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

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

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

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

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.

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.

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.

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

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.

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

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.

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

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.

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.

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.

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

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.

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

. 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.

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

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

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

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