Can a person with pacemaker, ICD or CRT have CT coronary angiography?

Can a person with pacemaker, ICD or CRT have CT coronary angiography?

This question is related to the potential problems of MRI in those with cardiac implantable electronic devices, which is well known. There are two aspects to this question. One is regarding the safety of computed tomographic (CT) angiography in those with implanted pacemakers and other cardiac implantable electronic devices. Second is regarding potential interferences in the evaluation of CT images due to the metallic structures in the implanted devices.

Pacemaker is a device used to give regular electrical pulses to the heart when heart’s on pacemaker is not functioning well or if the signals are not conducted down well to the lower chambers of the heart. Pacemaker is usually implanted under the skin of the chest and connected to the chambers of the heart using lead wires introduced through blood vessels. There is also a leadless pacemaker which can be implanted within the right lower chamber of the heart.

ICD is short form for implantable cardioverter defibrillator. It monitors heart rhythm continuously and treats them electrically when needed. If an abnormal fast rhythm from the lower chambers is detected, it will try to suppress it by giving signals at a faster rate. More dangerous rhythms are treated by a direct current internal shock delivered through specialized shocking coils implanted within the heart.

CRT is short form for cardiac resynchronization therapy. It is used in the treatment of heart failure in which medications are not fully effective. It gives timed electrical signals to the right upper chamber and both lower chambers of the heart to synchronize the contractions so that the pumping function of the heart is improved. All these devices are known collectively as cardiac implantable electronic devices (CIED).

US Food and Drugs Administration has reviewed the effects of X-ray irradiation from CT imaging on pacemakers and implantable cardioverter defibrillators in 2019. They have made some valuable conclusions on this aspect.

As per the US FDA review, the probability of CT X-rays causing clinically significant interference in CIED is extremely low. Probability of X-ray electromagnetic interference is lower when the radiation dose and the radiation dose rate are reduced. Interference can be completely avoided when the implantable device is outside of the primary X-ray beam of the CT scanner.

Now what about the artefacts caused by CIED on CT images? In a study of 15 patients undergoing CT along with positron emission tomography (PET), no artifacts from pacing leads were identified. But significant artifact was observed in half of the patient studies with ICD leads. The authors suggested software based corrections to be applied for accurate cardiac imaging in the presence of CIED.

Streak artifact arising from metal element of the device leads is an important reason for image degradation in CT imaging. Interference in the interpretation of all three major branches of the blood vessels of the heart have been reported. Special techniques using timing with ECG known as ECG gating has been used in CT machines to avoid these artifacts partly.

Single-energy metal artefact reduction (SEMAR) is another technique which has been used in volume data (3D) acquired with ECG gating. SEMAR has been shown to reduce metal artifacts from CIED and improve image quality of coronary arteries. A study published in 2020 showed the usefulness of SEMAR in 122 clinical CT studies of the heart with implanted metal.

CT coronary angiography can be done safely in persons with pacemakers, ICD and CRT as the interference in the function of these devices is extremely low, unlike in the case of magnetic resonance imaging (MRI). But there could be problems in interpretation of images, which is being taken care of by special techniques and software in CT machines. In case of MRI also, newer devices which are MRI conditional are available.