Credits:Dr Jiun Tuan, MBChB, MRCP; Dr Mohamed Jeilan, MBChB, MRCP; Dr Faizel Osman, MBChB, MD, MRCP; Dr Suman Kundu, MBChB, MRCP; Dr Rajkumar Mantravadi, MBBS, PhD MRCP; Dr Peter J Stafford*, MBChB, MD, FRCP; Dr G André Ng, MBChB, PhD, FRCP(Glasg), FRCP(London)
Cardiology group, Department of Cardiovascular Sciences, University of Leicester, Glenfield Hospital, Leicester, United Kingdom LE3 9QP, *Department of Cardiology, Glenfield Hospital, Leicester, United Kingdom LE3 9QP
Short title : High Density Mesh Ablation Catheter
Address for correspondence: Dr G André Ng, Department of Cardiovascular Sciences, Glenfield Hospital, Leicester, United Kingdom, LE3 9QP.
Background We evaluated the use of a novel High Density Mesh Ablator (HDMA) catheter in combination with
three-dimensional navigation for the treatment of paroxysmal atrial fibrillation.
The HDMA catheter was used to carry out pulmonary vein isolation in a consecutive series of
patients. Three-dimensional geometry of the left atrial-pulmonary vein (LA-PV)
junctions were first created with the HDMA catheter. Ostial, proximal and
distal sites within the pulmonary veins were tagged with catheter shadows on
the created geometry to allow for re-interrogation of these exact sites after
The HDMA catheter was successfully used to create three dimensional geometry of the LA-PV
junction in a total of 20 pulmonary veins which involved 5 patients. In all
cases, ostial ablation alone was sufficient to achieve electrical isolation. No
significant pulmonary vein stenosis was seen acutely after ablation.
We describe the successful use of the novel HDMA catheter to create three-dimensional geometry
of the LA-PV junction to assist with pulmonary vein isolation.
Keywords : Atrial Fibrillation, pulmonary vein isolation, ablation
Since it was first
described by Haissaguerre and colleagues, [1, 2]
catheter ablation of atrial fibrillation (AF) has become an important treatment
option in the management of this common arrhythmia. The very first ablation
procedures  described made
use of conventional catheters with radiofrequency (RF) energy to deliver
lesions point-by-point at sites at the left atrial-pulmonary vein (LA-PV)
junction, aiming to isolate atrio-venous and veno-atrial conduction i.e.
pulmonary vein isolation.
Attempts to improve
endocardial ablation efficacy have resulted in modifications to RF energy
delivery with the use of irrigated catheter tips [3, 4]
and also application of pulsed RF energy . Alternative energy
sources that have been explored include cryothermy , microwave , laser and ultrasound  .
To simplify and
improve the efficacy of pulmonary vein isolation, several studies have
evaluated different energy sources with novel catheter designs. Natale et al
reported on the successful use of a through-the-balloon delivery of ultrasound
energy for isolation of pulmonary veins . Results of ablation
using a high intensity focused ultrasound balloon catheter have also been
recently reported . Endoscopic
visualization to assist laser energy delivery through a balloon catheter is
another technology that is currently being evaluated [12, 13].
expandable multi-electrode HDMA catheter (High Density Mesh Ablator Catheter,
Bard Electrophysiology, Lowell, MA, USA) was introduced as a one catheter
solution to both mapping and ablation of the LA-PV junction with the use of
pulsed RF energy. While it is possible to use the HDMA catheter with
fluoroscopic guidance only, the addition of three-dimensional (3-D) navigation
and mapping can provide further anatomical information to help guide catheter
positioning and ensure delivery of ablation to optimal sites. We hereby describe
our technique of using this new ablation catheter in combination with a 3-D
navigation and mapping system, with the aim of assessing the technical aspects
of using this catheter in this context, and at the same time evaluating acute
results achieved with it.
The HDMA catheter
was used in a consecutive series of patients who had been referred for catheter
ablation of paroxysmal AF. All anti-arrhythmic therapies were discontinued for
more than 5 half-lives prior to the procedure.
