NEW ORLEANS—Most clinically significant strokes following cardiac surgery occur without evidence of significant carotid disease, according to data presented at the 2008 International Stroke Conference. Yuebing Li, MD, PhD, John Castaldo, MD, and colleagues found that although significant carotid stenosis is an indicator for postoperative stroke in patients who need open heart surgery, most strokes do not occur within the diseased carotid territory. In addition, combined carotid endarterectomy and cardiac surgery may increase the risk of stroke, thereby indicating that carotid revascularization does not play a significant role in stroke prevention, the investigators reported.
“While screening for carotid stenosis can be done for the estimation of postoperative stroke risk, patients with significant, even severe asymptomatic carotid stenosis should not be routinely offered preoperative revascularization procedures such as carotid endarterectomy or stenting,” said Dr. Li, Associate Professor of Clinical Medicine, Lehigh Valley Hospital and Health Network, Allentown, Pennsylvania.
Carotid Stenosis and Stroke
Prior to this five-year retrospective study, there was no consensus about whether candidates for open heart surgery should receive preoperative carotid assessment or carotid revascularization. “Neurologists regularly evaluate the risk of perioperative stroke and often quote guidelines for carotid stenosis generated from studies done on relatively healthy patients, such as the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the Asymptomatic Carotid Atherosclerosis Study (ACAS), which may not be applicable to candidates for open heart surgery—a population that may have higher stroke risk,” said Dr. Castaldo, Professor of Clinical Medicine, Lehigh Valley Hospital and Health Network. “Many retrospective analyses have been published, mainly in the field of vascular and cardiothoracic surgery, but only one or two have critically analyzed the true relationship between carotid stenosis and postoperative stroke. [Ours is] not the first retrospective study. However, this is perhaps the largest of its kind, and this is the first one to look at the distribution of strokes in relation to the diseased carotid.”
The researchers evaluated 4,335 open heart surgery patients to determine incidence of postoperative stroke and significant carotid stenosis, as well as the impact of significant carotid stenosis on stroke occurrence. All patients received nonurgent coronary artery bypass grafting (CABG), valve replacement, or a CABG/valve replacement combination between July 2001 and December 2006. Most carotid arteries were initially assessed with carotid duplex studies one month before surgery, and 91% of patients underwent carotid ultrasound evaluation. Those with greater than 70% stenosis were further examined by the researchers, who performed magnetic resonance angiography, CT angiography, or conventional angiography to verify severity. Neurologists evaluated all patients with neurologic complications, and only patients with acute stroke were included. Stroke subtypes were classified based on Trial of ORG 10172 in Acute Stroke Treatment (TOAST) criteria. The involved artery territory was then determined by independent review of the imaging.
Seventy-six patients had a postoperative stroke, the majority occurring within one day after surgery. Of these 76 cases, 75% were cardioembolic, 5% were large vessel, 13% were small vessel, and 7% were undetermined. Sixty patients had radiologically confirmed ischemic stroke. Thirty-seven patients had stroke outside a single carotid territory, and three had symptoms suggesting infarction in the posterior circulation, indicating that more than half of the 76 incidences of stroke occurred outside a single carotid distribution. Eighteen of the 76 patients had more than 50% carotid stenosis. Only four of the 18 patients had stroke within the diseased carotid territories, and three of these four patients had an ipsilateral carotid occlusion.
Among 3,942 patients evaluated by preoperative carotid ultrasound, 239 had greater than 50% carotid stenosis. Nearly 8% exhibited signs of perioperative stroke. Regarding carotid intervention, one of five patients who had carotid stenting and cardiac surgery had a stroke; 13.2% of those who had combined carotid endarterectomy and cardiac surgery had a stroke. Such combined surgeries were performed in 53 patients with significant (more than 70%) carotid stenosis without occlusion. However, no stroke occurred in 51 patients with equal degree of stenosis without any carotid revascularization prior to open heart surgery.
More Harm Than Good?
“Our data clearly show that combined open heart surgery and carotid endarterectomy does more harm than good,” commented Dr. Li. “In addition, [they show] that strokes that do occur during open heart surgery are rarely directly related to carotid stenosis. Therefore, offering carotid revascularization prior to open heart surgery does not improve clinical outcome.
—Taryn Fort