Clinical experience with the new detection algorithms for atrial fibrillation of a defibrillator with dual chamber sensing and pacing

Myocardial early systolic lengthening predicts mid-term outcomes in patients with hypertrophic cardiomyopathy

In this study, we investigated whether early systolic lengthening (ESL) which reflects subclinical ischemia and other echocardiographic and clinic parameters predict primary outcome [appropriate ICD shock, cardiovascular mortality and ventricular tachycardia (VT) or fibrillation] in patients with hypertrophic cardiomyopathy (HCM). 202 Patients with HCM (68% male, mean age 48 ± 13.9 years) were included in the study. Patients' clinical, electrocardiographic, 2D classic and speckle tracking echocardiography (STE) data were collected. ESL was defined as time from onset of the Q wave on ECG (onset of the R wave if the Q wave was absent) to maximum myocardial systolic lengthening. Patients were divided into two groups as occurrence or absence of primary outcome during 5 years follow up. During the follow-up period of 5 years (mean follow-up duration, 45.9 ± 10.8 months), 31 patients (15%) developed primary outcome [appropriate ICD shock 22 (11%), cardiovascular death 6 (3%), VT/VF 3(1.5%)]. Higher HCM Risk SCD score, longer ESL, and decreased global longitudinal peak strain (GLPS) were observed in patients with primary outcome. A Cox regression analysis, ESL, GLPS and HCM Risk SCD score were found to be independent predictors of occurrence of primary outcome. In ROC curve analysis, ESL > 53.5 msn could discriminate between groups with and without a primary outcome (AUC 0.768, 80% sensitivity and 60% specificity, CI 95% 0.666-0.871). ESL were found to be predictive for primary outcome in patients with HCM. Readily measurable ESL could be helpful to distinguish patients at high risk who could optimally benefit from ICD therapy.

Single-brand dual-chamber discriminators to prevent inappropriate shocks in patients implanted with prophylactic implantable cardioverter defibrillators: a propensity-weighted comparison of single- and dual-chamber devices

PURPOSE

Comparisons of the efficacy of dual- vs. single-chamber implantable cardioverter defibrillators (ICDs) in preventing inappropriate shocks have had contradictory results. We investigated whether dual-chamber devices have a lower risk of inappropriate shocks and the specific role of supraventricular tachycardia (SVT) discriminators.

METHODS

All heart failure (HF) patients without an indication for pacing and implanted with a prophylactic ICD were recruited from the nationwide multicenter UMBRELLA registry. Arrhythmic events were collected by remote monitoring and reviewed by a committee of experts.

RESULTS

Among 782 patients, single-chamber ICDs were implanted in 537 (68.7%) and dual-chamber devices in 245 (31.3%). During a mean follow-up of 52.2 ± 24.5 months, 109 inappropriate shocks were delivered in 49 patients (6.2%). In the propensity-score-matched analysis, dual-chamber ICDs were related to lower rates of inappropriate shocks as compared to single-chamber devices (0.9% vs. 11.8%, p = < 0.001, log-rank test). In multivariable Cox proportional analysis, independent predictors of inappropriate shock were history of atrial fibrillation (hazard ratio (HR) = 2.78, CI 1.37-5.64, p = 0.004), chronic kidney disease (HR = 6.15, CI 2.82-13.53, p < 0.001), and non-ischemic cardiomyopathy (HR = 2.84, CI 1.54-5.23, p = 0.001). Among ICD settings, PR logic was the only discriminator independently related to a reduced risk of inappropriate shocks (HR = 0.18, CI 0.06-0.48, p = 0.001), along with an SVT limit enabled over 200 bpm (HR = 0.24, CI 0.11-0.51, p < 0.001).

CONCLUSIONS

In this nationwide cohort of primary prevention ICD-only patients, dual-chamber devices were related to lower risk of inappropriate shocks compared to single-chamber ICDs. Besides, PR logic and SVT limit > 200 bpm emerged as protective factors.

