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Ann Thorac Surg 2005;79:387-388
© 2005 The Society of Thoracic Surgeons

Correspondence

Cerebral Embolization During Coronary Artery Bypass Grafting

Suzana M.F. Malheiros, MD, Ayrton R. Massaro, MD

Department of Neurology, Universidade Federal de São Paulo, Rua Botucatu, 740, 04023-900 São Paulo, SP Brazil

suzana{at}neuro.epm.br

To the Editor:

We read with great interest the article by Lund and co-workers [1]. The authors observed a significant reduction in intraoperative microembolic signals (MESs) detected by transcranial Doppler ultrasound in off-pump coronary artery bypass grafting (CABG) procedures compared with on-pump CABG operations. The number of MESs, however, could not be related to any significant difference in the neuropsychological outcome in this study population.

In 2001, we [2] presented a small series of 20 patients eligible for routine off-pump CABG who were randomized to either an on-pump or an off-pump operation. The two groups did not differ in respect to demographics, risk factors for cerebrovascular disease, grade of aortic atheromatous disease, and number of grafts. As in the study of Lund and co-workers, the frequency of MESs in the off-pump group was considerably lower, and there were no differences between groups in the results of the early postoperative neurological examination.

In our off-pump group, microemboli were related almost exclusively to aortic manipulation, a result suggested by the absence of MES detection in 5 patients receiving a single graft internal mammary artery–left anterior descending coronary artery with no aortic clamping required. In addition, the small number of MESs detected in our off-pump group associated with aortic manipulation suggests that they were preponderantly particulate in nature. On the other hand, MESs in our on-pump group probably included gaseous and microparticulate emboli generated by the pump circuit as well as microemboli associated with aortic manipulation. Therefore, we hypothesized at that time, that the size and the composition of MESs might be the most important mechanisms associated with neurological complications after CABG.

Furthermore, although neurological complications in on-pump CABG procedures had been mainly attributed to the number of MESs detected by transcranial Doppler monitoring, we [3] could not detect significant differences in early neurological and neuropsychological outcomes between patients undergoing on-pump CABG and those having off-pump CABG. These findings led us to question the clinical significance of MESs in these patients and suggested that the changes in flow velocity and pulsatility index frequently observed during off-pump CABG could indicate a potential contribution of hemodynamic mechanisms of brain injury [4].

Lund and co-workers confirmed our findings, and despite the limitation of the sample size, the difference in the number of MESs between the two groups is clear.

With the advent of angioplasty, fewer patients are eligible for CABG, and this may limit the randomization of large numbers of patients by a single center. Therefore, only large, prospective multicenter randomized trials will help to elucidate the controversial genesis of neurological complications in CABG procedures.

References

  1. Lund C, Hol PK, Lundblad R, et al. Comparison of cerebral embolization during off-pump and on-pump coronary artery bypass surgery. Ann Thorac Surg. 2003;76:765–770[Abstract/Free Full Text]
  2. Malheiros SMF, Massaro AR, Gabbai AA, et al. Is the number of microembolic signals related to neurologic outcome in coronary bypass surgery? Arq Neuropsiquiatr. 2001;59:1–5[Medline]
  3. Malheiros SMF, Brucki SMD, Gabbai AA, et al. Neurological outcome in coronary artery surgery with and without cardiopulmonary bypass. Acta Neurol Scand. 1995;92:256–260[Medline]
  4. Malheiros SMF, Massaro AR, Carvalho AC, et al. Transesophageal echocardiography and transcranial Doppler monitoring in coronary surgery without cardiopulmonary bypass: preliminary results. Cerebrovasc Dis. 1999;9:358–360[Medline]




This Article
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