NIR signatures: Heart to heart

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  • Published: Aug 1, 2013
  • Author: David Bradley
  • Channels: Infrared Spectroscopy
thumbnail image: NIR signatures: Heart to heart

Characterising arterial plaques

Credit: Madder/JACC/Elsevier Detection by Near-Infrared Spectroscopy of Large Lipid Core Plaques at Culprit Sites in Patients With Acute ST-Segment Elevation Myocardial Infarction

New imaging technology based on near infrared spectroscopy (NIRS) has been used by researchers at Spectrum Health's Frederik Meijer Heart & Vascular Institute to investigate patients in treatment following a heart attack. The technology allowed the researchers to identify the characteristic makeup, or signature, of arterial plaque that blocked an artery and led to the heart attack in the first place. The work might allow healthcare workers to scan at-risk individuals and identify those with fragile plaques that might cause life-threatening problems.

Earlier research carried out post mortem on cadavers has shown that most fatal heart attacks called ST-segment elevation myocardial infarctions (STEMIs) are triggered by a rupture in a lipid core plaque (LCP); these plaques lining the major arteries are rich in waxy cholesterol. Knowing precisely what kind of plaque is present in a narrowed artery, particularly those supplying oxygen to the heart can help a physician determine a patient's risk of having a potentially fatal heart attack as some plaques are more susceptible to rupture than others. New insights into the chemistry of different types of plaque might even lead to novel treatment options that could preclude what cardiologists euphemistically refer to as "a serious cardiac event" and which most people would refer to as a heart attack.

Have a heart

Ryan Madder and colleagues at Spectrum Health have turned to NIRS to help them study different plaques for the first time documenting LCP in living patients with STEMI. A coronary catheter allowed them to reach into the blood vessels to probe with NIRS. Using this technique Madder and his colleagues measured cholesterol in arterial plaques in twenty patients who had suffered a STEMI. The measurements were made after blood flow was re-established but prior to surgical insertion of a stent to keep the artery open. They published details of their study and their findings in the Cardiovascular Interventions Journal of the American College of Cardiology.

"We have discovered a NIRS signature of the plaques which caused myocardial infarction, a leading cause of death and injury worldwide," explains cardiologist Madder. "This signature is detectable at the time of cardiac catheterization using a novel intracoronary imaging device. It is our hope that this signature may be capable of predicting a myocardial infarction before it happens." Madder hopes to conduct a predictive study to determine whether or not patients with significant deposits of LCP have a significantly higher risk of heart attack, as these finding might suggest. "If using NIRS technology is validated as a reliable predictor of cardiac events, then randomized studies of promising systemic and local therapies could be conducted," he adds.

Combined effort

The combined NIRS and ultrasound catheter was developed by Infraredx. The company's Chief Medical Officer, James Muller suggests that Madder and his colleagues have taken an important step forward in predicting heart attack in at-risk patients. "It is likely that the signature of a heart attack identified in the study is present long before the event and could therefore be identified before a dangerous heart attack has occurred," says Muller, "The Spectrum Health study will lead to large prospective studies of this possibility." The combined system images key structural elements of a blockage using ultrasound and simultaneously carries out a spectroscopic analysis to produce a Chemogram map that indicates the location of LCP and quantifies the lipid core deposit in the artery.

Madder suggests that much work is yet to be done before this becomes a routine and viable clinical procedure. "Through an international collaboration with several other centres, further studies are currently underway and others are being planned to validate this signature and to determine if NIRS can accurately predict future myocardial infarction," he says.

Related Links

JACC: Cardiovasc Intervent 2013, 81, 430-434: "Detection by Near-Infrared Spectroscopy of Large Lipid Core Plaques at Culprit Sites in Patients With Acute ST-Segment Elevation Myocardial Infarction"

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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