Cardiovascular catheters and accessories are indicated for use in the assessment and management of critically-ill or high-risk patients including those with acute heart failure, cardiogenic shock, severe hypovolemia, complex circulatory abnormalities, acute respiratory distress syndrome, pulmonary hypertension, certain types of arrhythmias and other various medical emergencies. In these cases, cardiovascular catheters are used to measure intravascular pressures, intracardiac pressures, cardiac output, and oxyhemoglobin saturation. Secondary indications include venous blood sampling and therapeutic infusion of solutions or medications. In addition, some cardiovascular catheters are designed for temporary cardiac pacing and intra-atrial or intraventricular electrocardiographic monitoring.

Because patients with cardiovascular catheters and associated accessories may require evaluation using MR procedures or these devices may be considered for use during MR-guided procedures, it is imperative that a thorough ex vivo assessment of MR-safety be conducted for these devices to ascertain the potential risks of their use in the MR environment. For example, MR imaging, angiography, and spectroscopy procedures may play an important role in the diagnostic evaluation of these patients. Furthermore, the performance of certain MR-guided interventional procedures may require the utilization of cardiovascular catheters and accessories to monitor patients during biopsies, interventions, or treatments.

There is at least one report of a cardiovascular catheter (Swan-Ganz Triple Lumen Thermodilution Catheter) that "melted" in a patient undergoing MR imaging. This catheter contained a wire made from a conductive material that was considered to be responsible for this problem. Thus, there are realistic concerns pertaining to the use of similar devices in patients undergoing MR examinations. Therefore, an investigation was performed using ex vivo testing techniques to evaluate various cardiovascular catheters and accessories with regard to magnetic field interactions, heating, and artifacts associated with MR imaging.

A total of fifteen different cardiovascular catheters and accessories (Abbott Laboratories, Morgan Hill, CA) were selected for evaluation because they represent a wide-variety of the styles and types of devices that are commonly-used in the critical care setting (i.e., the basic structures of these devices are comparable to those made by other manufacturers). Of these devices, the 3-Lumen CVP Catheter, CVP-PVC Catheter (used for central venous pressure monitoring, administration of fluids, and venous blood sampling; polyurethane and polyvinyl chloride, respectively), Thermoset-Iced, and Thermoset-Room (used as accessories for determination of cardiac output using the thermodilution method; plastic), and Safe-set with In-Line Reservoir (used for in-line blood sampling; plastic) were determined to have no metallic components (Personal communications, Ann McGibbon, Abbott Laboratories, 1997). Thus, these devices were deemed safe for patients undergoing MR procedures and were not included in the overall ex vivo tests for MR safety. The remaining ten devices were evaluated for the presence of potential problems in the MR environment.

Excessive heating of implants or devices made from conductive materials has been reported to be a hazard for patients who undergo MR procedures. This is particularly a problem for a device that is a certain length or in the form of a loop or coil because, under certain conditions, current can be induced during operation of the MR system, to the extent that a first, second or third-degree burn can be produced.

Additional physical factors responsible for this hazard have not been identified or well-characterized (i.e., the imaging parameters, specific gradient field effects, size of the loop associated with excessive heating, etc.). For this reason, the afore-mentioned study examining cardiovascular catheters and accessories did not attempt to investigate the effect of various "coiled" catheter shapes on the development of substantial heating during an MR procedure, especially since there are many factors in addition to the shape or configuration of the catheter with a conductive component that can also influence the amount of heating that occurs during an MR procedure.

The thermodilution Swan-Ganz catheter and other similar cardiovascular catheters have nonferromagnetic materials that include conductive wires. A report indicated that a portion of a Swan-Ganz thermodilution catheter that was outside the patient melted during MR imaging. It was postulated that the high-frequency electromagnetic fields generated by the MR system caused excessive heating of either the wires within the thermodilution catheter or the radiopaque material used in the construction of the catheter.

This incident suggests that patients with this catheter or similar device that has conductive wires or other component parts, could be potentially injured during an MR procedure. Furthermore, heating of the wire or lead of a temporary pacemaker (e.g., the RV Pacing Lead) is of at least a theoretical concern for any similar wire in the bore of an MR system. Cardiac pacemaker leads are typically intravascular for most of their length and heat transfer and dissipation from the leads into the blood may prevent dangerous levels of lead heating to be reached or maintained for the intravascular segments of pacemaker leads. However, this remains to be evaluated.

For certain segments of these leads, it is at least theoretically possible that sufficient power deposition or heating may be induced within these leads (i.e., those unconnected to a pulse generator) to result in local tissue injury or burn during an MR procedure. An ex vivo study conducted by Achenbach et al. substantiates this contention, whereby temperature increases of up to 63.1 degrees C were recorded at the tips of pacemaker electrodes during MR imaging performed in phantoms. An investigation by Shellock et al. (2005) further substantiates that excessive temperatures occur for unconnected cardiac pacing leads at 1.5-Tesla.

A case report by Masaki et al. described an iatrogenic second-degree burn caused by a catheter (percutaneous transluminal coronary angioplasty or PTCA) encased by tubular, braided stainless steel. The presence of this PTCA catheter caused a superficial burn of the abdomen during an MRI procedure performed at 1.5-Tesla and further illustrates the potential risks associated with MRI examinations and cardiovascular catheters that are made from conducting, metallic materials.

Because of possible deleterious and unpredictable effects, patients referred for MR procedures with cardiovascular catheters and accessories that have internally or externally-positioned conductive wires or similar components should not undergo MR procedures because of the possible associated risks, unless MR-safety testing information demonstrates otherwise. Further support of this recommendation is based on the fact that inappropriate use of monitoring devices during MR procedures is often the cause of patient injuries. For example, burns have resulted in the MR environment in association with the use of devices that utilize conductive wires.

MR healthcare professionals are advised to contact the respective manufacturer in order to obtain the latest safety information to ensure patient safety relative to the use of an MR procedure.

REFERENCES

Achenbach S, Moshage W, Diem B, Bieberle T, Schibgilla V, Bachmann K. Effects of magnetic resonance imaging on cardiac pacemakers and electrodes. Am Heart J 1997;134:467-473.

Dempsey MF, Condon B, Hadley DM. Investigation of the factors responsible for burns during MRI. J Magn Reson Imag 2001;13:627-631.

ECRI, Health devices alert. A new MRI complication? May 27, 1988.

Masaki F, Shuhei Y, Riko K, Yohjiro M. Iatrogenic second-degree burn caused by a catheter encased tubular braid of stainless steel during MRI. Burns. 2007;33:1077-9.

Ratnayaka K, et al. Real-time MRI-guided right heart catheterization in adults using passive catheters. Eur Heart J. 2013;34:380-9.

Shellock FG, Crues JV, Editors. MRI Bioeffects, Safety, and Patient Management. Biomedical Research Publishing Group, Los Angeles, CA, 2014.

Shellock FG, Kanal E. Magnetic Resonance: Bioeffects, Safety, and Patient Management. Second Edition, Lippincott-Raven Press, New York, 1996.

Shellock FG, Shellock VJ. Cardiovascular catheters and accessories: Ex vivo testing of ferromagnetism, heating, and artifacts associated with MRI. J Magn Reson Imag 1998;8:1338-1342.

Shellock FG, Valencerina S, Fischer L. MRI-related heating of pacemaker at 1.5- and 3-Tesla: Evaluation with and without pulse generator attached to leads. Circulation 2005;112;Supplement II:561.