Tag: CCTA

AI of Cardiac CT Predicts Risk

Posted on by Brian Casey

In a landmark study of 40k patients from the UK published in The Lancet, an AI-derived score that analyzed coronary arterial inflammation on coronary CT angiography scans was effective in predicting future cardiac risk in people regardless of whether they had obstructive coronary artery disease.

CCTA’s power for predicting heart problems has been demonstrated in multiple studies, and it’s now considered a first-line test for individuals with chest pain. 

  • But the situation is trickier in those without obstructive disease – prompting researchers to ask whether CCTA’s ability to visualize subtle changes in cardiac structure and function could be leveraged – such as with AI – to deliver even more prognostic power. 

The Oxford Risk Factors And Noninvasive imaging (ORFAN) study in the UK is addressing that question by conducting CCTA scans in 40k patients as part of routine clinical care at eight hospitals. 

  • Researchers analyzed outcomes in the entire ORFAN population of 40k patients, then followed a subset of 3.4k higher-risk patients for 7.7 years to study the value of a perivascular fat attenuation index (FAI) score. 

FAI scores measure heart inflammation in coronary arteries and are calculated using Caristo Diagnostics’ CaRi-Heart AI software.

  • The scores are combined with other traditional risk factors to create an AI-Risk classification that predicts the likelihood of an adverse event.  

Researchers found that … 

  • Across the entire 40k cohort, patients without obstructive CAD accounted for 64% of cardiac deaths and 66% of MACE – twice as many as those with obstructive CAD
  • In the smaller higher-risk cohort, patients with an elevated FAI score in all three coronary arteries had a higher risk of cardiac mortality (HR=29.8) or MACE (HR=12.6)
  • Elevated FAI scores in any coronary artery also predicted cardiac mortality
  • AI-Risk scores were associated with cardiac mortality (HR=6.75) and MACE (HR=4.68) when comparing very-high-risk versus low- or medium-risk patients 

The first data point is worth noting, as it illustrates the need to improve risk stratification and management in people without obstructive CAD.

The Takeaway
The ORFAN results are an exciting development for cardiac CT AI (in addition to being a major coup for Caristo, which raised $16.3M last year to commercialize CaRi-Heart globally). Measurements of coronary inflammation could give clinicians another tool – in addition to plaque measurements and calcium scoring – to predict cardiac events.

Fine-Tuning Cardiac CT

Posted on by Brian Casey

CT has established itself as an excellent cardiac imaging modality. But there can still be some fine-tuning in terms of exactly how and when to use it, especially for assessing people presenting with chest pain. 

Two studies in JAMA Cardiology tackle this head-on, presenting new evidence that supports a more conservative – and precise – approach to determining which patients get follow-up testing. The studies also address concerns that using coronary CT angiography (CCTA) as an initial test before invasive catheterization could lead to unnecessary testing.

In the PRECISE study, researchers analyzed 2.1k patients from 2018 to 2021 who had stable symptoms of suspected coronary artery disease (CAD). Patients were randomized to a usual testing strategy (such as cardiac SPECT or stress echo), or a precision strategy that employed CCTA with selected fractional flow reserve CT (FFR-CT). 

The precision strategy group was further subdivided into a subgroup of those at minimal risk of cardiac events (20%) for whom testing was deferred to see if utilization could be reduced even further. In the precision strategy group….

  • Rates of invasive catheterization without coronary obstruction were lower (4% vs. 11%)
  • Testing was lower versus the usual testing group (84% vs. 94%)
  • Positive tests were more common (18% vs. 13%)
  • 64% of the deferred-testing subgroup got no testing at all
  • Adverse events were higher, but the difference was not statistically significant

To expand on the analysis, JAMA Cardiology published a related study that further investigated the safety of the deferred-testing strategy at one-year follow-up. Researchers compared adverse events in the deferred testing group to those who got the usual testing strategy, finding that the deferred testing group had…

  • A lower incidence rate of adverse events (0.9 vs. 5.9)
  • A lower rate of invasive cardiac cath without obstructive CAD per 100 patient years (1.0 vs. 6.5)

The results from both studies show that a strategy of deferring testing for low-risk CAD patients while sending higher-risk patients to CCTA and FFR-CT is clinically effective with no adverse impact on patient safety.