ICD discrimination of SVT versus VT with 1:1 V-A conduction: A review of the literature

Inappropriate ICD shocks are associated with increased mortality. They also impair patients' quality of life, increase hospitalizations, and raise health-care costs. Nearly 80% of inappropriate ICD shocks are caused by supraventricular tachycardia. Here we report the case of a patient who received a single-lead dual-chamber sensing ICD for primary prevention of sudden cardiac death and experienced inappropriate ICD shocks. V-A time, electrogram morphology, and response to antitachycardia pacing suggested atrioventricular nodal reentry tachycardia, which was confirmed in an electrophysiology study. Inspired by this case, we performed a literature review to discuss mechanisms for discrimination of supraventricular tachycardia with 1:1 A:V relationship from ventricular tachycardia with 1:1 retrograde conduction.

Does change in device detected frequency of non-sustained or diverted episodes serve as a marker for inappropriate shock therapy? Analyses from the INTRINSIC RV and ALTITUDE-REDUCES Trials

AIMS

Implantable cardioverter-defibrillators (ICDs) treat ventricular tachycardia or fibrillation but may also deliver unnecessary shocks. We sought to determine if the frequency of ICD-detected non-sustained or diverted (NSD) episodes increases before appropriate or inappropriate ICD shocks.

METHODS AND RESULTS

We evaluated NSD episodes in the INTRINSIC RV Trial and their relationship to ICD shocks (appropriate and inappropriate). Time from NSD to shock was analysed. Results were validated by utilizing 1495 adjudicated ICD and cardiac resynchronization therapy-defibrillator shocks following NSD episodes collected through the LATITUDE remote monitoring system as part of the ALTITUDE-REDUCES Study. In INTRINSIC RV, 185 participants received 373 shocks; 148 had at least 1 NSD episode. Non-sustained or diverted frequency increased 24 h before the first shock for those receiving an inappropriate (P < 0.01) but not an appropriate shock (P = 0.17). Patients with NSD episodes within 24 h of a shock were significantly more likely to receive inappropriate therapy [odds ratio (OR) = 3.12, P < 0.01]. At the receiver operator curve determined optimal cutoff, an NSD episode within 14 min before shock strongly predicted inappropriate therapy (sensitivity 48%, specificity 91%; OR = 8.8, and P < 0.001). The 14 min cut-off evaluated on an independent dataset of 1495 shock episodes preceded by an NSD in the ALTITUDE-REDUCES Study confirmed these results (sensitivity = 47%, specificity = 85%, OR = 5.0, and P < 0.001).

CONCLUSION

Device-detected NSD episodes increase before inappropriate but not appropriate shocks. Novel alerts or automated algorithms based on NSD episodes may reduce inappropriate shocks.

Innovative P-wave detection for discrimination between ventricular and supraventricular tachycardia in single-chamber ICDs: is the P-wave invisible during tachycardia?

AIMS

Differentiation between supraventricular tachycardia (SVT) and ventricular tachycardia (VT) remains a substantial clinical challenge in patients with single-chamber implantable cardioverter-defibrillators (ICDs) due to absence of visible P waves. Innovative optimization of intrathoracic electrogram (EGM) configuration will facilitate P-wave detection and rhythm differentiation during tachycardia.

