**1. Introduction**

164 Special Topics in Cardiac Surgery

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Conventional coronary artery by-pass grafting (CCABG) performed using cardioplegic arrest and cardiopulmonary by-pass is a very well documented treatment for ischemic heart disease. The operation often relieves chest pain and it improves survival for patients with triple- vessel disease and left main coronary artery disease.

Since it was introduced in the late 1960´es, CCABG has become one of the most commonly performed operations. In 2007, an estimated 408.000 surgical coronary revascularizations were performed in the United States alone (1)

Given the ageing populations in large parts of the world, CCABG is also increasingly being offered to elderly patients and to patients with co-morbidities. As a consequence, a significant number of operated patients suffer major or minor complications. Concerns have been raised that the use of cardiopulmonary by-pass (CPB) could cause neuro-cognitive dysfunction. Also, CPB has been linked to myocardial, renal and pulmonary damage. Several mechanisms have been suggested: Manipulation of the aorta during cannulation and clamping may cause dislodgment and embolization of atherosclerotic deposits, cardiac arrest may induce myocardial damage, and the long-lasting and repeated contact of blood with the non-biological surfaces of filters and tubing of the heart- lung- machine induce mechanical wearing of the formed elements and biochemical over-activation of the immuneand coagulation systems

Development of the Off-pump Coronary Artery By-pass (OPCAB) technique has been driven by concerns of these possible side-effects from CPB. On the other hand, concerns have been raised about whether the quality of anastomoses constructed "on the beating heart" - i.e. without cardiopulmonary by-pass and cardioplegic arrest – would be as good as that of the anastomoses performed during CCABG. The question remains controversial. Best estimates of the proportion of surgical coronary revascularizations performed as OPCAB in the United States is around 25%. Some surgical centres perform almost all coronary by-pass operations off-pump, while others hardly or never use this technique. Tradition and economy dictate that OPCAB is the preferred method in some parts of the developing world. In the beginning of the OPCAB-experience, evidence was limited to small, published series by individual surgeons (2-3). Although seemingly providing good results, these observations were hampered by the lack of a control group. Later studies from databases were difficult to interpret because the original intention-to-treat was not

Current Evidence of On-Pump Versus Off-Pump Coronary Artery By-Pass Surgery 167

favour of OPCAB (24). In this study, however, the absolute number of grafts was 0.2 lower

Allmost all of the earlier studies showed a trend towards poorer graft patency in OPCAB patients. A single, smaller study found this difference to be statistically significant (25). Also, the proportion of patent grafts in the largest study, the ROOBY-trial, was 82.6% in the OPCAB group and 87.8% in the CCABG group (p<0.01) (14). This difference, however, did

In studies performed by few, dedicated OPCAB surgeons, the difference in number of grafts was very small and not statistically significant (12, 24). The study by Khan (25), the SMART study (14), and the Best Bypass Surgery Study (26) differentiated the findings and found a higher proportion of occluded grafts at right and circumflex territories and fewer occlusions in the LAD territory. Lingaas et al only found differences in graft patency between OPCAB and CCABG to be significantly different when comparing vein grafts as opposed to internal

An important parameter is freedom from chest pain. In the Octopus trial (6, 24), 89.0% experienced freedom from chest pain in the OPCAB group compared to 89.3% in the CCABG-group (p=ns). At five years follow-up, these numbers were down to 82.3% and 87.7%, respectively (p=ns). At one year follow-up, ergometer testing was performed in 81% of the patients. It was found to be negative in 79.8% of CCABG patients and 83.1% of OPCAB patients (p=ns). In the SMART-study, chest pain was present at one-year follow-up in 0% of CCABG and 3% of OPCAB patients, respectively (p=ns) (12). In a separate publication, using a specific questionnaire on chest pain in the 400 patients involved in the BHACAS1 and BHACAS2-studies, no difference was found after a median follow-up of

Given the lower number of patent grafts in the OPCAB groups, a greater need for coronary re-intervention might be expected. Only few of the published trials have had long enough follow-up for this question to be evaluated. In the BHACAS-1 study, three percent of both OPCAB and CCABG patients had had a reintervention – either percutaneous or surgical – within a median three years follow-up (7). The longest follow-up, which was published by the Octopus trialists, reported 7.7% of OPCAB-patients and 5% of CCABG patients to have undergone reintervention after five years (6). In the ROOBY-trial, the proportion undergoing reintervention was 4.6% in the OPCAB group and 3.4% in the CCABG group at one year follow-up. Neither individual studies nor metanalyses found thiese differences to

A number of studies compare self-reported, health related quality of life after OPCAB and CCABG. Medical Outcomes Study-Short Form 36 (MOS SF-36) is the most commonly used tool. In this questionnaire eight scales cover physical, mental, and social well-being (28). One study found a significantly higher score among CCABG-patients in one of the eight scales ("Role emotional") in contrast to another study who favoured OPCAB patients in the dimension "Social Relationships", using another questionnaire (29,30). In general, few significant inter-group differences have been found, given the multiple tests being

not result in a higher number of myocardial infarctions in the OPCAB group.

in the OPCAB-group.

mammary artery grafts (10). *Recurrent or persistent chest pain* 

three years (27). *Reintervention* 

*Quality of life* 

performed.

be statistically significant (21, 26).

recorded. This may have caused high-risk patients to be moved from one treatment group to the other (4-5).

From the late 1990ies to 2002 a significant technical development in stabilizing equipment led to a fast rise in the number of OPCAB procedures. From 2002 results from the first randomized studies failed to show a clear benefit and interest has cooled somewhat. A significant number of randomized studies have been conducted comparing very different end-points after OPCAB and CCABG. This chapter aims to review the results of these studies to assess the comparative effectiveness and safety of the two techniques.