The HDMA catheter
utilizes an expandable high density array of wires arranged in 2 helices to
form a mesh geometry, carrying a total of 36 electrodes. It is designed to
provide high density mapping of the LA-PV junction by being able to conform to
different shapes to suit any variation in anatomy. In its low profile
configuration, it is able to enter and interrogate within the pulmonary vein
itself. In its fully deployed and expanded profile, it adopts a circular, disc
shape (30 mm diameter) to fit securely around the pulmonary vein ostium or
antral region (Figure 1). It is non-steerable, and is capable
of simultaneous delivery of pulsed RF energy at 5ms cycles alternating between
its even and odd electrodes to achieve circumferential pulmonary vein ablation.
The array of wires is divided into 4 quadrants with a thermocouple at each quadrant
to allow for energy delivery under temperature control.
Figure 1: Fluoroscopic image
of the HDMA catheter deployed at the left upper pulmonary vein (left anterior
oblique view) via a steerable transseptal sheath. A steerable decapolar
catheter has been advanced into the left atrium and a quadripolar catheter is
in the coronary sinus. A photograph of the catheter in its low (A) and expanded
(B) profile is shown in the inset.
were carried out with the use of local anaesthesia under conscious sedation.
Bilateral femoral venous access was used in all cases. Under fluoroscopic
guidance, a steerable decapolar catheter and quadripolar catheter were
positioned in the coronary sinus and His position respectively. After baseline
electrophysiology study, a single transseptal puncture was carried out
using a steerable 9F transseptal sheath (Channel sheath, Bard
Electrophysiology, Lowell, MA, USA) to gain access to the left atrium.
Following pulmonary vein angiography, the HDMA catheter was advanced into the
left atrium via the transseptal sheath. 3-D geometry of the pulmonary veins and
the left atrium were created using the Ensite NavX system version 7.0 (St. Jude
Medical Inc, St. Paul, Minnesota USA) by moving the HDMA catheter, focusing on
the pulmonary vein antral and ostial regions. The HDMA catheter was
semi-deployed to enter the pulmonary veins with gradual deployment allowing
contact with the pulmonary vein wall on pull-back whilst the ostial / antral /
atrial geometry was created with the catheter fully deployed as a circular
disc. Due care was taken to ensure that the
HDMA catheter was lined up with the long axis of the pulmonary vein to
facilitate ease of deployment. This was done by first keeping the HDMA catheter
in the transseptal sheath, before cannulating the pulmonary vein with the
steerable sheath. The HDMA catheter was then advanced to the tip of the sheath,
and gradual withdrawal of the sheath was then carried out to expose the HDMA
catheter in the vein, which then allowed for pull-back and formation of its
circular disc-shaped configuration. As the main areas of interest
were around the LA-PV junctions, only limited left atrial wall geometry was
created (Figure 2). A unipolar catheter that was actively
fixed in the right atrium was used as reference for the geometry. Electrical
signals were then recorded from proximal and distal sites within each pulmonary
vein as well as at the pulmonary vein ostia using the HDMA catheter, during
atrial pacing from the distal coronary sinus electrodes. Each of these sites
were tagged by application of a catheter shadow on the 3-D geometry (Figure 3). Once the HDMA catheter was deployed at the LA-PV
junction, RF energy was applied using a pulsed RF generator (Tempulse
pulsed RF controller, Bard Electrophysiology, Lowell, MA, USA). Each application of energy continued for a total duration of 300 seconds whenever
possible, aiming for a maximum target temperature of 58°C, with up to 100 W
power output. Satisfactory contact with tissue was maintained by gentle
pressure on the catheter or sheath. After ablation, mapping was carried
out at each pulmonary vein at previously tagged ostial, proximal and distal
sites as guided by the stored catheter shadows on the 3-D geometry to confirm
pulmonary vein isolation. The endpoint of ablation for each vein was
elimination of all sharp signals (either in the pulmonary veins or at the
ostia) suggestive of atrio-venous connection as mapped by the HDMA catheter.
