Detection of Vulnerable Plaque Crucial to MI Prevention
New technologies such as bevacizumab-eluting stents, vulnerable plaque-specific stents and photodynamic therapy may help prevent myocardial infarctions and mortality due to vulnerable plaque, according to Gregg W. Stone, MD, chairman of the Cardiovascular Research Foundation and Professor of Medicine at Columbia University Medical Center.
Stone presented information on Monday about imaging modalities that can be used to noninvasively diagnose ruptured plaque and gave an update on techniques for potentially identifying rupture-prone plaque.
“We’ve talked a lot today about the safety of drug-eluting stents relevant to bare-metal stents,” he said. “Neither drug-eluting stents nor bare-metal stents nor balloon angioplasty do anything to prolong survival or prevent heart attacks. The only place where we, as interventional cardiologists, make an impact on prolonging life is in treating acute coronary syndromes, such as unstable angina and acute MI.”
Stone emphasized the importance of identifying the rupture-prone lesion and treating it prophylactically.
Diagnostic techniques
According to Stone, most of the plaques that lead to mortality are mild atherosclerotic lesions. Thin cap fibroartheroma is the precursor lesion in many of these cases.
Several noninvasive diagnostic techniques can assess vulnerable plaque: electron beam tomography, multisection fast computed tomography (MSCT), magnetic resonance imaging/angiography, inflammation imaging, thrombosis imaging, nuclear imaging and measurement of endothelial dysfunction.
Focal imaging devices may detect disease before the plaque ruptures, Stone said. Optical frequency domain imaging yields dramatically increased imaging acquisition rates (prototype 106 fms at PB speed of 12 mm/s). And intracoronary near-infrared spectroscopy is now ready to go into larger natural history clinical trials.
PROSPECT trial
Stone said interim lessons from the PROSPECT trial indicate that three-vessel imaging of the coronary tree is feasible in most patients with acute coronary syndromes after the stenting of all visibly ruptured and angiographically significant lesions.
PROSPECT, which looked at over 300,000 mm of coronary artery, also found that by grayscale IVUS, about three untreated lesions per patient are still present in the proximal and midcoronary arteries. By virtual histology, the study investigators identified thin cap fibroatheromas in the proximal and midcoronary tree in about 35% of patients.
Stents for vulnerable plaque
Several new stents have been developed for use in intermediate lesions, Stone said. One elutes bevacizumab, a humanized monoclonal Ab that binds to VEGF. This antitumor agent prevents growth of new vessels and causes existing vessels to regress. The bevacizumab-eluting stent showed positive results in rabbit artheromatous iliac arteries at four weeks post-stent implantation.
A vulnerable plaque-specific stent, which specifically addresses the rupture of the fibrous cap, is also being developed, Stone said. A full report on this stent will be given during Thursday’s sessions (Figure).
Photoangioplasty with photodynamic therapy is another emerging treatment approach to vulnerable plaque, Stone said. With this technique, a photosensitizing chemical is intravenously injected and accumulates in artherosclerotic plaque throughout the body.