METHODS AND RESULTS

Innovative optimization of EGM configuration was originally performed to improve patient care. In this retrospective cohort study, we examined our database for records of 140 consecutive patients undergoing single-chamber ICD implantation. During the follow-ups of 61 included patients with optimized EGM configuration, 27 patients were identified to have VT and/or SVT. EGMs in the Can (generator) to superior vena cava (Can-SVC) configuration were compared with those conventionally from the Can to right ventricular coil (Can-RV coil) source in the same patients. In Can-SVC EGMs, the ratio of P/QRS amplitude was 14-fold higher (0.57 ± 0.08 vs. 0.04 ± 0.00, P < 0.001) compared with those in Can-RV coil EGMs during sinus rhythm. With Can-SVC configuration, the odds of atrioventricular dissociation detection in patients with VT was increased 15-fold (61.9% vs. 9.5% with Can-RV coil; odds ratio, 15.4; 95% confidence interval, 2.8 to 84.7; P = 0.0009). In patients with SVT, P-waves or retrograde P-waves were markedly more identifiable in Can-SVC configuration compared with Can-RV coil (odds ratio, 40; 95% confidence interval, 3.6 to 447.1; P = 0.0010).

CONCLUSION

P-wave recognition by optimizing EGM configuration provides a novel diagnostic tool for differentiation between VT and SVT in single-chamber ICDs. A potential discrimination algorithm would provide a cost-effective approach to improving the qualitative outcomes.

Dynamic analysis of cardiac rhythms for discriminating atrial fibrillation from lethal ventricular arrhythmias

BACKGROUND

Implantable cardioverter-defibrillators (ICDs), the first line of therapy for preventing sudden cardiac death in high-risk patients, deliver appropriate shocks for termination of ventricular tachycardia (VT)/ventricular fibrillation. A common shortcoming of ICDs is imperfect rhythm discrimination, resulting in the delivery of inappropriate shocks for atrial fibrillation (AF). An underexplored area for rhythm discrimination is the difference in dynamic properties between AF and VT/ventricular fibrillation. We hypothesized that the higher entropy of rapid cardiac rhythms preceding ICD shocks distinguishes AF from VT/ventricular fibrillation.

METHODS AND RESULTS

In a multicenter, prospective, observational study of patients with primary prevention ICDs, 119 patients received shocks from ICDs with stored, retrievable intracardiac electrograms. Blinded adjudication revealed shocks were delivered for VT/ventricular fibrillation (62%), AF (23%), and supraventricular tachycardia (15%). Entropy estimation of only 9 ventricular intervals before ICD shocks accurately distinguished AF (receiver operating characteristic curve area, 0.98; 95% confidence intervals, 0.93-1.0) and outperformed contemporary ICD rhythm discrimination algorithms.

CONCLUSIONS

This new strategy for AF discrimination based on entropy estimation expands on simpler concepts of variability, performs well at fast heart rates, and has potential for broad clinical application.

Multicenter automatic defibrillator implantation trial: reduce inappropriate therapy (MADIT-RIT): background, rationale, and clinical protocol

The implantable cardioverter defibrillator (ICD) is highly effective in reducing mortality due to cardiac arrhythmias in high-risk cardiac patients. However, inappropriate therapies caused predominantly by supraventricular tachyarrhythmias (SVTs) remain a significant side effect of ICD therapy despite medical treatment, affecting 8-40% of patients. The MADIT-RIT is a global, prospective, randomized, nonblinded, three-arm, multicenter clinical investigation to be performed in the Unites States, Europe, Canada, Israel and Japan, and will utilize approximately 90 centers with plan to enroll 1500 patients programmed to three treatment arms. The objective of the MADIT-RIT trial is to determine if dual-chamber ICD or CRT-D devices with high rate cutoff (MADIT-RIT-Arm B) and/or long delay in combination with detection enhancements (MADIT-RIT-Arm C) are associated with fewer patients experiencing inappropriate therapies than standard programming (MADIT-RIT-Arm A) during postimplant follow-up of patients with indication for primary prevention device therapy. This paper describes design and analytic plan for the MADIT-RIT trial.

