Download Ventricular Tachycardia Originating from the Right Ventricular

ECG & EP Cases
Ventricular Tachycardia
Originating from the Right
Ventricular Outflow Tract
Terminated by Steam Pop
Ki-Hun Kim, MD
Cardiology Division, Department of Internal Medicine, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea
Abstract
Steam pops occur when tissue temperature exceeds 100°C. This can lead to tissue disruption and
sometimes subsequent cardiac tamponade, especially in thin-walled structures such as the right
ventricular outflow tract (RVOT). This event is potentially disastrous; however, in our case,
ventricular tachycardia originating from the RVOT was successfully terminated by a steam pop,
although it required pericardiocentesis and drainage.
Key words: ■ catheter ablation ■ complication ■ ventricular tachycardia
Introduction
gency department with a 1-week history of waxing and waning palpitations that worsened and
Steam pops are infrequent in radiofrequency
persisted on the day of admission, with associat-
(RF) ablation for ventricular tachycardia (VT);
ed dizziness and chest discomfort. Hypertension
although they have been reported to occur in
had been diagnosed 2 years earlier and was con-
only 1~1.5% of all RF ablations, they can cause
trolled by an angiotensin receptor blocker. Her
cardiac tamponade, especially in the right ven-
family and social history were unremarkable. Her
tricular outflow tract (RVOT).1-3
initial blood pressure (BP) was 130/98 mmHg,
with a pulse rate of 170 beats/min and a respiration rate of 22 breaths/min. Her electrocardio-
Case Report
gram showed a wide QRS tachycardia with left
bundle branch block morphology, inferior axis,
A 57-year-old woman presented to our emer-
QRS width ›140 ms, aVL size slightly greater
than aVR, and a small r wave of ›0.2 mV in the
V2 lead, which suggested that the tachycardia
Received: July 19, 2013
Accepted: September 28, 2013
Correspondence: Ki-Hun Kim, MD, Division of Cardiology, Department
of Internal Medicine, Inje University College of Medicine, Busan, Korea
Tel: 82-51-797-3010, Fax: 82-51-797-3009
E-mail: [email protected]
28
The Official Journal of Korean Heart Rhythm Society
originated from the left superior free wall of the
RVOT (Figure 1). Rapid administration of intravenous adenosine and slowly repeated infusions
of diltiazem and verapamil had no effect. After
ECG & EP Cases
Figure 1. Initial electrocardiogram of the ventricular tachycardia originating from the right ventricular outflow tract
A
B
Figure 2. A, Catheter tip position on the ablation success point, targeting the ventricular tachycardia originating from the right ventricular outflow tract. Right anterior oblique view (30°). B, 3D electroanatomic mapping shows that the focus of ventricular tachycardia
originated from the right ventricular outflow tract.
sedation, biphasic direct cardioversion (50 J) was
cardia stopped during that infusion. Labora-
performed twice; however, the tachycardia con-
tory test results were within normal limits, and
tinued, and her BP dropped to 70/56 mmHg. A
a transthoracic echocardiogram showed normal
flecainide infusion was started, and the tachy-
left ventricular ejection fraction (64%) and mild
Vol.14 No.3
29
ECG & EP Cases
Figure 3. Electrogram when the ventricular tachycardia originating from the right ventricular outflow tract was terminated. Presystolic potential
at the ablation catheter (ABLd) was earlier than the surface QRS onset at lead V2 by approximately 22 ms.
Figure 4. Electrogram when the steam pop developed
30
The Official Journal of Korean Heart Rhythm Society
ECG & EP Cases
Figure 5. Final electrogram after the steam pop showing sinus rhythm
mitral regurgitation (grade I). The next day, an elec-
onset at lead V2 by approximately 22 ms, and the 3D
trophysiology study was performed. With the patient
mapping point was compatible with the point. Dur-
fasting and unsedated, a 6 Fr quadripolar catheter
ing RF ablation at the point on the VT state, VT was
was placed in the right ventricular (RV) apex and
successfully terminated (Figures 2 and 3). However,
a 7 Fr deflectable non-irrigation catheter (CelsiusTM,
some VPCs and non-sustained VTs remained after
Biosense Webster, Diamond Bar, CA, USA) via an
several additional ablations, which might have been
SR-0 sheath (St. Jude Medical, St. Paul, MN, USA)
associated with improper power delivery because of
was placed in the RVOT via the right femoral vein.
impedances and temperature limitations. Therefore,
After performing an angiogram of the RVOT area, 3D
we changed the ablation catheter to a 7 Fr unidirec-
electroanatomic mapping (Ensite , St. Jude Medical)
tional irrigated form (CelsiusTM Thermocool®, Biosense
was performed. The baseline rhythm was sinus with
Webster) for increased power delivery. RF ablation
occasional ventricular premature contractions (VPC),
(45 W, with the maximum catheter tip tempera-
whose morphology was compatible with the clinical
ture set to 50°C) was repeated at the same ablated
VT. VT originating from the RVOT (cycle length 400
site. Catheter irrigation was started automatically at
ms) was repeatedly induced by the RV burst pacing.
