This study focuses on evaluating the compatibility between CCTA and ICA using CAD-RADS 2.0 [2] in the diagnosis of CAD. This study, conducted with a large patient group, concentrates on the differences in diagnostic performance between CCTA and ICA, the impact of the Ca score, and the significance of the presence of HRP, offering an innovative perspective on CAD diagnosis and treatment approaches.

CAD continues to be a significant health issue in both developed and developing countries and maintains its position among the leading causes of death despite advancements in diagnostic methods and treatment options [3, 4]. In our study, with 144 (67.3%) being male and 70 (32.7%) female. The median age of the patients was 56 (range: 24–82), similar to studies in the literature indicating that CAD is more common in males and at advanced ages [5,6,7].

According to CAD-RADS 2.0, Ca scores are classified as P1, P2, P3, and P4 [2]. Our study found a statistically significant association between the Ca score and CAD-RADS score, consistent with other studies on Ca scoringn [8,9,10,11,12,13]. Specifically, CCTA provides detailed information about the characterization of the vessel wall and plaques, offering advantages over ICA. It suggests that CCTA may be a more useful guide for clinicians in follow-up and treatment.

When comparing our findings with a study conducted in 2024 [14], some differences are observed. In our study, the proportion of participants with a zero coronary Ca score is lower at 24.3%, and non-zero Ca scores appear approximately 15 years earlier in men than in women. Additionally, high-risk categorization (75th percentile) for Ca scores is reached at the age of 37 for men and 41 for women, indicating an earlier onset compared to the age limits set by the previous study. These differences can be attributed to our study population, which includes individuals with a higher suspicion of CAD, undergoing both CCTA and ICA; this suggests that our findings are derived from a high-risk group and should be evaluated in this context.

Our study includes patients with stents and grafts. Similar diagnostic parameters were identified between CCTA and ICA in evaluating these patients. Particularly, CCTA has been shown to offer comparable results to ICA in assessing stent and graft lumens. Additionally, CCTA provides extra advantages in evaluating extracardiac findings, extracoronary findings, and the assessment of intimal walls and lesion locations [15,16,17,18,19,20,21].

Our study includes the evaluation of extracardiac findings (Table 2) as recommended by the most latest version of CAD-RADS [2]. The capability of CCTA to diagnose these findings presents a significant advantage over ICA. Particularly when cardiac findings do not explain the patient's symptoms, exploring alternative causes is essential for appropriate treatment. Potential other causes of chest pain include smoking-related lung diseases, interstitial lung diseases, malignancies, anatomical anomalies, and pulmonary embolism. These conditions can be easily detected especially with the non-contrast CT examination for Ca scoring and the triphasic scanning protocol of CCTA [22,23,24,25]. Given the diverse patient population encountered in university hospitals, such examinations are deemed essential. Therefore, the examination for Ca scoring was conducted with a wide FOV covering the entire thorax and using a triphasic CCTA scanning protocol. In the literature, there are limited studies advocating the use of a wide FOV instead of a cardiac-focused FOV for diagnostic and cost benefits [24,25,26]. Therefore, especially for patients at medium and high risk recommended for CCTA, we suggest that the images taken for Ca scoring be scanned with a wide FOV considering factors such as age and smoking habits. According to the new guidelines published by the American Cancer Society in 2023, annual lung cancer screening is recommended for individuals aged 50 to 80 who currently smoke or have quit in the past and have a history of 20 pack-years or more. This recommendation can be combined with the recommended screenings for Ca scoring, making it possible to conduct both screenings simultaneously [27].

Studies have examined with similar rates in the literature (In patient-based analysis, patients with CAD-RADS 3 and higher scores) have shown that CCTA successfully detects [28,29,30,31,32,33] CAD with high sensitivity and specificity rates. Also, the study by Nikolou and colleagues [34] has shown high diagnostic performance for stenoses of 75% and greater. CCTA's diagnostic performance, when compared to the reference standard ICA, has been indicated to show high sensitivity and specificity in meta-analyses with exercise ECG and single photon emission computed tomography (SPECT) [35,36,37]. A study published in 2024 has demonstrated significant diagnostic performance of CCTA in detecting significant stenoses (more than 50%) with high sensitivity, specificity, NPV, and PPV [38]. All these studies and our research emphasize the strong diagnostic capacity of CCTA in the diagnosis of CAD and its advantages compared to alternative diagnostic methods.

