Background: In the present study, we have focused upon rates and clinical determinants of inappropriate shock (IS) after implantable cardioverter-defibrillator (ICD).
Methods: Data were collected prospectively in the German Device II Registry.
Results: A total of 783 patients were included. Three sub-groups were identified: non-shock (NS) included 725 patients (92.6%), IS 24 (3.1%), and appropriate shock (AS) 34 (4.3%). IS patients were younger (AS 68 (58-77); IS 59 (51-68); NS 66 (56-75) years; p = 0.03), had been mainly referred for primary prophylaxis (AS 42.4%; IS 70.8%; NS 67.3%; p = 0.01), had a higher resting heart rate (AS 70 (63-80); IS 80 (71-98); NS 70 (60-81) BPM; p = 0.003), had more often atrial fibrillation (AF) (AS 14.7%; IS 45.8%; NS 18.8%; p = 0.006), and shorter QRS duration (AS 100 (90-120); IS 95 (90-100); NS 120 (98-150) msec.; p = 0.001). VVI-ICD was more common in IS (AS 64.7%; IS 83.3%; NS 49.8%; p = 0.002). At a follow-up of 18.2 months (75% IQR 13.6-22.4), no deaths were observed in the IS group, one (2.9%) in the AS, and 36 (4.9%) in the NS (p = 0.9). At logistic regression, VVI-ICD implantation was the strongest IS independent determinant (OR 5.0; 95% CI 1.6-15.9; p = 0.004) together with age < 70 years (OR 4.6; CI 1.4-14.7; p = 0.009), AF at time of ICD implantation (OR 3.5; CI 1.3-9.1; p = 0.01), and resting heart rate > 70/min (OR 2.8; CI 1.0-7.3; p = 0.03).
Conclusion: In a contemporary setting, some specific conditions such as VVI-ICD, younger age, and faster resting heart rates remain important IS determinants after ICD implantation.
Keywords: Cardioverter; Defibrillator; Inappropriate; Shock.