Skin Burn at the Site of Indifferent Electrode after Radiofrequency Catheter Ablation of AV Node for Atrial Fibrillation.
Credits:Subba Reddy Vanga, MBBS, Mazda Biria MD†, Loren Berenbom MD†, James Vacek MD†, Dhanunjaya R Lakkireddy, MD†
* St. Luke’s Hospital, Chesterfield, MO; †Mid America Cardiology, University of Kansas Hospital, Kansas City, KS.
Financial Source: None.
Conflict of Interests: No potential conflicts of interests for all
Lakkireddy MD,Director for Excellence in AF and EP Research,Clinical
Assistant Professor,Bloch Heart Rhythm Center,Mid America Cardiology @ University of Kansas Hospital,3901 Rainbow Blvd, Kansas City, KS 66220
doi : 10.4022/jafib.v1i1.406
Radiofrequency Ablation of AV node with permanent pacemaker has been
used to achieve rate control in persistent symptomatic atrial fibrillation.
Although RF Ablation is safe, complications may occur in up to 3% of the procedures.
A rare complication of 2nd degree skin burn at indifferent electrode
site has been described here. This report highlights the rare but possible
complication in patients undergoing such a procedure and help in preventing by
taking appropriate measures.
Radiofrequency ablation, AV Node ablation, Indifferent electrode, Skin burn.
Radiofrequency (RF) energy is a low voltage
high frequency electrical energy which produces controlled focal tissue
ablation. It has revolutionised the treatment of refractory
supraventricular tachycardias. Although radiofrequency catheter ablation (RFCA)
is a safe procedure, application of RF energy is not without complications.
Major complications may occur in up to 3% of patients undergoing RFCA which
includes AV block, Cardiac tamponade, Coronary artery spasm, thrombosis,
Pericarditis, Vascular Injury, Thromboembolism, Transient ischemic attack and
or stroke, Pulmonary hypertension secondary to pulmonary vein stenosis,
Pneumothorax, Left atrial-esophageal fistula and Phrenic nerve paralysis1.
Most of the complications of RF ablation of supraventricular arrhythmias are
limited to the site of RF energy application and skin burn at the indifferent
electrode site was described in only case secondary to maladhesion2
of the electrode pads. We present a case of skin burn at the site of
indifferent electrode after an elective RF ablation for recurrent AF.
A 54 year old white obese woman (BMI 43) with 8 year
history of symptomatic paroxysmal atrial fibrillation was referred for AV nodal
ablation and permanent pacemaker insertion. Her past medical history is significant
for hypertension and aortic valve replacement (#19 St. Jude Prosthetic valve) for
congenital bicuspid aortic valve 9 years ago. She had multiple cardioversions
and was treated with multiple antiarrhythmic drugs to achieve rhythm
restoration. But AF remained unresponsive and she was symptomatic with fatigue,
dyspnea and congestive heart failure secondary to rapid ventricular response.
She underwent radiofrequency catheter ablation and pulmonary vein isolation
without any complications. But her AF recurred and was thought to be due to
severely dilated left atrium with extensive scarring from both Aortic Valve
replacement and RF ablation.
She was recommended RF ablation of AV node with permanent pacemaker
placement. She underwent the AV Nodal ablation under sedation, using the 8.0 mm
Biosense Webster Celsius catheter (50 Watt and 50 C Temp). The bundle of His
was successfully mapped and AV node was ablated with no ventricular escape. The
total time of RF energy delivery during the ablation was about 6 minutes. No
impedance raise was noticed during the procedure. After successful ablation,
skin, under the indifferent electrode pad on the lower abdominal wall, was
noted erythematous with second degree thermal burn (Fig. 1) at the leading edge
of the pad. The adhesion between the pad and skin was checked thoroughly and
was in good contact. There was no fluid around or in between the pad and skin. The
patient did not complain any pain during the procedure. The skin lesion became
necrotic with scabbing and turned out to be a third degree burn over next few
days requiring wound care and plastic surgery consultation. The wound required
well over 3 months to heal with a scar.
Figure 1: Skin burn at the leading edge of the indifferent electrode pad over the abdominal pannus.
Radiofrequency ablation has been proved to be safe
and effective procedure in the management of tachyarrhythmias. Radiofrequency
energy is a low voltage high frequency (30 KHz to 1.5 MHz)
electrical energy. It was first tested safely in animal models to create AV
nodal block by Huang et al3. The ability of usage of catheter to
deliver the RF energy coupled with the ability to create controlled focal
tissue destruction resulted in increasing use of RF energy. Ability to use
higher levels of RF energy in non-arrhythmic conditions such as in the
management of tumours has led to identify new potential complication of the
Skin burns at the indifferent electrode have been
identified and reported in electrosurgical procedures2, 4, 5 where
the procedure typically lasts longer and requires higher energies. The
electrical current passing through the body produces heat energy and increases
the temperature of the tissues. According to Ohm’s Law, the raise of
temperature depends on the amount of electrical energy, density of the energy
per attachment area, and the resistance to the flow of energy at the attachment
The biggest raise of temperature occurs at the tip of
the catheter, where the electrical density is highest. This ability to raise
the temperature which results in local tissue destruction makes the basic
principle of ablation. Although similar amount of electrical current flows
through the indifferent electrode, which completes the circuit, the temperature
rise is much less because of the use of the dispersive pads. Dispersive pad reduces
the electrical density by their size and wider area in contact with body and
does not result in “exit wounds” as seen in electrical injuries. It was postulated
that the temperature rise to 45-47°C at the
indifferent electrode site can cause skin burn6.
The modern RF ablation catheters typically use higher
energies. Faulty indifferent pads with cracks or loose connections may cause
excess resistance in the circuit. Skin burn at indifferent electrode sites have
described in the management of solid tumor ablations which typically require
higher energies and long duration of energy application than a typical
It is also known that the characteristics of the
current flow towards a contact depend on the shape of the contact8.
The typical shape of the pad at the skin contact is acute or convex and the
current density tends to be higher at such edges or sharp angles. It probably
resulted in differential temperature raise at the pad contact site making the
edges more vulnerable to burns. This might explain the ‘leading edge phenomemon’
described by Stenkie et al7. Electrical conductive media such as
normal saline or other body fluids which contain inorganic salts, when present
at the pad site can change the path of circuit and may result in unwanted
The rise in the temperature also depends on the
ability of the human body to disperse the heat generated which in turn depends
on the amount of blood flow, amount of the subdermal fat which acts as an insulator7.
When the surrounding room temperature is very low, it can result in
vasoconstriction of cutaneous blood vessels further resulting in poor heat
dissipation. The deep sedation of the patients during the procedure may result
in ignoring the discomfort and pain caused by the raise in temperature.
We believe that, in this patient, multifactorial
causes including obesity, excessive fat at the pad attachment site, deep
sedation and environmental conditions resulted in the generation of excess heat
at the pad site resulting in thermal injury.
Although rare, risk of skin burn at indifferent
electrode site should be considered especially in obese patients undergoing RF
catheter ablation. We believe that the poor blood circulation and excess fat at
the site of pad attachment resulted in poor dissipation of heat resulting in
the thermal burn in this patient. Using larger pads with wider area of contact,
choosing a site with better cutaneous perfusion, rotation of the pads or using
multiple ground pads with sequential activation, reducing the time of RF energy
delivery, choosing less energy settings and avoiding deep sedation during the
procedure may help in reducing such a complication.
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