Abstract 9973: Late Revealing ECG abnormalities in Patients With Idiopathic Ventricular Fibrillation and Unknown Cause Ventricular Tachycardia Undergoing Implantable Cardioverter Defibrillator

Abstract

Backgroud: Despite of meticulous evaluation to reveal the cause of sudden cardiac death, some patients have been implanted Implantable Cardioverter Defibrillator (ICD) without definitive cause. However, they might have certain electrocardiogram (ECG) abnormalities during follow up. Methods: We analyzed 145 patients (55.8±16.6 years old, 95 males) who underwent ICD implantation in single center from January 1999 to March 2012. 43 patients (29.7%) were designated as idiopathic ventricular fibrillation (VF) or unknown cause ventricular tachycardia (VT) without organic nor ECG abnormalities. ECG abnormalities including early repolarization (ER) were analyzed during 3.7±2.4 years median follow-up duration. Appropriate shock and electrophysiologic inducibility of recurrent VF/VT were analyzed in patients with late revealing ECG abnormalities. Results: 32 patients (77.4%) showed ECG abnormalities during long-term follow-up after ICD implantation. 3 patients (7.0%) revealed Brugada type 2 ECG abnormalities, and 29 patients (67.4%) revealed ER. In patients with ER, 16 patients (37.2%) showed notching J point elevation, whereas 13 patients (30.2%) showed slurred J point elevation. Also 9 patients (20.9%) showed rapidly upsloping ST segment elevation (STE), whereas 20 patients (46.5%) showed horizontal/descending STE. Appropriate shock was dominantly delivered in patients with horizontal/descending STE compared with in patients without horizontal/descending STE (40.4% vs. 17.4%, Odd Ratio [OR] 3.17, 95% Confidence Interval [CI] 0.78-6.86, p=0.09). In patients undergoing electrophysiology before ICD implantation, recurrent VF/VT were significantly induced in patients with horizontal/descending STE compared with upsloping STE (71.4% vs. 25.0%, p=0.035). In subgroup analysis, only patients with inferior leads ER received significantly higher appropriate shock than other leads ER (43.5% vs. 10.0%, p=0.015). Conclusions: Considerable patients had ECG abnormalities after ICD implantation, although initial meticulous evlaution did not reveal any structural or ECG abnormalities. Also, Horizontal/descending STE in inferior leads might predict further appropriate ICD shock.