1. A case of inappropriate ICD shock causing cardiac arrest
Dr Darragh Moran, Dr Niall Mahon

2. 2003 ED MMUH
16 year old male
Chest discomfort
Abnormal ECG
Normal coronaries

4. IVDd of 22mm
No LVOT gradient noted
Satisfactory TMET
Rx betablockade
Normal 24 holter
Episodic left-sided chest discomfort persisted
No family history of SCD

5. May 2007, aged 20
ED MMUH – collapse following game of soccer

6. At that time his ventricular septum had significantly increased in diameter, with diastolic measurements of 35-37mm. There was also noted to be an obstructive element to his myocardial hypertrophy on this occasion, with near cavity obliteration in systole.

7. At that time his ventricular septum had significantly increased in diameter, with diastolic measurements of 35-37mm. There was also noted to be an obstructive element to his myocardial hypertrophy on this occasion, with near cavity obliteration in systole.

8. At that time his ventricular septum had significantly increased in diameter, with diastolic measurements of 35-37mm. There was also noted to be an obstructive element to his myocardial hypertrophy on this occasion, with near cavity obliteration in systole.

9. No arrhythmia seen during inpatient monitoring
TMET – drop in blood pressure at peak exertion

10. ACC/ESC expert consensus HCM
One of the above features suggests ICD requirement
~1% annual risk of SCD in several series
No genotype risk stratification as yet, although there is data to suggest MYH7 genotype is associated with a more severe phenotype with a younger age of onset, more LVH, and more sudden death than mutations in the MYBPC3 gene.
Maron BJ, McKenna WJ, Danielson GK, Kappenberger LJ, Kuhn HJ, Seidman CE, et al. American College of Cardiology/European Society of Cardiology clinical expert consensus document on hypertrophic cardiomyopathy. A report of the American College of Cardiology Foundation Task Force on clinical expert consensus documents and the European Society of Cardiology Committee for practice guidelines. J Am Coll Cardiol 2003;42:1687–713.

11. 18 days later – ED MMUH
OHCA whilst cycling
Prolonged CPR, external DCCV for VF at scene
GCS 3, intubation and ventilation with inotropic support
GCS 11 day 2, GCS 15 day 4
Aspiration pnemonia
Post-traumatic amnesia, poor concentration, attention deficit

12. ICD interrogation: inappropriate ICD shock for T-wave oversensing whilst in sinus tachycardia
This inappropriate shock resulted in VF which was appropriately sensed by the device, however six 25J ICD shocks, as well as anti-tachycardia pacing during charging, failed to adequately defibrillate. Ultimately he required external DC cardioversion of 200J of biphasic energy, to restore sinus rhythm.

13. RV lead repositioning
DFT testing – failed 25J and 35J shocks requiring 200J external rescue shock

14. Because of this high defibrillation thresold (DFT), a transvenous coil was inserted into the superior vena cava (SVC). Different vectors were employed via device programming, however the lowest defibrillation thresold recorded was 35J, which was inappropriately high and did not afford an adequate safety margin.

15. A decision was made for insertion of a subcutaneous array to reduce the defibrillation threshold. The transvenous lead was extracted. Following this, defibrillation was succesful at 25J on two occasions and unsuccesful once, requiring a 35J rescue shock.

16. Defibrillation testing was repeated 1 week later
Defibrillation testing was repeated 1 week later. No further T wave oversensing was detected during this interrogation. VF was appropriately sensed by the ICD, both a 20J and 25J shock were unsuccesful, with a 30J rescue shock being required to restore sinus rhythm. The patient was discharged home in the days that followed.

17. 2/12 later, patient returned to hospital as SC array had dislodged whilst swimming

18. Cardiac theatre was booked for the insertion of an epicardial patch, which was succesfully carried out and a defbrillation threshold of 25J was obtained, with a RV coil to epicardial patch vector. The VF detection rate was increased to 215bpm.

19. 2 years of uneventful follow-up
2009 – threatened pocket erosion of device
Deep submuscular repositioning
Device check April 2010, high impedance values, >200J, sensitivity of 0.6mV
Admitted for revision and testing of leads and epicardial patch

20. . The procedure was complicated by the finding of a subtotal occlusion of the SVC. Percutaneous venoplasty was attempted, however vessel patency was not satisfactorily restored. The epicardial patch impedance was found to be >200J, and his RV lead impedance was within normal limits. The defibrillation vector was changed to RV to can, excluding the failed epicardial patch. No defibrillation testing was done at that time.

21. 3/7 later patient returned for DFT testing
1st 35J shock was unsuccessful, 2nd successfully restored SR
Long discussion with patient regarding risks and benefits of further intervention
Discharged home, albeit with unsatisfactory DFT

22. Pain and swelling around device insertion site
Few months later…
Pain and swelling around device insertion site
Chronic pocket infection
Device explanted
He was diagnosed with a chronic pocket infection, most likely the result of repeated, time-consuming revisions, thereby increasing his infection risk. His device was explanted, and his RV lead was left in situ as severe fibrosis resulted in failure to extract this lead. His RV lead was cut as short as possible during the procedure. The epicardial patch and lead was also left in situ

23. He was diagnosed with a chronic pocket infection, most likely the result of repeated, time-consuming revisions, thereby increasing his infection risk. His device was explanted, and his RV lead was left in situ as severe fibrosis resulted in failure to extract this lead. His RV lead was cut as short as possible during the procedure. The epicardial patch and lead was also left in situ

24. 7 years of device complications
No ventricular events in that time
High risk of SCD
SC implantable defibrillator offered
AEDs located at workplace and also at the gym patient attends to reduce risk of SCD
No further symptoms/adverse events to date