DOI:10.2214/AJR.05.1399
AJR 2007; 189:890-892
© American Roentgen Ray Society
Pacemaker Reprogramming After Radiofrequency Ablation of a Lung Neoplasm
Jay H. Donohoo1,2,
Maria T. Anderson1,3 and
William W. Mayo-Smith1
1 Department of Diagnostic Imaging, Rhode Island Hospital, 593 Eddy St.,
Providence, RI 02903.
2 Present address. Department of Radiology, Division of Abdominal Imaging and
Interventional Radiology, Massachusetts General Hospital, Boston, MA.
3 Division of Cardiology, Rhode Island Hospital, Providence, RI.
Received August 10, 2005;
revised December 7, 2005;
Address correspondence to W. W. Mayo-Smith
(wmayo-smith{at}lifespan.org).
Keywords: chest • lung • pacemaker • percutaneous ablation • radiofrequency ablation
Introduction
Percutaneous extracardiac radiofrequency ablation is a relatively new
technique of minimally invasive management of thoracic neoplasms
[1,
2]. Although implanted cardiac
pacemakers are known to be susceptible to high-frequency electromagnetic
interference from intracardiac sources
[3,
4], abdominal radiofrequency
ablation has been performed almost without complication in patients with
pacemakers [5,
6]. Tong and colleagues
[7] reported a case of
radiofrequency interference causing temporary pacemaker malfunction and
increased heart rate during right adrenal gland ablation. Radiofrequency
ablation from intracardiac and extracardiac sources is known to have effects
on pacemaker function, including reset of parameters to
manufacturer-determined alternative settings, inhibition of pacing, and
premature triggering of the battery replacement indicator (device reference
guide, InSync model 8040; Medtronic). This information is available in
industry manuals, but little has been published in the medical literature
about the effects of radiofrequency ablation on pacemakers. We present a case
of electric reset of a pacemaker during radiofrequency ablation of carcinoma
of the left upper lobe of the lung.
Case Report
A 67-year-old man with biopsy-proven squamous cell carcinoma of the lung
presented for radiofrequency ablation. The patient had severe chronic
obstructive pulmonary disease and was not a surgical candidate. Two and a half
years before the ablation procedure, a left pectoral biventricular pacemaker
(InSync model 8040, Medtronic) had been implanted because the patient had
nonischemic cardiomyopathy with severe left ventricular dysfunction and
congestive heart failure. The patient was pacemaker dependent. Before the
procedure, a cardiologist with experience in pacemaker electrophysiology
interrogated and reprogrammed the device to a pacing mode. In this mode, the
ventricle was paced at a rate of 60 beats/min without atrial or ventricular
sensing to prevent inappropriate inhibition of pacing due to sensing of
radiofrequency energy. External pacing–defibrillation pads and a cardiac
monitor were placed. A radiofrequency tissue ablation system with a cluster
electrode (Cool-tip, Valleylab) was used.
The patient underwent imaging in the supine position, and four grounding
pads were applied to the thighs. Chest radiography and CT before the procedure
showed a 2-cm mass abutting the major fissure in the posterior left upper lobe
of the lung (Fig. 1A,
1B,
1C). The patient had a chest
tube in place because of pneumothorax from a diagnostic lung biopsy performed
1 week before ablation. Two radiofrequency ablations were performed through an
anterior approach medial to the pacemaker and inferolateral to the cardiac
lead (Fig. 1C). The first
ablation, in the inferior part of the tumor, had a baseline impedance of 115
.. Ablation was performed with a current of 0.96 A and power of 102 W
for 12 minutes and reached a maximum temperature of 53°C. The second
ablation, in the superior portion of the tumor, had a baseline impedance of 81
.. This ablation was performed with 1.35 A and 142 W for 12 minutes
with a peak temperature of 70°C.
