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Inappropriate shocks in patients receiving internal cardioverter-defibrillators for malignant ventricular arrhythmias
K Prasad1, A G Kishore, M H Anderson
1Department of Cardiological Sciences, St. George's Hospital Medical School, London.
Insights
Internal cardioverter defibrillators (ICDs) can deliver inappropriate shocks, often due to atrial fibrillation. This study highlights the frequency of these shocks in patients receiving ICDs for malignant ventricular arrhythmias.
Area of Science:
- Cardiology
- Medical Devices
Background:
- Implantation of internal cardioverter defibrillators (ICDs) is a treatment for malignant ventricular arrhythmias.
- Therapy failure and inappropriate shocks are known complications of ICDs.
Purpose of the Study:
- To investigate the incidence and causes of shocks in patients receiving ICDs.
- To assess the long-term outcomes of ICD implantation.
Main Methods:
- Study included 81 patients undergoing ICD implantation.
- Data collected via Holter monitoring, telemetry, device memory, and clinical follow-up.
- Follow-up duration was 36 months for 58 patients.
Main Results:
- 35 patients experienced 337 spontaneous shocks; 12 were inappropriate.
- Supraventricular arrhythmias, particularly atrial fibrillation, caused 55% of inappropriate shocks.
- Lead malfunction occurred in 4 patients; no mortality observed.
Conclusions:
- Inappropriate shocks are frequent in patients with ICDs.
- Atrial fibrillation is a primary cause of inappropriate shocks.
- Shocks are most frequent in the initial six months post-implantation.
Abstract:
Implantation of internal cardioverter defibrillators (ICDs) for treatment of malignant ventricular arrhythmias is complicated by failure of therapy or inappropriate shocks. We studied 81 patients (age range 16-72 years; mean 48 +/- 13 years) who underwent ICD implantation for device therapy. The underlying aetiology was ischaemic heart disease (39%), cardiomyopathies (32%) and others (28%). Information regarding shocks was collected using Holter monitoring, telemetry or device memory (stored electrograms) and lastly by clinical follow-up. Fifty-eight patients completed 36 months of follow-up. Thirty-five patients experienced 337 spontaneous shocks, appropriate in 21, inappropriate in 12, and both in two patients. Of the 74 episodes of inappropriate discharges for rhythms other that ventricular tachycardia (VT) or ventricular fibrillation(VF), 55 percent were due to supraventricular arrhythmias (atrial flutter or fibrillation). Lead malfunction occurred in four and the device was replaced in two. Additional drugs controlled AF in one. There was no mortality in any of the 81 patients. The frequency of shocks was highest in the first six months after implantation and atrial fibrillation remains the main cause. In conclusion, inappropriate shocks are frequent in patients undergoing ICD implantation.