Background
Acute myocardial infarction, commonly known as a heart attack, usually occurs when a plaque in a coronary artery ruptures or erodes and triggers a blood clot that blocks blood flow. However, not all dangerous plaque changes happen in the artery that causes the heart attack. In some patients, plaques in other coronary arteries that are not responsible for the infarction, called non-infarct-related arteries or non-IRAs, may also rupture. These ruptures may be silent, meaning they do not immediately cause symptoms or ischemia because they do not create a major blockage.
This study asked an important question: how often do silent plaque ruptures occur in non-obstructive lesions of non-IRAs in patients with acute myocardial infarction, what do these lesions look like at baseline, and how do they change over time if left untreated?
Understanding this matters because coronary artery disease is not just about one culprit lesion. It is a whole-artery and whole-patient disease. Identifying which plaques are vulnerable can help improve risk assessment, guide follow-up imaging, and potentially inform prevention strategies in the future.
Study Design
This investigation pooled data from two clinical trials, IBIS-4 and PACMAN-AMI. Patients with acute myocardial infarction underwent multimodality intracoronary imaging of non-IRA lesions at baseline and again after 52 weeks. The imaging approach combined different techniques to examine plaque structure in detail, allowing researchers to evaluate plaque burden, vessel remodeling, and fibrous cap thickness.
The focus was on non-obstructive lesions, meaning plaques that were not severely narrowing the artery at the time of imaging. The study also examined whether blood biomarkers, including lipid and inflammation markers, differed between patients with and without plaque rupture.
Key Findings at Baseline
At baseline, 783 lesions from 336 patients were evaluated. Plaque rupture was identified in 41 lesions from 40 patients, representing 12% of the assessed lesions. This shows that silent rupture in non-IRA non-obstructive lesions is not rare in the setting of acute myocardial infarction.
Patients with plaque rupture did not show major differences in circulating lipid or inflammation biomarkers compared with those without rupture. In other words, standard blood tests alone were not enough to distinguish patients with ruptured plaques from those without rupture in these non-culprit vessels.
However, the imaging findings were clearly different. Lesions with rupture had a larger percent atheroma volume, meaning they contained more plaque material relative to the vessel size. They also had a larger external elastic membrane area, reflecting a larger overall vessel size and positive remodeling. Positive remodeling is a process in which the artery expands outward to accommodate plaque growth, which can preserve the lumen and hide the severity of disease on routine angiography. In addition, ruptured lesions had a thinner minimum fibrous cap, a feature associated with plaque vulnerability.
These differences support the idea that silent ruptures tend to occur in plaques that are biologically and structurally unstable, even if they are not severely obstructing blood flow.
What Happened Over 52 Weeks
Among the 41 rupture sites that were followed serially, 21 sites, or 51%, had healed by 52 weeks. Healing likely reflects natural repair processes, including thrombus organization, endothelial recovery, and fibrotic stabilization. This is clinically important because it suggests that not every plaque rupture leads to persistent instability or progressive obstruction.
At follow-up, 10 rupture sites were newly identified. When the baseline appearance of these new ruptures was examined, the most frequent underlying morphology was thin-cap fibroatheroma, often abbreviated TCFA. TCFA is a classic vulnerable plaque phenotype characterized by a large lipid-rich necrotic core covered by a very thin fibrous cap. Such plaques are especially prone to rupture because the cap can fail under mechanical stress.
The serial imaging findings therefore reveal a dynamic process: some ruptured plaques heal and become more stable over time, while others evolve and later rupture, especially if they already had high-risk features at baseline.
Clinical Interpretation
The main message of this study is that silent plaque rupture in non-obstructive non-IRA lesions is common enough to matter and is strongly associated with vulnerable plaque morphology rather than with blood biomarkers alone. Larger plaque volume, positive remodeling, and thin fibrous cap thickness were the most important imaging features linked to rupture.
This helps explain why some plaques can rupture without causing immediate infarction or symptoms. A plaque may rupture, but if the rupture is small, the thrombus is limited, or the vessel remains sufficiently open, ischemia may not occur. These lesions may still carry prognostic significance because they reflect unstable atherosclerosis.
The finding that more than half of untreated ruptures transitioned into stable morphologies is also reassuring and highlights the body’s capacity for vascular healing. At the same time, the appearance of new ruptures at follow-up underscores that coronary atherosclerosis remains an active and evolving disease process.
Why Biomarkers Were Not Enough
One of the notable observations in this study was the lack of meaningful differences in lipid and inflammatory biomarkers between patients with and without rupture. This suggests that systemic blood markers, although useful for overall cardiovascular risk assessment, may not capture local plaque instability very well.
In clinical practice, this reinforces the value of advanced imaging when detailed plaque characterization is needed. It also indicates that a patient with apparently similar laboratory results may have very different plaque biology in their coronary arteries.
Implications for Practice
At present, routine imaging of all non-culprit coronary lesions after myocardial infarction is not standard for every patient, and these findings do not immediately change treatment guidelines. However, the study provides important mechanistic insight. It suggests that some non-obstructive plaques in non-IRAs are already ruptured but silent, and that imaging features such as plaque burden, remodeling, and fibrous cap thickness may identify lesions at higher risk.
For clinicians, this reinforces aggressive secondary prevention after myocardial infarction, including intensive lipid-lowering therapy, antiplatelet treatment as appropriate, blood pressure control, smoking cessation, diabetes management, and lifestyle modification. These measures aim to stabilize plaques throughout the coronary tree, not only the culprit lesion.
In the future, serial intracoronary imaging may help refine how we identify high-risk plaques and monitor whether therapy is successfully stabilizing them. For now, the study adds to the evidence that coronary vulnerability is widespread and often clinically silent.
Limitations
As with any pooled analysis, there are limitations. The study population came from two trials, which may differ in design and patient selection. Intracoronary imaging provides detailed structural information, but it still cannot capture every aspect of plaque biology. Also, the presence of rupture does not always mean a lesion will become clinically dangerous; the outcome depends on many factors, including thrombus burden, local hemodynamics, and systemic risk.
Even so, the large number of imaged lesions and the serial follow-up strengthen the reliability of the findings. The study offers a rare look at the natural history of silent rupture in non-culprit coronary arteries over time.
Conclusion
In patients with acute myocardial infarction, silent plaque rupture was found in 12% of non-obstructive lesions in non-infarct-related arteries. Ruptured lesions were characterized by greater plaque burden, larger vessel remodeling, and thinner fibrous caps. More than half of untreated rupture sites healed within 52 weeks, while new ruptures that appeared during follow-up were most often preceded by thin-cap fibroatheroma.
Overall, the study shows that coronary plaque rupture is often a dynamic and silent process outside the culprit artery. It also highlights the value of multimodality intracoronary imaging for understanding plaque vulnerability and healing over time.
Reference: Kakizaki R, Biccirè FG, Losdat S, et al. Silent plaque ruptures in non-obstructive lesions of non-infarct-related arteries: a multimodality, serial intracoronary imaging study. European Heart Journal. 2026;47(22):2814-2826. PMID: 41795942.
