84501098 angle-study-thuy

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Alternate Site Right Ventricular Pacing:
Defining Template Scoring
Harry G Mond OAM, MD, FRACP, FACC, FCSANZ, FHRS,
Alexander Feldman MD, Raphael Rosso MD and Thuy To Hung MD.
Department of Cardiology, Royal Melbourne Hospital, Melbourne, Australia
Address for correspondence:
Assoc. Prof. Harry G Mond,20
Suite 22, Private Medical Centre, The Royal Melbourne Hospital,
Victoria, 3050, Australia. Tel: 613 9347 4296 Fax: 613 9347 6760
E-mail: hmond@bigpond.net.au

2
Running title: Right Ventricular Pacing
Key words: Right Ventricular Pacing
Template Scoring
Disclosures:
Dr Mond designed the right ventricular septal stylet used in the study,30
but has no financial interest in the commercially available product.
Abstract:
Background: Prolonged right ventricle (RV) apical pacing is associated with
left ventricular (LV) dysfunction due to dysynchronous ventricular activation
and contraction. Alternate RV pacing sites with a narrower QRS compared to
RV pacing might reflect a more physiological and synchronous LV activation.
The purpose of this study was to introduce a new and novel way of evaluating
alternate site RV pacing sites using a template scoring system. This involved
measuring the angle of lead attachment to the endocardium in the 40o left40
anterior oblique (LAO) fluoroscopic view. The effect of altering the loop of lead
in the RV was also investigated.
Methods: 23 consecutive patients with an indication for RV pacing were
enrolled in the study. Standard 58cm active fixation leads were positioned in
either the RVOT septum or mid RV septum. Using LAO cine fluoroscopy, a

3
generous loop of lead was inserted into the RV chamber and the change in
angle of attachment to the endocardium determined.
Results: Successful positioning of the pacing leads at the RVOT septum (18)
and mid RV septum (5) was achieved without complications. The angle of
attachment of the lead tip altered in all patients over a range of 6o to 32o with50
a mean of 14.6o ± 6.6o. In 91% of patients, the range was predominantly
within the same template score.
Conclusions: This prospective study shows that a template scoring system
can be applied to lead attachment in alternate RV sites, but more work is
required to determine the accuracy and efficacy of the templates. .
. 257 Words

4
Introduction:
Prolonged pacing from the right ventricular (RV) apex is associated with
progressive left ventricular (LV) dysfunction1,2,3,4,5 which appears related to a
remodeling process consequent to abnormal ventricular activation and60
contraction.6,7,8,9,10,11,12,13,14,15 This deleterious effect has lead to a growing
interest in alternate ventricular pacing sites with a more favorable
hemodynamic profile. Such a site is the RV septum, which is theoretically
associated with a more physiological ventricular activation resembling that of
normal atrio-ventricular conduction.16 The techniques and tools for reliable
placement of pacing leads onto the right ventricular septum have only recently
been described17,18 and consequently pacing from these areas have not been
studied in detail.
From recent studies, the 40o left anterior oblique (LAO) fluoroscopic view70
appears to be the most desirable investigation to determine RV positioning
outside the apex. It can be easily performed during lead implantation and 40o
has been chosen as it is the near maximum orientation in the oblique position
that can be achieved without compromising the sterile field. The view,
however, has not been proven to be the gold standard and like many potential
clinical investigations is subject to patient anatomical variability. Other
methods to determine RV lead position may include echocardiography,
computerized tomography scanning and in patients with compatible pacing
systems even magnetic resonance imaging. However, such investigations are
currently limited to post operative evaluation.80

