History
A 64-year-old male patient, with a positive family history of myocardial ischemia and coronary artery disease, presented himself to the hospital complaining of atypical chest discomfort during exercise and palpitations at rest. A blood test revealed a normal level of cholesterol and a slight elevation of triglycerides (204 mg/dl). In a recent stress-ECG examination, ventricular extrasystoles were observed during the maximum exercise phase and the primary post-exercise phase. Given the low to intermediate pretest probability of coronary artery disease (CAD), in line with current international guidelines, [1] a coronary CT angiography (CCTA) was performed on a Dual Source photon-counting CT (PCCT), NAEOTOM Alpha®, using an ultra-high resolution (UHR) mode (Quantum HD cardiac) to rule out exercise-induced coronary insufficiency as a potential underlying cause of his symptoms.
Diagnosis
The assessment of the calcium score revealed a severe coronary plaque burden (P4) with an Agatston score of 1172, being beyond the 90th age- and gender-percentile. Extensive calcifications were shown in the proximal left anterior descending artery (LAD) and proximal right coronary artery (RCA). To reduce the potential calcium blooming interferences and to improve the visualization of the spatial details, a UHR mode was selected for the following cCTA which provided diagnostic images – two mixed plaques with high-risk features in the proximal LAD and RCA were evident, characterized by a hypoattenuating plaque component (<30HU) and positive remodeling. Mild coronary stenoses (25–49%) were visualized in the proximal LAD and RCA. The circumflex (Cx) showed non-calcified plaques, however, was free from stenosis. The left ventricle was of a normal size, with a normal ejection fraction (EF) of 69%, without any hypertrophy. According to the CAD-RADS 2.0 consensus statements, [2] this patient’s CCTA was classified as CAD-RADS 2/P4/HRP. Subsequently, the patient was referred to an outpatient cardiologist. Risk factor modification, intensive preventive pharmacotherapy with statins and a short-term clinical follow up were recommended.
Fig. 1: Axial images from the calcium scoring scan show extensive calcifications in the proximal LAD (Fig. 1a) and RCA (Fig. 1b) resulting in an Agatston score of 1172, being beyond the 90th age- and gender-percentile.
Fig. 2: Curved Multiplanar Reformations (MPR, 0.2 mm) of the coronary arteries reveal non-obstructive stenoses (<50%) in the proximal LAD (Fig. 2a) and RCA (Fig. 2b) with a clear lumen exhibiting no noticeable blooming artifact interference despite of the presence of extensive calcifications. Two mixed plaques with high-risk features, characterized by a hypoattenuating plaque component (<30HU) and positive remodeling, are evident in the proximal LAD and RCA. The Cx (Fig. 2c) shows non-calcified plaques, and is free from stenosis.
Fig. 3: Three-dimensional Cinematic Rendering images highlight the calcified plaques in the proximal LAD and RCA (in blue). Note that the images used for the rendering are reconstructed at 0.2 mm with a sharp kernel of Bv64.
Comments
High risk plaque (HRP), previously known as “vulnerable plaque”, featuring spotty calcifications, low attenuation plaque (< 30 HU), positive remodeling, and the “napkin ring sign”, is associated with a higher risk of future acute coronary syndrome (ACS) and lesion specific ischemia, independent of stenosis severity. HRP has been incorporated in the CAD-RADS recommendations as a modifier, suggesting that the identification of the HRP should signify the need for more aggressive preventive therapies, also including nonobstructive lesions. [2] Studies have shown that half of culprit plaques that cause major adverse cardiovascular events (MACE) arise from plaques that had previously caused a stenosis < 50% [3]. It is of crucial importance for patient management to have a more accurate, patient-specific risk stratification. In this case, a statin therapy is primarily indicated due to the presence of extensive coronary calcification, patient’s age and family history, despite the absence of an elevated cholesterol level and severe coronary stenosis. However, the identification of the HRP warrant a closer clinical follow-up, and imaging monitoring of lesion-specific plaque progression, inducing changes in the decision making of patient management to a more patient- and lesion-specific targeted approach.
Identifying the HRP features in CT imaging requires optimal spatial and temporal resolution, as well as minimization of blooming interference caused by calcified plaques. This case applies a UHR mode featuring a slice collimation of 120 x 0.2 mm for image acquisition and a sharp kernel (Bv64) for image reconstruction – a special scan mode that is currently only available on PCCT. [4] Recent clinical studies have reported an impressive success rate and diagnostic accuracy using this mode for coronary evaluation, even in the presence of extensive calcification. [5] The incorporation of Quantum iterative reconstruction at full strength (QIR level 4) further reduces image noise and enhances image clarity.
As shown in this case, CCTA with UHR mode provides crucial information about the patient's cardiac health even in the presence of severe coronary calcifications – it helps the physicians identify HRP and rule out obstructive coronary heart disease. Owing to the optimal image quality achieved by Quantum HD cardiac, CT findings help in patient risk stratification, and guiding patient management. As this patient did not need to undergo invasive angiography after CT evaluation, the associated cost could be reduced.
Examination Protocol