Electrical isolation was considered to have been achieved if there was
evidence of entrance block or if dissociated pulmonary vein firing was seen . Before ablation of
the right sided pulmonary veins, pacing from the electrodes on the HDMA
catheter was carried out to exclude any diaphragmatic stimulation. If this was evident, the HDMA catheter is rotated and
re-orientated into a new position while ensuring adequate endocardial contact
and repeat stimulation carried out. This manoeuvre is repeated until diaphragmatic
stimulation was no longer possible. In our experience this is usually adequate
to prevent phrenic nerve injury, which was not seen in any of the patients
presented here. Pacing manoeuvres [14, 15] (using a steerable decapolar catheter in the left atrium) were also
used to differentiate far-field atrial signals from local conduction when
checking for pulmonary vein isolation. This was achieved by replacing the
decapolar catheter with the quadripolar His catheter in the coronary sinus,
followed by advancement of the decapolar catheter into the left atrium through
the existing trannsseptal access. Once all pulmonary veins had been
isolated, repeat pulmonary vein angiography in the same views was performed to
assess for pulmonary vein stenosis. Heparin was administered throughout the
procedure to maintain an activated clotting time of around 300s. All
electrograms were recorded on an electrophysiology review and recording
workstation (Labsystem pro, Bard Electrophysiology, Lowell, MA, USA).
Figure 2: High density 3-D geometry of the LA-PV junctions (with limited LA geometry) created with the HDMA catheter using Ensite NavX. The left atrial appendage is labelled LAA and the pulmonary veins are shown as grids. HDMA catheter shadows in the left upper pulmonary vein (LUPV) and its ostium indicate sites mapped by the catheter.
Figure 3: HDMA catheter
shadows marking ostial, proximal and distal left upper pulmonary vein (top) and
demonstration of lesions delivered by the HDMA catheter (bottom)
variables are expressed as mean ± standard deviation. Normally distributed
paired data were analysed using paired Student’s t-test. Full consent for the
procedure was obtained in all patients.
A total of 20
pulmonary veins in 5 patients were ablated with the HDMA catheter (Table 1). High density mapping and 3-D pulmonary vein and
limited left atrial geometry creation with the HDMA catheter were successfully
carried out in every patient. No pulmonary venous anomaly or common ostia were
noted in any of the patients. All patients had a history of paroxysmal AF and
mean left atrial dimensions on echocardiography was 40 ± 5 mm, measured in the
parasternal long axis view; all patients were in sinus rhythm at the start of
the procedure. One patient developed sustained AF during catheter manipulation
in the atrium but this reverted to sinus rhythm during circumferential
pulmonary vein ablation. All 20 pulmonary veins were successfully
isolated. The number of energy applications per patient was 13.6 ± 4.2 and
duration of total energy delivered was 3093 ± 622 s. Number of energy
applications per vein was 3.4 ± 1.05 and duration of energy application per
vein was 773 ± 156 s. Two patients developed transient bradycardia and lowering
of blood pressure consistent with a significant vagal response during ablation
of the left upper pulmonary veins but this resolved without the need for specific
intervention. Mean fluoroscopy time was 68 ± 97 minutes and procedure duration
was 286 ± 30 minutes. Pulmonary vein ostial dimensions before and after
ablation showed no statistical difference when comparing measurements obtained
from fluoroscopy (Table 2).
Table 1: Procedural details of each patient
Table 2: Comparison of pulmonary vein ostial dimensions on fluoroscopy pre- and post-ablation with the HDMA catheter (all measurements are in mm)
*P = 0.17, †P = 0.18, ‡P = 0.11, §P = 0.13
LUPV = Left upper pulmonary vein, LLPV = Left lower pulmonary vein, RUPV = Right upper pulmonary vein, RLPV = Right lower pulmonary vein
In all cases,
pulmonary vein signals which were mapped and tagged at proximal and distal
portions of each pulmonary vein, were completely abolished after delivery of
pulsed RF energy with the HDMA catheter at the pulmonary ostia alone. Examples
of intracardiac signals before and after pulmonary vein isolation are shown in
Figure 4. Apart from minor groin haematoma in 1
patient, no other significant procedure-related complications were encountered acutely
in patients reported in this study.
