use of cardiopulmonary bypass (ONCAB), yet over the past 20 years off-pump coronary artery bypass grafting (OPCAB) has been increasingly used because of the increased awareness of the deleterious effects of cardiopulmonary bypass (CPB) and aortic manipulation. Small, prospective, randomized controlled trials have lacked sufficient sample size to demonstrate differences in early and long-term outcomes. Larger observational studies that are better powered to statistically compare outcomes have shown more favorable in-hospital outcomes and equivalent long-term outcomes with OPCAB and ONCAB. The benefits of OPCAB techniques may be more apparent for patients at high risk for complications associated with CPB and aortic manipulation. Recent studies have demonstrated improved outcomes in higher-risk patients undergoing OPCAB, as well as improved neurological outcomes. The purpose of this review is to outline the recent literature comparing OPCAB with ONCAB, and to demonstrate efficacy of OPCAB as a useful technique for coronary revascularization.