The Takeaway
The new findings don’t take any of the luster off cardiac CT; they simply add to the body of knowledge demonstrating when to use – and not to use – this incredibly powerful tool for directing patient care. And in the emerging era of precision medicine, that’s what it’s all about.

Is CCTA Set for Cardiac Screening?

Posted on by Brian Casey

A new study out of Denmark suggests that coronary CTA could be headed for population-based screening for heart disease. Researchers found that CCTA was remarkably effective in identifying individuals without symptoms who were more likely to experience heart attacks in years to come.

CCTA has proven so effective for cardiac imaging that it’s become a first-line test for stable chest pain, usually for those with symptoms. But researchers have debated whether CCTA’s value could be extended to asymptomatic individuals – which could set the stage for broad-based heart disease screening programs.

To investigate CCTA’s potential in the asymptomatic, researchers in Denmark scanned 9,533 individuals 40 years and older as part of the Copenhagen General Population Study, reporting their results in Annals of Internal Medicine. CCTA scans were conducted with Canon Medical’s 320-detector-row Aquilion One Vision scanner. 

Atherosclerosis was characterized as either obstructive (a luminal stenosis ≥ 50%), extensive (stenoses widely prevalent but not obstructive), or both. Researchers then tracked myocardial events over a median follow-up of 3.5 years. 

They found that 46% of study subjects had evidence of subclinical coronary atherosclerosis, with the type of atherosclerosis impacting risk of myocardial infarction: 

  • Extensive atherosclerosis had eight times higher risk 
  • Obstructive atherosclerosis had nine times higher risk
  • Both extensive and obstructive disease had 12 times higher risk

What’s more, researchers found that 10% of their study population had obstructive disease – which is just 10 percentage points under the 60% atherosclerosis threshold at which therapeutic intervention should be considered for asymptomatic people. 

Participants in the CGPS study did not receive treatment as part of the study, but the researchers have a follow-up study underway – DANE-HEART – in which asymptomatic people will get CCTA scans and some will be directed to preventive treatment if they meet clinical guidelines.

The Takeaway

This study demonstrates not only the widespread incidence of subclinical coronary atherosclerosis, but also CCTA’s ability to detect CAD before symptoms appear. Preventive treatment initiated and directed by CT findings could have a major impact on heart disease morbidity and mortality.

Given CCTA’s prognostic ability and the heavy burden of heart disease on society (more women die of heart disease than breast cancer, for example), how long before calls emerge to add CT-based heart screening to the arsenal of population-based screening programs? DANE-HEART may offer a clue.

CCTA AI Predicts Ischemia and MBF

Posted on by Jake Fishman

A Cedars-Sinai and Amsterdam UMC-led team developed a machine learning system that analyzes quantitative plaque in coronary CTA exams to identify patients with ischemia and impaired myocardial blood flow (MBF), potentially creating an alternative to current methods.

The researchers trained the ML model using invasive FFR data from 254 patients (484 FFR vessels) to predict ischemia and impaired MBF by analyzing plaque data in CCTA exams. 

They then tested it with CCTAs from 208 patients (581 vessels) who also underwent invasive FFR and H2O PET exams, finding that the CCTA ML scores:

  • Predicted FFR-defined ischemia far more accurately than standard CCTA stenosis evaluations, while rivaling FFRCT assessments (AUCs: 0.92 vs. 0.84 & 0.93)
  • Predicted PET-based impaired MBF more accurately than standard CCTA stenosis evaluations and FFRCT assessments (AUCs: 0.80 vs. 0.74 & 0.77)

Because the ML scoring system operates locally, the authors highlighted its potential to quickly assess high-risk patients before invasive coronary angiography (avoiding off-site processing delays) or to assess low-risk patients at earlier stages, helping to improve ICA efficiency and accuracy.

The researchers plan to continue to develop their CCTA plaque AI solution, including adding more plaque features and CCTA metrics, and potentially seeking regulatory approval depending on the results of future validation studies.

