People with diabetes are more likely to develop coronary artery disease and may face a higher risk of complications after treatment for narrowed heart arteries. A new analysis from the ILUMIEN IV trial examined whether detailed imaging inside the coronary arteries could improve outcomes after a stent procedure.
The findings provide useful information, but they do not identify one procedure that is best for every person with diabetes.
Quick answer
The study followed 2,487 people undergoing percutaneous coronary intervention, commonly called PCI or a heart stent procedure. Of these participants, 1,044 had diabetes.
After two years, participants with diabetes had higher rates of cardiovascular complications than those without diabetes. Using optical coherence tomography, or OCT, to guide the procedure did not significantly reduce the study’s main clinical outcomes compared with standard angiography.
This does not mean OCT has no value. It provides detailed images that can help cardiologists size and position a stent. However, better imaging alone did not remove the broader cardiovascular risk associated with diabetes.
Key takeaways
- People with diabetes experienced more complications after PCI than people without diabetes.
- The greatest risk was seen in people who had both diabetes and complex coronary artery disease.
- OCT produced more detailed images of the artery and helped improve some technical aspects of stent placement.
- OCT guidance did not significantly reduce target-vessel failure or serious major cardiovascular events over two years.
- The study did not compare PCI with bypass surgery or medical treatment alone.
- People should not change heart or diabetes medicines because of this study.
What is PCI?
Percutaneous coronary intervention is a procedure used to open a narrowed or blocked coronary artery.
A cardiologist usually passes a thin tube called a catheter through an artery in the wrist or groin and guides it towards the heart. A small balloon may be inflated to widen the narrowed section, and a mesh tube called a stent is usually inserted to help keep the artery open.
PCI may be used during a heart attack or to treat selected people with symptoms from coronary artery disease.
How is angiography used during PCI?
Coronary angiography uses contrast dye and X-rays to show blood flowing through the coronary arteries. It allows the cardiologist to see narrowed or blocked areas and guide the procedure.
Angiography mainly shows the outline of the space through which blood flows. It provides less information about the artery wall, the type of plaque or how closely a stent is sitting against the artery.
What is OCT?
Optical coherence tomography is an imaging technique used from inside the coronary artery. It uses near-infrared light to produce detailed cross-sectional images.
During PCI, OCT can help the cardiologist:
- measure the artery more precisely;
- choose an appropriate stent size;
- check whether the stent has fully expanded;
- identify gaps between the stent and artery wall;
- look for damage at the edges of the treated area.
OCT is a procedure-guidance tool. It is not a treatment for diabetes or a substitute for controlling cardiovascular risk factors.
What did the researchers study?
The original ILUMIEN IV trial randomly assigned people undergoing PCI to one of two approaches:
- PCI guided by OCT plus angiography; or
- PCI guided by angiography alone.
The trial included people with medication-treated diabetes or complex coronary artery lesions. A total of 2,487 participants were included in the current analysis:
- 1,044 had diabetes;
- 1,443 did not have diabetes.
Researchers followed participants for two years. They examined whether diabetes was associated with poorer outcomes and whether the effects of OCT guidance differed between people with and without diabetes.
It is important to understand that participants were randomly assigned to the imaging methods, but they were not randomly assigned to have diabetes. Comparisons between participants with and without diabetes therefore show associations, not proof that diabetes directly caused every difference.
What did the study find?
Target-vessel failure
Target-vessel failure was a combined outcome that included cardiac death, a heart attack linked to the treated artery or the need for another procedure on that artery because of reduced blood flow.
Over two years, target-vessel failure occurred in:
- 9.9% of participants with diabetes
- 6.3% of participants without diabetes
After adjustment for differences between the groups, the hazard of target-vessel failure was 48% higher in participants with diabetes. The observed absolute difference between the groups was 3.6 percentage points.
Serious cardiovascular events
The study also examined a combined outcome of cardiac death, heart attack involving the treated artery or stent thrombosis.
These events occurred in:
- 5.3% of participants with diabetes
- 2.7% of participants without diabetes
After adjustment, the hazard was 77% higher in the diabetes group. The observed absolute difference was 2.6 percentage points.
Diabetes and complex coronary disease
Participants who had both diabetes and complex coronary lesions experienced the highest event rates.
Complex lesions can include long, heavily calcified or branching areas of disease. These procedures may be technically more difficult, but the exact implications depend on the person’s coronary anatomy and overall health.
Did OCT improve clinical outcomes?
In this analysis, OCT-guided PCI did not significantly reduce target-vessel failure or serious major cardiovascular events compared with angiography-guided PCI.
