MRI saves limbs: Blood flow check

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  • Published: Feb 1, 2016
  • Author: David Bradley
  • Channels: MRI Spectroscopy
thumbnail image: MRI saves limbs: Blood flow check

Muscular flow

Blood oxygenation level-dependent cardiovascular magnetic resonance (BOLD-CMR), performed after right femoral endarterectomy and iliac angioplasty/stenting, detects improved perfusion in all calf muscle groups Credit for this image and the thumbnail graphic: Modarai et al/JACC

Researchers at St Thomas’ Hospital, London, funded by the British Heart Foundation (BHF) have developed a new way of mapping blood delivered to the leg muscle immediately after surgery on people with severely reduced blood flow to their limbs. Currently surgeons may need to wait days or weeks to see how successful the surgery has been. The new technique will give them a much more timely prognosis and ultimately reduce the need for amputations required if sufficient blood flow is not restored.

Critical limb ischaemia (CLI) occurs when the arteries supplying the limbs with oxygenated blood become blocked, leading to reduced blood flow to the legs and feet. It is a condition associated with high blood pressure, a high cholesterol level, smoking and diabetes. It leads to severe pain, makes patients bed bound, causes ulceration and gangrene and unfortunately more than one in three patients with CLI eventually have to have the affected limb amputated. However, surgery to bypass a blocked artery with a prosthetic artery or insertion of a stent to widen it sufficiently for blood flow are common treatments for CLI. A magnetic resonance imaging (MRI) or computerised tomography (CT) scan is carried out prior to the operation so that the surgeon can see which portion of the affected artery needs to be treated. However, MRI and CT do not provide a detailed view of the smallest blood vessels in the legs nor how much blood is flowing to the limb's muscles.

Mapping technique

The new study used a novel MRI-based mapping technique, blood oxygenation level-dependent cardiovascular magnetic resonance (BOLD-CMR), to determine how much blood was reaching the muscles in the legs of 34 people with CLI, before and after treatment and in 22 healthy people as control subjects. A small biopsy of leg muscle would confirm the MRI data.

Bijan Modarai, who led the research, hopes that the new technique could eventually be used to quickly see whether or not a particular surgical intervention, whether bypass or stent, had increased blood flow to the limb sufficiently. Currently, the only way of determining the success of surgery is to wait for a period of days to see whether the leg improves; if it does all is well, but if it doesn't it often too late at that point to save the limb and an amputation is the likely outcome.

Modarai is a BHF Intermediate Fellow and Reader/Consultant in Vascular Surgery at King’s College London and St Thomas’ Hospital: "Here at Guy's and St Thomas' NHS Foundation Trust we treat over 500 people with critical limb ischaemia each year. By using this new imaging technique we hope to be better placed to offer the best possible treatment to people suffering from this disease and therefore reduce the likelihood of limb amputation."

Case study

A seventy-year old patient from Dartford, one Valerie Ellis, had surgery in 2015 to treat CLI in her right leg with two stents. "The pain in my foot was terrible, I couldn't lie down or get to sleep at night. I saw my GP and was sent to St Thomas' where they did some scans and found that a blood vessel in my right leg was clogged," Ms Ellis says. The surgery was a complete success for her. "The strength of this study is that it shows that this new imaging technique could be used widely to accurately show whether blood flow to the small vessels in the leg is improved sufficiently by stenting or bypass surgery," explains Modarai. "By using this technique surgeons will quickly gain a clear indication of whether treatment has been successful."

Related Links

J Am Coll Cardiol 2016, 67, 420-431: "Blood Oxygenation Level-Dependent CMR-Derived Measures in Critical Limb Ischemia and Changes With Revascularization"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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