In graft evaluation, while ICA is considered the gold standard, it increases the radiation dose exposed to both the patient and the doctor. Sometimes these evaluations can be inadequate [38, 39]. In a study conducted with 100 patients with bypass using ICA and CCTA, similar to our study, all diagnostic performance parameters were obtained as 100% [40]. In another study conducted on 84 patients with grafts, sensitivity was reported as 97% and specificity as 100% [41]. A meta-analysis examining 12 studies evaluating patients with grafts found sensitivity and specificity of 98% [42]. In our study, there were 20 grafts, and the evaluation in patients with grafts found perfect agreement between CCTA and ICA, with sensitivity, specificity, PPV, and NPV all found to be 100%.

In our study, there are a total of 35 stents in 21 patients, with CCTA finding sensitivity of 85.7%, specificity of 89.3%, PPV of 66.7%, and NPV of 96.2%. A meta-analysis evaluating 35 studies on patients with stents found sensitivity of 90% and specificity of 94% for stenoses of 50% and greater [43].

In the literature, the presence of HRP, even in low-risk patients such as those with CAD-RADS 1 and 2, is suggested to require more aggressive preventive treatments. In the literature, CT Fractional Flow Reserve (CT FFR), CT perfusion (CTP), stress imaging or, if necessary, ICA are recommended as additional examination in patients with CAD-RADS 3 and HRP [2]. The presence of HRP is thought to triple a patient's risk of death or nonfatal myocardial infarction (MI) [11]. A study found that HRP was less common in women and the risk of myocardial infarction (MI) was lower. Additionally, HRP was found to increase the risk of MI, independent of Ca score (Ca score), obstructive disease, gender and cardiovascular risk factors (Odds Ratio: 1,6) [44]. A 2024 article [45] emphasized that the optimal management of HRP has not yet been determined and that this issue needs further discussion. In our study, we found that HRP is more common in men and the average age is consistent with the literature. 13 patients with HRP (5 patients with CAD-RADS 1 and 2) received medical treatment, and 19 patients received stent and surgical intervention (11 stents, 8 surgeries). It is believed that the treatment approaches and follow-up of these patients could make significant contributions to the literature.

In the literature, it is recommended to use functional evaluation methods such as CT-FFR, CTP, or stress tests to document or rule out the presence of ischemia in patients with CAD-RADS 3 scores [2]. Our study emphasizes the need for personalized treatment for CAD-RADS 3 patients, as stated in the literature [2]. This approach helps determine the necessity of invasive treatment. In our study, CADRADS 3 patients were questioned for major cardiac events. A major cardiac event was not observed in 31 patients who received medical treatment (minimum 3 months, maximum 22 months, average 10 months) or four patients who received stent treatment (minimum 4 months, maximum 8 months, average 6 months). This finding is important, and similar follow-up studies with larger numbers of CAD-RADS 3 patients are needed.

CCTA has important advantages such as identifying complications related to stents and grafts, recognizing non-atherosclerotic stenosis, and determining plaque burden and characterization. These features make CCTA a valuable imaging method for both doctors and patients.

Our study is generally compatible with the treatment recommendations stated in the CAD-RADS score. The presence of HRP, which can be easily evaluated by CCTA, may increase the severity and possible risks of CAD. This supports the recommendation of more aggressive treatment methods, such as invasive evaluation and potential revascularization, especially for patients with CAD-RADS scores of 3, 4 and 5. The detection of HRP plays an important role in the early and accurate identification of CAD and is critical in determining appropriate treatment strategies.

Our study offers a significant advantage in evaluating patients with CAD-RADS 2.0 and presenting a high number of patients compared to similar studies in the literature. However, our study has some limitations. Particularly, the fact that the study is single-center and retrospective is an important limitation. Other limitations include the low number of patients with HRP and CAD-RADS 3 scores and the lack of advanced methods such as CT-FFR in our unit. Especially, we believe that diagnosing, treating, and following up patients with HRP and CAD-RADS 3 scores with more extensive participation studies is necessary for managing these patients..

In conclusion, our study supports the importance of HRP in CAD management and the efficacy of CCTA in detecting these plaques, while also demonstrating compliance with the treatment recommendations based on the CAD-RADS score. Additionally, our study emphasizes the advantages of the imaging protocol used for Ca scoring, taken with a wide FOV and a triphasic scanning protocol. These findings provide significant contributions to the development of diagnosis and treatment strategies for CAD.