Figure 4: Left lower pulmonary vein ostium (a), proximal vein (b), and distal vein (c) signals mapped from odd-numbered electrode pairs of the HDMA catheter before (left panel) and after (right panel) ablation, during distal coronary sinus pacing. The remaining electrical signals seen at the ostium after ablation were found to be from far-field sites by using pacing manoeuvres. Corresponding locations on the 3-D geometry are shown in the bottom panel.
At the time of
writing, 4 out of the 5 patients reported in this series had reported
significant symptomatic improvement and were free of AF as assessed by routine
24 hour Holter monitoring more than 3 months after the ablation (3 off
anti-arrhythmic medication). One patient had documented recurrence of
symptomatic, paroxysmal AF at 3 months post-procedure. No long term
procedure-related complications were encountered. Mean duration of follow-up
for all patients was 112 ± 19 days.
We have hereby
described our technique of using the novel High Density Mesh Ablator catheter
in conjunction with 3-D navigation and mapping using the Ensite NavX system. While
the catheter has been developed with the intention for it to be used as a
single mapping and ablation catheter for pulmonary vein isolation without
employing 3-D mapping assistance, the HDMA catheter is still a relatively new
product and published experience of its use in humans is limited. In our group
of patients, we successfully used the HDMA catheter to create high density 3-D
geometries of the pulmonary veins and the ostial / antral regions to help guide
catheter manipulation and also to re-check specific sites in and around the
pulmonary veins when assessing for electrical isolation. Although not
encountered in our series, 3-D navigation will be especially useful in the
delineation of any anomalous venous anatomy or common ostia which may limit the
ability of the catheter to deliver effective lesions at desired sites. This is
particularly relevant as the shape of the expanded HDMA catheter is designed to
fit normal pulmonary venous ostia and could have difficulty conforming to
anatomical variation. Having a 3-D geometry will help guide positioning of the
HDMA catheter. In all cases, ablation was
limited to only to the LA- PV junction as non-pulmonary vein triggers of AF
were not encountered in any of the patients. While the HDMA catheter is capable
of ablation around pulmonary vein ostial and antral regions, we expect that ablation
of non-pulmonary vein foci remote from the LA-PV junction will require the use
of standard ablation catheters. These, however, have previously been shown to
occur less frequently than pulmonary vein triggers. 
above, the HDMA catheter uses pulsed RF energy for lesion creation. Pulsed RF
energy delivery for endocardial ablation has previously been found to be
superior when compared to conventional RF that is delivered continuously. By
carrying out both in vivo and in vitro experiments on pig hearts, Erdogan et al found that pulsed RF
energy delivery resulted in deeper and more homogenous lesions than continuous
RF. Erdogan et al  also compared the
use of continuous and pulsed RF energy to isolate pulmonary veins in pig
hearts, and found that pulsed RF produced greater lesion depth and volume at
circumferential ostial ablation sites. In another study, both irrigated and
pulsed RF energy were found to create deeper lesions compared to conventional
RF, with irrigated RF achieving the greatest lesion depth .
