• Chest pain is one of the most common symptoms of heart disease. This could be due to narrowing in heart's blood vessels, which needs to be investigated.
• Currently, people with a low risk of narrowing of heart vessels usually have a CT scan of the heart first. This scan is good at identifying those who do not have significant narrowing. However, the scan has some drawbacks, such as exposure to a small amount of radiation.
• We are exploring if ultrasound of the neck vessels might give us similar kind of information as the CT scan.
• You will be asked to attend the hospital for one visit to have an ultrasound scan of your neck.
• The findings of your neck vessels will be compared with the CT scan of your heart vessels to see if there is a similarity.

In the era of rising coronary artery disease burden, various investigations ranging from CTCA, SE, CMR, PET, SPECT and CA are being extensively relied upon to detect CAD and prevent CVD events. According to current guidelines, patients falling in the subgroup of low likelihood of obstructive CAD are investigated with CTCA and CAC score as the first line of investigation to rule out obstructive coronary artery disease [6,8]. Based on the CACS-CL alone, the low-risk RF-CL patients can be reclassified to identify more patients with very low risk of obstructive CAD, thereby allowing for deferral of further testing [6]. This method has demonstrated a high degree of reliability in the process of downgrading patients from the low-likelihood subgroup to the very-low-likelihood of obstructive CAD subgroup [29]. The reclassification of patients to the 'very low likelihood of obstructive CAD' subgroup is important, as it ensures that patients can be safely reassured, with no further requirement for investigations for obstructive CAD and at the same time reduces pressure on already compromised resources. In order to determine the CAC score, patients are exposed to ionising radiation. It is not only expensive but also requires advanced equipment, while carotid ultrasound offers a safer, quicker and more affordable option without radiation. With growing evidence connecting carotid plaque with CAD in both asymptomatic and symptomatic individuals, its role in risk reclassification of symptomatic patients warrants further investigation. The objective of this study is to determine the accuracy of carotid ultrasound in reclassifying a specific patient subgroup compared to CAC score. Should carotid ultrasound be able to demonstrate the desired accuracy as of CAC score in this sub-group, it would be feasible to investigate such patients without exposure to ionising radiation or iodinated contrast, while concomitantly reducing costs.

Inclusion Criteria:

1. Age > 18 years old
2. Symptomatic patients with suspected CCS, judged by the clinician to require CTCA with CAC scoring, for the diagnosis of CAD
3. Have a RF-CL 5-15%, as calculated using ESC guidelines
4. Able to give informed consent to participate in the study and its follow up

Exclusion Criteria:

1. Age <18 years old
2. Diagnosed ACS requiring hospitalization or urgent or emergent testing
3. Known CAD with prior MI, PCI, CABG or any angiographic evidence of CAD (≥50% lesion in a major epicardial vessel)
4. History of previous stroke or known peripheral vascular disease
5. Known significant cardiac congenital abnormalities
6. Pregnancy
7. Life expectancy < 1 years
8. Unable to provide written informed consent