Incidence and prognostic significance of sustained ventricular tachycardias in heart failure patients implanted with biventricular pacemakers without a back-up defibrillator: results from the prospective, multicentre, Mona Lisa cohort study.

AIMS: The aim of this study was to investigate the 12-month incidence, predictive factors, and prognosis of sustained ventricular tachycardia (VT) in chronic heart failure patients implanted with biventricular pacemakers without a back-up defibrillator (CRT-P), assessed by continuous intracardiac ventricular electrograms. METHODS AND RESULTS: The Mona Lisa study, a prospective, multicentre, cohort study, designed to determine the incidence of sustained VT and its prognostic impact in CRT-P recipients within the year after implant enrolled 198 patients with moderate or severe chronic heart failure, despite optimal pharmacological therapy. An independent committee reviewed the data from all arrhythmic episodes as well as causes of death according to predefined criteria. During a mean follow-up of 9.8 +/- 3.1 months after implantation, 8 patients experienced at least one episode of sustained VT [4.3%; 95% confidence interval (CI), 1.1-7.5] and 21 deaths occurred, giving a 12-month mortality rate of 11.7% (95% CI, 6.4-16.9). The presence of sustained VT was associated with a high risk of sudden cardiac death (SCD) and the lowest 12-month overall survival (P < 0.0001). CONCLUSION: The incidence of sustained VT remains relatively low in the first year after CRT-P implantation, but when present appears closely associated with short-term adverse outcomes, especially SCD. This emphasizes the possible value of remote monitoring to detect high-risk patients for urgent upgrading.

Brady-tachy syndrome: rapid atrial pacing efficacy in preventing atrial fibrillation recurrence assessed by reliable electrograms: the prefib pilot study.

AIMS: Recent studies have tested different atrial pacing rates, modes, and sites for preventing atrial fibrillation (AF) recurrence. Present generation pacemakers offer reliable electrograms (EGMs) storage for optimizing the arrhythmia diagnosis. Based on these EGMs, the study objective was to assess the rate of AF recurrence at two different pacing rates. METHODS: Thirty patients suffering exclusively from symptomatic brady-tachy syndrome (BTS) resistant to > or =2 drugs, were implanted with a DDDR pacemaker. After a 5-days observation period, the DDD pacing rate was randomly programmed at 60 bpm (-15 bpm hysteresis) or at 80 bpm for 12 weeks. The two sequences were crossed over at the end of this fixed period or when earlier symptomatic AF recurred. Antiarrhythmics were maintained. Stored EGMs of > or =4 s duration identified all AF recurrence. RESULTS: Thirty patients (17 males, 77.2 +/- 8.1 years old) were included. One patient withdrew prematurely for severe heart failure associated with AF recurrence and rapid ventricular response. For the remainder of the 29 patients, fast atrial pacing neither provoked symptoms nor haemodynamic change. AF recurred in 16 patients paced at 60 (-15) bpm (mean time: 29 days; range 1-61) and in 9 patients paced at 80 bpm (mean time: 55 days; range 5-83) (P < 0.05). AF recurrence was asymptomatic in 50% of patients. CONCLUSIONS: These results confirm that rapid atrial pacing is 1) significantly effective for preventing AF recurrence in symptomatic BTS patients, and 2) haemodynamically well tolerated.

Performance of a dual-chamber implantable defibrillator algorithm for discrimination of ventricular from supraventricular tachycardia.

BACKGROUND: Inappropriate therapies remain a major problem in patients with implantable cardioverter defibrillators (ICDs). Decreasing the proportion of inappropriate therapies is a major objective. With the addition of atrial detection and advanced algorithms, dual-chamber ICDs are designed to offer better discrimination of ventricular (VT) and supraventricular (SVT) arrhythmias. The present multicentre, open study aimed to evaluate the performance of a dual-chamber detection algorithm, the Atrial View algorithm, incorporated in a dual-chamber ICD, the Ventak AV (Guidant Inc., St. Paul, Minnesota, USA). METHODS AND RESULTS: Fifty-one patients (45 males, 62+/-11 years, ejection fraction 42+/-15%) with standard indications received a Ventak AV ICD which analyzes, within the VT zone RR stability, tachycardia onset, atrial rate and AV relationship. Predischarge enhanced-detection algorithms were prospectively programmed: stability 24 ms, onset 9%, atrial fibrillation threshold 200 beats/min, and Vrate>Arate. An additional sustained rate duration criterion was programmed at least at 30 s. ICDs were interrogated every 3 months or when patients received shocks. A blinded review of electrograms for arrhythmia diagnosis and appropriateness of therapy was performed by 2 experts. Over the follow-up period (12+/-3.6 months), a total of 400 tachycardia episodes was recorded within the VT zone. After the review of stored electrograms, 237 (59%) true positive, 143 (36%) true negative, 17 (4%) false positive and 3 (1%) false negative episodes were diagnosed. Considering the 3 VTs incorrectly detected by the detection algorithms, therapy was delivered in 2 cases after sustained rate duration and 1 VT reverted spontaneously. Inappropriate therapy occurred in 17 cases. All but 1 were related to SVT with 1:1 atrioventricular relationship. Finally, on a per episode basis, the detection algorithm sensitivity was 99% and specificity was 89%. CONCLUSIONS: Programming of detection criteria based on stability, onset, atrial fibrillation rate threshold and Vrate>Arate allows a 99% sensitivity and an 89% specificity in Guidant ICDs. Discrimination of SVT with 1:1 atrioventricular relationship, however, remains a challenge for which new algorithms have to be designed.

Contributions of high resolution electrograms memorized by DDDR pacemakers in the interpretation of arrhythmic events.

The accuracy of information retrievable from the memories of DDDR pacing systems has been limited by the absence of actual electrograms confirming the proper sensing of spontaneous cardiac activity versus that of extraneous signals. This study examined the diagnostic power of a new arrhythmia interpretation scheme, which includes the recording and storage of high resolution endocavitary atrial and ventricular electrograms (HREGM). HREGM stored in the memories of new generation pacemakers (PM) in response to nonsustained ventricular tachycardia (NSVT), sustained VT, and atrial arrhythmias were analyzed in a follow-up registry of 520 patients at 1 month, and 3 to 6 months after implantation of a PM for standard indications. For each sequence of stored HREGM, the accuracy of the PM response was examined, classified as accurate (true positive), versus inaccurate (false positive), versus undetermined, and the relative contribution of the HREGM in verifying the PM diagnosis was measured. During a follow-up of 4.9 +/- 2 months, 256 (49%) of the 520 patients had an event recorded, which was confirmed to be arrhythmic on the basis of HREGM. Overall, approximately 34% of atrialtachy response (ATR) episodes were confirmed to be appropriate. Similar percentages of episodes were prompted by oversensing of signals unrelated to cardiac arrhythmias, while nearly 12% of the episodes could not be clarified because of such brief duration as to preclude recording of their onset. Approximately one-third of NSVT, and one-half of VT detections were false positive. Ventricular oversensing, most often due to myopotential interference in presence of unipolar sensing, and atrial undersensing were both identified as sources of false-positive detections of ventricular events. The proportion of true-positive detections was significantly higher in the bipolar (83%) than unipolar configuration. Among 520 PM recipients, miscellaneous episodes of atrial arrhythmias were confirmed by HREGM in 37% of patients within 3 to 6 months of follow-up. Atrial fibrillation was confirmed in only 6% of patients, of whom over 50% already had histories of atrial fibrillation. The prevalence of unsuspected atrial arrhythmia in this unselected population was lower than previously reported.