Predictors and clinical impact of inappropriate implantable cardioverter-defibrillator shocks in Korean patients

Limited data are available on inappropriate shocks in Korean patients implanted with an implantable cardioverter-defibrillator (ICD). We investigated the impact of inappropriate shocks on clinical outcomes. This retrospective, single-center study included 148 patients treated between October 1999 and June 2011. The primary outcome was a composite event of all-cause mortality or hospitalization for any cardiac reason. The median follow-up duration was 29 months (interquartile range: 8 to 53). One or more inappropriate shocks occurred in 34 (23.0%) patients. A history of atrial fibrillation was the only independent predictor of inappropriate shock (hazard ratio [HR]: 4.16, 95% confidence interval [CI]: 1.89-9.15, P < 0.001). Atrial fibrillation was the most common cause of inappropriate shock (67.7%), followed by supraventricular tachycardia (23.5%), and abnormal sensing (8.8%). A composite event of all-cause mortality or hospitalizations for any cardiac reason during follow-up was not significantly different between patients with or without inappropriate shock (inappropriate shock vs no inappropriate shock: 35.3% vs 35.4%, adjusted HR: 1.06, 95% CI: 0.49-2.29, P = 0.877). Inappropriate shocks do not affect clinical outcomes in patients implanted with an ICD, although the incidence of inappropriate shocks is high.

Recollection of pain due to inappropriate versus appropriate implantable cardioverter-defibrillator shocks

BACKGROUND

Although inappropriate shocks are known to be an important consequence of implantable cardioverter-defibrillators (ICDs), the subjective experience of pain intensity perceived by those receiving inappropriate versus appropriate shocks has not previously been examined.

METHODS

One hundred ICD patients underwent a standardized interview by an investigator blinded to the clinical history. Patients with a previous ICD shock were asked to describe the intensity of the associated pain on a standard 0-10 scale (10 being the worst pain they had ever experienced). Medical charts were then examined for any history of inappropriate and/or appropriate ICD discharges.

RESULTS

Thirty-five of the 100 patients had a record of at least one ICD shock, and 17 had experienced at least one inappropriate shock. Those with a history of an inappropriate shock described a significantly higher median pain scale (9, interquartile range [IQR] 8-10) compared to those with a history of only appropriate shocks (median 4, IQR 2-8, P = 0.0011). In multivariable analysis, a history of an inappropriate shock was the only predictor statistically significantly associated with an increase in shock pain: the pain scale for those with inappropriate shocks was higher by 2.8 points on average after multivariable adjustment (95% confidence interval 0.29-5, P = 0.030). Eighteen patients had considered having their device deactivated, and a history of an inappropriate shock was the only factor independently associated with this consideration.

CONCLUSIONS

Compared to those who have received only appropriate shocks, inappropriate ICD shocks are associated with a recollection of greater pain and consideration of device inactivation.

Early therapy following myocardial infarction: arguments for and against implantable cardioverter-defibrillators

The implantable cardioverter-defibrillator (ICD), when implanted in the late phase of myocardial infarction (MI) in the primary prevention of sudden cardiac death, reduces total mortality by 23-31%. Current guidelines recommend ICD implantation at least 40 days after MI. Despite optimal MI therapy, the risk of sudden cardiac death or cardiac arrest remains highest within the first 30 days after index infarction. Two randomized trials with ICD implantation early after MI failed to show the reduction of total mortality in a long-term follow-up study. The decrease of sudden cardiac death incidence was counterbalanced by an increase of nonsudden deaths, which may have been caused by the augmentation of heart failure deaths in ICD groups, presumably due to ICD interventions. Therefore, optimizing ICD appears to be the most important issue influencing the long-term outcome.

Tools and strategies for the reduction of inappropriate implantable cardioverter defibrillator shocks

Implantable cardioverter defibrillators (ICDs) have been shown to provide a survival benefit in patients at high risk of sudden cardiac death. A major problem associated with ICD therapy is the occurrence of inappropriate shocks which impair patients' quality of life and may also be arrhythmogenic. Despite recent technological advances, the incidence of inappropriate shocks remains high, thus posing a challenge that we have to meet. In the present review we summarise the available tools and the strategies that can be followed in order to reduce inappropriate ICD shocks.

