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Abstracts & Commentary
Sources: Alamowitch S, et al. For The North American Symptomatic Carotid Endarterectomy Trial (NASCET) Group. Risk, causes and prevention of ischemic stroke in elderly patients with symptomatic internal carotid artery stenosis. Lancet. 2001;357:1154-1160; Rothwell PM. Commentary: Carotid endarterectomy and prevention of stroke in the elderly. Lancet. 2001;357:1142-1143.
Previous reports from Nascet and related stories indicated that carotid endarterectomy (CEA) benefits patients with symptomatic internal carotid artery (ICA) stenosis of 70% or greater (Lancet. 1998;351:1379-1387). In elderly patients the benefit of CEA has been uncertain and physicians have been reluctant to recommend CEA to them. Therefore, Alamowitch and colleagues compared patients 75 years of age and older enrolled in NASCET with those aged 65-74 years, and those aged younger than 65 years for risk of ipsilateral ischemic stroke at 2 years according to baseline characteristics, degree of ICA stenosis, and treatment with CEA or best medical therapy.
Elderly patients were less likely than younger patients to have a history of most of the other risk factors for atherosclerosis: smoking, diabetes, hyperlipidemia, claudication, diastolic hypertension, and recent TIA or stroke. Intracranial disease was equally present in all age groups.
Among patients with 70-99% ICA stenosis, the absolute risk reduction of ipsilateral ischemic stroke with CEA was 29% for patients aged 75 years or older (n = 71), 15% of those aged 65-74 years (n = 285), and 10% for the youngest group (n = 303). Among patients with 50-69% ICA stenosis, the absolute risk reduction was significant only in the older than 75 age group (n = 145).
The 5.2% rate of perioperative stroke and death among the 172 elderly patients was lower than that in younger patients, but the difference was not significant.
Subgroup analysis showed that advanced age was associated with an increased risk of stroke in the medically treated group. Therefore, elderly patients in NASCET benefited more from CEA than younger patients in each category of symptomatic ICA stenosis.
This latest subgroup analysis from NASCET is welcome and may dispel the erroneous perception among both physicians and patients that the risks of CEA in the elderly are prohibitive. Nevertheless, physicians must remember that the elderly NASCET patients had less severe carotid atherosclerotic disease, a lower prevalence of contralateral ICA occlusion, and a lower frequency of intermittent claudication. Therefore, this group of healthy elders may have tolerated surgery because they had fewer of the risk factors that can increase the rate of perioperative complications (Rothwell PM, et al. BMJ. 1997;315:1571-1577).
In study patients, advanced age was associated with an increased risk of subsequent stroke in the medically treated group. Therefore, the risk reduction in the surgically treated group must have been due to a decrease in large-artery atherothrombotic and artery-to-artery embolic stroke. Experience indicates, however, that the elderly are at risk for cardioembolic stroke due to nonvalvular atrial fibrillation. The prevalence of cardioembolic stroke mandates a careful search for intracardiac disease and paroxysmal arrhythmias in this group.
Finally, how old is elderly? As pointed out by Rothwell in his commentary on the article, the clinical dilemma now is whether to operate on patients aged 85, 90, or even older. The decision, therefore, comes down to whether the elderly patient will survive long enough to benefit from CEA.
The NASCET results (Lancet. 1998;351:1379-1387) indicate that the reduction in stroke risk after CEA is evident within 6 months of surgery and peaks by 2 years. Since the average life expectancy at age 85 in the United States is 6 years, most 85 year olds will survive long enough after CEA to benefit. Therefore, physicians should clinically investigate elderly patients who have had a recent TIA and consider CEA as treatment in appropriate patients. —John J. Caronna