When performing on-pump coronary artery bypass grafting (CABG), cardiac surgeons can control very few factors to reduce the risk of stroke – with the exception of which method of aortic manipulation they use. Debate and controversy, however, have surrounded which aortic manipulation technique is best: single- or double-clamp occlusion.
A large retrospective study of almost 8,500 patients who had CABG at the Mayo Clinic in Rochester, Minn., over a 17-year period showed that, while use of the single-aortic cross-clamp (SC) technique steadily increased, the risk of stroke is virtually the same as it is with the partial aortic cross-clamp (PC), or double cross-clamp, technique. The study authors, led by Dr. Juan C. Araque, published their results online in the Journal of Thoracic and Cardiovascular Surgery (J. Thorac. Cardiovasc. Surg. 2015 [doi:10.1016/j.jtcvs.2015.04.010]).
“It is intuitive that less aortic manipulation would result in less risk of stroke,” Dr. Araque and colleagues said, but even off-pump CABG, which requires no aortic manipulation, is not without stroke risk.
“It is conceivable that there is some inherent risk of stroke associated with any cardiac operation, and that risk may increase with manipulation of the ascending aortic with the aortic cross clamp,” they wrote. “Our data would suggest, however, that the risk does not increase further with the additional aortic manipulation of the partial occlusion clamp.”
The study comes on the heels of a 2008 meta-analysis that found no benefit of SC in comparison to PC (Interact. Cardiovasc. Thorac. Surg. 2008;7:500-3), while another study in 2011 suggested that less aortic manipulation carried a significantly lower stroke risk (Heart Lung Circ. 2011;20:318-24).
The Mayo study evaluated the SC technique in 2,051 patients and PC in 6,446 patients who had isolated on-pump CABG between 1993 and 2010. The rate of stroke was 1.2% in the SC group and 1.5% among those who had PC. In two propensity-matched cohorts of 1,333 patients each, the stroke rate was 1.2% in each group. The investigators used the Society of Thoracic Surgeons’ risk calculator variables to create the propensity-matched cohorts.
The study group excluded high-risk patients, including those who had off-pump operations or previous cardiac surgeries or required replacement of a cross clamp during an unplanned operation.
The goal of the study was not to compare outcomes with the off-pump technique. “It is only to bring attention to the associated non-zero stroke rate with both techniques,” Dr. Araque and colleagues said.
Their findings are significant because on-pump CABG is the preferred operation of cardiac surgeons, accounting for more than 80% of the CABG operations in the SYNTAX study (N. Engl. J. Med. 2009;360:961-72). “The ‘anaortic’ off-pump technique may be a more specialized technique, representing less than 15% of operations in one large series,” Dr. Araque and coauthors said.
They acknowledged a few limitations resulting from the observational nature of the study, including that surgeons may have missed some strokes because they did not use a routine, standardized procedure for evaluating stroke signs along with the lack of documented assessment of the descending aorta. But they also stated that the large number of patients in the study, along with the use of propensity matching, addresses some of the bias inherent in an observational study.
The study authors disclosed no relationships.