A 53 year-old patient with atypical, stress-induced chest pain and a catalogue of typical cardiovascular risk factors presented to the cardiology department to rule out coronary artery disease. A bicycle stress ECG was possible only up to 75 watts and therefore non-diagnostic.
To rule out coronary artery disease in this patient, specific care was taken to choose a low dose, coronary CT angiography (CTA) protocol. Coronary CTA was performed in Flash Spiral mode (prospectively ECG triggered spiral acquisition, 0.28 second rotation time, pitch 3.4) utilizing 100 kV tube voltage and 320 mAs/rot. 60 ml of contrast agent (Ultravist 370) followed by the same amount of saline solution was injected at 6 ml/s to ensure a homogenous enhancement of the coronary arteries. Nitroglycerin was administered for good vasodilatation of the coronary arteries. The entire heart was scanned in just 230 milliseconds. Right coronary artery (RCA), posterior descending artery (PDA), left main- (LM) and left anterior descending (LAD), left circumflex (LCX) and even relatively small side branches such as the marginal branch (M1) or diagonal branch (D1,D2) were reliably visualized and the absence of stenoses was clearly demonstrated. Neither calcified nor non-calcified plaque was detected. The patient showed a regular coronary anatomy, ventricular size was normal and no incidental, non-cardiac findings were identified. The scan was performed with a DLP of 56, translating into an effective dose of 0.7mSv.
The examination demonstrates that it is possible to reliably rule out coronary artery stenoses with a dose below 1 mSv. In addition, the absence of any detectable coronary atherosclerotic plaque – whether calcified or non calcified - indicates a very low cardiac event risk in the future.