Molloy J, Khan N, Markus H S
Department of Clinical Neurosciences, King's College School of Medicine and Dentistry, London, UK.
Stroke. 1998 Jun;29(6):1129-32. doi: 10.1161/01.str.29.6.1129.
Although asymptomatic embolization can be detected in patients with carotid artery stenosis, its temporal variability is unclear. An understanding of this is important in designing optimal recording protocols for future prospective studies of the predictive value of embolic signals (ES). We determined the effect of repeating and extending recording times in patients with symptomatic and asymptomatic carotid stenosis.
In 20 asymptomatic and 20 symptomatic subjects with > 60% carotid stenosis, we used transcranial Doppler ultrasound to record for ES in the ipsilateral middle cerebral artery. Three 1-hour recordings were performed on three separate days, and on one occasion (not necessarily the first) the recording was extended to 2 hours. The recordings were saved onto digital tape for subsequent blinded analysis.
Marked temporal variability was seen in symptomatic patients in whom the cumulative proportion of subjects with ES increased from 10 (50%) after a single hour of recording to 12 (60%) and 15 (75%) after two and three recordings, respectively. Extending the recording to 2 hours increased the yield of ES-positive patients from 6 (30%) to 8 (40%). In symptomatic patients there was excellent agreement between whether patients were positive for ES during each of two consecutive 1-hour recordings (kappa = 0.78, P = 0.0003) but poor agreement between the results of two single-hour recordings performed on different days (kappa = 0.22, P = 0.27). In asymptomatic patients, 4 (20%) were ES positive during the first hour; this increased to 5 (25%) after the recording was repeated once, with no further increase after the third recording. Extending the recording to 2 hours increased the yield from 3 (15%) to 7 (35%). In contrast to symptomatic stenoses, in patients with asymptomatic stenoses there was fair agreement between whether patients were ES positive on two consecutive 1-hour recordings (kappa = 0.49, P = 0.01) or two single-hour recordings performed on different days (kappa = 0.48, P = 0.02). Symptomatic subjects were more likely to have ES (when all 1-hour recordings were considered, 24/60 versus 10/60; P = 0.0046). ES in symptomatic subjects had a higher relative intensity increase than in asymptomatic subjects (P = 0.01).
The temporal variability of ES needs to be taken into account in the design of optimal recording protocols and comparisons of results from different studies. Extending the duration of recording beyond an hour in symptomatic stenoses is of less value, but repeating the recording on a different day will often identify additional subjects with ES. In intervention studies in symptomatic patients, the time since last symptoms must be considered. In asymptomatic stenosis, extending the duration of recording beyond an hour will increase the proportion of patients positive for ES.
尽管在颈动脉狭窄患者中可检测到无症状性栓塞，但其时间变异性尚不清楚。了解这一点对于设计最佳记录方案以进行未来关于栓子信号（ES）预测价值的前瞻性研究很重要。我们确定了重复和延长记录时间对有症状和无症状颈动脉狭窄患者的影响。
在20例无症状和20例有症状且颈动脉狭窄>60%的受试者中，我们使用经颅多普勒超声记录同侧大脑中动脉的ES。在三个不同的日子进行三次1小时的记录，并且有一次（不一定是第一次）记录延长至2小时。记录被保存到数字磁带上以便后续盲法分析。
在有症状的患者中观察到明显的时间变异性，其中有ES的受试者累积比例从单次记录1小时后的10例（50%）分别增加到两次和三次记录后的12例（60%）和15例（75%）。将记录延长至2小时使ES阳性患者的比例从6例（30%）增加到8例（40%）。在有症状的患者中，连续两次1小时记录期间患者是否ES阳性之间有极好的一致性（kappa = 0.78，P = 0.0003），但在不同日子进行的两次单次1小时记录结果之间一致性较差（kappa = 0.22，P = 0.