5
An LAO fluoroscopic template has been designed which defines the position
of the RV lead in the heart as septal, anterior or free wall. However, in order to
apply this template, we have investigated the effect of altering the amount of
lead in the heart to determine if this variable, adversely affects the
interpretation of lead positioning.
Methods:
Study population:
The study group consisted of 23 consecutive patients with indications for a
single or dual chamber pacemaker implant, undergoing the initial procedure at90
the Royal Melbourne Hospital. In all patients, RV septal pacing was desirable.
Template Scoring:
Prior to the commencement of the study, a template was created using LAO
fluoroscopic examples of RV lead positioning from an ongoing data base of
over 500 lead implantations (figure 1). The lead position was determined
using measured angles from 0o to 140o in the LAO view.
The RV anterior position of the lead is a narrow zone where the lead tip lies
on or immediately adjacent to the septum on the front of the heart and is100
ltraversed by the left anterior descending coronary artery. The angulation
onthe template is from 80o to 100o and for ongoing studies, this zone is
awarded “0” points. To the left is a zone 60o to 80o, where the lead points
slightly towards the spine and is a transition zone between septal and anterior
and is awarded one point. True septal pacing is awarded either “2” (40o to

6
60o) or “3” (0o to 40o) points. To the right of true anterior is another transition
zone (100o to 120o) between anterior and free wall and is awarded “-1”. True
free wall is designated 120o to 140o and awarded “-2” points. Both septal and
free wall lead positions can have angulation beyond these limits, but this has
not been seen in the data base. Such positions would still be awarded “3” and110
“-2” points.
Implant procedure:
The pacemaker implantation was performed or supervised by a single
operator (HM) with experience in RV septal lead placement. Pacemaker
implantation was done under local anesthesia, conscious sedation and pre-
operative prophylactic intravenous antibiotics. The RV lead was inserted via
the left or right cephalic or subclavian venous approach. Commercially
available 58 cm bipolar active fixation leads with steroid-eluting electrodes
were used for RV implants. A specifically shaped stylet designed to facilitate120
positioning of active fixation ventricular leads onto the RV septum (Mond®
RVOT Stylet, model 4140, St.Jude Medical, St. Paul, MN, USA) was used for
all RV lead implants. The positioning of the ventricular leads into the RV was
guided by the posterior-anterior fluoroscopic view. In all cases, the lead was
passed to the pulmonary artery and withdrawn across the pulmonary valve
into the RV outflow tract (RVOT) or mid RV. The first lead position was
accepted and no septal mapping attempted. The implant technique has been
described in detail.18
Septal deployment of the lead was confirmed by the LAO position and cine130

7
recordings were made at a frame rate of 10 per second. Immediately prior to
the recording, the RV lead was partially withdrawn, so as to leave a minor
loop in the RV (figure 2). During the 3 second recording, the amount of loop in
the RV was rapidly increased until a bend was noted across the tricuspid
annulus or the distal end of the lead became distorted at its deployment site
(figure 2). Following this recording, the lead was once again slowly withdrawn
about 1cm under fluoroscopic control until the desired final position was
determined and the extra-vascular portion secured by the collar using non-
absorbable sutures.
140
Following recruitment of patients, the cine fluoroscopies of all cases were
analyzed and hard copy prints made for every alternate frame, so as to have
approximately 20 prints per case. In all instances, the first and last images
were excluded, because of the extreme positions. In a number of cases,
significant lead tip distortion was still noted after first and last recordings were
excluded. As such distortion would never be accepted as the final position,
these recordings were also excluded.
The images were all analyzed by hand using a protractor to determine the
angles of the lead tip in the LAO position (figure 2). The limits of the angles150
during lead insertion were determined to see if the scores for any individual
patient moved from one template group to another. The study was accepted
as a quality assurance/quality improvement project by the hospital Research
Directorate and Ethics Committee, thus not requiring ethical review or formal
patient consent.

