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.