This article will describe the use of intracardiac echo to monitor and guide PV isolation using the circular mapping approach in a patient with permanent AF.
are from the Section of Pacing and Electrophysiology, Department
of Cardiovascular Medicine, Cleveland Clinic Foundation,
This article was previously published in the publication
(2002;70:93-96). It is reprinted with the permission of Siemens
AG (Erlangen, Germany) and the authors. ©2002 Siemens AG.
Atrial ectopic beats within the pulmonary veins (PV) have been
proven responsible for initiation of atrial fibrillation (AF).
Different approaches have been developed to electrically confine PV
triggers using longitudinal mapping, three-dimensional mapping
systems, empirical anatomical isolation of the PV ostia, and
circular mapping guided ostial isolation.
This article will describe the use of intracardiac echo to monitor
and guide PV isolation using the circular mapping approach in a
patient with permanent AF.
A 59-year-old white male with no structural heart disease and a
history of symptomatic permanent AF since 1999 failed multiple
antiarrhythmic drugs including flecainide, sotalol, amiodarone and
dofetilide, and was referred to our laboratory for mapping and
ablation of his arrhythmia.
A custom made catheter (Cardiac Assist Device Inc., Cleveland,
OH) was advanced in the coronary sinus (CS). The proximal eight
electrodes were positioned between the superior vena cava (SVC) and
the high crista terminalis whereas the distal eight electrodes were
in the CS. A transesophageal recording lead was used to record the
left atrial posterior wall activation. A 10-F phase array
intracardiac echo (ICE)-probe (AcuNav
Diagnostic Ultrasound Catheter, Acuson, a Siemens Company) was
positioned in the right atrium using fluoroscopic guidance. Mapping
of the left atrium and pulmonary veins (PV) was completed after
approaching the left atrium via a transseptal approach. Two
separate ICE-guided (Figure 1) transseptal punctures were obtained.
A 6-French multielectrode circular mapping catheter (Lasso,
Biosense-Webster, Baldwin Park, CA) with a deflectable shaft and 2
cm diameter loop was used to map ostial PV potentials.
Besides guiding the transseptal approach, the phase array ICE
probe (AcuNav catheter, Acuson) appeared useful to define the PV
ostia and to monitor energy delivery. The circular mapping catheter
was positioned at the PV ostium. Correct placement was obtained
through the ICE image (Figure 2). Radiofrequency energy was
delivered using a power controlled cooled-tip ablation catheter (50
Watt generator; EPT, Sunnyvale, CA). Energy delivery was titrated
to the maximum value within 4560 seconds. Energy delivery was
terminated after 4560 seconds. ICE was utilized to monitor bubble
Two types of bubble patterns were seen with ICE. This included
bubbles limited to the area around the ablation catheter (type 1),
reflecting appropriate lesion formation versus a shower of dense
bubbles extending to the left atrial cavity (type 2) and reflecting
tissue overheating (Figure 3). Dense generation of bubbles appeared
to precede impedance elevation by a few seconds. Intravenous
heparin was titrated to maintain the activated clotting time (ACT)
between 350 and 400 sec after the transeptal puncture.
The patient was presented to the electrophysiology laboratory in
AF with ventricular response of 98 bpm. After positioning the Lasso
catheter in the left upper PV (LUPV) and the ablation catheter in
the right upper PV (RUPV), DC cardioversion was performed. Early
recurrence of AF initiated by an atrial premature contraction from
the LUPV was documented. ICE guided isolation of the LUPV and left
lower pulmonary vein (LLPV) ostia were performed during AF. The
maximum power, temperature and impedance during energy delivery
were 40 Watts, 40°C and 173 Ohms, respectively. Type 2 bubbles
occurred 6 times during ablation. Table 1 lists energy parameters
associated with type 2 bubbles formation.
Following isolation of the left PVs, repeated DC cardioversion
was successful and the patient was maintained in sinus rhythm.
Isolation of RUPV and right lower pulmonary vein (RLPV) was then
conducted in the same manner.
Doppler flows of all four PV were recorded prior, during, and
after PV isolation. The diastolic flow velocities were 0.6 m/s in
the LUPV, 0.48 in the LLPV, 0.7 in the RUPV and 0.6 in the RLPV
before ablation, versus 0.7 m/s in the LUPV, 0.6 in the LLPV, 0.8
in the RUPV and 0.8 in the RLPV after isolation.
At six months follow-up, the patient was still in sinus rhythm
off antiarrhythmic drugs. A spiral CT scan was conducted 3 months
after ablation and excluded PV stenosis.
Intracardiac echo facilitates PV isolation by 1) rendering
transseptal access easier and safer; 2) by helping in proper
placement of the circular mapping catheter at the vein ostium; and
3) by optimizing power titration during radiofrequency energy
delivery through detection of bubbles at the catheter-tissue
interface. Prompt detection of dense bubbles (type 2 bubbles) could
also prevent impedance rise and avoid the milieu for thrombus
formation. In addition, monitoring PV flow velocity offers the
potential to prevent excessive swelling at the PV ostium, which
could lead to chronic PV stenosis. In this respect, ablation at the
PV ostium should be aborted when the PV diastolic flow velocity
exceeds 1 m/sec. *