8
Statistical analysis
All continuous data was tested for normal distribution using One-sample
Kolmogorov-Smirnov test and Q-Q plots. All variables were found to follow
normal distribution and hence were expressed as mean (SD). The
comparison of continuous variables between the two groups was done using160
independent student t-test. For categorical variables, the Fisher’s exact test
was used. A P value of <0.05 was accepted as indicating significance.
Results:
The study group was composed of 23 patients with 13 males and a mean age
of 77  6 years. The indications for the pacemaker were high grade atrio-
ventricular block in 9, sick sinus syndrome in 7, paroxysmal or established
atrial fibrillation in 5 and syncope of unknown cause in 2. The pacing leads
used were the St. Jude Tendril® 1888TC in 14 cases, the Medtronic
CapsureFix® Novus 5076 (Medtronic Inc., Minneapolis, MN, USA) in 5 and170
the Boston Scientific Dextrus® 4137 (Boston Scientific Inc. Natick, MA, USA)
in 4 cases.
Lead Measurements at RVOT and mid-septal locations
Electrical parameters for the RV leads at implant were satisfactory, regardless
of their positioning at the RVOT or mid RV septum (table 1).
Ventricular pacing lead positioning
In 18 patients (88.2%), the pacing leads were deployed in the RVOT and in 5

9
the mid RV septum. In 5 cases, (4 RVOT and 1 Mid RV), the leads were180
classified during study analysis as within the transition zone between anterior
and septal (figure 3). In no cases were difficulties encountered deploying the
RV lead. There were no complications associated with the study.
Angle of lead tip during loop formation:
By increasing the loop of lead in the RV, the angle of attachment of the lead
tip altered in all cases (figure 3). The range was from 6o to 32o with a mean of
14.6o ± 6.6o. In 9 cases, the angle classification was 3, in 6 cases it was 2, in
5 cases it was 1 and indeterminate in 3 cases (between 2 and 3). Although
there was some overlap, in 87% of cases, the angle change was190
predominantly within one group.
Discussion:
The ideal ventricular pacing site should resemble normal ventricular
depolarization with the synchronicity of ventricular activation as observed with
an undamaged conduction system. RV septal pacing allows a narrower QRS
compared to RV apical pacing,7 which in turn might reflect a more
physiological and synchronous form of ventricular activation.7,19,20,21 In theory
RV septal pacing should be preferable to RV apical pacing, but the
physiological advantages as demonstrated with long-term studies, although200
suggestive, have yet to be confirmed.7, 22, 23, 24

10
One of the main reasons that such studies have not been confirmatory is that
true RV septal pacing has until recently been difficult to consistently achieve.
Some of these difficulties relate to the lack of suitable lead technology, the
non-standardized nomenclature and the inability to consistently and
accurately position pacing leads onto the septum because of its posterior
orientation within the RV chamber.25 We now have a much clearer
understanding of the relationship between the anatomy of the RV chamber
and the fluoroscopic appearances and electrocardiographic patterns, which in210
turn has allowed successful development of tools to reliably direct active
fixation leads onto the true RV septum.26
To date, the most important tool for septal pacing confirmation is the LAO
fluoroscopic view, which can be performed during RV lead implantation.
However, more studies are required to confirm whether this truly identifies septal
positioning. In this study, a LAO fluoroscopic template method has been
developed to assist in assessing lead position. The endocardial attachment of
pacing leads in alternate RV pacing sites can be identified and graded as to
whether the lead attachment is septal, anterior or free wall. This template can220
be used to determine the success or otherwise of different implant strategies
and tools. However, before this can be done a number of variables that could
alter the angulation of the RV lead attachment must be considered.
An important variable is chest wall shape. Factors such as pulmonary and
vertebral column disease can distort the positioning and orientation of the

