Case report
A 49-year-old male patient affected by ischemic heart disease leading to
HFrEF and with a history of two episodes of out-of-hospital resuscitated
sudden cardiac arrest (SCA) underwent s-ICD implantation by means of an
EMBLEM MRI system (Boston Scientific, Massachusetts, United States).
Eight months after s-ICD implantation, the patient complained of fatigue
and inconstant dyspnea on moderate effort. Beta-blocker therapy had been
withdrawn months earlier, owing to symptomatic sinus bradycardia. ECG
showed profound sinus bradycardia with heart rate (HR) 38 bpm, PR
interval of 200 msec and aspecific IVCD with spontaneous QRS (sQRS) 115
msec. Echocardiography revealed LVEF 35%, which was unaltered from 8
months before. Coronary angiography with intra-vascular ultrasound
imaging excluded coronary lesions requiring invasive treatment.
Continuous ECG monitoring confirmed profound sinus bradycardia with
minimum HR 34 bpm and revealed episodes of II degree Mobitz type 2 AVB,
requiring PPM implantation.
Considering the need for CRT4, we chose to perform
CRT-P with HOT-CRT implantation and preservation of the s-ICD, rather
than biventricular ICD (CRT-D) implantation and subsequent s-ICD
extraction. This approach was selected for three reasons: to reduce
costs; to reduce generator size and therefore the risk of pocket-related
complications, owing to the small amount of subcutaneous pectoral tissue
present; and in accordance with patient preference. HBP with RVP lead
implantation on the His Bundle was chosen in order to guarantee correct
pQRS recognition by the s-ICD, with possible bail-out to ICD lead
implantation in the case of unsatisfactory intraprocedural pQRS
identification by the s-ICD.
After creation of a left pre-pectoral pocket and acquisition of left
subclavian vein access, an active-fixation bipolar HBP lead (Ingevity
MRI 7842 59 cm, Boston Scientific) was implanted by means of SSPC3
delivery (Boston Scientific) and a pace-mapping approach, obtaining
non-selective capture. A quadripolar LV lead (Acuity X4 Straight, Boston
Scientific) was then implanted, after coronary sinus (CS) angiography,
in an antero-lateral branch of the CS (Fig. 1 ). Correct pQRS
identification by the s-ICD was established by means of intraprocedural
device interrogation, and was confirmed for HBP, LVP (LV1-LV2
configuration) and biventricular pacing (BiVP), i.e. HBP with sequential
LVP after 20 msec. BiVP yielded a pQRS morphology similar to that of the
sQRS, albeit shorter, i.e. pQRS 100 msec vs. sQRS 115 msec (Fig
2, Fig. 3 ). A passive-fixation right atrial lead (Fineline II Sterox
Atrial J Model 4480 52 cm, Boston Scientific) was implanted and the
leads were then fixed to the muscle plane with silk sutures. The leads
were connected to the CRT-P generator, which was placed in the pocket.
Vicryl 0 and 3-0 sutures were used to close the pocket. Electrical
parameters were optimal, with capture thresholds below 1 V @ 0.4 msec.
The device was programmed in DDD-R 60 bpm mode, with an AV interval 150
msec, and LVP configuration LV1-LV2 with a pacing delay of 20 msec after
HBP, obtaining 100% BiVP. The bipolar-to-unipolar safety switch was
turned off in order to avoid accidental activation of the unipolar
configuration, which is contraindicated in the presence of an s-ICD. To
avoid under-sensing of the CRT-P during ventricular arrhythmias (which
could lead to inappropriate pacing and therefore suboptimal recognition
of arrhythmias by the s-ICD), the autosensing algorithm (Automatic Gain
Control) was activated. After the procedure, QRS recognition by the
s-ICD was tested again, both by device interrogation and by the
automated s-ICD screening tool (AST, Boston Scientific), both of which
confirmed correct pQRS identification in both the supine and standing
positions (Fig. 3 ).