CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 5, June 2012
AFRICA
275
Methods
This was a prospective, single-centre, single-operator study
performed at the Christiaan Barnard Memorial Hospital, Cape
Town, South Africa. The data of all consecutive symptomatic
patients with AF who underwent robotically assisted catheter
ablation therapy using the Sensei X robotic navigation system
(Hansen Medical, Mountain View, CA) from July 2009 (the time
of acquisition of the robotic system) to July 2010 were recorded
in an electronic database.
The exclusion criteria were: (1) patients with cardiac
dysrhythmia without documented AF, e.g. only atrial flutter
(AFlut) or regular supraventricular tachycardia (SVT), (2)
congestive heart failure with New York Heart Association
class IV or ejection fraction of
<
30%, (3) recent acute
coronary syndrome within two weeks, (4) impaired mental
status that may affect timely taking of anti-arrhythmia drugs, (5)
severe cerebrovascular disease, and (6) patient’s decline to sign
informed consent. Ninety-five patients were finally included.
Institutional research board approval was waived for this study.
AF types were defined based on the latest European Society
of Cardiology (ESC) guidelines
5
as follows: paroxysmal AF is
a self-terminating episode that lasts up to seven days; persistent
AF either lasts between seven days and one year, or requires
termination by cardioversion with drugs or direct current; long-
standing persistent AF lasts a year or more.
Screening (fluoroscopy) time involved the total minutes the
X-ray was applied by the operator to visualise the position of
devices or set up the system in the patient, using single-plane
pulsed fluoroscopy with a rate of seven frames per second,
i.e. the time needed to place the diagnostic catheter in the
coronary sinus, to perform a trans-septal puncture, to assist
with the initial creation of a three-dimensional (3D) map, and
occasionally thereafter to verify accuracy of 3D mapping.
Ablation (radiofrequency) time was defined as the total minutes
the operator used electrical current to ablate the rebel atrial
foci. The procedure time was defined as the time between first
venipuncture in the operating room and full recovery of the
patient from anaesthesia.
All high-risk patients (CHADS
2
score
≥
2 or patients with
impaired left ventricular function) and all patients with long-
standing persistent AF were anticoagulated on warfarin for
four weeks until five to seven days prior to the procedure.
Subcutaneous enoxaparin (1 mg/kg daily) was administered
three to four days pre-procedure. Low-risk patients (CHADS
2
score
<
2) who had persistent AF by definition but who were in
sinus rhythm prior to the procedure because of drugs or recent
direct-current cardioversion were not always anticoagulated on
warfarin. All patients were instructed not to ingest any solid
foods within six hours prior to their procedure.
Three-dimensional mapping was performed to facilitate
robotically assisted catheter ablation. In all patients, 3D
reconstruction of the corresponding atrial chamber anatomy was
performed with either the EnSite NavX system (76 patients) or
CARTO electro-anatomic mapping system (19 patients).
Procedure
All procedures were performed under general anaesthesia using
propofol and remifentanil. All patients received a bolus of
dexamethasone as part of the anesthesia to reduce the incidence
of postoperative nausea. The use of corticosteroids may also
be effective for preventing post-ablation recurrence of atrial
tachycardia.
16
A temperature probe was routinely placed into the oesophagus
for continuous intra-oesophageal monitoring during radio-
frequency (RF) ablation. A multipolar catheter was placed into
the coronary sinus via a 7F sheath in the right femoral vein.
An ablation catheter, either a 3.5-mm ThermoCool
®
catheter
(Biosense-Webster, Diamond Bar, CA, USA) or a Cool Path™
Duo RF ablation catheter (St Jude Medical, St Paul, MN, USA)
was placed into the Artisan sheath (Hansen Medical, Mountain
View, CA). The steerable sheath system (SSS) was inserted via a
14F sheath in the right femoral vein and advanced manually into
the right atrium under fluoroscopic visualisation.
Approximately 0.5 cm of the ablation catheter was exposed.
After placement of the SSS in the inferior right atrium was
confirmed, the position of the SSS was registered into the robotic
catheter remote-control system. This registration involved the
use of LAO 30 and RAO 30 fluoroscopic views of the heart
(anterior–posterior and lateral) to allow localisation of the SSS
in the 3D space.
In all patients, one trans-septal puncture was performed
under fluoroscopic guidance. In exceptional patients trans-
oesophageal echocardiographic guidance was used to facilitate
trans-septal puncture. The trans-septal puncture was performed
manually. Through this trans-septal puncture, a long sheath was
advanced into the left atrium, and a circular mapping catheter
was introduced into the left atrium. The ablation catheter was
robotically guided into the left atrium through the same trans-
septal puncture site (adjacent to the shaft of the circular mapping
catheter). This catheter was used for ablation.
Systemic anticoagulation was initiated after the first trans-
septal puncture with the use of intravenous unfractionated heparin
with a target activated clotting time (ACT) of approximately 250
s. A 15–25 variable loop Biosense LASSO circular mapping
catheter (Biosense-Webster, Diamond Bar, CA, USA) was
used for mapping the pulmonary vein (PV) antrum. With this
configuration, the final set up before initiation of ablation
included the following: a robotically controlled steerable sheath
housing the ablation catheter (this is performed by a physician at
the console) and a manually controlled circular mapping catheter
handled and moved by the same physician at the procedure
tableside.
When intra-oesophageal temperature rises were noted, power
output was reduced to 20 W. At the end of the procedure,
systemic anticoagulation was discontinued and occasionally
partially reversed with intravenous protamine before removal of
the vascular sheaths.
Ablation
Ablation along the pulmonary vein antrum, which encompasses
the posterior wall, septal aspect of the right-sided pulmonary
veins, and the ridge between the left atrial appendage and left
pulmonary veins, was performed with the Artisan robotic system
until disappearance of local PV potential, with the endpoint of
electrical isolation of all PV antra. Radiofrequency power was
set at 30 W with a maximum temperature limit of 45°C with
irrigation using a heparinised saline infusion (2 000 IU/l) at a
rate of 17 ml/min via the Cool Flow pump (Biosense-Webster,
