Screening Test May Detect Narrowing

Great advances have been made in treating blockages in the arteries of the brain using angioplasty to widen the narrowed artery and a stent to hold the artery open. However, in-stent stenosis, or a re-blockage of the artery within the stent due to scar tissue or blood clots, is estimated to occur in up to 30 percent of patients and can cause a stroke or death.

Noninvasive imaging such as magnetic resonance angiography (MRA) and computerized tomography angiography often cannot provide an accurate diagnosis of in-stent stenosis because the image is distorted by the reflection of metal stents or coils. Due to this problem, conventional angiography continues to be used routinely after stent placement to screen for in-stent stenosis. However, conventional angiography requires threading a catheter from the arteries in the groin to the brain and carries a slight risk of neurological and non-neurological procedural complications.

Quantitative MRA (QMRA) is a flow analysis system that uses traditional MRI to produce a 3D model of the vasculature and quantify vessel blood flow. The procedure is completely non-invasive and no contrast is needed. Recent studies have established this technology's use in the measurement of arterial blood flow in various cerebrovascular conditions and carotid bypass surgery. However, this is the first study to assess the use of QMRA in the detection of intracranial in-stent stenosis.

It found that low blood flow as measured by QMRA at sites of intracranial stent placement was significantly associated with in-stent stenosis by catheter-based angiography. As a screening tool to predict greater than 50 percent in-stent stenosis, QMRA was 100% sensitive. In other words, QMRA was able to detect narrowing of stented arteries in all cases where invasive angiography showed greater than 50 percent stenosis.

Due to the small sample size of the study, the scientists suggest larger prospective studies to confirm their findings.; Source: Rush University Medical Center