More Support for Cardiac CT’s Value

A new study in Radiology offers more support for the value of CT-based coronary artery calcium scoring, finding that people with higher CAC scores had worse outcomes, and suggesting that those with scores of 0 could potentially avoid invasive coronary angiography. 

Evidence has been building that by measuring calcium buildup in the heart, CAC scores can predict clinical outcomes, in particular major adverse cardiac events, particularly in patients with stable chest. 

  • Studies ranging from MESA to SCOT-HEART to PROMISE have found that patients with CAC scores of 0 have MACE risk that’s lower than 2% – meaning they could be discharged without further invasive workup. 

The new study is an update to the DISCHARGE trial, which in 2022 published results comparing a CT-first evaluation strategy to one with invasive coronary angiography. The new study investigates the value of CAC scoring by analyzing its prognostic power in patients with stable chest pain who were referred for invasive coronary angiography. 

  • The DISCHARGE study is notable for its diversity – 26 clinical centers in 16 European countries – as well as its use of 13 different models of CT scanners from all four major CT OEMs from 2015 to 2019. 

In all, 1.7k patients were studied, and CAC scores were generated based on CT scans and used to stratify patients into one of three groups; they were then followed for 3.5 years and rates of MACE were correlated to CAC levels, finding … 

  • Patients with CAC scores of 0 had the lowest rates of MACE compared to those with scores of 1-399 and ≥400 (0.5% vs. 1.9% & 6.8%)
  • Rising CAC scores corresponded to higher prevalence of obstructive coronary artery disease (0=4.1% vs. 1-399=29.7% & ≥400=76%)
  • Revascularization rates rose with CAC scores (0=1.7% vs. ≥400=46.2%)

While the authors steered away from commenting on the study’s impact on clinical management, the findings – if confirmed with additional studies – suggest that stable chest pain patients may not need invasive coronary angiography.

  • And in another interesting wrinkle to the study, the researchers pointed out that 57% of the DISCHARGE study’s patient population were women, a fact that addresses sex bias in previous research. 

The Takeaway

The DISCHARGE study’s findings are yet another feather in the cap for cardiac CT, with higher CAC scores indicating the long-term presence of atherosclerosis. Should they be confirmed, individuals with stable chest pain in the future will benefit from less invasive – and less expensive – management.

Is CCTA Set for Cardiac Screening?

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.

Chest Pain Implications

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

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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