Response to Letter by Cote
We thank Dr Cote for his interest in our study. We fully agree with him that optimal treatment of vascular risk factors in patients at high risk of new or recurrent vascular events is highly important. A recent study shows that vascular event rates increased with the number of symptomatic arterial disease locations after 1 year follow-up, ranging from 12.6% for patients with one, 21.1% for patients with two, and 26.3% for patients with three symptomatic aterial disease locations.1 This points toward important predictive information in the number of vascular localization in addition to that of traditional vascular risk factors. Asymptomatic carotid artery stenosis is one of those markers in patients with various clinical manifestations of atherosclerosis, as shown in our article.
Indeed, asymptomatic carotid artery stenosis can lead to ischemic stroke. In our study we found an annual stroke risk of <1%. This low annual risk is probably because patients with previous cerebral ischemic events were excluded from analyses. Fifty patients (1.9%) had an incomplete follow-up in SMART (mean 2.7 years), which is very low and unlikely to affect the outcome of the study. During follow-up, patients (or the patient’s family) were biannually asked about important medical conditions and events during the past 6 months. Given the nature of the outcome events (myocardial infarction, ischemic stroke, vascular interventions) and the adjudication of events by 3 members of an end point committee, misclassification or under-reporting is very unlikely to happen. Adding information on the occurrence of TIAs would be interesting in concept, but given the difficulty of diagnosing TIAs this end point is not used in large intervention trials. From a prognostic point of view, only baseline data on carotid artery stenosis are relevant for predicting future vascular events.
Progression of symptomatic and asymptomatic carotid artery stenosis is indeed associated with a higher risk of ischemic stroke.2,3,4 Close monitoring of carotid artery stenosis with duplex ultrasound has the advantage to identify patients with disease progression, which may have clinical consequences, although this remains to be studied. The domain of our study was patients with clinical manifest vascular diseases already deserving optimal risk factor management. Information on progression of carotid artery stenosis would not change that.