The risk of
pulmonary vein stenosis is reduced by ablating at the ostium or antral region
rather than within the vein [18, 19]. The further the ablation catheter is placed from the pulmonary
vein, the lower the risk of pulmonary vein stenosis. The HDMA catheter was
designed with this in mind and its configuration in the expanded profile
prevents the catheter from entering the vein, and ensures that all ablation is
delivered from the atrial aspect of the ostium. However, a potential problem
with circumferential pulmonary ostial ablation is the persistence of LA-PV
conduction. This would not be detectable by mapping the ostium alone and
further interrogation within the pulmonary vein itself is desirable and often
necessary. In our study the use of 3-D navigation and geometry tagging to mark
proximal and distal pulmonary vein and ostial sites allowed these exact
locations to be accurately re-visited and assessed post-ablation to ensure
complete isolation. Our experience so far, using the above technique, indicates
that ostial ablation alone with the HDMA catheter to eliminate ostial
potentials can lead to successful isolation of the pulmonary veins, without
causing any significant pulmonary venous stenosis. This is in agreement with a
feasibility study of a similar HDMA catheter carried out on canine hearts . where it was used
to successfully isolate the right superior pulmonary vein, without causing any
significant pulmonary venous stenosis on both post-ablation and also on follow-up
pulmonary vein angiography.
This report consists of a small number of patients with short term
follow-up. However, we would like to stress that the intention of this paper is
to document the feasibility of combining the HDMA catheter with 3-D navigation
and mapping, and to highlight the possible advantages of such an approach. As this is a description of our early experience using the HDMA
catheter, a considerable amount of time was spent on setting up equipment,
manipulating the catheter, and also checking for pulmonary vein isolation. This
will account for the fluoroscopy time and also overall procedure time reported
in this study. With more operator experience and familiarity, it is anticipated
that the procedure time would be significantly reduced.
demonstrated that pulmonary vein isolation can be carried out with the HDMA
catheter in combination with 3-D navigation to create high density
three-dimensional geometry of the LA-PV junction, and that this can assist with
catheter placement and confirmation of pulmonary vein isolation. Using this
technique, the HDMA catheter is capable of circumferential ostial isolation of
the pulmonary veins without causing significant pulmonary vein stenosis acutely
on angiography. Our data serves as a favourable
feasibility assessment of the above technique and further evaluation of its
safety and efficacy in a larger cohort of patients should be performed.
Jais P, Haissaguerre M, Shah DC, Chouairi S, Gencel L, Hocini M, Clementy J. A focal source of atrial fibrillation treated by discrete radiofrequency ablation. Circulation 1997;95:572-6.
Haissaguerre M, Jais P, Shah DC, Takahashi A, Hocini M, Quiniou G, Garrigue S, Le Mouroux A, Le Metayer P, Clementy J. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. The New England journal of medicine 1998;339:659-66.
Petersen HH, Chen X, Pietersen A, Svendsen JH, Haunso S. Temperature-controlled irrigated tip radiofrequency catheter ablation: comparison of in vivo and in vitro lesion dimensions for standard catheter and irrigated tip catheter with minimal infusion rate. Journal of cardiovascular electrophysiology 1998;9:409-14.
Calkins H, Epstein A, Packer D, Arria AM, Hummel J, Gilligan DM, Trusso J, Carlson M, Luceri R, Kopelman H, Wilber D, Wharton JM, Stevenson W. Catheter ablation of ventricular tachycardia in patients with structural heart disease using cooled radiofrequency energy: results of a prospective multicenter study. Cooled RF Multi Center Investigators Group. Journal of the American College of Cardiology 2000;35:1905-14.
Erdogan A, Grumbrecht S, Carlsson J, Roederich H, Schulte B, Sperzel J, Berkowitsch A, Neuzner J, Pitschner HF. Homogeneity and diameter of linear lesions induced with multipolar ablation catheters: in vitro and in vivo comparison of pulsed versus continuous radiofrequency energy delivery. J Interv Card Electrophysiol 2000;4:655-61.
Dubuc M, Talajic M, Roy D, Thibault B, Leung TK, Friedman PL. Feasibility of cardiac cryoablation using a transvenous steerable electrode catheter. J Interv Card Electrophysiol 1998;2:285-92.
Whayne JG, Nath S, Haines DE. Microwave catheter ablation of myocardium in vitro. Assessment of the characteristics of tissue heating and injury. Circulation 1994;89:2390-5.
Saksena S, Gielchinsky I, Tullo NG. Argon laser ablation of malignant ventricular tachycardia associated with coronary artery disease. The American journal of cardiology 1989;64:1298-304.
