Discussion
The incidence of ventricular arrythmias (VAs) in LVAD patients is high,
ranging between 19% and 34% even after only 8 to 12 months post LVAD
implantation.8 Risk factors for VAs in such patients
include electrolyte abnormalities, acidosis, hypoxemia, cardiac
ischemia, etiology of the underlying cardiomyopathy, and VAs prior to
LVAD implantation.9,10,11 Interestingly, despite
providing adequate hemodynamic support and offloading the left
ventricle, LVADs do not reverse the underlying arrhythmogenicity.
Majority of LVAD patients have ICDs implanted for primary or secondary
prevention of sudden cardiac death prior to the LVAD surgery. Recently,
in a large retrospective observational study of 122 LVAD patients,
Galand et al13 reported that 15% of the patients
exhibited a greater than 50% decrease in right ventricular (RV)
sensing, 42% had >100 Ω increase/decrease in RV pacing
impedance, and 20% experienced >50% increase in RV pacing
threshold after LVAD implantation. Similar results have been reported by
Foo et al4, Thomas et al6 and
Boudghène-Stambouli et al.12 These changes can result
impact the ability of the ICD to detect and treat VAs. On one end under
sensing VA may lead to no therapy being delivered by the ICD, on the
other end, the device may inappropriately deliver therapy when not
indicated. Furthermore, recently there have been increasing reports of
LVAD patients presenting with multiple ineffective ICD shocks. Since
routine DFT testing is not performed at the time of initial ICD
implantation and pre and/or post LVAD placement, it is not known whether
elevated DFTs in such patients is due to LVAD placement per se or simply
reflect the severity of the patient’s cardiomyopathy. If LVAD placement
does increase DFT’s, the mechanism(s) could be multifactorial including:
1. Vector shifts caused by the introduction of intrathoracic metal from
the LVAD i.e., the LVAD itself may act as a current sink and shunt
current away from the heart. 2. Dislodgement of the RV
lead.4 3. Change in orientation of the heart after
LVAD implantation and 4. Use of antiarrhythmic drugs that raise
DFTs.5
When an LVAD patient presents with ineffective ICD discharges, the ICD
should be immediately disarmed, and the patient should be externally
defibrillated.15 The subsequent evaluation of such
patients should include: 1. A detailed history to search for any factors
that could provoke malignant ventricular arrythmias (heart failure
exacerbation, ischemia, unusual physical/mental stress etc.). Special
attention should be paid to exclude recent initiation of any drugs that
could raise DFTs, 2. Meticulous, physical examination 3. Laboratory
evaluation including serum electrolytes, 4. Chest X- ray to look for
appropriate placement of ICD lead, and exclude lead fracture, and 5.
Comprehensive interrogation of the patients ICD.
In our patient, thorough history and history guided physical examination
lead us to investigate any role that the metal tongue ring may have
played to result in ineffective ICD shocks. We decided to perform
defibrillation testing after removal of the metal tongue ring. Lo and
behold, after the ring was removed, the ICD was successfully able to
defibrillate the patient by delivering a shock 10 J lower than the
previously programmed shock output. The latter proved that the metal
tongue ring was indeed responsible for the failed ICD shocks in our
patient. We hypothesize that a portion of the electric charge was
shunted away from the myocardium towards the patients face due to the
presence of a large metallic ring. The latter was further supported by
an increase in the shock impedance upon removal of the tongue ring.
(Table 1).
Our case also brings into question the safety of wearing metallic body
piercings in patients with ICDs. The reduced efficacy of the ICD shocks
observed in our LVAD patient, could likely also be true for patients
without LVADs. Further, whether the location of the metal body piercing
is relevant also remains to be determined. Larger studies investigating
patients with ICDs and body piercings are
indicated.Conclusion
Clinicians should be aware of the potential for ineffective ICD shocks
in LVAD patients. Thorough history and history guided physical
examination are critical in determining the cause of failed ICD shocks
in such patients. Additionally, metal piercings may result in failed ICD
shocks, but this needs to be investigated in larger studies.