Low value of simple echocardiographic indices of ventricular dyssynchrony in predicting the response to cardiac resynchronization therapy.

AIMS: A recent study suggested that no single echocardiographic index of cardiac dyssynchrony can reliably identify candidates for cardiac resynchronization therapy (CRT). We examined the value of three simple echocardiographic indices for predicting the 6-month clinical and echocardiographic responses to CRT. METHODS AND RESULTS: We analysed data from 75 CRT-D system recipients. Standard echocardiography was used to measure aortic pre-ejection delay (APED), interventricular mechanical delay (IVMD), and delayed activation of the left ventricular (LV) infero-lateral wall (OVERLAP). Clinical responders were defined as patients who had an improved status, based on rehospitalization for heart failure, NYHA class, and peak oxygen consumption. Echocardiographic responders had a > or =10% decrease in LV end-systolic volume. During the study, one patient died and five were lost to follow-up. Of the remaining 69 analysable patients, 50 (72.5%) were classed as clinical responders and 41 (59.4%) as echocardiographic responders to CRT. Before CRT implantation, APED, IVMD, and OVERLAP were similar in responders and non-responders. The value of these indices of dyssynchrony as single or combined predictors of the clinical or echocardiographic response to CRT was low, with sensitivities ranging between 4 and 63%, and specificities between 37 and 100%. CONCLUSION: Simple echocardiographic indices of dyssynchrony were poor predictors of response to CRT.

Low energy biphasic cardioversion of atrial flutter: results from a pilot trial.

A pilot study was performed to determine the efficacy of low energy biphasic external cardioversion in common type atrial flutter. In the majority of patients (70%) successful cardioversion was achieved with low energy levels of 20 or 30 J; however a considerable number of patients (15%) were initially cardioverted to atrial fibrillation, needing an additional cardioversion with an even higher energy level.

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.

The 1+1 trial: a prospective trial of a dual- versus a single-chamber implantable defibrillator in patients with slow ventricular tachycardias.

BACKGROUND: The tachycardia detection interval (TDI) in implantable cardioverter/defibrillators (ICDs) is conventionally programmed according to the slowest documented ventricular tachycardia (VT), with a safety margin of 30 to 60 ms. With this margin, VTs above the TDI may occur. However, longer TDIs are associated with an increased risk of inappropriate therapy. We hypothesized that patients with slow VTs (<200 bpm) may benefit from a long TDI and a dual-chamber detection algorithm compared with a conventionally programmed single-chamber ICD. METHODS AND RESULTS: Patients with VTs <200 bpm were implanted with a dual-chamber ICD that was randomly programmed to a dual-chamber algorithm and a TDI of > or =469 ms or to a single-chamber algorithm with a TDI 30 to 60 ms above the slowest documented VT cycle length and the enhancement criteria of cycle length variation and acceleration. The primary combined end point was the number of all inappropriate therapies, VTs above the TDI, and VTs with significant therapy delay (>2 minutes). After 6 months, a crossover analysis was performed. Total follow-up was 1 year. One hundred two patients were included in the study. The programmed TDI was 500+/-36 ms during the dual-chamber phase and 424+/-63 ms during the single-chamber phase. For the primary end point (inappropriate therapies, VTs above the TDI, or VTs with detection delay), a moderate superiority of the dual-chamber mode was found: Mann-Whitney estimator=0.6661; 95% CI, 0.5565 to 0.7758; P=0.0040. CONCLUSIONS: Dual-chamber detection with a longer TDI improves VT detection and does not increase the rate of inappropriate therapies despite a considerable increase in tachycardia burden.

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.

Safety and efficacy of a dual chamber implantable cardioverter defibrillator capable of slow ventricular tachycardia discrimination: a randomized study.

New developments in dual chamber implantable cardioverter defibrillators (ICD) have increased the specificity of therapy delivery. This study was performed to examine the performance of an algorithm, focusing on its ability to distinguish slow ventricular tachycardia (VT) from sinus rhythm or supraventricular tachyarrhythmias. The patient population included 77 men and 13 women, 63 +/- 11 years old, treated with ICDs after episodes of spontaneous or inducible ventricular tachyarrhythmias. They were randomized to programming of the ICD to a lower limit of VT detection at 128 beats/min (group I, n = 44), versus 153 beats/min II (group II, n = 46). The primary endpoint of the study consisted of comparing the specificity and sensitivity of the algorithm between the two groups of patients. Over a 10.1 +/- 3.5 months follow-up, 325 episodes were detected in the Tachy zone in group I, versus 106 in group II. The sensitivity and specificity of the algorithm in group I were 98.8% and 94.4%, respectively, versus 100% and 89% in group II (NS). A single episode of VT at a rate of 132 beats/min was diagnosed as SVT in group I. The sensitivity and specificity of the algorithm for tachycardias <153 beats/min were 97.4% and 94.5%, respectively. Overall VT therapy efficacy was 100% in both groups. The performance of this algorithm in the slow VT zone supports the programming of a long Tachy detection interval to document slow events, and allows to treat slow VT, if necessary, without significant risk of inappropriate interventions for sinus tachycardia.

Mortality, morbidity, and complications in 3344 patients with implantable cardioverter defibrillators: results fron the German ICD Registry EURID.

ICDs are the therapy of choice in patients with life-threatening ventricular arrhythmias. Mortality, morbidity, and complication rates including appropriate and inappropriate therapies are unknown when ICDs are used in routine medical care and not in well-defined patients included in multicenter trials. Therefore, the data of 3,344 patients (61.1 +/- 12.1 years; 80.2% men; CAD 64.6%, dilated cardiomyopathy 18.9%; NYHA Class I-III: 19.1%, 54.3%, 20.1%, respectively; LVEF > 0.50: 0.234, LVEF 0.30-0.50: 0.472, LVEF < 0.30: 0.293, respectively) implanted in 62 German hospitals between January 1998 and October 2000 were prospectively collected and analyzed as a part of the European Registry of Implantable Defibrillators (EURID Germany). The 1-year survival rate was 93.5%. Patients in NYHA Class III and aLVEF < 0.30 had a lower survival rate than patients in NYHA Class I and a preserved LVEF (0.852 vs 0.975,P = 0.0001). Including the 1-year follow-up, 49.5% of patients had an intervention by the ICD, 39.8% had appropriate ICD therapies, 16.2% had inappropriate therapies. Overall, 1,691 hospital readmissions were recorded. The main causes for hospital readmissions were ventricular arrhythmias (61.3%) and congestive heart failure symptoms (12.9%). Thus, demographic data and mortality of patients treated with an ICD in conditions of standard medical care seems to be comparable and based on, or congruent with, the large secondary preventions trials. When ICDs are used in standard medical care, the 1-year survival rate is high, especially in patients with NYHA Class I and preserved LVEF. However, nearly half of all patients suffer from ICD intervention.