The Takeaway

CCTA plaque AI is already one of the hottest segments on the commercial side of imaging AI, and this study highlights similar advances in academic centers, while showing that CCTA plaque AI can quickly and accurately predict both ischemia and lower MBF.

Chest Pain Implications

Posted on by Jake Fishman

The major cardiac imaging societies weighed-in on the AHA/ACC’s new Chest Pain Guidelines, highlighting the notable shifts coming to cardiac imaging, and the adjustments they could require.

The cardiac CT and MRI societies took a victory lap, highlighting CCTA and CMR’s now-greater role in chest pain diagnosis, while forecasting that the new guideline will bring:

  • Increased demand for cardiac CT & MR exams and scanners
  • A need for more cardiac CT & MR staff, training, and infrastructure
  • Requests for more cardiac CT & MR funding and reimbursements
  • More collaborations across radiology, cardiology, and emergency medicine

The angiography and nuclear cardiology societies were less celebratory. Rather than warning providers to start buying more scanners and training more techs (like CT & MR), they focused on defending their roles in chest pain diagnosis, reiterating their advantages, and pointing out how the new guidelines might incorrectly steer patients to unnecessary or insufficient tests.

FFR-CT’s new role as a key post-CT diagnostic step made headlines when the guidelines came out, but the cardiac imaging societies don’t seem to be ready to welcome the AI approach. The nuclear cardiology and radiology societies called out FFR-CT’s low adoption and limited supporting evidence, while the SCCT didn’t even mention FFR-CT in its statement (and they’re the cardiac CT society!).

Echocardiography maintained its core role in chest pain diagnosis, but the echo society clearly wanted more specific guidelines around who can perform echo and how well they’re trained to perform those exams. That reaction is understandable given the sonographer workforce challenges and the expansion of cardiac POCUS to new clinical roles (w/ less echo training), although some might argue that echo AI tools might help address these problems.

The Takeaway

Imaging and shared decision-making play a prominent role in the new chest pain guidelines, which seems like good news for patient-specific care (and imaging department/vendor revenues), but it also leaves room for debate within the clinic and across clinical societies. 

The JACC seems to understand that it needs to clear up many of these gray areas in future versions of the chest pain guidelines. Until then, it will be up to providers to create decision-making and care pathways that work best for them, and evolve their teams and technologies accordingly.

Chest Pain Imaging Guidance

Posted on by Jake Fishman

If it seemed like coronary imaging folks were more excited than usual last week, it’s because the AHA/ACC’s long-awaited chest pain guidelines just set the stage for a lot more imaging.

The Guidelines – The American Heart Association (AHA) and the American College of Cardiology (ACC) released their first clinical guidelines for the assessment and diagnosis of chest pain, outlining a range of new standards, processes, and pathways, while giving coronary imaging a central diagnostic role.

Front-Line Coronary CTA – The new guidelines made coronary CTA a front-line coronary artery disease test, assigning CCTA their highest recommendation level and proposing it for a large group of patients (mid-high risk of CAD, stable chest pain, <65yrs).

FFRct Next in Line – HeartFlow’s FFRct analysis will often serve as the next diagnostic step when CCTA exams reveal obstructive CAD (40-90% stenosis) or are inconclusive, with FFRct results either clarifying diagnosis or supporting treatment decisions. 

Stress Imaging Pathways – The AHA/ACC guidelines also gave stress imaging (e.g. TTE, echo, CMRI, PET, etc.) their highest recommendation level, positioning stress imaging for more serious cases (likely or confirmed obstructive CAD, ≥65yrs) as well as for diagnosing myocardial ischemia and estimating risks of major cardiac events among patients with less severe cases (intermediate risk, no known CAD, acute chest pain).

Takeaway – These new guidelines are a big deal for coronary imaging, given the millions of people who show up at US emergency departments with chest pain each year. It’s also going to require some big changes across EDs, imaging centers, and radiology departments/practices, who will have to retool their imaging protocols/fleets and be able to expertly interpret a wave of coronary imaging exams (and handle a wave of incidentals).

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