Prevention of inappropriate shocks in ICD recipients: a review of 10,000 tachycardia episodes.

BACKGROUND: The efficacy of dual-chamber ICD arrhythmia classification algorithms is crucial to prevent inappropriate shocks. We report our experience from a meta-analysis of five prospective clinical studies with inclusion phases ranging between 1997 and 2003. METHODS: Dual-chamber ICD using standard dual-chamber arrhythmia classification algorithms were implanted in 802 patients (mean age = 64 +/- 11 years, 88% men) in 74 medical centers. The ICD indication was secondary prevention in 95% of patients. Supraventricular tachyarrhythmias (SVT) were previously documented in 26% of patients. All spontaneous tachyarrhythmic events documented by the device memories were analyzed by a adjudicating committee. The episodes lasting > 12 seconds and/or treated by the ICD were analyzed. RESULTS: Over a mean follow-up of 302 +/- 113 days, 9,690 events were reported. Mean heart rate at the time of events was 131 +/- 45 bpm (100-430). Events were classified as oversensing in 1.4%, sinus tachycardia (ST) in 66%, SVT in 13%, slow (< 150 bpm) ventricular tachycardia (VT) in 8.7%, and VT or ventricular fibrillation (VF) in 10.3%. The sensitivity of slow VT detection was 94%, and of VT/VF detection 99.3%. The specificity of sinus rhythm/ST/SVT recognition was 94%, positive predictive value 79.3%, and negative predictive value 99.2%. A total of 1,918 episodes were treated in 330 patients: 1,472 appropriately in 213, and 446 inappropriately in 117 (15% of the overall population) patients. Only 62 episodes were inappropriately treated by shocks in 40 patients, representing 5% of the overall population. CONCLUSIONS: In this conventional ICD population, the overall specificity of standard dual-chamber arrhythmia detection settings reached 94%. This feature allows efficient detection of fast as well as slow VT events with a very low rate of inappropriate shocks.

Incidence and clinical relevance of slow ventricular tachycardia in implantable cardioverter-defibrillator recipients: an international multicenter prospective study.

BACKGROUND: This study aims to assess the incidence and clinical relevance of slow ventricular tachycardia (VT) and the effectiveness and/or deleterious effects of antitachycardia pacing in slow VT in implantable cardioverter-defibrillator recipients. METHODS AND RESULTS: This multicenter prospective randomized study included 374 patients (326 men) without prior history of slow VT (<148 bpm) implanted with a dual-chamber implantable cardioverter-defibrillator. Patients had a 3-zone detection configuration: a slow VT zone (101 to 148 bpm), a conventional VT zone (>148 bpm), and a ventricular fibrillation zone. Patients were randomized to a treatment group (n=183) with therapy activated in the slow VT zone or a monitoring group (n=191) with no therapy in the slow VT zone. During follow-up (11 months), 449 slow VTs occurred in 114 patients (30.5% slow VT incidence); 181 VTs (54 patients) occurred in the monitoring group; 3 were readmitted to the hospital; and lightheadedness and palpitations occurred in 4 and 250 (60 patients) in the treatment group treated by antitachycardia pacing (89.8% success rate) and shock delivery (n=2). There were 10 crossovers from the monitoring to treatment group and 3 crossovers from the treatment to monitoring group (P=0.09). Quality of life scores were not different between groups. CONCLUSIONS: Slow VT incidence (<150 bpm) is high (30%) in implantable cardioverter-defibrillator recipients without prior history of slow VT, has limited clinical relevance, and is efficiently and safely terminated by antitachycardia pacing.

Enhanced specificity of a dual chamber ICD arrhythmia detection algorithm by rate stability criteria.

Inappropriate therapy remains an important limitation of implantable cardioverter defibrillators (ICD). PARAD+ was developed to increase the specificity conferred by the original PARAD detection algorithm in the detection of atrial fibrillation (AF). To compare the performances of the two different algorithms, we retrospectively analyzed all spontaneous and sustained episodes of AF and ventricular tachycardia (VT) documented by state-of-the-art ICDs programmed with PARAD or PARAD+ at the physicians' discretion. The results were stratified according to tachycardia rates <150 versus > or =150 beats/min. The study included 329 men and 48 women (64 +/- 10 years of age). PARAD was programmed in 263, and PARAD+ in 84 devices. During a mean follow-up of 11 +/- 3 months, 1,019 VT and 315 AF episodes were documented among 338 devices. For tachycardias with ventricular rates <150 beats/min, the sensitivity of PARAD versus PARAD+ was 96% versus 99% (NS), specificity 80% versus 93% (P < 0.002), positive predictive value (PPV) 94% versus 91% (NS), and negative predictive value (NPV) 86% versus 99% (P < 0.0001). In contrast, in the fast VT zone, the specificity and PPV of PARAD (95% versus 84% and 100% versus 96%) were higher than those of PARAD+ (NS, P < 0.001). Among 23 AF episodes treated in 16 patients, 3 episodes triggered an inappropriate shock in 3 patients, all in the PARAD population. PARAD+ significantly increased the ICD algorithm diagnostic specificity and NPV for AF in the slow VT zone without compromising patient safety.

Study of precursors of ventricular tachycardia from data stored in the memory of a dual chamber implantable cardioverter defibrillator.

This study was performed to examine precursors of ventricular tachyarrhythmias in patients who experienced a sustained ventricular tachyarrhythmia and received appropriate therapy by ICD. From an overall consecutive population of 77 patients, 18 patients (1 woman, mean age 61.7 +/- 10.8 years) were selected for having experienced a sustained ventricular tachyarrhythmia and received at least one appropriate ICD therapy preceded by 20 minutes of internal information. The number of premature ventricular complexes (PVCs)/min for each of the 20 minutes preceding the onset of ventricular tachyarrhythmia, the shortest coupling intervals between PVC and normal sinus beat, and the presence of short-long-short (SLS) interval sequences were examined. Data were stratified according to underlying disease, left ventricular ejection fraction, rate of ventricular tachyarrhythmia, and antiarrhythmic therapy. One hundred twenty-eight episodes of spontaneous ventricular tachyarrhythmia were retrieved. Rapid ventricular tachyarrhythmia (>160 beats/min) were preceded by a significantly greater mean number (3.71 +/- 6.36)of PVCs than slower ventricular tachyarrhythmia (