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Fig. 1A —67-year-old man with 2-cm carcinoma in left upper lobe of
lung and implanted left pectoral pacemaker. Chest radiograph before
radiofrequency tumor ablation shows proximity of tumor (arrowheads)
to pacemaker and leads.
|
|
View larger version (134K):
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Fig. 1B —67-year-old man with 2-cm carcinoma in left upper lobe of
lung and implanted left pectoral pacemaker. Helical CT scan before
radiofrequency tumor ablation shows planned trajectory of cluster electrode
(white line).
|
|
During both ablations, the pacemaker captured the left pectoralis major
muscle in synchrony with the QRS complex. In both instances, this abnormality
resolved when the ablation was completed. After the procedure, the
cardiologist interrogated the pacemaker and found that the settings had
changed from the previous configuration. The new settings included ventricular
pacing at a heart rate of 65 beats/min, ventricular sensing of electric
activity, and the potential to inhibit pacemaker function on the basis of
sensed electric activity. Interrogation also revealed that the elective
battery replacement indicator had been activated. The battery voltage measured
2.74 V before treatment and 2.72 V afterward, but both values were above the
elective battery replacement indicator level for this device. The leads were
in a bipolar configuration, which was unchanged from before the procedure.
After the procedure, the pacemaker was reprogrammed to its pretreatment
parameters, including both atrial and ventricular pacing, sensing, and
potential for inhibition of pacing in response to sensed cardiac activity. At
interrogation the next day, the battery voltage had returned to its original
level of 2.74 V, and other parameters were unchanged since the postprocedural
reprogramming. The patient's condition was asymptomatic throughout treatment,
and no complications resulted from the effects of radiofrequency on the
pacemaker. The patient was discharged from the hospital in good condition 19
days after ablation, after a persistent air leak had resolved and the chest
tube had been removed.
Discussion
The changed pacemaker parameters were consistent with electric reset of the
device, a condition that occurs when a pacemaker senses a high amount of
electric energy. Reset parameters vary by manufacturer but generally result in
high-output ventricular pacing. These parameters, however, may not prevent
inappropriate pacing inhibition by sensed electric activity. According to the
manufacturer of our patient's pacemaker (device reference guide, InSync model
8040; Medtronic), a pacemaker can sense electric activity farther than 15 cm
from its leads and is at risk of electric reset from activity within 15 cm, as
occurred in this patient. Permanent damage to the pacemaker can result with
contact between the energy source and the pacing box or leads. In our patient,
the lung lesion was 9.0 cm from the nearest pacing lead and 11.5 cm from the
pacing unit in the chest wall. The side of the insulated radiofrequency probe,
however, was only 2.4 cm from the nearest pacing wire adjacent to the superior
margin of the implanted pacer. Tong et al.
[7] recommended that the
radiofrequency electrode be kept at least 5 cm from the pacing leads.
The cause of pectoral stimulation was likely transient unipolar pacing
during radiofrequency delivery. During electric reset of a pacemaker, the
atrial and ventricular leads can become reprogrammed from bipolar to unipolar.
During unipolar pacing, the pacemaker generator itself becomes part of the
electric pacing circuit. At high pacing outputs, as during electric reset,
underlying muscle can be captured. It is interesting in this case that at
interrogation after ablation, the leads remained programmed as bipolar and
that apparent unipolar pacing occurred only during radiofrequency
delivery.
The elective replacement indicator is thought to be triggered during
electric reset when sensed electric energy prevents normal reading of battery
voltage during and immediately after radiofrequency delivery. Followup
interrogation is required to ensure normal battery function, as in this
case.
Although electric reset and other effects of radiofrequency delivery on
pacemakers are known to occur, few case reports of this phenomenon exist
outside industry literature. Because radiofrequency ablation is being
increasingly used to manage neoplasms in an older patient population, more
patients with pacemakers and defibrillators will be offered this therapy.
Awareness of the potential effects on the device is critical, both for
obtaining informed consent from patients and for preventing loss of a stable
cardiac rhythm during and after the procedure.
Radiofrequency ablation has been safely performed in the chests and
abdomens of patients with pacemakers, perhaps because of the distance between
the radiofrequency electrode and the pacing device. The importance of our case
is that radiofrequency ablation near a pacemaker can cause electric reset of
the device. Despite preablation programming to prevent it, electric reset can
result in a mode in which inappropriate pacemaker inhibition is possible. In a
pacemaker-dependent patient, bradycardia and asystole can result. Careful
planning between radiologist and cardiologist is essential to avoid adverse
outcome of thoracic radiofrequency ablation in patients with pacemakers or
implanted defibrillators, particularly if the tumor to be ablated is adjacent
to an implanted device. Close attention should be paid to changes in heart
rate and to capture of adjacent muscle, which can indicate that pacemaker
reset has occurred. Further information is needed to identify a reliably safe
distance between radiofrequency delivery and leads or a cardiac device.
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Introduction
Case Report
