How to make good images in arrythmic patients?

The following question has been sent by Rusli Muljadi M.D., Indonesia:

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

Stephan Achenbach, M.D., University of Erlangen-Nuernberg:

Imaging in patients with arrhythmias remains challening. In spite of the high temporal resolution of DSCT, the fact that the heart may be in different states of contraction at an ectopic beat – or in beats with variably cycle length in the case of atrial fibrillation – can cause problems.

Here are a few things you can do:

1. In image reconstruction, edit the ECG trace to remove/deactivate beats that would include image reconstruction during an ectopic beat.
2. It is usually better to use a “ms” trigger (e.g., -300 ms or +350 ms) than “%” trigger in case of arrhtyhmias
3. If the ectopic beat is excluded and a long pause occurs afterwards, which does not give the scanner enough “material” to reconstruct images with, it may be possible to insert an additional trigger instant in the long diastole (see attached image). The same may hold true in the case of bradycardia that you describe.
4. In cases of atrial fibrillation, reconstruction at +´300 ms or -100 ms often renders good image quality.
5. When scanning patients with arrhythmic heart rates, consider a) deactivating ECG pulsing (may use 100kV instead) and b) entering a heart rate that is substantially lower than the actual heart rate, which will facilitate excluding arrhythmic beats afterwards.
6. When reconstructing, always stay clear of the P wave!

However, as said above, image reconstruction in arrhythmic patients can often be very challenging!

Good Luck
Stephan Achenbach

See answer of Thorsten R.C. Johnson M.D. to the same question.