Recurrence of symptomatic ventricular arrhythmias in patients with implantable cardioverter defibrillator after the first device therapy: Implications for antiarrhythmic therapy and driving restrictions

OBJECTIVES The purpose of this study was to investigate whether clinical or electrophysiologic characteristics could predict initial and subsequent implantable cardioverter defibrillator (ICD) therapy. BACKGROUND Identification of markers to predict subsequent ICD therapy and symptoms after the first event could affect patient management. METHODS We analyzed baseline and follow-up data on 125 ICD patients followed for 408 ± 321 days. Medications and ICD programming were not changed after first ICD therapy. RESULTS Implantable cardioverter defibrillator therapy occurred in 58 patients (46%). Clinical features were as follows: mean left ventricular ejection fraction (LVEF) 29% ± 15%; coronary artery disease 84%; presenting arrhythmia with sustained monomorphic ventricular tachycardia (SMVT) in 68%. In a multivariate analysis the relative risk for ICD therapy in patients presenting with SMVT versus cardiac arrest (CA) was 2.57 (range, 1.32 to 5.01), and for patients with LVEF ≤25%, 1.95 (1.11 to 3.45), respectively (p < 0.05). Implantable cardioverter defibrillator therapy was not predicted by any other variable. Forty-six patients had second ICD therapy. Mean time to second ICD therapy was only 66 ± 93 days compared with 138 ± 168 days for first ICD therapy (p < 0.05). No predictor for second ICD therapy was found. Regarding symptoms, impaired consciousness during initial ICD therapy was predicted only by SMVT cycle length <250 ms at electrophysiologic testing. In contrast, symptoms were similar between first and second ICD therapy (p = 0.0001). Of note, ventricular tachycardia cycle length preceding first and second ICD therapy was similar (r = 0.76, P = 0.001). CONCLUSIONS First ICD therapy tends to occur in patients presenting with SMVT and LVEF ≤25%. Subsequent therapy occurs sooner and is unpredictable, suggesting that antiarrhythmic drug therapy should be considered after the first symptomatic ICD therapy. Symptoms during first ICD therapy predict subsequent symptoms, and patients presenting with SMVT and asymptomatic first ICD therapy are at very low risk for future syncopal ICD therapy.