The effect was similar in people with and without diabetes. This means the trial did not demonstrate that routinely adding OCT removed the additional cardiovascular risk seen in the diabetes group.
The original ILUMIEN IV trial found that OCT guidance produced slightly greater stent expansion. It also recorded fewer cases of stent thrombosis with OCT, although the trial did not show a significant reduction in its main clinical outcome of target-vessel failure.
What do these results mean for people with diabetes?
The clearest message is not that one imaging technique has failed. It is that cardiovascular risk in diabetes extends beyond the technical placement of a stent.
A stent treats a specific narrowed section of an artery. It does not remove atherosclerosis elsewhere in the circulation or address all the factors that influence future risk.
Long-term cardiovascular care may involve:
- taking prescribed antiplatelet treatment correctly after a stent;
- managing blood pressure and cholesterol;
- reviewing glucose management;
- stopping smoking;
- attending cardiac rehabilitation when offered;
- remaining physically active within individual medical limits;
- discussing treatments with proven cardiovascular benefit when appropriate.
The American Diabetes Association recommends comprehensive cardiovascular-risk management for people with diabetes rather than concentrating on glucose alone. Treatment should be personalised, particularly for people who already have cardiovascular or kidney disease.
What the study does not tell us
The findings should not be interpreted as showing that:
- OCT is unnecessary during every stent procedure;
- angiography is always the better option;
- every person with diabetes will experience a complication;
- PCI is preferable to bypass surgery;
- bypass surgery is preferable to PCI for every person with diabetes;
- tighter glucose control immediately before a procedure would remove the observed risk;
- a person should stop or change prescribed medication.
The choice between medical treatment, PCI and coronary artery bypass surgery depends on symptoms, the number and location of affected arteries, heart function, surgical risk, other medical conditions and personal preferences.
Questions to ask before or after a stent procedure
- How does diabetes affect my individual procedural risk?
- Is my coronary disease considered complex?
- Why are you recommending PCI rather than bypass surgery or medical treatment alone?
- Would OCT or another form of intravascular imaging be useful in my procedure?
- How long will I need antiplatelet medication?
- What should I do if I miss a dose?
- Which blood pressure, cholesterol and glucose goals apply to me?
- Would cardiac rehabilitation be appropriate?
- Are any of my diabetes medicines being used for cardiovascular protection?
- Which symptoms should prompt urgent medical attention?
Study limitations
- The comparison between people with and without diabetes was not randomized.
- This was an analysis of an existing trial rather than a separate trial designed to compare diabetes outcomes.
- Combined outcomes can bring together events with different levels of clinical importance.
- Follow-up was limited to two years.
- The results apply to people selected for PCI and may not apply to everyone with coronary artery disease.
- The study was funded by Abbott Vascular, a manufacturer of OCT technology, and several investigators reported industry relationships.
- The trial did not compare PCI with bypass surgery or medical therapy alone.
When to seek urgent help
Call local emergency services for possible heart-attack symptoms, including new or severe chest pressure, pain spreading to the arm, back, neck or jaw, marked breathlessness, collapse, cold sweating or sudden unexplained weakness.
After PCI, urgent assessment may also be needed for severe chest pain, significant bleeding, rapidly increasing swelling at the catheter site, a cold or discoloured limb, fainting or sudden breathing difficulty.
Do not stop antiplatelet medication after a stent without urgent advice from the treating cardiology team. Stopping it unexpectedly can increase the risk of a blood clot forming inside the stent.
The bottom line
The ILUMIEN IV analysis found that people with diabetes continued to experience a higher risk of cardiovascular complications after PCI, particularly when coronary lesions were complex.
OCT provided more detailed procedural imaging, but it did not significantly reduce the trial’s main two-year clinical outcomes compared with angiography alone. The results reinforce the need to combine careful procedural planning with long-term management of cholesterol, blood pressure, diabetes, smoking and other cardiovascular risks.
The best procedure and prevention plan will differ between individuals and should be agreed with the cardiology and diabetes teams.
Sources
- Gaede L, et al. Impact of Diabetes on Outcomes of Contemporary PCI Guided by OCT vs Angiography: The ILUMIEN IV Trial. JACC: Cardiovascular Interventions. 2026. DOI: 10.1016/j.jcin.2026.06.028.
- Ali ZA, et al. Optical Coherence Tomography-Guided versus Angiography-Guided PCI. New England Journal of Medicine. 2023.
- American Diabetes Association Professional Practice Committee. Cardiovascular Disease and Risk Management: Standards of Care in Diabetes 2026. Diabetes Care. 2026.
This article is for general education and does not replace individual medical advice, diagnosis or treatment.