How to make good images in arrhythmic patients

The following question has been sent by Rusli Muljadi MD, Indonesia:

How to make good picture in arrhythmia patient: We have performed cardiac CT of 3 patient with arrhythmia by Dual source CT. The pictures show motion artifact/ stepping. The type of of arrhythmia are ventricular extrasystole of 1 patient, supraventricular extrasystole of 1 patient and sinus bradikardi of 1 patient.

Thorsten Johnson, M.D., University Hospitals Grosshadern, Munich:

In single extrasystoles, especially interponated supraventricular beats, it is usually sufficient to disable the trigger by right-clicking it in the ‘Trigger’ card. If the resulting pause should be too long, a systolic reconstruction with fixed delay can help. Generally, a systolic reconstruction with a fixed delay of 280-300 ms after the R-peak is optimal in arrhythmic patients, e.g. in atrial fibrillation. This is usually very successful with DSCT in controlled atrial fibrillation.

Sinus bradycardia is generally accounted for by the automatic pitch adaptation. However, it can be necessary to manually adjust the ‘estimated heart rate’ on the ‘Exam’ card to a lower value in order to limit the pitch. We have the patient hold his or her breath prior to the scan in order to see whether changes in heart rate occur with breath-holding, which can be further accentuated by the increased preload due to contrast material injection. If we see a drop in heart rate, we adjust the ‘estimated hart rate’ accordingly. The reason is that otherwise the table is moving too fast and the data is undersampled, i.e. you get gaps in z-direction because not every phase of the cardiac cycle is covered for every z-position. It is not possible to compensate this with a specific reconstruction – you have to take this into account prior to the scan.

What you can do with such a dataset is to do a multiphase reconstruction and see whether you are able to evaluate each segment, even though in different phases. This is cumbersome and doesn’t give you nice images but may be sufficient to rule out significant disease if there is no atherosclerosis.

See answer of Stephan Achenbach, M.D. to the same question.