a flow rate of 30 mL/min at the start of the abla-
The earliest ventricular potential was recorded at the
tion. During ablation, a sudden audible steam pop
left-superior area between the free wall and septum
developed (Figure 4). Energy delivery was immedi-
of the RVOT, and pace-mapping showed an identi-
ately stopped after the pop occurred. However, the
cal VT morphology. The presystolic potential at the
patient’s BP suddenly dropped and she became stu-
ablation catheter was earlier than the surface QRS
porous. After confirmation of cardiac tamponade by
TM
Vol.14 No.3
31
ECG & EP Cases
portable transthoracic echocardiography, peri-
gested that pops occurred when power exceeded
cardiocentesis with drainage was performed. Af-
48 W, and pop formation was limited when pow-
ter drainage, the patient’s BP improved to 100/70
er remained under 42 W.7 However, Seiler et al.
mmHg. Fortunately, after this event, no more
showed no significant difference between power
VPCs or VTs were observed for ›30 min (Figure
settings for lesions with and without pops, and
5). We finished the procedure, keeping the peri-
found that limiting RF power to achieve an im-
cardial drainage in place. After 3 days of sup-
pedance decrease of ‹18 Ω is a feasible method
portive care, she was discharged. There were no
of reducing steam pops.1 Nonetheless, higher
further events over the 2-year follow-up period.
maximum energies and larger impedance falls
are associated with steam pops.4 Koruth et al.
Discussion
RF ablation causes lesion development by inducing cell death when tissue temperature exceeds 50°C; however, it can also cause steam
pops when the tissue temperature is ›100°C,
sometimes far exceeding the catheter tip temperature.1,3 When steam explosions occur, which
maybe audible as steam pops, they can cause
cardiac perforation. This dangerous situation
occurs more commonly in the RV than in the
left ventricle because of the thin-walled structure of the RV.2,4 Externally irrigated RF ablation
can cool the catheter-tissue interface, making
it possible to increase power delivery and reduce
coagulum formation. However, irrigated RF also
causes an imbalance between tissue and catheter
demonstrated that steam pops can be predicted
by the rate of temperature rise and the maximum
volumetric temperature measured by microwave
radiometry during irrigated RF ablation.3 Increasing contact force also was proportionally
associated with more steam pops.8 In our case,
the relatively high power (45 W) and technically
increasing contact force may have been related
causes of the steam pops, but we could not check
the spike in impedance because of the unstable
situation. Whether the VT focus was abolished
by elevated RF power delivery or the steam pop, the interpretation was tangled. Anyway careful
handling of the ablation catheter and monitoring of impedance and catheter tip temperature,
and possibly a low power setting, is required to
prevent steam pops.
tip temperatures during ablation, causing difficulty in predicting steam pops.3 Cooper et al.
found a relationship between pops and electrode
temperature during atrial ablation and recommended maintaining a catheter tip temperature
‹40°C to prevent steam pops.5 However, steam
pops were observed when the mean catheter tip
temperature was 39°C with open irrigation and
even occurred with catheter tip temperatures as
low as 34°C.1 Yokoyama et al. demonstrated that
steam pops occurred more frequently as power
was increased from 30 to 50 W.6 Hsu et al. sug32
The Official Journal of Korean Heart Rhythm Society
References
1. Seiler J, Roberts-Thomson KC, Raymond JM, Vest J, Delacretaz
E, Stevenson WG. Steam pops during irrigated radiofrequency
ablation: feasibility of impedance monitoring for prevention. Heart
Rhythm. 2008;5:1411-1416.
2. Tokuda M, Kojodjojo P, Epstein LM, Koplan BA, Michaud GF, Tedrow
UB, Stevenson WG, John RM. Outcomes of cardiac perforation
complicating catheter ablation of ventricular arrhythmias.
Circ Arrhythm Electrophysiol. 2011;4:660-666.
3. Koruth JS, Dukkipati S, Gangireddy S, McCarthy J, Spencer D,
Weinberg AD, Miller MA, D'Avila A, Reddy VY. Occurrence of
ECG & EP Cases
Steam Pops During Irrigated RF Ablation: Novel Insights from
Microwave Radiometry. J Cardiovasc Electrophysiol. 2013 [Epub
ahead of print].
4. Tokuda M, Tedrow UB, Stevenson WG. Silent steam pop detected by
intracardiac echocardiography. Heart Rhythm. 2012 [Epub ahead of
print].
5. Cooper JM, Sapp JL, Tedrow U, Pellegrini CP, Robinson D, Epstein
LM, Stevenson WG. Ablation with an internally irrigated
radiofrequency catheter: learning how to avoid steam pops.
Heart Rhythm. 2004;1:329-333.
6. Yokoyama K, Nakagawa H, Wittkampf FH, Pitha JV, Lazzara R,
Jackman WM. Comparison of electrode cooling between internal
and open irrigation in radiofrequency ablation lesion depth and
incidence of thrombus and steam pop. Circulation. 2006;113:11-19.
7. Hsu LF, Jais P, Hocini M, Sanders P, Scavee C, Sacher F, Takahashi Y,
Rotter M, Pasquie JL, Clementy J, Haissaguerre M. Incidence and
prevention of cardiac tamponade complicating ablation for atrial
fibrillation. Pacing Clin Electrophysiol. 2005;28 Suppl 1:S106-109.
8. Yokoyama K, Nakagawa H, Shah DC, Lambert H, Leo G, Aeby N,
Ikeda A, Pitha JV, Sharma T, Lazzara R, Jackman WM. Novel contact
force sensor incorporated in irrigated radiofrequency ablation
catheter predicts lesion size and incidence of steam pop and
thrombus. Circ Arrhythm Electrophysiol. 2008;1:354-362.
Vol.14 No.3
33