Discussion
CRT remains a landmark therapy for HFrEF4,
particularly in the context of HF with a high expected percentage of
RVP5. HOT-CRT was recently shown to be safe and
potentially superior to conventional CRT in the case of
IVCD6. To our knowledge, ours is the first-in-human
case of TV CRT-P implantation in an s-ICD patient, and also the first
case of HOT-CRT in an s-ICD patient to be described in the literature.
As already mentioned, this approach was chosen in order to reduce both
costs and generator size, and to respect patient preferences, while
ensuring possible bailout to conventional CRT-D during implantation in
the event of suboptimal pQRS recognition by the s-ICD.
Many cases of the concomitant use of s-ICD and
TV-PPM9,10, epicardial PPM11,
epicardial CRT-P12, and HBP
devices13 have been reported. In addition, there are
numerous case-reports of the associated use of leadless PPM (LP) and
s-ICD14. Indeed, Boston Scientific has developed a
hybrid LP (EMPOWER) plus s-ICD (EMBLEM) system that is able to provide
anti-bradycardia pacing and anti-tachycardia pacing together with
shocks15, and which is currently under investigation
(Modular ATP trial, NCT04798768). In one case, a completely leadless
CRT-D system was created by using an LP (Medtronic Micra TPS) combined
with a WiSE-CRT system (EBR Systems, Sunnyvale, CA) and an
s-ICD16. When conventional ICD lead implantation has
proved impossible, other strategies have been adopted, such as the use
of a hybrid subcutaneous and trans-venous CRT-D approach using the
Medtronic 6996SQ Finger subcutaneous array lead17, and
ICD lead implantation in the coronary sinus in the context of
CRT-D18. In one case, an s-ICD with a right
parasternal electrode plus an AAI PPM was implanted19,
and in another case, owing to multiple ventricular lead fractures
causing inappropriate shocks, an s-ICD was implanted and the existing
TV-ICD was reprogrammed as an AAI pacemaker20.
However, a few cases of device-device interaction between the s-ICD and
both the TV21 and epicardial PPM22have been described. To avoid this eventuality, we chose HOT-CRT as the
pacing strategy; this yielded a pQRS which was similar to the sQRS,
albeit shorter. Moreover, we ensured correct pQRS recognition by the
s-ICD both intra-procedurally, with the possibility of bailout to
conventional CRT-D during implantation, and post-procedurally, by means
of both s-ICD interrogation and the AST in multiple body positions. Of
note, screening by means of the AST has been tested in patients with
PPM23, HBP13 and
CRT24 devices, with variable results. One group found
an association between s-ICD screening and response to
CRT25, which may have been due to the fact that
correct pQRS identification by the s-ICD might depend on the pQRS being
narrow, therefore predicting better outcomes of CRT.
In conclusion, considering that potentially up to 5.2% of s-ICD
patients develop a need for permanent pacing7, we
demonstrated that CRT-P, and particularly HOT-CRT implantation in an
s-ICD patient, was both feasible and safe, yielding optimal electrical
parameters and correct pQRS identification by the s-ICD both intra- and
post-procedurally. In the event of suboptimal intra-procedural pQRS
recognition by the s-ICD, bailout to conventional CRT-D is a
possibility.