Clinical Outcome of Nonculprit Plaque Ruptures in Patients With Acute Coronary Syndrome in the PROSPECT Study

Study Questions:

Do plaque ruptures in nonculprit lesions lead to different clinical outcomes in patients with acute coronary syndromes (ACS)?

Methods:

Plaque ruptures are the most common reason for ACS. Although subclinical plaque ruptures have been seen in nonculprit lesions of patients with ACS, the natural history of these lesions is largely unknown. The PROSPECT (Providing Regional Observations to Study Predictors of Events in the Coronary Tree) study investigators reported the frequency, patient and lesion-related characteristics, and clinical outcomes of subclinical plaque ruptures.

Results:

After successful percutaneous coronary intervention (PCI) in 697 patients with ACS, three-vessel grayscale and intravascular ultrasound virtual histology (IVUS-VH) was performed in the proximal-mid segments of all three coronary arteries to characterize nonculprit lesions. Among 660 patients with complete IVUS data, 128 plaque ruptures were identified in 105 nonculprit lesions in 100 arteries from 93 patients. This number did not differ between ST-segment elevation myocardial infarction (STEMI) and non-STEMI patients, but plaque ruptures in nonculprit lesions were associated with other lesions with high-risk characteristics. Nonculprit lesions with plaque rupture also differed from those lesions without plaque rupture in important ways, as they had higher plaque burden and were more often classified as fibroatheroma; however, minimum lumen area (MLA) did not differ. The authors reported: “Independent predictors of a plaque rupture were lesion length (per 10 mm; odds ratio, 1.30; p < 0.0001), plaque burden at the MLA site (per 10%; odds ratio, 2.56; p < 0.0001), vessel area at the MLA site (per 1 mm2; odds ratio, 1.13; p < 0.0001), and VH–thin-cap fibroatheroma (odds ratio, 1.80; p = 0.016).” Importantly, the incidence of overall cardiac events was low over a 3-year follow-up and did not differ significantly between the patients with and without plaque ruptures.

Conclusions:

The authors concluded that, within the population of PROSPECT, nonculprit lesions with plaque ruptures occurred in 14% of patients with ACS and were not associated with adverse clinical outcomes.

Perspective:

This is an interesting study by the PROSPECT investigators that explores the nature of secondary plaque ruptures in nonculprit lesions of patients with ACS using advanced imaging modalities (IVUS-VH). The study suggests that the prevalence of these lesions is not inconsequential, but may be less than in prior reports. The morphology of these lesions is consistent with other work, and suggests that these plaque ruptures are associated with more complex patient and lesion characteristics as well as additional lesions. Finally, the study was underpowered to detect clinical outcomes given an overall low rate of cardiac events. However, the data do suggest that with optimal medical therapy, the natural history of these plaque ruptures is fairly reassuring and do not require specific coronary interventions. It also is uncertain how this type of information will be placed in the context of recent provocative studies, like the PRAMI trial, that suggest treatment of nonculprit lesions in specific clinical scenarios (e.g., STEMI) may be beneficial in reducing outcomes.

Clinical Topics: Acute Coronary Syndromes, Invasive Cardiovascular Angiography and Intervention, Interventions and ACS

Keywords: Acute Coronary Syndrome, Follow-Up Studies, Plaque, Atherosclerotic, Coronary Vessels, Cost of Illness, Percutaneous Coronary Intervention


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