Cardiovascular magnetic resonance (CMR) is a new and important tool for the evaluation of patients with cardiovascular disease. Because of relative unfamiliarity, some cardiologists may not be fully conversant with safety issues associated with this technique in patients with cardiovascular implants and devices. The aim of this article is to summarise where the problems are and what solutions are available or forthcoming. In some areas, we will also dispel myths which are sometimes held in the absence of any actual evidence and present a common sense approach which has been adopted by expert centres in clinical practice using 1.5 Tesla (T) scanners.

The basic principle of MR relies upon the application of radiofrequency pulses (RF) within a strong magnetic field. Hydrogen nuclei absorb the RF, and re-emit it after a short delay as a detectable signal which can be converted into images. Because there are no x rays, there are no known genetic effects or changes in chemical binding. Thus CMR shares with ultrasound an inherent safety advantage over x ray techniques. However, unlike either ultrasound or x ray techniques, there is interaction of the magnetic field with ferromagnetic materials (potential for movement) and electronic circuits (dysfunction or damage), and the RF may produce heating under certain limited circumstances.¹ These phenomena require special attention for CMR.

GENERAL PRINCIPLES

Ferromagnetism

The prefix ferro- in ferromagnetism relates to the element Iron (Fe). Iron is, however, not the only magnetic element and four other transition …