Extending CT Stroke Scan to the Heart Boosts Clot Detection

ABU DHABI, UAE — Extending the simple CT angiography (CTA) scan given to all patients with acute stroke on presentation to the hospital to include the upper part of the heart increased the detection of a cardioaortic thrombus by almost sixfold compared with standard care stroke workup, results of a new randomized trial showed.

“This simple and easy extension of the scan that all suspected stroke patients already receive creates hardly any extra work but allows the identification of high-risk patients with clots in their heart, who can be prioritized for anticoagulation and AF monitoring as appropriate,” lead investigator Luciano Sposato, MD, told Medscape Medical News.

Sposato, who is professor of neurology and head of the Stroke Program at the London Health Sciences Centre, London, Ontario, Canada, presented the DAYLIGHT trial on October 24 at the 16th World Stroke Congress (WSC) 2024.

Up to 25% of patients with ischemic stroke do not have an identifiable cause after a full stroke workup is completed and are classified as having embolic stroke of an undetermined source, he noted.

“These patients have a high stroke recurrence rate, but we don’t know what to do for them in terms of best secondary prevention.”

Sposato explained that most patients undergo a transthoracic echo during hospitalization to look at the heart, but, while this is good at identifying a patent foramen ovale, it has a low diagnostic yield for embolic sources of only around 1%.

Some patients may get more advanced cardiac imaging such as transesophageal echo, which is better at identifying clots, but this is expensive, invasive, and not available in most centers.

“All patients with suspected acute stroke routinely have a CTA scan of the brain and neck on initial presentation. That is the standard of care. So, we thought, why don’t we go a little bit lower, and we can include part of the heart as well to see if we can identify clots,” Sposato said.

There have been a few observational studies suggesting that this technique can result in a high detection of clots, but this is the first randomized trial to investigate this approach.

For the DAYLIGHT study, 830 patients with suspected acute stroke or transient ischemic attack (TIA) presenting to the emergency department were randomized to receive the standard of care (CTA) scan or to an extended CTA scan going 6 cm below the carina (the division of the bronchi in the airways) to include the top part of the heart — specifically the left atrial appendage, which is where most clots in the heart are found.

After excluding the 365 patients who were not diagnosed with ischemic stroke or TIA, there were 465 patients in the final cohort. Of those, 239 received the standard of care CTA, and 226 received the extended CTA.

The primary endpoint was the number of patients in whom a clot was detected. This was 1.7% of patients in the standard CTA group vs 8.8% in the extended CTA, giving an odds ratio of 5.7 (95% CI, 1.9-17.0; P = .002).

“So just by looking at a normal CT scan, this is something we can detect in a few seconds — as soon as the image is available on the screen. It doesn’t require any AI or post-processing. It’s very simple,” said Sposato.

The primary safety endpoint was time to complete CTA from the activation of the code stroke. This was just 1 minute longer in the extended scan group — 21 minutes vs 20 minutes in the standard care group.

There was a mild increase in radiation exposure (16 mSv in the extended scan group vs 15 mSv in the standard care group), which Sposato said was not clinically relevant.

During the discussion of the trial, there were several questions as to what actions would be taken on detecting clots in this way.

Implications for Practice?

Commenting on the trial for Medscape Medical News, chair of the WSC session at which it was presented, Craig Anderson, MD, The George Institute for Global Health, Sydney, Australia, described the study as “very novel and well conducted. It’s interesting to show that about 5%-10% of patients have a clot in the heart that would not otherwise have been identified.”

But Anderson wondered what the findings would mean for clinical practice.

“I guess the old adage remains — if you look, you will find. So, while this seems like a pretty safe thing to do and it doesn’t really interfere with workflow or compromise patient care, the questions for me are: What do these clots mean? Are they the cause of the stroke? And then what do we do about them? Should all these patients go on anticoagulation, and will this improve outcomes? I don’t think we know all that.”

He noted that the additional information might aid in identifying possible stroke causes at the time of a patient’s arrival without compromising care. However, it’s uncertain if this would directly affect treatment decisions. While these clots may not definitively be the cause of a stroke, their presence could indicate an increased risk in the patient.

Candidates for Anticoagulation

Sposato believes all the patients in whom a clot was detected would be candidates for anticoagulation.

“If a patient has had an acute ischemic stroke, and we think it is an embolic stroke from the pattern of blockages in the brain, and we don’t have another cause, but we can see clots in the left atrial appendage, then I would have said that the stroke is likely to have been caused by those clots. I would treat with anticoagulation early in order to prevent a second stroke that could occur at any time,” he said.

He pointed out that patients normally get cardiac imaging several days later after the acute stroke has been treated, but that many patients would have received thrombolytic therapy, which would probably dissolve these clots, and they would no longer be detectable.

Sposato also noted that the extended CT scan could identify other risk factors in addition to clots, such as slow flow in the left atrial appendage. “This is associated with atrial fibrillation, and so can help select patients who may benefit more from prolonged cardiac monitoring to identify AF,” he noted.

In this study, slow flow was found in 24.3% of patients who underwent the extended CT, compared with 7.1% in the standard of care group — a fourfold significant increase.

He suggested that there were multiple other implications too.

“We found things that were not specially looking for. Some patients had a new pulmonary nodule and were diagnosed with cancer, which can now be treated earlier, just because we went a little bit lower with the CT scan. We also found patients with asymptomatic pulmonary embolism,” he said.

“This is just an initial trial. It’s such a simple thing to do, but it has potentially enormous implications,” said Sposato.

“I am going to do this extended CT scan now at our hospital because, even if I don’t have proof that it improves outcomes, knowing that a clot is there helps my decision-making process,” he added.

DAYLIGHT 2 Coming Soon

Going forward, Sposato recommends that if a clot is detected on this simple CT scan, then patients go on to have a more dedicated cardiac scan.

The extended CT scan in the current trial was a non-gated, single-phase scan, the simplest and quickest type. The researchers are now working on a new protocol (DAYLIGHT 2) to do an immediate delayed phase CT scan to get a better image if a suspected clot or slow flow is seen in the single phase.

“The delayed phase scan gives time for the IV contrast to get to left atrium and left atrium appendage. It can be done at the same time but would probably add on another few minutes to the scanning process,” Sposato noted.

Sposato reported no relevant disclosures.