October 22, 2002
Prof. C.J. Kalkman, MD, PhD
Prof. D.E. Grobbee, MD, PhD
P.P.Th. de Jaegere, MD, PhD
The complications associated with in coronary artery bypass surgery (CABG) using cardiopulmonary bypass (CPB) have led to a renewed interest in coronary bypass surgery on the beating heart. The primary objective of the Octopus Study was to compare cognitive outcome between patients randomized to off-pump or on-pump CABG.
In chapter 2, the literature suggesting that CABG may impair cognitive function is systematically reviewed and chapter 3 describes in detail the rationale and design of the Octopus Study.
In chapter 4, the cerebral outcome and quality of life after off-pump and on-pump CABG are presented. From March 1998 through August 2000, 281 patients were enrolled. At 3 and 12 months after surgery, there was no difference in quality of life between the two groups. At 3 months, cognitive decline (or stroke) occurred in 21% in the off-pump group and 29% in the on-pump group (relative risk 0.65; 95% CI 0.36-1.16; p=0.15). At 12 months, cognitive decline occurred in 31% in the off-pump group and 34% in the on-pump group (relative risk 0.88; 95% CI 0.52-1.49; p=0.69).
Chapter 5 is a prediction study on cognitive outcome. The previously identified determinants of cognitive outcome were no predictor of cognitive outcome in the present patient sample. The only variables that were significantly associated with cognitive outcome after 3 months, were measures of cognitive outcome 4 days after surgery.
In chapter 6 measures of early clinical outcome after off-pump and on-pump CABG are compared. Completeness of revascularization was similar in both groups. Blood products were needed during 3% of the off-pump procedures and 13% of the on-pump procedures (p<0.01). Release of creatine kinase muscle-brain isoenzyme was 41% less in the off-pump group (p<0.01). Off-pump patients were discharged 1 day earlier. At 1 month, operative mortality was zero in both groups, and quality of life had improved similarly.
In chapter 7, a comparison of cardiac outcome and cost-effectiveness one year after off-pump and on-pump CABG is reported. One year survival free from stroke, myocardial infarction and coronary re-intervention was 88.0% after off-pump surgery and 90.6% after on-pump surgery (p=0.48). Survival free from angina was 89.3% vs 89.0% (p=0.93). Graft patency, determined in a randomized subset of patients, was 91% after off-pump and 93% after on-pump surgery (p=0.65). Off-pump surgery reduced costs by $2,329 (13.1%) per patient ($ 15,479 vs $ 17,808 p<0.01). Quality adjusted life years (0.82 vs 0.83; p=0.74) and event free survival years (1.02 vs 1.03; p=0.23) did not differ.
Finally, Chapter 8 comprises a general discussion of the Octopus Study. It is concluded that in selected patients, off-pump CABG is safe and yields a cardiac outcome that is comparable to that of on-pump CABG. Avoiding CPB is cost-effective and slightly decreases the need for blood transfusion, but other clinically relevant benefits of off-pump CABG are not established yet. Patients undergoing off-pump CABG have better cognitive outcome at 3 months after surgery, but the effect is of limited size.