Title: Left Bundle Branch Pacing in a Patient with Dextroposed
Heart: A Case Report
Abstract :
The Right Ventricular (RV) apex has been the standard site for pacing in
symptomatic bradyarrhythmias, but chronic RV pacing can cause adverse
effects such as atrial arrhythmias and left ventricular dysfunction.
Physiological pacing, including His bundle and left bundle pacing,
offers alternatives with fewer complications. We present a 66-year-old
male with a dextroposed heart and fibrotic right lung requiring left
bundle branch pacing due to a high RV pacing burden. The procedure
involved modified lead placement and a medial subclavian vein puncture,
successfully achieving good electrical parameters and post-procedural
device function, highlighting left bundle branch pacing’s feasibility in
complex anatomical conditions.
Keywords: His bundle pacing, Left bundle pacing, dextroposed heart.
Introduction :
The right ventricular (RV) apex has long been preferred site for pacing
for management of symptomatic bradyarrhythmia. However, chronic RV
pacing can cause various adverse effects in the form of atrial
arrhythmias, left ventricular dysfunction, higher hospitalization and
has been documented in numerous literatures [1]. This has generated
a lot of interest in a new pacing strategy where left His bundle or the
left bundle branch is paced using pacing lead. This strategy is known as
physiological pacing. Although clinical benefits of pacing His bundle
permanently have been demonstrated in various studies, concerns remain
in various issues such as higher pacing thresholds, smaller R-wave
amplitude, early battery depletion and risk of developing distal
conduction block [2]. These challenges can be addressed by
selectively pacing left bundle branch which provides excellent
threshold, and good lead stability [3]. The proximal left bundle
branches travel through the left ventricular septum and then fan out,
offering a larger area for pacing compared to the His bundle. During the
procedure, radiographic landmarks and intracardiac signals are crucial.
Here, we report a case involving dextroposition and altered radiographic
landmarks where left bundle pacing was successfully performed
Case history :
A 66 years old non-diabetic, non-hypertensive male came to us with
recurrent episodes of syncope. He had past history of pulmonary
tuberculosis in childhood. On examination, apex beat was found to be in
right 5th intercostal space just medial to midclavicular line.
Methods :
The blood reports were unremarkable. His baseline electrocardiogram
(ECG) was suggestive of bifascicular heart block (Figure 1). High
resolution computed tomography (HRCT) thorax was suggestive of fibrotic
right lung with shifting of mediastinum towards right (dextroposed).
Echocardiogram revealed a case of situs solitus and levocardia; with
normal cardiac chamber sizes and biventricular function grossly
rightwards shifted apex. 24 hour Holter showed multiple 2:1 episodes and
he was likely to get more than 40% RV pacing, so conduction system
pacing was considered in his case. Coventional Venogram of bilateral
upper limbs revealed shifted drainage of left and right subclavian veins
and superior vena cava. As this was not truly situs inversus
dextrocardia, ECG electrode placement was the key step to success of the
procedure. Measurement of left ventricular activation time (LVAT) and
ECG morphology in V1 is essential for successful left bundle branch
(LBB) capture, besides narrowing of QRS duration. Therefore, modified
placement of chest leads was done with echocardiographic as well as
fluoroscopic guidance as depicted in (Figure 2). As there was anatomical
displacement of innominate vein and SVC more towards right, we
contemplated the length of C 315 sheath might be insufficient to reach
the upper IVS. Hence puncture for the subclavian vein was done more
medially so that the C 315 sheath could reach the septum. There was
additional curve given to the sheath as there was sharp angulation at
the junction of left innominate with superior vena cava. At first,
atrial lead was positioned in right ventricle for pacing back up during
right ventricular lead placement. It also provided idea about right
ventricle and location of tricuspid valve. The 315 sheath was then
guided towards the interventricular septum. After a few attempts, site
with good electrical parameters showing upright QRS in lead II and QRS
discordance in aVL and aVR on electrocardiogram was selected (Figure 3).
