Experiences with the execution of intercultural, intercontinental trials - part I.

Large scale, international clinical trials are formidable challenges, but they are the most effective means of answering important clinical questions in a definitive, generalizable manner. They require adequate funding and must be rigorously conducted. Much can be gleaned from such studies, which address the important research questions and provide answers to related questions. Such trials are enormously rewarding and are worth the expense and effort.

Unique experiences with intercontinental trials in stroke - part II.

Supported by the Canadian Medical Research Council we performed a randomized trial extending from Newfoundland to British Columbia. With others a number of observations showed that aspirin will reduce stroke. With National Institute of Neurological Disorders and Stroke support we learned who would benefit and not from surgery in these stroke threatened carotid diseased patients. We evaluated the upper limits of acceptability of complications beyond which harm was done. Amassing this large data base of approximately 5000 individuals, followed for five years, previously unknown carotid phenomena were observed: 1. Ischemic stroke occurs in patients with prolapsing mitral valves; 2. There is risk of stroke in patients with residual thrombi in the occluded stump of the carotid artery; 3. We detected a lower risk than expected in patients with nearly occluded carotid arteries. We support the contention of Yusuf and Cairns' that Canada needs to give more financial support to purely clinical research. It pays off !

Endarterectomy for symptomatic carotid stenosis in relation to clinical subgroups and timing of surgery.

BACKGROUND: Carotid endarterectomy reduces the risk of stroke in patients with recently symptomatic stenosis. Benefit depends on the degree of stenosis, and we aimed to see whether it might also depend on other clinical and angiographic characteristics, and on the timing of surgery. METHODS: We analysed pooled data from the European Carotid Surgery Trial and North American Symptomatic Carotid Endarterectomy Trial. The risk of ipsilateral ischaemic stroke for patients on medical treatment, the perioperative risk of stroke and death, and the overall benefit from surgery were determined in relation to seven predefined and seven post hoc subgroups. RESULTS: 5893 patients with 33000 patient-years of follow-up were analysed. Sex (p=0.003), age (p=0.03), and time from the last symptomatic event to randomisation (p=0.009) modified the effectiveness of surgery. Benefit from surgery was greatest in men, patients aged 75 years or older, and those randomised within 2 weeks after their last ischaemic event, and fell rapidly with increasing delay. For patients with 50% or higher stenosis, the number of patients needed to undergo surgery (ie, number needed to treat) to prevent one ipsilateral stroke in 5 years was nine for men versus 36 for women, five for age 75 years or older versus 18 for younger than 65 years, and five for those randomised within 2 weeks after their last ischaemic event, versus 125 for patients randomised after more than 12 weeks. These results were consistent across the individual trials. INTERPRETATION: Benefit from endarterectomy depends not only on the degree of carotid stenosis, but also on several other clinical characteristics such as delay to surgery after the presenting event. Ideally, the procedure should be done within 2 weeks of the patient's last symptoms.

Sex difference in the effect of time from symptoms to surgery on benefit from carotid endarterectomy for transient ischemic attack and nondisabling stroke.

BACKGROUND AND PURPOSE: Early studies showed that carotid endarterectomy (CEA) carried a high risk if performed within days after a large ischemic stroke. Therefore, many surgeons delay CEA for 4 to 6 weeks after any stroke. To determine the effect of delay to CEA on operative risk and benefit, we pooled data from the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial. METHODS: Risk of ipsilateral ischemic stroke in the medical group, operative risk of stroke and death, and overall benefit from surgery were determined in relation to the time from the last symptomatic event to randomization. Operative risk of stroke and death was also determined in relation to the time to surgery. Analyses were stratified by sex and type of presenting event. RESULTS: The 30-day perioperative risk of stroke and death was unrelated to the time since the last symptomatic event and was not increased in patients operated <2 weeks after nondisabling stroke. In contrast, the risk of ipsilateral ischemic stroke in the medical group fell rapidly with time since event (P<0.001), as did the absolute benefit from surgery (P=0.001). This decline in benefit with time was unrelated to the type of presenting event but was more pronounced in women than men (difference P<0.001). Benefit in women was confined to those randomized <2 weeks after their last event, irrespective of severity of stenosis. CONCLUSIONS: CEA can be performed safely within 2 weeks of nondisabling ischemic stroke. Benefit from endarterectomy declines rapidly with increasing delay, particularly in women.

Occurrence of hemispheric and retinal ischemia in atrial fibrillation compared with carotid stenosis.

BACKGROUND AND PURPOSE: The goal of this study was to examine the hypotheses that retinal ischemia is caused more often by carotid atherosclerosis than by atrial fibrillation and that the odds of retinal events compared with hemispheric events increase with worsening carotid stenosis. METHODS: We used data from the Stroke Prevention in Atrial Fibrillation (SPAF) I through III trials and North American Symptomatic Carotid Endarterectomy Trial (NASCET), calculating hemispheric:retinal (H:R) odds for the territory of ischemic events during follow-up in patients with atrial fibrillation and medically treated 50% to 99% carotid stenosis or occlusion in the respective trials. RESULTS: The H:R odds were 25:1 in the SPAF aspirin-assigned patients and 2:1 for NASCET vessels. In NASCET patients, the H:R odds of recurrent ischemic events were 1:4 for vessels randomized initially for retinal symptoms compared with 6:1 for those randomized for hemispheric events (significant difference; P<0.001). Moreover, the H:R odds of first events in the territory of the contralateral asymptomatic artery were 1:1 if the randomized vessel had retinal symptoms compared with 4:1 if the randomized vessel had hemispheric symptoms (significant difference; P<0.01). Increasing carotid stenosis in the 50% to 99% range had no effect on H:R odds (P=0.8). CONCLUSIONS: These findings confirm that retinal symptoms are more typical of carotid stenosis. Hemodynamic effects do not appear to be more important in the pathogenesis of retinal events than hemispheric ones in carotid stenosis. The retinal versus hemispheric location of initial symptoms is strongly predictive of the location of subsequent events in patients with carotid stenosis, even when new symptoms are contralateral to the original ones.

