Coronary CTA on Asymptomatic Patients Provides Little to No Clinical Benefit
Asan Medical Center research team finds increasing rate of coronary CTAs on domestic asymptomatic patients but little subsequent diagnostic, survival benefit
A cardiology research team from Asan Medical Center (AMC) has discovered that carrying out coronary computed tomography angiographies (CTA) on asymptomatic patients does not increase the diagnostic rate or mortality rate of obstructive coronary artery disease (CAD).
The team, led by Professor Park Duk-woo from Asan Medical Center, department of cardiology, found that despite the increasing number of coronary CTAs performed on domestic asymptomatic individuals without CAD, the rate of diagnosis was strikingly low.
Based on study findings, Park and colleagues strongly suggested that coronary CTAs would be justified on asymptomatic patients only after pre-test risk stratification and analysis on results from symptom-based optimal decision-making algorithms while warning against excessive coronary CTAs.
This study was published in the Journal of the American Heart Association on September 8, 2020.1
Coronary CTA on asymptomatic patients increasing despite lack of evidence
Coronary CTA is a heart imaging test that diagnoses CAD and is known to be more accurate than functional testing. As a non-invasive test, CTAs are being used extensively in Korea, with the number of performed tests on the rise.
According to the AMC study, the overall number of coronary CTAs performed increased steeply from 2007 to 2013. Data gathered on 39,906 patients without known CAD who received a coronary CTA at AMC showed an increase from 1,587 CTAs in 2007 to 7,416 in 2013, indicating more than a three-fold increase. The number of CTAs on asymptomatic patients also rose significantly from 42.6 percent in 2007 to 60.3 percent in 2013 (P for trend <0.001).
However, international guidelines published by the National Institute for Health and Care Excellence (NICE) and European Society of Cardiology (ESC) delineate CTAs as a first-line diagnostic tool and a Class I recommendation only for patients with suspected CAD or atypical heart symptoms.
Korean guidelines recommend coronary CTAs for patients suspected to have CAD. The Health Insurance Review and Assessment Service (HIRA) recommends coronary CTA for low-to-medium risk patients in the ER presenting acute heart pain who are unsuccessfully diagnosed with an electrocardiogram or cardiac markers. HIRA also recommends coronary CTA for patients presenting stable chest pain who objectively cannot undergo the exercise test or when result analysis is problematic.
Although proceeding with a coronary CTA when stable CAD is strongly suspected is justified, questions remained over whether coronary CTAs are beneficial for asymptomatic patients. Along with the lack of evidence in this group of patients, coronary CTAs on asymptomatic patients also pose potential harm, such as unnecessary radiation exposure and side effects of contrast agents.
Obstructive CAD diagnostic rate rises proportionally only with symptoms and CVD risk
Despite the rising demand for coronary CTAs, AMC¡¯s study confirmed that the obstructive CAD diagnostic rate increased proportionally only with the presence of symptoms and the patient¡¯s cardiovascular risk level determined by the Framingham risk score.
According to the study, a coronary CTA led to an obstructive CAD diagnosis in 15.3 percent of patients (6,108 patients). Among these patients, 23.7 percent had reported symptoms while 9.3 percent had no symptoms. The research team pointed out that more than half – 63.9 percent – of asymptomatic patients received a coronary CTA through the national health screening test and this phenomenon reflects rising patient demand for status updates on their respective cardiovascular health.
¡°The increasing rates of coronary CTAs on asymptomatic patients may be attributed to rising demand by Korean patients concerning their want to check on their overall health and respective cardiovascular health status,¡± AMC professor Park noted.
Regarding the Framingham risk score, data showed that the rate of obstructive CAD diagnosis increased with level of cardiovascular risk. The research team found a 10 percent diagnosis rate in the low-risk group, 10-20 percent rate in the moderate-risk group, and more than a 20 percent rate in the high-risk group.
Based on these findings, Park¡¯s research team strongly suggested that coronary CTAs should be performed only after evaluating the patient¡¯s symptoms as well as clinical risk factors.
¡°The frequency of cardiovascular disease diagnosis increased in proportion to the patient¡¯s symptoms and the Framingham risk score,¡± Park stressed. ¡°This study proves that it is more efficient to order a coronary CTA after extensively reviewing the patient¡¯s risk factors, or lack thereof.¡±
Professor Park Duk-woo also pointed out that cardiac catheterization was performed in about 19 percent of symptomatic patients after testing. Of these patients, treatment was appropriate in around 80 percent.
Meanwhile, cardiac catheterization was performed in about four percent of asymptomatic patients after coronary CTA, and treatment was justified for only eight percent.
Follow-up of an average of five years showed that the primary composite endpoint occurred in five percent of symptomatic patients and two percent of asymptomatic patients, indicating a statistically significant difference (P<0.001).
The risk of primary composite endpoint occurrence was also 1.34 times higher in the patient group diagnosed with obstructive CAD on the CTA than the undiagnosed patient group (aHR 1.34; 95% CI 1.17~1.54).
However, the incremental value of obstructive CAD on coronary CTA over conventional risk factors for predicting death or myocardial infarction was limited.
¡°Coronary CTAs on asymptomatic patients should be last resort¡±
Based on these findings, the research team stressed the importance of predicting a high-risk CAD patient group by identifying patients with pre-test risk stratification and analyzing them based on symptom-based optimal decision-making algorithms when deciding on a coronary CTA.
¡°We confirmed that the diagnostic benefits with a coronary CTA is relevant to high-risk patient groups who are symptomatic,¡± Park said. ¡°Follow-up studies are needed to confirm the precise level of risk that justifies a coronary CTA and the subsequent clinical benefits obtained with the risk standard.¡±
Park¡¯s research team also noted that the study has limitations in that it only analyzed patients who received a coronary CTA at AMC. Despite this limitation, the team said the study was performed on a sizable 30,000 patient pool, and could be applied generally to other settings.
¡°Although the single-center study carries limitations, findings clearly show that asymptomatic patients did not benefit from a coronary CTA. In this regard, the study can be used as a reference point in drawing up CTA recommendations for asymptomatic patients.,¡± said Park.
¡°This study warns against the general and excessive use of CTAs on asymptomatic patients and further studies identifying patient groups that benefit from heart imaging tests are needed,¡± He added.