11
heart in the mediastinum, thus potentially altering the lead position in the LAO
fluoroscopic view. However, this should be obvious with the postero-anterior
and right anterior oblique fluoroscopic views and thus taken in to account
when observing the LAO fluoroscopic view. To also minimize this variable230
from patient to patient, exact 40o LAO angulation is essential and has been
strictly adhered to in this study.
The effect of the amount of loop left in the RV at the end of implantation was
investigated by measuring the change of angle when more lead is introduced.
As expected the angle of attachment did alter as more lead was delivered to
the RV. However, this was only important in 13% of patients, where the angle
changed from one zone to the next. To overcome this and thus minimize this
variable, the amount of loop left in the RV follows a strict protocol at
implantation in order to prevent lead dislodgement.18240
Another variable not investigated was the effect of the cardiac cycle on lead
angulation. This would require an electrical gate to synchronize the
fluoroscopic images with the ECG, which in a practical sense is infrequently
used. An attempt was made to do this visually without ECG gating, but
became impractical as many patients had poor left ventricular function and
therefore little change in fluoroscopic appearances during the cardiac cycle.
However, during the loop study there were at least two cardiac cycles within
each study and thus the change in angulation with cardiac contraction was
within the range demonstrated in figure 3. A further variable to be considered250

12
is respiration. Because of sedation and shallow respiration, it was never
necessary to control breathing during the cine fluoroscopy acquisition and
thus this variable is of little significance.
The template defines two narrow zones close to zero angulation. Although
previously defined as septal or free wall, these zones appear so close to zero
that in reality they may well be actually anterior. This indeterminate or
transition zone needs further investigation, but in the interim they are
allocated only 1 or -1 points.
260
Study Limitations:
This manuscript describes a new and novel way of evaluating pacing or ICD
lead positioning in alternate RV sites. Potential limitations of the templates
such as body shape, the loop of lead in the RV chamber and effects of the
cardiac cycle and respiration have been addressed. More work needs to be
done to determine the accuracy of the templates and whether they have
relevance to physiologic studies or evaluating implantation tools and
techniques.
Conclusions:270
The RV septum has been proposed as a safer and hopefully more physiologic
pacing site than the RV apex. True septal pacing can be recognized by the
LAO fluoroscopic view during implantation, but more work is required to
establish this as a gold standard. A new and novel way of evaluating alternate

13
RV pacing sites using a template scoring system is proposed to assist in future
studies. This involves measuring the angle of lead attachment to the
endocardium in the LAO fluoroscopic view. A number of variables that may
alter the angle of attachment have been investigated and although the angle
does alter, nevertheless, leaving a standard loop of lead in the RV will
minimize this variable.280
Legend to the Illustrations:
Figure 1: Template scores for LAO lead positioning.
The lead attachment angles range from 0o - 140o. True anterior positioning is
from 80o - 100o and allocated “0” points, whereas septal positioning is divided
into two areas 40o - 60o “2” points and 0o - 40o “3” points. Free wall positioning
is from 120o - 140o and allocated “-2” points. To each side of true anterior are
transition zones with 60o - 80o allocated “1”point and 100o - 120o allocated “-1”
point.
290
Figure 2: Four fluoroscopic prints from a single 3-second cine run to
demonstrate the change in angle of attachment with insertion of more lead (1
to 4) into the RV. The angles drawn and measured visually are shown. A
guide wire for right atrial lead insertion also lies in the heart.
Figure 3: The angle distribution for the 23 patients in the study. There are
nine instances allocated 3 points, six with 2 points and five with 1 point. In
three instances, the angle range lies in the zone between 2 and 3 points and

14
labeled *. The allocation of points in these instances would depend on the
measured cine frame in each individual case. The RVOT leads are the solid300
lines and the mid RV leads broken lines.
Figure 1

16
Figure 3:
Table 1:
Parameter All Patients
23
RVOT
18
Mid RV
5
P Value
(RVOT/Mid RV)
Males(%) 13 (56.5) 9 (50) 4 (80) 0.24 (ns)
Age (years) 77±7.8 76.5±7.8 78.8±7.6 0.57 (ns)
R wave (mV) 12±5 12±5 14±5 0.41 (ns)
Threshold (V) 0.9±0.4 0.9±0.3 1±0.5 0.56 (ns)
Impedance (Ω) 829±181 821±186 854±180 0.73 (ns)
320

17
References:
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