Stroke prevention in the elderly.

The incidence of stroke and risk factors peak in subjects > or = 75 years. Highest risk patients benefit most from effective therapy. For this reason, all strategies of proven value in stroke prevention must be assiduously applied. Control of hypertension, hyperlipidemia, diabetes mellitus and cessation of cigarette smoking are obligatory at all ages but are of special importance in the elderly. Antithrombotic drugs have been proven beneficial for patients at high risk. Lower risk subjects, including those with asymptomatic carotid artery disease, gain no proven benefit from anti-platelet drugs. Patients with non-valvular atrial fibrillation (NVAF), a condition that increases with age, require anticoagulant therapy. Strict regulation of the INR is required otherwise aspirin is recommended. Without evidence of organ failure, elderly patients with severely stenotic symptomatic carotid artery disease should receive endarterectomy. They benefit most. The evidence for benefit from endarterectomy in asymptomatic subjects at any age is weak and cannot be recommended.

Analysis of pooled data from the randomised controlled trials of endarterectomy for symptomatic carotid stenosis.

BACKGROUND: Endarterectomy reduces risk of stroke in certain patients with recently symptomatic internal carotid stenosis. However, investigators have made different recommendations about the degree of stenosis above which surgery is effective, partly because of differences between trials in the methods of measurement of stenosis. To accurately assess the overall effect of surgery, and to increase power for secondary analyses, we pooled trial data and reassessed carotid angiograms. METHODS: We pooled data from the European Carotid Surgery Trial (ECST), North American Symptomatic Carotid Endarterectomy Trial, and Veterans Affairs trial 309 from the original electronic data files. Outcome events were re-defined, if necessary, to achieve comparability. Pre-randomisation carotid angiograms from ECST were re-measured by the method used in the other two trials. RESULTS: Risks of main outcomes in both treatment groups and effects of surgery did not differ between trials. Data for 6092 patients, with 35000 patient-years of follow-up, were therefore pooled. Surgery increased the 5-year risk of ipsilateral ischaemic stroke in patients with less than 30% stenosis (n=1746, absolute risk reduction -2.2%, p=0.05), had no effect in patients with 30-49% stenosis (1429, 3.2%, p=0.6), was of marginal benefit in those with 50-69% stenosis (1549, 4.6%, p=0.04), and was highly beneficial in those with 70% stenosis or greater without near-occlusion (1095, 16.0%, p<0.001). There was a trend towards benefit from surgery in patients with near-occlusion at 2 years' follow-up (262, 5.6%, p=0.19), but no benefit at 5 years (-1.7%, p=0.9). INTERPRETATION: Re-analysis of the trials with the same measurements and definitions yielded highly consistent results. Surgery is of some benefit for patients with 50-69% symptomatic stenosis, and highly beneficial for those with 70% symptomatic stenosis or greater but without near-occlusion. Benefit in patients with carotid near-occlusion is marginal in the short-term and uncertain in the long-term.

Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis.

BACKGROUND: Without strong evidence of benefit, the use of carotid endarterectomy for prophylaxis against stroke rose dramatically until the mid-1980s, then declined. Our investigation sought to determine whether carotid endarterectomy reduces the risk of stroke among patients with a recent adverse cerebrovascular event and ipsilateral carotid stenosis. METHODS: We conducted a randomized trial at 50 clinical centers throughout the United States and Canada, in patients in two predetermined strata based on the severity of carotid stenosis--30 to 69 percent and 70 to 99 percent. We report here the results in the 659 patients in the latter stratum, who had had a hemispheric or retinal transient ischemic attack or a nondisabling stroke within the 120 days before entry and had stenosis of 70 to 99 percent in the symptomatic carotid artery. All patients received optimal medical care, including antiplatelet therapy. Those assigned to surgical treatment underwent carotid endarterectomy performed by neurosurgeons or vascular surgeons. All patients were examined by neurologists 1, 3, 6, 9, and 12 months after entry and then every 4 months. End points were assessed by blinded, independent case review. No patient was lost to follow-up. RESULTS: Life-table estimates of the cumulative risk of any ipsilateral stroke at two years were 26 percent in the 331 medical patients and 9 percent in the 328 surgical patients--an absolute risk reduction (+/- SE) 17 +/- 3.5 percent (P less than 0.001). For a major or fatal ipsilateral stroke, the corresponding estimates were 13.1 percent and 2.5 percent--an absolute risk reduction of 10.6 +/- 2.6 percent (P less than 0.001). Carotid endarterectomy was still found to be beneficial when all strokes and deaths were included in the analysis (P less than 0.001). CONCLUSIONS: Carotid endarterectomy is highly beneficial to patients with recent hemispheric and retinal transient ischemic attacks or nondisabling strokes and ipsilateral high-grade stenosis (70 to 99 percent) of the internal carotid artery.