NIRS-IVUS Imaging Helps Detect Vulnerable Plaques, Patients at High Risk for Adverse Cardiac Events
PROSPECT II results presented at TCT Connect 2020 show combined intracoronary imaging helps identify lipid-rich non-flow limiting lesions associated with higher MACE risk
Near-infrared spectroscopy (NIRS)-intravascular ultrasound (IVUS) intracoronary imaging can be used to identify vulnerable plaques that pose higher MACE risk in coronary artery disease, providing a potential segue into treatment that can lower cardiac event incidence.
David Erlinge, MD, PhD (University of Lund, Sweden) – who presented these findings from the investigator-sponsored, multicenter, prospective, natural history PROSPECT II study at TCT Connect 2020 on Oct. 18 – reported that patients with vulnerable plaques on NIRS-IVUS had a significantly increased risk of future MACE and signaled the potential of advanced imaging techniques in identifying and reducing the risk of adverse events with patient-tailored treatment.
ˇ°NIRS identified lipid-rich angiographically mild non-flow-limiting plaques that were responsible for future coronary events and data shows three-vessel intracoronary imaging with NIRS-IVUS was safe,ˇ± Erlinge said. ˇ°By combining lipid-rich plaques along with a large plaque burden and small lumen area, we can pinpoint vulnerable plaques that expose patients to future MACE risk.ˇ±
ˇ°Whether prophylactic treatment of these high-risk plaques is safe and effective was investigated in the integrated PROSPECT ABSORB trial,ˇ± he added.
PROSPECT ABSORB was a randomized trial nested within the PROSPECT II study that showed treating vulnerable plaques with AbbottˇŻs discontinued Absorb bioresorbable vascular scaffold resulted in an expanded minimum lumen area (MLA) at two-year follow-up compared to untreated plaques.
PROSPECT II shows benefit of combined imaging technique
Plaque rupture causing acute coronary syndrome is a leading cause of global mortality. NIRS-IVUS has become a promising tool to detect rupture-prone vulnerable plaques to predict and prevent MACE with patient-tailored treatment.
NIRS is a novel catheter-based intravascular imaging technique that snaps a chemogram of the coronary artery wall, helping identify the lipid core and quantify lipid accumulation, referred to as the lipid-core burden index (LCBI). Retrospective reports and prospective studies have suggested that vulnerable plaques detected by NIRS-IVUS are associated with adverse outcomes.
The PROSPECT II study aimed to evaluate NIRS-IVUS usefulness in 898 individuals treated at 16 centers in Sweden, Denmark, and Norway who had a recent myocardial infarction categorized as either STEMI or troponin-positive NSTEMI.
Recent MI patients included in the trial had one or more non-flow-limiting lesions with a 65 percent plaque burden and were successfully treated with PCI. Patients subsequently underwent intravascular imaging with a combination NIRS-IVUS catheter in proximal 6-10 cm of all three coronary arteries. Patients were 63 years old on average and about 20 percent were female.
Investigators used IVUS to identify untreated non-culprit lesions (NCLs) and blinded NIRS to assess lipid content. The primary endpoint was designated as MACE during long-term follow-up, encompassing the composite of cardiac death, MI, unstable angina, or progressive angina either requiring revascularization or with rapid lesion progression.
The study aimed to explore the relationship between high-risk features of untreated NCLs (plaques with high lipid content, large plaque burden, and minimum lumen area) and patient-level/lesion-level outcomes.
Among the 898 patients with untreated NCLs, MACE occurred in 13.2 percent of patients at a median 3.7-year follow-up with 8 percent of events occurring in untreated NCLs. Culprit-lesion MACE occurred in 4.2 percent of patients, BVS lesion-related MACE in 4.3 percent, and indeterminate MACE in 2.5 percent.
Analysis showed that patients who fell into the upper quartile of the maximum 4 mm lipid core burden index (LCBI) – defined as maxLCBI4mm ˇĂ 324.7 – had a MACE risk of 10.1 percent compared to a 4.8 percent risk in patients with lesser plaque burden, indicating MACE risk doubled in patients with a larger plaque burden (OR 2.08, 95% CI 1.18-3.69).
Furthermore, MACE incidence in patients with lesions of a plaque burden ˇĂ 70% versus that in patients with a smaller plaque burden was 11 and 3.6 percent, respectively, which showed severe plaque burden was associated with a three-fold risk jump (OR 3.09; 95% CI 1.65-5.76).
Upon combining the two high-risk features, analysis showed that MACE incidence in patients who had lesions with both large plaque burden and high lipid content was 7.0 percent, serving as a stark contrast to the 0.2 percent MACE incidence in patients who did not have the two high-risk features.
In fact, statistical analysis showed patients presenting plaques with both high-risk features had an 11-fold higher risk of NCL-related MACE than other patient groups (OR 11.33; 95% CI 6.10~21.03) and a near 37 times higher risk than those with plaques without either high-risk feature – highlighting a significantly increased risk of NCL-related MACE in patients with high-risk plaques.
Meanwhile, major complications of NIRS-IVUS were only reported in two patients (a case of stenosis due to spasm/dissection requiring balloon angioplasty and an acute obstruction due to air infusion during additional stenting), proving the safety of NIRS-IVUS.
Upon presenting these findings, Erling concluded that ˇ°PROSPECT II showed that three-vessel intracoronary imaging with NIRS-IVUS was safe. The combination of lipid-rich plaque and large plaque burden identified vulnerable plaques that placed patients at especially high risk for future MACE.ˇ±