Discussion
Obliteration of the apices of the affected ventricles due to fibrosis is
the hallmark of EM. Endocardial calcification marks the burnt-out phase
of EMF2. Though conduction abnormalities are common,
pacing is rarely required in such patients1.
Activation pattern of conduction system is impaired by fibrosis which
provides substrate for wavelet breaks and reentry. Etiology of heart
block in EMF has been much debated. Subendocardial fibrosis frequently
occurs due to the inflammatory reaction which affects the conduction
system traversing within, leading to CHB.
These patients had atrial arrhythmia and CHB which demanded pacing.
Atrial arrhythmia in RV restrictive physiology suggested significant
underlying RA fibrosis, hence VVI was the only viable option and
atrial-based pacemakers like AAI or DDD are not appropriate in these
cases. For conventional RV endocardial pacing, obliteration of the RV
cavity due to EMF is a major concern. In these patients, capture
threshold is likely to be high and moreover, local sensing of R wave
amplitude is likely to be unacceptably low. In addition, loss of
trabeculations in RV will not allow a passive lead fixation as it is
being practiced in many countries even now. Tricuspid regurgitation can
also lead on to lead instability. Large RA and likely septal involvement
on the endocardial aspect of the RV side could be concerns for
conduction system (left bundle or His bundle pacing pacing). Epicardial
lead placement is an option; however, the high risk profile of these
patients makes it not the primary option. Transvenous pacing through
coronary sinus tributaries offer many advantages in this case.
There is ample experience with the LV pacing, and long term stability of
the CS lead has already been established3. Not
crossing the tricuspid valve gives an advantage of not worsening the
pre-existing TR. Dilated CS tributaries make procedure relatively easier
in these cases. Long term stability may demand anchoring of the lead in
a large tributary and the use of an active fixation lead a safer option
as we did in the first case.
In conclusion, EMF provides unique challenges to endocardial pacing.
Transvenous epicardial pacing through CS tributary using an LV lead can
provide a safe and effective alternative mode of pacing with optimal
long-term pacing outcome.
- Author contributions: Dr. C Sundaram: The principal author.
Responsible for the preparation of case report and its editing.
- Dr. Viswanatha, Kartik S: Responsible for selection of the case and
drafting the case report and editing.
- Dr. Narayanan Namboodiri: The corresponding author. Responsible for
performing the procedure, idea, drafting the case report and revising
it critically.
- Dr. Valaparambil, Ajitkumar: Responsible for the performing the
procedure mentioned in this case report..