Ventricular lead was then screwed and the paced left ventricular
activation time (LVAT) was 58 mSec with QRS duration of 96 mSec. Pacing
threshold was found to be 0.9 V. Later, atrial lead was positioned into
right atrium. Since the anatomy of the patient was distorted, after
multiple efforts with site with acceptable threshold and sensing was
selected on the lateral wall of right atrium and right atrial lead was
fixed. Post procedural pacing check, done on next day demonstrated
normal device function with atrial lead\RL’s threshold of 0.875V,
ventricular lead\RL’s threshold 0.25V with 88.1% atrial pacing and
99.9% ventricular pacing. Post-procedure period was uneventful and the
patient was discharged in haemodynamically stable condition. (Figure 4)
Discussion :
Cardiac pacing is the only therapy for symptomatic bradyarrhythmia.
Chronic right ventricular pacing has various hemodynamic problems,
because of which other alternative pacing sites are being considered.
These include right ventricular septum, right ventricular outflow tract,
left ventricle, His bundle and left bundle branch pacing. His bundle
pacing, developed by Desmukh et al [4] has some inherent problems
like low sensed R wave amplitude which can result in atrial over sensing
and ventricular undersensing. Also it has high pacing thresholds either
during implantation or during follow-up which can cause early battery
depletion in 5%-10% of cases [3]. Left bundle branch area pacing
may be a viable solution for patients experiencing His bundle pacing
failure. Advantage of left bundle branch pacing is that it can correct
the distal conduction system disease and the pacing lead effectively
bypasses the diseased proximal segment [5]. It is also considered to
be an alternative to cardiac resynchronization therapy in patients with
dilated cardiomyopathy with left ventricular dysfunction and left bundle
branch block pattern [6].
Position of heart may be different either in congenital heart diseases
or in diseases of mediastinum or lung. In our case, the patient is
having dextroposition of heart due to fibrosis of right lung. We
considered CSP ahead of RV pacing in this case, as it was better option
especially when the patient had compromised lung ( so he is not going to
tolerate any deterioration of LV function ) in the background of
expected pacing burden of more than 40%. But, mere thinking was not
sufficient in this case as the anatomical hurdles of left bundle branch
pacing in this patient needed to be addressed. More medial puncture than
usual, positioning atrial lead first in the right ventricle, giving
additional curve to the sheath were done to overcome the anatomical
complexities in this patient. Finally, the atrial lead was secured to
the lateral wall of the right atrium. There are very few reporting on
left bundle branch area pacing in literature but they were done in situs
inversus dextrocardia [7-9] and to our knowledge this is the first
reporting of case of left bundle branch area pacing in dextroposed
heart.
Conclusion :
In conclusion, the case presented highlights the challenges and
considerations in opting for left bundle branch area pacing as an
alternative to traditional right ventricular pacing in patients with
anatomical variations like dextroposition of the heart. Despite
anatomical complexities such as mediastinal shift and altered venous
drainage, careful procedural planning and modification of conventional
techniques enabled successful implantation of the pacing system. This
case underscores the importance of tailored approaches in pacing
strategies, particularly in patients at risk of adverse effects from
chronic right ventricular pacing. Further studies and case reports are
warranted to explore the efficacy and long-term outcomes of left bundle
branch area pacing in diverse anatomical settings, ensuring optimal
management of symptomatic bradyarrhythmias while minimizing potential
complications associated with traditional pacing techniques.
Key clinical message :
Chronic right ventricular pacing can cause complications such as atrial
arrhythmias and left ventricular dysfunction. Left bundle branch area
pacing offers a physiological alternative, especially for patients with
anatomical variations like dextroposition. This case demonstrates
successful pacing despite anatomical challenges, highlighting the need
for tailored pacing strategies in complex cases.
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10.1016/j.jaccas.2022.07.019. PMID: 36213881; PMCID: PMC953710: His
bundle pacing, Left bundle pacing, dextroposed heart.