QRS duration does not predict occurrence of ventricular tachyarrhythmias in patients with implanted cardioverter-defibrillators.

OBJECTIVES: The aim of this study was to determine whether QRS duration (QRSd) correlates with occurrence of ventricular arrhythmia in patients with coronary disease (CAD) receiving implantable cardioverter-defibrillators (ICDs). BACKGROUND: A QRSd measured on a standard electrocardiograph (ECG) correlates with total mortality risk in CAD patients at high risk for sudden death; however, the relationship between QRSd and risk of ventricular tachyarrhythmias (ventricular tachycardia/ventricular fibrillation [VT/VF]) is unclear. METHODS: PainFREE Rx II was a randomized trial, comparing efficacy of antitachycardia pacing versus shock therapy for VT/VF in patients receiving ICDs. We retrospectively correlated the QRSd and specific ECG conduction abnormalities on the 12-lead ECG at study entry with occurrence of VT/VF in 431 patients with CAD enrolled in the trial. RESULTS: The QRSd was < or =120 ms in 291 of 431 (68%) patients. Left bundle branch block (LBBB) was present in 65 patients, right bundle branch block (RBBB) in 48 patients, and nonspecific intraventricular conduction delay (IVCD) was present in 124 patients. Over 12 months' follow-up, VT/VF occurred in 95 (22%) patients (22% of patients with QRSd < or =120 ms vs. 23% of patients with QRSd >120 ms, p = NS). Patients with LBBB were less likely to experience at least one VT/VF episode than patients with QRSd <120 ms. Patients with RBBB and nonspecific IVCD did not differ from patients with narrow QRS complexes with regard to occurrence of tachycardias. CONCLUSIONS: The QRSd and ECG conduction abnormalities are not useful to predict ICD benefit in patients having the characteristics of our study population. The utility of QRSd to predict VT/VF events in patients with CAD requires further prospective evaluation.

Appropriate and inappropriate ventricular therapies, quality of life, and mortality among primary and secondary prevention implantable cardioverter defibrillator patients: results from the Pacing Fast VT REduces Shock ThErapies (PainFREE Rx II) trial.

BACKGROUND: Implantable cardioverter defibrillators (ICDs) reduce mortality in primary and secondary prevention. Quality of life, mortality, appropriate therapies for specific ventricular rhythms, and inappropriate therapies for supraventricular tachycardia (SVT) were compared among 582 patients (primary prevention=248; secondary prevention=334) in PainFREE Rx II, a 634-patient prospective, randomized study of antitachycardia pacing or shocks for fast ventricular tachycardia (FVT). METHODS AND RESULTS: ICDs were programmed identically with 3 zones (ventricular tachycardia [VT] <188 bpm; FVT=188 to 250 bpm; ventricular fibrillation [VF] >250 bpm) but randomized to antitachycardia pacing or shock as initial therapy for FVT. All treated episodes with electrograms were adjudicated. Primary prevention patients had lower ejection fractions and more coronary artery disease. beta-Blocker use, antiarrhythmic drug use, and follow-up duration were similar. Over 11+/-3 months, 1563 treated episodes were classified as VT (n=740), FVT (n=350), VF (n=77), and SVT (n=396). The distribution of VT, FVT, and VF was not different between primary and secondary prevention patients (respectively, VT 52% versus 54%, FVT 35% versus 35%, and VF 14% versus 10%). More secondary prevention patients had appropriate therapies (26% versus 18%, P=0.02), but among these patients, the median number of episodes per patient was similar. Inappropriate therapies occurred in 15% of both groups and accounted for similar proportions of all detected and treated episodes (46% in primary prevention patients versus 34% in secondary prevention patients, P=0.09). Quality of life improved modestly in both groups, and mortality was similar. CONCLUSIONS: Primary prevention patients are slightly less likely to have appropriate therapies than secondary prevention patients, but episode density is similar among patients with appropriate therapies. SVT resulted in more than one third of therapies in both groups, but quality of life and mortality were similar.

A trial design for evaluation of empiric programming of implantable cardioverter defibrillators to improve patient management.

