|Year : 2009 | Volume
| Issue : 2 | Page : 74-76
Management of inappropriate internal cardiac defibrillator shocks
H Zaky, H Elzein, O Aljassim
Dubai Heart Center, Dubai, United Arab Emirates
|Date of Web Publication||17-Jun-2010|
P O Box 21910, Dubai
United Arab Emirates
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Zaky H, Elzein H, Aljassim O. Management of inappropriate internal cardiac defibrillator shocks. Heart Views 2009;10:74-6
| Introduction|| |
Inappropriate ICD (internal cardiac defibrillator) shocks are a common complication of ICDs and remain a major concern for ICD patients. The incidence is around 32%  . The efficacy of ICD depends mainly on its ability to correctly detect life threatening arrhythmia and deliver high-voltage shocks  ; However, shocks can be painful, thus affecting the quality of life in patients with ICD  .
In clinical practice, adjunctive antiarrhythmic drugs might be administered to between 49 and 69% of patients who have an ICD  . However, the selection of the most appropriate drug may be a challenge since their use is not exempt of risks , . In this paper we reporting how we managed a series of cases of inappropriate ICD shocks in our patient population.
A 65-year-old male patient, post CABG, post PCI (to left circumflex and LIMA-LAD junction), and post ICD implantation presented to the pacemaker clinic with a history of ICD shock which occurred two days prior to his clinic visit. ICD was implanted one year prior to his clinic visit. Investigation and testing of the episode revealed an attack of paroxysmal atrial fibrillation (AF) with rapid ventricular response, for which he received a shock of 25 joules and reversion to sinus rhythm after one burst of unsuccessful anti-tachycardia pacing. SVT discrimination criteria, namely sudden onset and stability algorithm of the ICD were activated. Five days after, the patient presented to the emergency room with another episode of inappropriate shock for paroxysmal atrial fibrillation with rapid ventricular rate. The discriminator SVT algorithm was enabled. In addition, the patient was started on bisoprolol 2.5 mg. Nine months later, the patient was admitted for evaluation of chest pain, dizziness, and paroxysmal AF with a ventricular rate of 110/min. Cardiac markers were normal and ECG showed HR of 55/min after resolution of AF episode. During that hospitalization, ECG did not show acute changes of myocardial infarction and no further ICD shocks. To slow AV conduction and minimize episodes of inappropriate shocks due to rapid ventricular rate during episodes of fast AF, the patient was put on amiodarone 200 mg. Since that time, he has not had episodes of inappropriate ICD shocks.
A 75-year-old female patient, post CABG, and post dual chamber ICD implantation was admitted due to repeated episodes of ICD shocks. The patient had a four-year history of left ventricular dysfunction with an ejection fraction of 35% and paroxysmal AF of three years. The dual chamber ICD was interrogated and tested and revealed 15 inappropriate shocks for rapid ventricular response due to paroxysmal atrial fibrillation. No programming change was needed as stability and onset were on. Amiodarone was added to enhance control of AV conduction and possible maintenance of sinus rhythm. However, she continued to have short paroxysms of AF and therefore, digoxin 0.25 mg also added. She developed drug-induced complete heart block ("medical ablation of the AV node"). She had no further episodes of inappropriate ICD shocks but two weeks after, the patient came to the pacemaker clinic distressed and emotionally upset and complaining of another "shock". The device was interrogated but revealed no shock events. The patient was reassured that the device did not "fire" and that she was probably experienced phantom shock due to psychological stress from previous episodes of multiple shocks.
An 80-year-old gentleman, post CRT/D (cardiac resynchronization therapy with defibrillator) implantation presented to the pacemaker clinic complaining of two episodes of ICD shocks one year after insertion of the device. Indication for the device was severe left ventricular dysfunction (EF 25%), NYHA class III symptoms, and LBBB on ECG (QRS >120 msec). Medications included ASA 100 mg; lasix, 40 mg; aldactone 25 mg; pravastatin 20 mg; and carvedilol 6.25 mg twic daily.
The device was checked and showed two episodes of inappropriate ICD shocks due paxysmal supraventricular tachycardia [Figure 1]. The dose of the beta blocker carvedilol was gradually increased to 25 mg twice daily over three weeks. The onset and stability algorithms of the device were activated. Follow-up six months afterwards showed the device to be functioning well and there were no arrhythmias detected.
In December 2007, a 27-year-old man with B-thalasemia major, dilated cardiomyopathy (EF 20%), insulin dependent diabetes mellitus, and hypothyroidism (on replacement therapy) developed serious ventricular arrhythmia and received direct cardioversion. In addition he had paroxysmal atrial flutter and on electrophysiological study, atrial flutter was induced. Ablation to cavotricuspid isthmus was performed. A single chamber ICD was implanted for secondary prophylaxis of ventricular arrhythmia. He was put on amiodarone therapy. He did very well on this regimen for 18 months but in March 2009, he presented with frequent ICD discharge (8 shocks), occurring over two days.
Interrogation of the device revealed high impedance of the pace/sense component of the RV defibrillator lead (impedance > 3000W) with hypersensitivity (noise) on the RV tip to RV ring channel and normal sinus rhythm on the shocking coil-can channel consistent with fractured pace/sense component [Figure 2]. Also the lead type has a recall from the manufacturer (sprint fidelis, Medtronic company). Our plan was to implant another lead but the patient preferred to undego the procedure in another center.
| Discussion|| |
Most studies have shown that, the most common cause of inappropriate shock in patients with ICD device is supraventricular tachycardia  , especially atrial fibrillation with rapid ventricular response .
In this report, we tried in the first three cases to decrease the incidence of inappropriate shocks by making sure that the discrimination and the stability algorithms were activated. These algorithm programs are: the sudden onset algorithm which differentiates sinus tachycardia, which starts gradually from ventricular tachycardia, which starts suddenly and the stability algorithm which differentiates atrial fibrillation from the more stable R-R interval ventricular tachycardia, keeping in mind that two patients had dual chamber ICD and one had CRT/D with atrioventricular discrimination algorithms (Medtronic, PR logic). In addition, adjunctive antiarrhythmic drugs were instituted starting with beta blocker optimization and then if more atrioventricular junction block was needed, amiodarone was added. If more AV blockade was needed, then digoxin was added. This management is in line with published literature ,.
Phantom shocks are not uncommon and it reflects psychological stress of the patients who received multiple shocks  .
For case number 4 it was inevitable that the lead should be abandoned and another lead should be implanted instead and this in agreement with most authors and also keeping in mind that this lead had been recalled by the manufacturer due industrial defect (sprint fidelis, Medtronic company) , .
In conclusion, a large number of inappropriate ICD shocks can be prevented by proper programming of the devices and adjunctive antiarrhythmic drugs and sometimes radiofrequency ablation for both supraventricular as well as ventricular arrhythmia is indicated. Phantom shocks and a fractured lead are not uncommon complications.
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[Figure 1], [Figure 2]