Multislice computed tomography data acquisition All examinations were performed with a 16-slice or higher CT system (Multi-vendor). First, a prospectively triggered coronary calcium CT data set was obtained using standardized CT parameters. Thereafter CTCA was performed after the administration of a bolus (60-100ml) non ionic contrast material (Multi-vendor) at flow rate of 4-6ml/s depending on patient status. All injections were performed by power injector via an antecubital vein and were followed by 50 ml of saline bolus chase at the same flow rate. A bolus tracking technique was used to determine the initiation of CT data acquisition. CTCA was performed with the best available parameters, depending on scanner type and generation. The reconstruction slice thickness and increment were 0.5-0.75mm and 0.3-0.5mm respectively. Intra-venous beta-blocker (e.g. atenolol 5-10mg) was administered to all patients with a heart rate >65 beats/min and without contraindication (known asthma or bronchospasm, systolic blood pressure <100mmHg). In addition, nitro-glycerine was administered sublingually to all patients, albeit contraindications (known significant aortic stenosis, systolic blood pressure <100mmHg). Patients with atrial fibrillation or frequent premature beats were included in the study. To obtain optimal image quality, datasets were reconstructed at least at two points of the cardiac cycle using a retrospective ECG gating algorithm (one diastolic cardiac phase usually at -350msec from the R waves and one end-systolic phase at +275msec). In the presence of motion artefacts, as in the case of cardiac arrhythmias, additional reconstructions were made at different time points of the R-R interval. At the time of the study, tube current modulation was not used. The estimated radiation dose would be 5-20mSv. Axial data sets are transferred to a remote workstation (Multi-vendor) for post-processing and subsequent evaluation.