|How minimalized extracorporeal circulation compares with the off-pump technique in coronary artery bypass grafting
|Harling L, Warren OJ, Rogers PL, Watret AL, Choong AM, Darzi A, Angelini GD, Athanasiou T
The review concluded that there was little difference between minimalised extracorporeal circulation and off-pump coronary artery bypass procedures for coronary artery bypass grafting surgery. These findings appeared to be supported by the evidence, but given the paucity of studies and potential methodological limitations of the data, the conclusions should be interpreted with caution.
To compare off-pump coronary artery bypass with minimalised extracorporeal circulation for coronary artery bypass grafting.
PubMed, EMBASE, and the Cochrane Library were searched for studies in any language up to the start of January 2010; the 'related articles' function was used. Search terms were reported. Google Scholar and databases of peer-reviewed journals in cardiac surgery, artificial organs and extracorporeal circulatory support were searched. Published conference proceeding abstracts were scanned (details not reported). Reference lists of previous reviews and retrieved articles were screened.
Studies that compared off-pump coronary artery bypass with minimalised extracorporeal circulation in patients undergoing coronary artery bypass grafting were eligible for inclusion in the review. Studies that also included additional study arms (such as conventional extracorporeal circulation) were also included. Specific outcomes eligible for inclusion were length of stay in intensive care unit or hospital, haemorrhage, cerebrovascular events, neurocognitive disturbance, and mortality.
All of the included studies used a closed-circuit minimalised extracorporeal circulation unit (supplied by MAQET or Jostra) without a venous cardiotomy reservoir, but the rest of the system varied between studies. There were considerable variations between studies in the types of equipment and techniques used to place patients on miniaturised bypass. Seventy-five percent of the included studies assessed elective patients; one study included emergent and re-do procedures, and one study did not specify the admission type. All of the studies included some form of matching of patient characteristics, although half of the studies did not report details of patient inclusion/exclusion criteria. Where studies did report inclusion criteria, five to 14 of the criteria were used. Most trials included a high proportion of men (range 72.9 to 100%). Patients with three vessel disease ranged from 43 to 90% in the minimalised extracorporeal circulation group and 6 to 80% in the off-pump coronary artery bypass group. Preoperative characteristics varied between the studies; further details were reported in the review.
Three reviewers independently assessed the studies for inclusion; disagreements were resolved through discussion with a senior reviewer.
Assessment of study quality
The authors did not state that they assessed study quality.
Three reviewers independently extracted all outcomes as reported in the studies; discrepancies were resolved through discussion. Dichotomous data were extracted and used to report odds ratios (ORs) with 95% confidence intervals (CIs); for continuous outcomes, mean differences with 95% confidence intervals were reported.
Methods of synthesis
Studies were grouped according to outcome. Pooled odds ratios and 95% confidence intervals were calculated using a random-effects model. Mean differences were used to calculate pooled weighted mean differences (WMDs) with 95% confidence intervals. Heterogeneity was assessed using Χ2 and I2. Significant heterogeneity was defined as I2<50%. Further sensitivity analyses included the use of a fixed-effect model and the removal of any outlying studies.
Publication bias by visual inspection of funnel plots.
Results of the review
Six studies (n=2,072 patients, 930 off-pump coronary artery bypass and 1,142 minimalised extracorporeal circulation) were reported in the review, including two randomised controlled trials (RCTs), three non-randomised prospective case controlled trials and one non-randomised retrospective case controlled trial.
There were no statistically significant differences between off-pump coronary artery bypass and minimalised extracorporeal circulation during coronary artery bypass grafting surgery for hospital or intensive care unit length of stay (length of stay; three studies), blood loss (three studies), mean number of patients transfused (three studies), neurocognitive disturbance (three studies), number of cerebrovascular events (four studies) or 30-day mortality (six studies).
Although no statistically significant heterogeneity was detected for most analyses, substantial heterogeneity was detected for intensive care unit length of stay (I2=86.1%) and mean blood loss (I2=83.5%).
There appeared to be little difference between minimalised extracorporeal circulation and off-pump coronary artery bypass techniques, but further research was required.
This review answered a clearly defined review question, although the types of eligible studies designs used broad criteria. Several sources were searched for eligible studies; the risk of language bias was low, but the risk of publication bias was unclear, as there was little evidence of any attempt to locate unpublished data. The review was well-conducted for the selection of studies and extraction of data.
The methodological quality of the studies was not assessed, so the reliability of the data is unclear; as only one study was randomised, most studies were likely to be subject to various methodological biases. The authors acknowledged that there was a lack of studies comparing these two techniques and that the methodological quality of the data was low; their recommendations for further research appeared justified.
The findings of the review appeared to be supported by the evidence, but given the paucity of studies and potential methodological limitations of the data, the conclusions should be interpreted with caution.
Implications of the review for practice and research
Practice: The authors did not state any implications for practice.
Research: The authors stated that further large high-quality randomised controlled trials were required to assess the long-term outcomes of minimalised extracorporeal circulation in comparison with off-pump coronary artery bypass for coronary artery bypass grafting. In particular, high-risk patients should be further investigated and outcomes standardised in areas should as blood loss, neurocognitive effects, cerebrovascular events, length of stay and mortality. Subgroup analyses were also required for relevant patient groups.
Harling L, Warren OJ, Rogers PL, Watret AL, Choong AM, Darzi A, Angelini GD, Athanasiou T. How minimalized extracorporeal circulation compares with the off-pump technique in coronary artery bypass grafting. ASAIO Journal 2010; 56(5): 446-456
Subject indexing assigned by NLM
Coronary Artery Bypass /adverse effects /methods; Coronary Artery Bypass, Off-Pump /adverse effects /methods; Extracorporeal Circulation /adverse effects /methods; Female; Humans; Male
Database entry date
This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.