Progresses and Challenges in Reducing Stroke at Cardiac Surgery

No complication resulting from a medical intervention could make patients more apprehensive than the possibility of a stroke. The toll of stroke can be horrible, as patients may lose quality of life and the ability to care for themselves, possibly becoming a burden for their family. Most patients would prefer to lose some life expectancy than experience a major stroke.

Stroke around cardiac surgery essentially arises from 3 situations: the biological substrate of the patient prior to the surgery; the cardiac and aortic manipulations that are performed during operation; and the medical issues that occur after cardiac surgery. With regards to the biological substrate, cardiac surgical patients often exhibit vascular atherosclerosis and a propensity for thrombogenicity, itself made worse by urgent conditions such as acute coronary syndrome or aortic dissection (with resultant intravascular coagulation). Intraoperatively, cardiac surgeons--by operating on the heart and great vessels from where the cerebrovascular vasculature arises--may manipulate and inadvertently dislodge debris, clots, or entrapped air. Patients may experience intraoperative hypotension, which also correlates with stroke.¹ Occasionally, a hemorrhagic stroke may be caused or worsened by the enormous doses of IV heparin that are administered during cardiac surgery. Postoperatively, cardiac surgery patients are uniquely at risk for developing conditions predisposing them to stroke, such as heparin-induced thrombocytopenia, new onset atrial fibrillation, a requirement for blood transfusions, etc. It is, therefore, important that every cardiac surgeon and team member be aware of the latest suggestions summarized here by Gaudino et al that aim at avoiding stroke in cardiac surgery patients.

Fortunately, the incidence of stroke around cardiac surgery is decreasing. With common operations such as coronary artery bypass grafting (CABG) and aortic valve replacement, the incidence of stroke has decreased to approximately 1%.² For surgery on the ascending aorta and aortic arch, stroke still occurs in 3-5% of patients. There remain wide geographic and centre-specific variations in the incidence of stroke after cardiac surgery. With CABG, off-pump surgery has failed to provide widespread benefit in preventing stroke across several large randomized studies. Similarly, no randomized evidence supports the efficacy of no touch CABG, which avoids all aortic manipulation and supplies new blood to the heart exclusively from pedicled internal thoracic arteries. It appears that a continued focus on stroke around cardiac surgery, including the efforts of the Society of Thoracic Surgeons through their database and quality program as well as from numerous research endeavors, has helped decrease its incidence. Stroke rates at CABG are lower today than even just 10-15 years ago when the SYNTAX and FREEDOM trials were initiated. One major research issue is that stroke remains very difficult to study, as its ~1% incidence mandates very large sample sizes to allow for the randomized prospective comparison of treatments aiming at decreasing its occurrence.

The American Heart Association Scientific Statement by Gaudino et al provides useful and detailed guidance for the entire cardiac surgery team, in order to enable the lowest possible probability that a patient would experience a stroke before, during, or after a heart or great vessel operation.³ Preoperative issues are carefully reviewed to their current state of knowledge. Notably, it remains unknown whether a patient with an acute coronary syndrome should be maintained on dual antiplatelet therapy prior to urgent CABG, due a potential for stroke being mediated by the acute, diffuse vascular inflammation.⁴ In the scientific statement, intraoperative tools such as the use of bilateral versus unilateral cerebral perfusion, pH management during hypothermia, and the treatment of postoperative atrial fibrillation are also carefully reviewed, one by one. As surgical ligation of the left atrial appendage becomes more commonplace, it is possible that its use during routine cardiac surgery may become more prevalent, even as a prophylactic measure. Data from the ongoing LAAOS III trial, performed in over 4800 patients and whose results are expected in the next 2 years, should provide guidance to clinicians.⁵

Avoiding stroke in every patient is key to providing the highest level of care in cardiac surgery, which in turn may save lives for so many patients. As such, the statement by Gaudino et al is timely, deserves a careful read and warrants a dedicated team effort at implementation, as well as represents a stimulus to undertake further research in this important field.