The delivery of implantable cardioverter defibrillator (ICD) therapy is sophisticated and requires the programming of over 100 settings. Physicians tailor these settings with the intention of optimizing ICD therapeutic efficacy, but the usefulness of this approach has not been studied and is unknown. Empiric programming of settings such as anti-tachycardia pacing (ATP) has been demonstrated to be effective, but an empiric approach to programming all VT/VF detection and therapy settings has not been studied. A single standardized empiric programming regimen was developed based on key strategies with the intention of restricting shock delivery to circumstances when it is the only effective and appropriate therapy. The EMPIRIC trial is a worldwide, multi-center, prospective, one-to-one randomized comparison of empiric to physician tailored programming for VT/VF detection and therapy in a broad group of about 900 dual chamber ICD patients. The trial will provide a better understanding of how particular programming strategies impact the quantity of shocks delivered and facilitate optimization of complex ICD programming.

Prospective randomized multicenter trial of empirical antitachycardia pacing versus shocks for spontaneous rapid ventricular tachycardia in patients with implantable cardioverter-defibrillators: Pacing Fast Ventricular Tachycardia Reduces Shock Therapies (PainFREE Rx II) trial results.

BACKGROUND: Successful antitachycardia pacing (ATP) terminates ventricular tachycardia (VT) up to 250 bpm without the need for painful shocks in implantable cardioverter-defibrillator (ICD) patients. Fast VT (FVT) >200 bpm is often treated by shock because of safety concerns, however. This prospective, randomized, multicenter trial compares the safety and utility of empirical ATP with shocks for FVT in a broad ICD population. METHODS AND RESULTS: We randomized 634 ICD patients to 2 arms-standardized empirical ATP (n=313) or shock (n=321)-for initial therapy of spontaneous FVT. ICDs were programmed to detect FVT when 18 of 24 intervals were 188 to 250 bpm and 0 of the last 8 intervals were >250 bpm. Initial FVT therapy was ATP (8 pulses, 88% of FVT cycle length) or shock at 10 J above the defibrillation threshold. Syncope and arrhythmic symptoms were collected through patient diaries and interviews. In 11+/-3 months of follow-up, 431 episodes of FVT occurred in 98 patients, representing 32% of ventricular tachyarrhythmias and 76% of those that would be detected as ventricular fibrillation and shocked with traditional ICD programming. ATP was effective in 229 of 284 episodes in the ATP arm (81%, 72% adjusted). Acceleration, episode duration, syncope, and sudden death were similar between arms. Quality of life, measured with the SF-36, improved in patients with FVT in both arms but more so in the ATP arm. CONCLUSIONS: Compared with shocks, empirical ATP for FVT is highly effective, is equally safe, and improves quality of life. ATP may be the preferred FVT therapy in most ICD patients.

Safety and efficacy of advanced atrial pacing therapies for atrial tachyarrhythmias in patients with a new implantable dual chamber cardioverter-defibrillator.

OBJECTIVES: This study evaluated the safety and efficacy of atrial pacing therapies for the treatment and prevention of atrial tachycardia (AT) or atrial fibrillation (AF) in a new dual chamber implantable cardioverter defibrillator (ICD). BACKGROUND: Patients with an ICD may also experience AT or AF that is amenable to pace termination. METHODS: The efficacy of atrial antitachycardia pacing (ATP) therapies for atrial tachycardia or atrial fibrillation (AT/AF) was determined in 151 patients after implantation of a GEM III AT ICD (Medtronic Inc., Minneapolis, Minnesota). The percentage of episodes successfully terminated was adjusted for multiple episodes per patient. RESULTS: A total of 717 of 728 (96%) episodes classified as AT or AF were judged to be appropriate detections. By device classification, atrial ATP terminated 187 of 383 (40% adjusted) episodes classified as AT compared with 65 of 240 episodes classified as AF (26% adjusted, p = 0.013). Atrial Ramp or Burst+ ATP terminated 184 of 378 episodes of AT (39% adjusted), whereas 50-Hz Burst pacing therapy terminated only 12 of 109 episodes of AT (12% adjusted) and 65 of 240 episodes of AF (26% adjusted). If efficacy was defined as termination of AT/AF within 20 s of delivery of the pacing therapy, ATP therapies terminated 139 of 383 (32% adjusted) episodes of AT compared with 34 of 240 episodes of AF (15% adjusted, p = 0.003). Efficacy was dependent on AT cycle length. Frequent transitions between AT and AF predicted inefficacy of atrial ATP (p < 0.001). Ventricular proarrhythmia secondary to atrial ATP was not observed. CONCLUSIONS: Atrial ATP therapies terminate many episodes of AT without ventricular proarrhythmia. The addition of 50-Hz Burst pacing has minimal efficacy for AT/AF.