He DS, Zimmer JE, Hynynen K, Marcus FI, Caruso AC, Lampe LF, Aguirre ML. Application of ultrasound energy for intracardiac ablation of arrhythmias. European heart journal 1995;16:961-6.
Natale A, Pisano E, Shewchik J, Bash D, Fanelli R, Potenza D, Santarelli P, Schweikert R, White R, Saliba W, Kanagaratnam L, Tchou P, Lesh M. First human experience with pulmonary vein isolation using a through-the-balloon circumferential ultrasound ablation system for recurrent atrial fibrillation. Circulation 2000;102:1879-82.
Nakagawa H, Antz M, Wong T, Schmidt B, Ernst S, Ouyang F, Vogtmann T, Wu R, Yokoyama K, Lockwood D, Po SS, Beckman KJ, Davies DW, Kuck KH, Jackman WM. Initial experience using a forward directed, high-intensity focused ultrasound balloon catheter for pulmonary vein antrum isolation in patients with atrial fibrillation. Journal of cardiovascular electrophysiology 2007;18:136-44.
Reddy VY, Neuzil P, Themistoclakis S, Bonso A, Rossillo A, Raviele A, Saliba W, Schwiekert R, Ernst S, Kuck K-H, Ruskin JN, Natale A. Abstract 2439: Visually-Guided Pulmonary Vein Isolation Using a Balloon Ablation Catheter to Treat Patients with Paroxysmal Atrial Fibrillation: One-Year Clincial Outcome Following a Single Ablation Procedure. Circulation 2007;116:II_536-a-.
Phillips KP, Schweikert RA, Saliba WI, Themistoclakis S, Raviele A, Bonso A, Rossillo A, Burkhardt JD, Cummings J, Natale A. Anatomic location of pulmonary vein electrical disconnection with balloon-based catheter ablation. Journal of cardiovascular electrophysiology 2008;19:14-8.
Shah D, Haissaguerre M, Jais P, Hocini M, Yamane T, Macle L, Choi KJ, Clementy J. Left atrial appendage activity masquerading as pulmonary vein potentials. Circulation 2002;105:2821-5.
Takahashi Y, O'Neill M D, Jonsson A, Sanders P, Sacher F, Hocini M, Jais P, Clementy J, Haissaguerre M. How to interpret and identify pulmonary vein recordings with the lasso catheter. Heart Rhythm 2006;3:748-50.
Erdogan A, Walleck E, Rueckleben S, Neumann T, Tillmanns HH, Waldecker B, Hoelschermann H, Heidt M. Comparison between pulsed and continuous radiofrequency delivery. J Interv Card Electrophysiol 2007;20:21-4.
Erdogan A, Grumbrecht S, Neumann T, Neuzner J, Pitschner HF. Microwave, irrigated, pulsed, or conventional radiofrequency energy source: which energy source for which catheter ablation? Pacing Clin Electrophysiol 2003;26:504-6.
Robbins IM, Colvin EV, Doyle TP, Kemp WE, Loyd JE, McMahon WS, Kay GN. Pulmonary vein stenosis after catheter ablation of atrial fibrillation. Circulation 1998;98:1769-75.
Macle L, Jais P, Weerasooriya R, Hocini M, Shah DC, Choi KJ, Scavee C, Raybaud F, Clementy J, Haissaguerre M. Irrigated-tip catheter ablation of pulmonary veins for treatment of atrial fibrillation. Journal of cardiovascular electrophysiology 2002;13:1067-73.
20 Arruda MS, He DS, Friedman P, Nakagawa H, Bruce C, Azegami K, Anders R, Kozel P, Chiavetta A, Marad P, MacAdam D, Jackman W, Wilber DJ. A novel mesh electrode catheter for mapping and radiofrequency delivery at the left atrium-pulmonary vein junction: a single-catheter approach to pulmonary vein antrum isolation. Journal of cardiovascular electrophysiology 2007;18:206-11.