Author + information
- Ayman Hussein, MD,
- Ameer Abutaleb, MS,
- Jean Jeudy, MD,
- Timothy Phelan, MD,
- Ronak Patel, MD,
- Melsjan Shkullaku, MD,
- Faisal Siddiqi, MD,
- Vincent See, MD,
- Anastasios Saliaris, MD,
- Stephen R. Shorofsky, MD, PhD and
- Timm Dickfeld, MD, PhD∗ ()
- ↵∗Division of Cardiology, University of Maryland, 22 South Greene Street, Baltimore, Maryland 21201
We would like to thank Dr. Donnino and colleagues for their valuable comments regarding our study on the safety of computed tomography (CT) imaging in patients with cardiac rhythm management (CRM) devices (1). We agree with the authors’ comments regarding electrocardiography (ECG)-gated studies in patients who are pacemaker dependent. In clinical practice, non–ECG-gated CT is by far a more common situation in which CRM devices would be exposed to radiation and it was in this context that the original Food and Drug Administration advisory was prompted. ECG-gated studies are typically associated with higher radiation doses than conventional CT scanning and theoretically would be more likely to interfere with CRM devices. Classically, the doses of ECG-gated CT studies have ranged from 12 to 23 mSv depending on protocol and vendor. However, the most current techniques of prospective triggering and iterative reconstruction have helped to reduce radiation doses to ranges comparable to and even below the doses seen with conventional studies.
As pointed out by Dr. Donnino and colleagues, CT scans are rarely performed for the evaluation of left ventricular (LV) function. In pacemaker-dependent patients who are undergoing cardiac ECG-gated CT imaging, the assessment of LV function would be compromised by CT interference due to oversensing and pacing inhibition. While the scenario proposed by the authors is not commonly encountered, it is important to recognize to choose the most appropriate imaging study and to avoid unnecessary radiation exposure to patients. Pre-CT programming of the device to an asynchronous pacing mode would be warranted to avoid the effect of such interference on CT quality and to be able to assess LV function.
Oversensing with pacing inhibition would be limited to the duration of direct exposure of the device to radiation beams (2,3) and for the vast majority of diagnostic CT exams would not affect CT quality. Most importantly, routine diagnostic CT imaging appears to be safe and less likely to result in clinically significant events, as suggested by our findings. For patients in whom CT imaging may expose the device to direct radiation beams for longer than a few seconds, such as in patients undergoing CT-guided interventions, oversensing with pacing inhibition would carry significant risks, including a systole, which might be under-estimated by clinicians performing such interventions. Our findings from routine diagnostic CT scans cannot be extrapolated to this group of patients. Shall such procedures be clinically required in pacemaker-dependent patients; programming of the device to an asynchronous pacing mode would be needed to avoid the clinical consequences of oversensing.
Please note: Dr. Dickfeld has received consulting and grant support from Biosense Webster; and grant support from General Electric. All other authors have reported that they have no relationships relevant to the contents of the paper to disclose.
- American College of Cardiology Foundation