INAPPROPRIATE THERAPY IN PATIENTS WITH IMPLANTABLE CARDIOVERTER
DEFIBRILLATORS. R Iyer*, C. Singleton, V. Booth, M. Bayfield, P. Bannon, M.A. McGuire. Departments of Cardiology and Cardiothoracic Surgery, Royal Prince Alfred
Hospital, Camperdown, NSW. Background: Implantable cardioverter defibrillators (ICDs) are effective
for the prevention of sudden death in patients with ventricular arrhythmias.
However, ICDs sometimes deliver therapy inappropriately, when ventricular
arrhythmias are not present. We reviewed instances of inappropriate therapy in
a cohort of 193 patients with ICDs, (161 men and 32 women, aged 62 ± 13 years), who
were followed for 26 ± 17 months. Methods and Results: Information was obtained from a prospectively
maintained database of the clinical follow-up and telemetric device
interrogation. Therapy was delivered in 105 (54%) patients. In 91 patients
(47%) this was appropriate therapy for ventricular arrhythmias. In 35 patients
(18%) therapy was inappropriate. Twenty-one patients (11%) received both
appropriate and inappropriate therapy at different times. Inappropriate
therapies were DC shocks in 30 patients, anti-tachycardia pacing in 6 patients
and both in 1 patient. No patient died from inappropriate therapy. Cause
of inappropriate therapy N % Atrial
fibrillation or flutter 24 12.4 Supraventricular
tachycardia 3 1.6 Sinus
tachycardia 3 1.6 Galvanic
stimulation 2 1.0 T
wave sensing 2 1.0 Skeletal
myopotential sensing 1 0.5 Of the patients who received inappropriate shocks, 15 patients (42%)
never developed ventricular arrhythmias. No patients received inappropriate
therapy because of electromagnetic interference or lead fracture. In all
patients further episodes of inappropriate therapy were prevented either by
re-programming, anti-arrhythmic drug therapy or catheter ablation. Conclusion:
Inappropriate therapy occurs in approximately one fifth of patients with ICDs
followed for 2 years, but in most cases further episodes can be prevented.
