To determine the efficacy of the use of the left internal mammary artery (LIMA) for revascularisation of the left anterior descending coronary artery (LAD).

The authors report that "all articles from the first published article by Green in 1972 to the most recently published series of MIDCABG in 1998 were analysed".

Study designs of evaluations included in the review

Studies of minimally invasive (MIDCABG) or conventional coronary artery bypass grafting were included. Published series containing information regarding vein graft patency after coronary artery bypass grafting were not included.

Specific interventions included in the review

Conventional and minimally invasive coronary artery bypass grafting (MIDCABG) using LIMA grafting of the LAD were studied.

Participants included in the review

Patients having coronary artery bypass grafting were included.

Outcomes assessed in the review

Graft patency assessed by post-operative or intra-operative angiography was assessed.

How were decisions on the relevance of primary studies made?

The authors do not state how the papers were selected for the review, or how many of the authors performed the selection.

The authors do not state that they assessed validity.

The following data were extracted: the percentage of patients operated on who underwent post-operative angiography; the interval at which patients were studied; graft patency; and specific exclusions from the studies. No details were given of methods used to extract data.

How were the studies combined?

The studies were combined in a narrative review.

How were differences between studies investigated?

The authors do not state how differences between the studies were investigated.

A total of 27 published series were included.

7 series gave results of early angiography one month or less after conventional CABG (1639 patients).

5 series gave results of intermediate angiography (> one month to one year or less) after conventional CABG (at least 1129 patients).

14 series gave results of late angiography (> one year) after conventional CABG (at least 2219 patients).

7 series gave results of angiography at varying intervals after conventional CABG (at least 1202 patients).

5 series gave results of angiography after left internal mammary graft in minimally invasive coronary artery bypass grafting (584 patients).

Patency after conventional CABG as ascertained by early angiography: percentage of patients studied ranged from 45% to 100%; graft patency ranged from 94% to 99%.

Patency after conventional CABG as ascertained by intermediate angiography: percentage of patients studied ranged from 23% to 96%; graft patency ranged from 88% to 95%.

Patency after conventional CABG as ascertained by late angiography: percentage of patients studied ranged from 6% to 92%; graft patency ranged from 70% to 98%.

Patency after conventional CABG as ascertained by angiography at varying intervals (ranging from 2 weeks to 15 years): percentage of patients studied ranged from 6% to 49%; graft patency ranged from 40% to 97%.

Patency as ascertained by angiography after left internal mammary graft in minimally invasive coronary artery bypass grafting: interval ranged from intra operative to 1 year with most being assessed at less than 96 hours; percentage of patients studied ranged from 62% to 100%; graft patency ranged from 93.7% to 100%.

Meaningful comparison of LIMA graft patency between arrested heart, conventional coronary artery bypass grafting and minimally invasive direct coronary artery bypass grafting is difficult: however, early graft patency by both techniques can confidently be predicted as being 90% or greater. The late patency of the grafts performed by MIDCABG remains unknown.

The aims of the review were stated. Some relevant information was presented in tabular format. The discussion included mention of the lack of comparability of series and reporting of results for only a percentage of patients.

There were no details of literature search or of methods used to select primary studies or extract data. No attempt was made to locate unpublished studies. Inclusion criteria were not defined. Full details of primary studies such as characteristics of subjects and methods used to select participants would have been welcome. No assessment of validity was undertaken and discussion on differences between studies was minimal. A narrative review was appropriate given the lack of comparability of the series. Results were reported for sub-groups of patients and no details were given of methods used to select these patients. Most results for patients undergoing MIDCABG (54% of patients) were assessed at less than 96 hours post-operatively. One study (271 patients) reported patency results for MIDCABG at less than one year but no interval was specified. Without details of methods used to select participants, it is not certain that the patients whose results were presented are representative of all patients undergoing these procedures. Thus the authors conclusions on early patency rates cannot be considered supported by the evidence presented.

Practice: The authors do not state any clinical implications of the review.

Research: The authors consider that answers are required to the following questions: does early graft patency correlate with late graft patency? What does an abnormal early angiogram mean? Do all abnormal grafts need to be revised? Do they result in late graft occlusions or do the findings resolve?

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.