Imaging of progression of carotid atherosclerosis - case unproven

A study I recently read in the Lancet reports results of an individual patient data meta-analysis, which show that cIMT progression is not associated with incident myocardial infarction, stroke, or vascular death in the general population (hazard ratio 0·98, 95% CI 0·95–1·01, adjusted for age, sex, mean common carotid artery intima-media thickness, and vascular risk factors).

A single measure of carotid IMT may be useful for predicting risk in asymptomatic intermediate risk adults, although far less so than calcium scoring by CT according to the most recent guidelines.

Guidelines For Assessment Of Cardiovascular Risk In Asymptomatic Adults

ACCF/AHA guidelines - nice summary of current thoughts.

Similar guidelines were published recently by the European Society of Cardiology.

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Images above show non-invasive cardiac imaging using CT, compared (bottom) to invasive coronary angiography - 'A'. Note the distal left main stem 'soft' plaque visible on the contrast CT - 'C', invisible on the non-contrast calcium scoring CT scan in 'B'.

Dangerous plaques are missed by calcium scoring alone in maybe 5% scans in symptomatic subjects.

Carotid plaque inflammation predicts early stroke recurrence

This study, just published in the highly respected journal 'Annals of Neurology' lends support to the concept of persisting inflammation, as detected by 18FDG PET, portends early stroke recurrence. In fact, 18FDG uptake was the only factor on multivariate analysis to predict recurrence, out-performing stenosis degree and age. If the SUV was above 2.1, 80% of subjects had recurrent events within 90 days.

What we need now is a prospective study of an FDG PET-guided approach to risk stratification and management compared with standard medical/surgical care.

The SUV value is in the same ballpark as that seen in other PET studies of atherosclerosis, and less than frequently noted in untreated active vasculitis.

This study provides a counterpart to the MRI one I published here yesterday.

Any thoughts?

Low healing rate amongst complex carotid artery plaques - a longitudinal MRI study

What surprised me the most about this elegant study was the very low rate of healing of complex plaques that had caused cerebrovascular events. We know that the risk of recurrent events is very high immediately after TIA but drops off rapidly. Presumably, even high-resolution structural imaging takes some time to reflect this change in risk.

I believe this is the first longitudinal study to address this issue in humans.

Non-invasive imaging of atherosclerosis review in EHJ

A very comprehensive review from an eminent group of authors appeared in EHJ recently.

Non-invasive anatomic and functional imaging of vascular inflammation and unstable plaque

It covers:

1. Pathobiology of plaque, including lipid accumulation, oxidation, inflammation, matrix breakdown, apoptosis and calcification (both macro- and micro-).

2. Imaging techniques PET, SPECT, CT, MRI and ultrasound

There were some interesting comments on the increasing use of FDG PET imaging for detection of inflammation in atherosclerosis : -

Despite these attractions, some issues require resolution before embracing FDG uptake in this regard. Firstly, only limited prospective data correlate FDG uptake, or changes in FDG uptake, with cardiovascular events or altered rates of such complications,42 and we eagerly await the results of larger prospective cohort studies, such as the High Risk Plaque Initiative and BioImage studies."

"In this regard, nuclear agents that image hypoxia, already in use in oncology, may be
useful in imaging atherosclerosis, as hypoxic conditions may prevail in the core of lesions."

I quite agree on point 1 and keep watching this space for point 2!

Day 3 ESC

A very well attended session at the ESC today concerned novel approaches to imaging the vulnerable plaque.

We heard from Zahi Fayad (New York), Jagat Narula (Orange, Ca) and Beat Kaufmann from Basel in Switzerland. I gave an over-view of vascular PET imaging, both with FDG and novel targeted ligands against plaque macrophages.

The session tried to communicate not only the state of play in 2010, but also to predict what may be around the corner for imaging. There seems to be a move towards more platform integration, with the appearance of combined PET/MR hardware. This will allow high sensitivity/high resolution imaging of the artery wall. I guess this will have large impact in brain imaging and likely also in cardiology for myocardial imaging.

For CT, as well as a move to lower radiation dose, Zahi Fayad talked about multi-color CT, something that holds great promise in separating out the various plaque elements, to a much greater extent than currently feasible with single energy imaging with iodine contrast agents. This work was recently published in Radiology (Cormode D et al - see image below).

We also heard a great review of ultrasound imaging of vulnerable plaque, using targeted microbubbles against selectins and adhesion molecules. Whilst very exciting, the field is confined right now to small animal models of disease, and to epitopes expressed on endothelial cells. But there is promise of eventual human translation.

What caught your eye in Stockholm today?