Standard pacemaker lead position and thus stimulation from Right
Ventricle Apex (RVA), is character-ized by prolonging transseptal
and intraventricular impulse conduction, with QRS duration at least
doubling from normal duration (1). Pacemaker stimulation from Right
Ventricle Outflow Tract (RVOT) gives us faster stimulus conduction,
and enables chamber activation from septum to the rest of the
myocardium which in turn gives less dissinchrony and shorter QRS
duration (2-4). However, in ventricle lead positioning, the problem
in identifying RVOT remains beside the fluoroscopy from different
directions and QRS morphology measuring on ECG (5, 6). Based on up
to date multi center randomized trials, the benefit of alternative
pacemaker stimulation site is clear (7), but the question still
remains about the reliability and long term stability of RVOT
The aim of the study is an assessment of difference of RVOT and RVA
lead position in pacemaker stimulation, on leads stability
parameters, in a 12 month follow up period.
PATIENTS AND METHODOLOGY
This was a prospective, randomized, follow up study, which lasted
for 12 months.
Our research enveloped 132 consecutive patients who were implanted
with permanent antibradicardiac pacemaker, at Pacemaker center –
Health Care Centre Zaječar, during the period 2009-2011. The
pacemakers used were SJM Verity ADx XL SR 5156 VVI, and Medtronic
Sensia SEDR01 DDD. Regarding the right ventricle lead position the
pts were divided into two groups: RVA group - 61 pts, with right
ventricle apex lead position; RVOT group -71 pts, with right
ventricle outflow tract lead position. In RVA group, ventricle
passive fixation leads, Medtronic 4074-58 were used. In RVOT group
an active fixation ventricle lead SJM Tendril 188TC/58 were used.
All the patients with DDD pacemakers had a “J” passive fixation
atrial lead Medtronic 4592-53.
Parameters of lead stability were measured on implantation
(impedance, threshold, sensing), as well as during the follow up.
Statistical analasys: We used analytical and descriptive statistical
methods: absolute and relative num-bers, central tendency measures
(arithmetic average), dispersion measures (SD). Parameter tests: t
test, ANOVA for repeated measures. Non-parameter tests: Hi square
test, McNemar test.
On study enrollment there was no group difference in distribution
of sex, age, BMI (body mass index), VVI to DDD pacemaker
implantation ratio and atrial impendance, senzing, threshold and
radioscopy duration, judged by the above mentioned tests. The only
difference betwen groups was in the ventricular impendance, senzing,
threshold (Table 1).
Table 1. Comparisson of RVA to RVOT group on study enrollment. BMI,
QRSs - QRS duration in intrizing rhythm (senzing), QRSp - QRS
duration in pacemaker stimulation, V-Ventricle, A-Atrial
|Test and statistic
The stability analysis of ventricle electrodes gave the
conclusion that the electrodes impedance after the 12 month follow
up was significantly lower in both groups as compared to the
beginning. (Table 2). There was no group influence to the impedance
Both groups had the same R wave sensing (Table 2). The position of
the lead had no influence on sens-ing value (p=0.29).
Threshold remained the same in RVA, and was statistically higher in
RVOT group (p<0.001) (Table 2). Threshold was dependent on the lead
The stability analysis of atrial leads gave that impedance values,
threshold, and P wave sensing remained unchanged in both groups
during the 12 month follow up period. (Table 2).
Table 2: Pacemaker programming parameters comparison on 1-th month
and 12-th month after pacemaker implantation in RVOT and RVA groups
||RVA group n-61
||Test and statistic
||RVOT group n-71
||Test and statistic
Our research enveloped pts which were followed in regards to
pacemaker lead position in different positions in right ventricle,
comparing its influence on leads stability, during the 12 month
period in real life circumstances.
RVOT represents a trapezoid shaped space between the tricuspid and
pulmonary valve, bordered with right chamber free wall in front, and
with the upper part of the interventricular septum from the back
(2-4, 8). In literature, RVOT is often presented as the above
described, but also as a mid portion of the septum, and some-times
even as the region near apex. So, this confusion in defining the
RVOT leads to the term of Non RVA pac-ing (5). Bharat et al (4)
measured whether the RVOT lead positioning needed extra fluoroscopy
time compared to RVA. They concluded that no extra fluoroscopy time
was needed compared to RVA, 8.95 min for RVOT and 9.37 min for RVA.
Our analysis also did not show any difference in fluoroscopy time
between RVOT and RVA, 3.39 min and 3.26 min respectively. The same
authors (4) also analyzed stability parameters on implantation, and
concluded that threshold level in RVOT group was significantly
higher than in the RVA group. Impedance and sensing did not differ.
In the other paper, analysis of lead parameters on implantation, in
RVA and RVOT, showed similar values for sensing and impedance, while
the threshold was higher in RVOT group (9).
Our analysis implantation values were practically the same as in
other studies, the lead position influ-enced the stimulation
threshold, which was significantly higher in RVOT group compared to
RVA. However, impedance and R sensing also showed significant
difference. This was due to the different type of electrode used in
RVOT, compared to RVA, active fixation vs. passive fixation lead,
respectively. This was confirmed by the fact that atrial leads
showed no difference, due to the fact that they were passive
fixation type in both groups.
Long term follow up of the patients with RVOT lead position, showed
that the lead was stable after one (10) and nine (11) years.
Kristiansen et al followed the CRT patients with the right ventricle
lead was implanted in RVA or RVOT. Stability parameters showed no
difference between the groups after 2 year follow up (12). The data
analysis from 20 randomized trials, on 1,114 patients showed the
same stability characteristics in RVOT during a long term follow up
as in RVA (13). The stability of RVOT lead position was also
demonstrated with the results of long term follow up of threshold
levels, which did not differ from RVA (10, 14-16).
In our study , after a one year follow up, impedance was equally
changed in both groups, which was explained with electrode
maturation, there was no group influence on impedance level change
(p=0.44). R sens-ing did not change significantly after one year in
both groups. Threshold level remained the same in RVA group.
However, the average threshold level on ventricle lead in RVOT group
was 0,72V (p<0.001) which was statisti-cally significant higher
value compared to the implantation value, but still within the
clinically acceptable range, meaning that it had no influence on
The atrial lead stability analysis showed no change of threshold,
impedance and sensing after a 12 month follow up.
RVOT lead positioning did not require additional fluoroscopy
time. Acute parameters on implantation differed only due to active
fixation lead being used in RVOT group. After 12 months of follow
up, analyzing stability parameters, we found that the RVOT position
was equally reliable as the RVA position.
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