A satellite meeting sponsored by BIOTRONIK at the ESC Congress in 2013 on new challenges for cardiovascular implantable electronic device therapy is reported here
Rani Khatib BPharm(Hons) PGDipClinPharm IPresc DPharm PhD
Senior Cardiology Pharmacist and Lecturer,
Leeds Teaching Hospitals NHS Trust and
University of Leeds, UK
Cardiovascular implantable electronic device (CIED) therapy in the form of implanted pacemakers (PM) and/or implantable cardioverter defibrillator (ICD) systems is currently used by several million patients worldwide. Despite the great benefits of CIED therapy, it has prevented patients who have these devices from having a magnetic resonance (MR) scan when clinically needed during their lifetime. Patients with CIEDs had to settle for a CT scan instead of a MR scan. During this session, Biotronik announced the launch of a new technology (BIOTRONIK’s ProMRI® technology), which will allow patients with new types of implanted PM and ICD to safely undergo an MR scan. This will give this category of patient access to images of much higher quality and detail, as well as providing accuracy, without exposing them to the radiation used in X-ray imaging.
Potential risks
Professor Antonio Curnis (Electrophysiologist, Spedali Civili di Brescia, Italy) addressed the potential risks for CIED patients when undergoing MR scans, how they can be avoided, and how patient care can be assured after scanning. Dr Christoph Tillmanns (Cardiologist, Diagnostikum Berlin, Germany) and Dr Philippe Cart (Radiologist, Hospital Charleville-Mézières, France) elaborated on the challenges of MR scanning in conjunction with CIED therapy in daily practice, why there continues to be barriers to MR scanning for CIED patients, and which further hurdles need to be overcome.
MR scanning – challenges for CIED therapy
Professor Curnis started by introducing some facts about CIED therapy. The first PM was implanted in the 1950s. Today, 3.25 million patients have PMs and 180,000 have ICDs. It is estimated that 400,000–500,000 new implants are taking place per annum. For example, in the UK, the number of implants per million population is 200, compared with 600 in Belgium. The number of patients with CIED is rapidly increasing, with 50% of all implants since 1983 having been in last past five years.
The need for MR scans has also been on the increase. In the past ten years, there has been a 243% increase in the need for an MR scan. It is most needed in patients between 55 and 80 years of age. This same group of patients is more likely to receive a CIED. Until recently, MRI scans were contraindicated for patients with CIED therapy. It is estimated that, every three minutes in the US and every six minutes in Europe, an MR scan access is denied to patients because they have a PM or ICD.
MR scans are used in a wide range of conditions affecting various organs. In 26% of cases, the MR scan is needed to examine the spine and, in 25% of cases, to examine the brain. MR scans are becoming the gold standard in diagnostics in cardiology. Cardiovascular MR is now considered the gold standard for the assessment of regional and global systolic function, myocardial infarction and viability, and congenital heart disease.(1) The main advantages over CT scans are the absence of exposure to radiation and the quality of images produced, which enables the evaluation of soft tissue, tendon, spinal cord and brain tumours.
Despite the implementation of an exclusion zone (for example, the heart and liver), MR scanning with ProMRI® technology would enable the examination of 88.4% of common areas of the body that needs scanning, such as the head, cervical and lumbar spine and extremities. In mid-August 2013, patients implanted with the Evia single- and dual-chamber devices were given the go-ahead to undergo 100% of all required scans, including liver and heart scans.
When defining the safety of CIEDs in patients undergoing MR scanning, it is important to use the correct terminology. In its statement on the safety of MRI in patients with cardiovascular devices,(2) the joint American societies identified three categories:
(1) MR safe – no known hazards in any MRI environments, MR scan can be used whenever needed (for example, for coronary and peripheral vascular stents)
(2) MR conditional – no known hazards in a specific MRI environment with specific conditions of use. MR scan should only be used under specific conditions (for example, most CIED–MR scan-compatible devices
(3) MR unsafe – hazards in all MRI environments. MR scans should never be used (for example, abandoned endocavitary pacing lead).
Therefore, all approved MR-compatible CIEDs would be classed as MR conditional. There are currently no MR‑safe CIED systems on the market.
The main risks for patients with CIED in an MR environment are: oversensing or pacing inhibited, asynchronous pacing or arrhythmia induction, heating on the lead tip and loss of capture, and device damage or malfunctioning.
CIED devices that are considered appropriate to use during MR scanning undergo detailed investigation to understand risks and ensure safety through simulation of worst-case scenarios. The safety tests include computer modelling, bench testing, phantom testing and animal studies.
CIEDs appropriate to use during MR scans are designed with MRI requirements in mind. Examples of those considerations include:
- Minimisation of mechanical forces (vibrations)
- Non-ferromagnetic materials
- Induced current control and appropriate lead and pacemaker design to avoid:
– Threshold changes
– Uncontrolled pacing in vulnerable rhythm phases
– Uncontrolled pacing rate
- Dedicated lead coil design to decrease coupling between gradient field and lead
- MRI mode dedicated to MRI scan that permits control of behaviour of the device
Both cardiologists and radiologists should use check lists before they would deem it appropriate for a patient with a CIED to undergo an MR scan. The cardiologist check list would include items such as:
- ‘MR conditional’ system (CIED and leads)
- Device implanted > six weeks
- System implanted in pectoral region
- No other leads, device or adapter implanted and/or abandoned in the patient
- Leads electrically working (impedance between 200 and 1500 Ω)
- Capture threshold less than 2.0V at 0.4ms
- MRI mode programmed ON before scan and OFF after scan
The radiologist’s check list would include items such as:
- ‘MR Conditional’ system (pacemaker, ICD and leads)
- Closed tube MRI at 1.5 T in normal operating mode
- SAR (specific absorption rate) ≤2Wkg for the body and <3.2 for the head
- Maximum gradient slew rate ≤200T/m/s.
