Ref: EJVES Nov 2015
This question has no clear unquestionable answer unfortunately! If you pick up a ‘highly vulnerable’ lesion in asymptomatic patient, who has no stroke history and referred, electively, to your clinic, then you still have to think TWICE! Adding haemodynamic data to static ones may also help you in the decision: finding small ‘blebs’ on doppler scan for example, or from a more accurate dynamic imaging in the future, would certainly help convincing both you and the patient that there is a dangerous plaque here. If you adopt a policy in the centre to operate on asymptomatic patients with significant stenosis (or with highly vulnerable plaque), then your results should follow the major trial results, and you would be able to estimate how many have you helped before one was harmed!
In this work from Toby Richards and team at UCL, highly vulnerable lesions were considered as those having several structural plaque characteristics that distinguish the “vulnerable” from the “non-vulnerable” plaque, which includes plaque ulceration, intraplaque haemorrhage (IPH), thin or ruptured fibrous cap (FC), lipid-rich necrotic core, and the presence of calcification. (1) Inflammation may also play a role in the development and progression of disease as well as identifying the vulnerable plaque.(2)
(1) A.V. Finn, M. Nakano, J. Narula, F.D. Kolodgie, R. Vierman. Concept of vulnerable/unstable plaque. Arterioscler Thromb Vasc Biol, 30 (2010), pp. 1282–1292
(2)M. Marnane, S. Prendeville, C. McDonnell, I. Noone, M. Barry, M. Crowe, et al. Plaque inflammation and unstable morphology are associated with early stroke recurrence in symptomatic carotid stenosis. Stroke, 45 (2014), pp. 801–806
The conclusion is even more interesting:
US, CT, MRI, and PET are non-invasive imaging techniques that show promise for identifying vulnerable plaque characteristics beyond the degree of stenosis.
Although the aforementioned imaging parameters are promising, at present there is no single imaging technique that can clearly identify the vulnerable plaque. This is because (a) there is no single imaging modality that can detect all vulnerable plaque features, (b) plaque imaging is expensive, time-consuming, and requires a reviewer with advanced experience, and (c) prospective natural follow-up studies analysing the value of these imaging modalities for future cerebral events are limited. It is therefore important to realise that even if we could reliable identify ulceration, LRC, thin FC, and IPH as characteristics of the vulnerable plaque, at this stage there is not enough evidence that these patients indeed have a higher risk of stroke.
MRI has the most potential, with good sensitivity and specificity for most plaque characteristics, of course, within the above limitations …