[Therapeutic exhaustion in patients with an implantable cardioverter-defibrillator. Are there predisposing factors?].
In patients (pts) with implantable cardioverter-defibrillators (ICD), antitachycardia pacing (ATP) schemes may be used followed by a limited number of endocavitary shocks in the same episode of ventricular tachycardia (VT) with the potential risk of therapeutic exhaustion.


OBJECTIVE
To assess the incidence of episodes of therapeutic exhaustion in a population of ICD carriers with ATP programmes and to attempt to determine their correlation with clinical variables.


METHODS
Study of the episodes of VT treated by ICD in 8 patients (6 male; 2 female) with an average age of 56 +/- 17 years with a follow-up > 6 months. The underlying pathology was: ischemic heart disease-5 patients; arrhythmogenic dysplasia of the right ventricle-1 patient; hypertrophic cardiomyopathy-1 patient; and operated pulmonary valve stenosis-1 patient. The authors considered therapeutic exhaustion to be the occurrence of episodes in which VT persisted after the application of ATP and the maximum number of shocks. The patients with episodes of therapeutic exhaustion (group A-3 patients) were compared with the remaining patients (group B-5 patients) with regard to the following parameters: age; ejection fraction; previous myocardial infarction (pMI; cardiac frequency during VT (cfVT); number of episodes of non-maintained VT (NMVT) without therapeutic intervention; > 20% reduction of the VT cycle after ATP (VTATP); intensity of programmable shocks (Icho); and medication with anti-arrhythmia drugs (AA).


RESULTS
In a total of 262 VT records (duration > 2.5 sec. after detection) with treatment by ICD during an average follow-up of 11 months, 6 episodes (2.3%) of therapeutic exhaustion were detected in 3 patients. Four of the episodes occurred in the same patient in a period of 4 hours, hospitalisation being necessary following syncope. In the other two cases, there were complaints of dizziness which subsided spontaneously a short time after the application of the last shock by the ICD. [table: see text]


CONCLUSIONS
Therapeutic exhaustion occurred in about 2% of the VT treated with this population. The possibility of a high number of non maintained VT episodes being associated to a greater possibility of therapeutic exhaustion may have implications on ICD programming.
Oliveira
M
M
Serviço de Cardiologia, Hospital de Santa Marta, Lisboa.
da Silva
N
N
Antunes
E
E
Sousa
L
L
Bico
P
P
Conceição
J M
JM
Roquette
J
J
Antunes
A M
AM
D000328:Adult; D000368:Aged; D016009:Chi-Square Distribution; D017147:Defibrillators, Implantable / Q000706:statistics & numerical data; D004868:Equipment Failure / Q000706:statistics & numerical data; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D017180:Tachycardia, Ventricular / Q000628:therapy; D017211:Treatment Failure