Results of PROSPECT II Natural History Study, demonstrate high-risk plaques identified by NIRS + IVUS Imaging are linked to future coronary events

PROSPECT ABSORB, a randomized substudy, showed treatment of high-risk plaque with BVS is safe and associated with favorable long-term clinical outcomes compared to GDMT alone.

The studies were led by Prof David Erlinge, Lund University and Prof Gregg Stone, Clinical Research Foundation, NYC.

Positive results from the PROSPECT II and PROSPECT ABSORB studies were presented today as a "Late breaking clinical trial" at TCT, the 32nd annual scientific symposium from the Cardiovascular Research Foundation. The PROSPECT II study demonstrated the ability of near-infrared spectroscopy (NIRS) imaging plus intravascular ultrasound (IVUS) to identify plaques responsible for future coronary events. The randomized substudy PROSPECT ABSORB, which was simultaneously published in the Journal of the American College of Cardiology (JACC), showed treatment of high-risk vulnerable plaques with a bioresorbable vascular scaffold (BVS) was safe and substantially associated with favorable long-term clinical outcomes compared to guideline-directed medical therapy (GDMT) alone.

Several autopsy studies have shown that high-fat plaques are the underlying cause of most coronary heart disease, and when these high-fat plaques rupture and thromboticize, they cause the majority of heart attacks and infarction-related sudden death. The PROSPECT II study aimed to further demonstrate that high-fat plaques that are not seen on coronary X-rays, but which are detected by NIRS, are causing future heart attacks or angina.

The investigator-initiated, multicenter, prospective study included 898 patients from 16 sites in Sweden, Denmark and Norway and was coordinated by the Uppsala Clinical Research Center (UCR). Patients with recent myocardial infarction (MI) were enrolled after all visible and flow-restricting stenoses were treated with PCI (balloon dilation and stenting). A NIRS-IVUS catheter was used to image all three coronary arteries. The system uses NIRS to detect high-fat plaques and automatically displays a color-coded map, called a chemogram. The chemogram shows high-fat plaques in yellow and the absence of fat in red. High plaque content was revealed with IVUS.

A total of 3629 untreated plaques were characterized, an average of 4 per completed patient. Study results showed that adverse heart events occurred in 13.2 percent of patients within four years, with 8.0 percent from untreated plaques. The incidence of high fat content (> 325%) was an independent predictor of myocardial infarction or new-onset angina at both patient and plaque levels. The presence of high-fat plaques showed a 2.3-fold and 7.8-fold higher probability for patient level and lesion level, respectively. If there was a high-fat plaque that also had a high plaque burden, a 3.7-fold and 36.7-fold higher probability were seen at patient level and lesion level, respectively, compared if they did not have any of these high-risk criteria. The study authors concluded that lipid-rich plaques detected by NIRS-IVUS identify lesions that cause future heart events.

  - An important result was that most of the future heart events were caused by plaques that were not revealed by angiography and pressure measurement, the methods used today. Instead, the combination of high-fat plaque and high plaque load was the strongest prognostic factor, says Prof David Erlinge.

PROSPECT ABSORB was a substudy that randomized 182 patients to stenting (93 patients) or medical treatment (89 patients). The study evaluated whether stenting could certainly improve the lumen of the coronary artery for plaques not identified on coronary angiography but where IVUS found plaque burden ≥65 percent (previously known risk factor). Follow-up with coronary x-ray was done after 25 months and the median for clinical follow-up was 4.1 years. Study results showed that follow-up of the minimum lumen area (MLA) in stented lesions was 6.9 ± 2.6 mm2 and 3.0 ± 1.0 mm2 in medically treated lesions, a difference of 3.9 mm2 which was very significant. Cardiac events (myocardial infarction and recurrent angina) occurred in 4.3 percent of the stented patients compared with 10.7 percent of the medically treated patients. The study authors concluded that PCI of lesions that are not considered significant on coronary angiography but with a large plaque burden was safe, increased coronary lumen and was associated with favorable long-term clinical outcomes compared with medical treatment alone.

  - In addition to the important medical results, which provide an opportunity to better assess future risk and prevent coronary artery disease, we can be proud that the study was successfully conducted in Scandinavia by a unique network of PCI operators led by David Erlinge. We are grateful that InfraRedX, Abbot, the Medicines Company / Novartis, gave us the confidence to coordinate the entire study and objectively review outcome events, says Jonas Oldgren, head of UCR


Prof David Erlinge
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Cardiology,Professor at Department of Clinical Sciences
Hjärtkliniken, Skånes Universitetssjukhus

Jonas Oldgren
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Chef UCR, Uppsala Clinical Research Center
Cardiology, Professor at Department of Medical Sciences
Upsala University