Therapeutic irradiation over a permanent cardiac pacemaker

Radiotherapy in patients with pacemakers and implantable cardioverter defibrillators: a literature review

An increasing number of patients with implantable cardiac rhythm devices undergo radiotherapy (RT) for cancer and are thereby exposed to the risk of device failure. Current safety recommendations seem to have limitations by not accounting for the risk of pacemakers and implantable cardioverter defibrillators malfunctioning at low radiation doses. Besides scant knowledge about optimal safety measures, only little is known about the exact prevalence of patients with devices undergoing RT. In this review, we provide a short overview of the principles of RT and present the current evidence on the predictors and mechanisms of device malfunctions during RT. We also summarize practical recommendations from recent publications and from the industry. Strongly associated with beam energy of photon RT, device malfunctions occur at ∼3% of RT courses, posing a substantial issue in clinical practice. Malfunctions described in the literature typically consist of transient software disturbances and only seldom manifest as a permanent damage of the device. Through close cooperation between cardiologists and oncologists, a tailored individualized approach might be necessary in this patient group in waiting time for updated international guidelines in the field.

Radiotherapy to patients with artificial cardiac pacemakers

BACKGROUND

The in vitro studies show that the modern cardiac pacemakers utilising the complementary metal-oxide semi-conductor (CMOS) circuitry can be adversely affected by therapeutic radiation. However, the published clinical data are sparse regarding the safety of radiotherapy delivery to patients with artificial pacemakers. Despite the potential risk of life threatening complications, there are no national guidelines and most radiotherapy departments have no formal clinical risk management strategy in place. A literature review was performed to assess the risks involved in irradiating patients with pacemakers and to identify strategies, which minimise the risk of pacemaker malfunction. Recommendations for radiotherapy departments are made.

CONCLUSION

Modern multi-programmable pacemakers are very sensitive to therapeutic megavoltage irradiation. There is no safe radiation threshold for megavoltage radiation. The low energy kilovoltage X-rays used for radiotherapy simulation cause no pacemaker malfunction. Megavoltage radiation can be safely delivered to patients with cardiac pacemakers provided direct irradiation of pacemakers is avoided, adequate monitoring is done during and after irradiation, and the dose to the pacemaker generator is kept below 2 Gy. Close liaison with cardiologists and a pacemaker clinic is essential and radiotherapy departments should have protocols in place to identify and care for cancer patients with pacemakers.

Pacemaker function during irradiation: in vivo and in vitro effect

With an ageing population in Australia, one would expect the probability of treating cancer patients who have a cardiac pacemaker to increase. In this paper the effect of ionizing radiation and electromagnetic interference on pacemaker function is discussed. A case of a cancer patient, with pacemaker, treated with radiotherapy without ill effect, is described. Concurrently, four pacemakers were tested in vitro with gamma radiation from a 60 Cobalt machine and no adverse effect was found. A list of precautions is recommended.