Evaluating Radiation Exposure in Patients with Stable Chest Pain in the SCOT-HEART Trial

Abstract

A ccurate diagnosis is central to treatment strategies for patients with stable symptoms who are suspected of having coronary artery disease (1). However, radiation exposure remains an important concern in cardiovascular imaging because of its relation to lifetime cancer risk (2-5). Coronary CT angiography (CTA), SPECT, myocardial perfusion imaging, and invasive coronary angiography (ICA) all involve radiation, with radiation doses varying between centers. The impact of a diagnostic strategy based on coronary CTA on long-term cumulative radiation exposure is currently uncertain. Short-term cumulative radiation exposure in patients presenting with stable chest pain has previously been assessed in the Prospective Multicenter Imaging Study for Evaluation of Chest Pain (PROMISE) trial, which compared functional testing to coronary CTA (6). They found that the median cumulative radiation exposure per patient at 90 days was lower in the coronary CTA group compared with the functional testing group, using the 0.014 mSv/mGy • cm conversion factor for CT. Participants who underwent coronary CTA had a lower radiation dose than those who underwent nuclear stress Background: In the Scottish Computed Tomography of the Heart (SCOT-HEART) trial in individuals with stable chest pain, a treatment strategy based on coronary CT angiography (CTA) led to improved outcomes. Purpose: To assess 5-year cumulative radiation doses of participants undergoing investigation for suspected angina due to coronary artery disease with or without coronary CTA. Materials and Methods:This secondary analysis of the SCOT-HEART trial included data from six of 12 recruiting sites and two of three imaging sites. Participants were recruited between November 18, 2010, and September 24, 2014, with follow-up through January 31, 2018. Study participants had been randomized (at a one-to-one ratio) to standard care with CT (n = 1466) or standard care alone (n = 1428). Imaging was performed on a 64-detector (n = 223) or 320-detector row scanner (n = 1466). Radiation dose from CT (dose-length product), SPECT (injected activity), and invasive coronary angiography (ICA; kerma-area product) was assessed for 5 years after enrollment. Effective dose was calculated using conversion factors appropriate for the imaging modality and body region imaged (using 0.026 mSv/mGy • cm for cardiac CT).Results: Cumulative radiation dose was assessed in 2894 participants. Median effective dose was 3.0 mSv (IQR, 2.6-3.3 mSv) for coronary calcium scoring, 4.1 mSv (IQR, 2.6-6.1 mSv) for coronary CTA, 7.4 mSv (IQR, 6.2-8.5 mSv) for SPECT, and 4.1 mSv (IQR, 2.5-6.8 mSv) for ICA. After 5 years, total per-participant cumulative dose was higher in the CT group (median, 8.1 mSv; IQR, 5.5-12.4 mSv) compared with standard-care group (median, 0 mSv; IQR, 0-4.5 mSv; P < .001). In participants who underwent any imaging, cumulative radiation exposure was higher in the CT group (n = 1345; median, 8.6 mSv; IQR, 6.1-13.3 mSv) compared with standard-care group (n = 549; median, 6.4 mSv; IQR, 3.4-9.2 mS...