Post-MR scanning, the regular monitoring of the patient is important. Systems such as the BIOTRONIK Home Monitoring® programme are a further assurance for patient care post-MR scan. They ensure continuous access to important data, such as lead status with threshold trends, battery status and atrial and ventricular rhythms. If the MRI mode is not programmed back to its original setting, the user receives a notification.
While this new technology is exciting, the talk was concluded with some open issues that need to be considered in practice such as: How should we deal with patients who already have non-MR conditional devices? How do we address patients with MR conditional devices and leads, but with non-MR conditional abandoned leads? There is a clear need for a consensus document that will establish behaviour guidelines depending on clinical need (URGENCY, DIAGNOSTIC, THERAPEUTIC).
Yes, we scan!
Dr Cart started by reflecting on the benefits and risks of scanning, according to a radiologist. Patients with CIED may suffer from other conditions that require diagnostic MR scanning. This warrants a need for MR scanning-compatible devices.
Patients undergoing an MR scan are exposed to a magnetic field that is 30,000 times more powerful than the magnetic field of earth. MR machines use very high magnetic fields and can lead to:
- Pacemaker desynchronisation
- Moving of the intracardial catheter
- Device alteration
- Local heating of the device and lead.
The new MR conditional CIED devices such as ProMRI® are very exciting. The challenge, however, will be convincing the healthcare professionals and patients who for many years were informed that patients with CIEDs are not allowed to have a MR scan. Family doctors should be informed that, with the new generation of CIEDs, it is possible for patients to have access to MR scans if they have a compatible PM or ICD. Cardiologists should help support their radiology colleagues when they have a problem examining patients with MR scanning-compatible CIEDs. Radiologists should be assured that MR scans should be performed easily and rapidly on patients with CIEDs.
In France, radiologists pose the greatest challenge because:
- The number of machines is insufficient to accommodate new patients. The number of MR scanning machines per million inhabitants in France in 2010 was only 8.7 compared to the average of 17 in Europe (excluding France) in 2009
- Lack of knowledge of cardiac pathology and being too cautious to perform an examination on patients with a PM, even if the device is compatible
- They think that taking charge of these patients will decrease their work flow, financially compromising their practices.
MR scanning use has been on the increase in France, estimated at 14% per year. Several factors contributed to this phenomena, such as the increase in some pathologies (for example, Alzheimer’s, cancers and AVC (stroke)), and the increase in the ageing population (over 60 years of age: 15% every ten years). The demand for MR examinations is twice as high in patients 65+ years of age than in younger people. It is estimated that 17% of patients who received CIEDs are potential candidates for MR scanning in the first year of implantation.(3)
Data from surveys show that 43% of patients with PMs suffer from other comorbidities that may require MR scanning (for example, rheumatic disease, cerebral vascular ischaemia lesion, breast and colorectal cancer).(4) MR scanning is preferred due to better diagnostic properties, especially in nervous system pathology.
Dr Cart concluded that the arrival of MR conditional CIEDs is real progress, but extra work needs to be done to educate patients and health professionals about the safe use of these devices. This will require joint working of cardiologists and radiologists, informing radiologists that this kind of examination can be performed quickly and safely, educating patients about the safety of the new CIEDs, and increasing overall knowledge through creation of reference centres, such as Dr Tillmanns’ in Berlin.
MR scanning of CIED patients – not just for hospitals
Dr Tillmanns reviewed the figures of MR scans and CIED implantations in Germany. Of 107,142 examinations performed in a year at the Diagnostikum Berlin Centre, 26,000 were MR scans. Similar to what was highlighter earlier, there is a continual increase in both the number of pacemaker implantations and need for MR scans in hospital and non-hospital settings.
There is an increasing number of intersecting cases, where patients with pacemakers need to have MR scanning. It is estimated that 17% of patients with pacemakers will need an MR scan in the first year of implantation and 50–75% of them will need an MR scan within the operation time of a PM.(5)
Dr Tillmanns introduced a couple of cases where patients who had had CIED needed a MR scan. In one of the cases, a 76-year-old male patient with sick sinus syndrome, recurrent syncopes and a PM implanted in Nov 2011, needed an MR scan of the lumbar region, due to suspected spinal stenosis. Dr Tillmanns went through the issues that should be considered before, during and after the scan covering the issues highlighted by Professor Curnis’s ‘check lists’. The total imaging time needed was only 11 minutes to make an absolute diagnosis of spinal canal stenosis. The procedure was smooth, with no complications what so ever.
The session was concluded with an emphasis on the growing demand for MR scans in general and in CIED patients. Current practice in Germany shows that these scans should not only be reserved for hospitals, but need to be offered in outpatient settings as well, with the benefit of greater convenience for the patient. Finally, the extensive MR imaging experience is without doubt evidence that MR scans are possible for all kind of CIED patients (PM, ICD, CRT-D and CRT-P) and also easy to conduct.
References
- Cardiovascular Magnetic Resonance Imaging Cardiology Clinics. February 2007;25(1):
- Levine GN et al. Safety of magnetic resonance imaging in patients with cardiovascular devices. Circulation 2007;116;2878–91.
- Marseille, France — Lors du congrès annuel ELECTRA 2010, le Dr Olivier Piot (Centre Cardiologique du Nord, Saint-Denis).
- Survey from Medtronic on Doctissimo.fr, printemps 2010, résultats complets téléchargeables en ligne.
- Kalin R, Stanton MS. Current clinical issues for MRI scanning of pacemaker and defibrillator patients. Pace 2005;28:326–8.