Inappropriate implantable cardioverter-defibrillator shocks in MADIT II: frequency, mechanisms, predictors, and survival impact

OBJECTIVES

This study sought to identify the incidence and outcome related to inappropriate implantable cardioverter-defibrillator (ICD) shocks, that is, those for nonventricular arrhythmias.

BACKGROUND

The MADIT (Multicenter Automatic Defibrillator Implantation Trial) II showed that prophylactic ICD implantation improves survival in post-myocardial infarction patients with reduced ejection fraction. Inappropriate ICD shocks are common adverse consequences that may impair quality of life.

METHODS

Stored ICD electrograms from all shock episodes were adjudicated centrally. An inappropriate shock episode was defined as an episode during which 1 or more inappropriate shocks occurred; another inappropriate ICD episode occurring within 5 min was not counted. Programmed parameters for patients with and without inappropriate shocks were compared.

RESULTS

One or more inappropriate shocks occurred in 83 (11.5%) of the 719 MADIT II ICD patients. Inappropriate shock episodes constituted 184 of the 590 total shock episodes (31.2%). Smoking, prior atrial fibrillation, diastolic hypertension, and antecedent appropriate shock predicted inappropriate shock occurrence. Atrial fibrillation was the most common trigger for inappropriate shock (44%), followed by supraventricular tachycardia (36%), and then abnormal sensing (20%). The stability detection algorithm was programmed less frequently in patients receiving inappropriate shocks (17% vs. 36%, p = 0.030), whereas other programming parameters did not differ significantly from those without inappropriate shocks. Importantly, patients with inappropriate shocks had a greater likelihood of all-cause mortality in follow-up (hazard ratio 2.29, p = 0.025).

CONCLUSIONS

Inappropriate ICD shocks occurred commonly in the MADIT II study, and were associated with increased risk of all-cause mortality.

Prevention of inappropriate therapy in implantable defibrillators: A meta-analysis of clinical trials comparing single-chamber and dual-chamber arrhythmia discrimination algorithms

INTRODUCTION

A proposed benefit of dual-chamber arrhythmia discrimination is a reduction in inappropriate therapy in implantable cardioverter-defibrillators (ICDs). The aim of this meta-analysis was to establish whether dual-chamber arrhythmia discrimination algorithms reduce inappropriate device therapy.

METHODS AND RESULTS

Public domain databases, MEDLINE, EMBASE, and Cochrane Register of Controlled Trials, were searched from 1996 to 2006. Two investigators abstracted data independently. Pooled estimates were calculated using both fixed-effects and random-effects models. We retrieved 5 prospective studies comparing dual-chamber with single-chamber arrhythmia discrimination, accumulating data on 748 patients. Pooled per-patient based analysis demonstrated that the number of patients receiving inappropriate ICD therapy was not different between single- and dual-chamber devices (odds ratio [OR] 1.23; 95% CI, 0.83 to 1.81; p=0.31). Per-episode based analysis demonstrated a favoring benefit for dual-chamber arrhythmia discrimination (OR 0.64; 95% CI, 0.52 to 0.78; p<0.001). A mean reduction of 1.1 inappropriately treated atrial episodes per patient was observed with dual-chamber arrhythmia discrimination (p<0.001).

CONCLUSIONS

Dual-chamber arrhythmia discrimination is associated with a reduction in the number of inappropriate treated episodes. The number of patients who experience inappropriate therapy is not reduced by dual-chamber discrimination.

Socio-economic analysis of cardiac resynchronization therapy

The field of electrical device therapy has benefited from two basically independent lines of investigation demonstrating mortal benefit from either cardiac resynchronization therapy (CRT) or implantable cardioverter-defibrillator (ICD) therapy in patients with heart failure. Current clinical evidence data is insufficient to conclude that CRT-defibrillation (CRTD) offers an advantage over CRT-pacing (CRTP) alone. The cost of adding a defibrillator to the CRTP device is substantial and will act as a barrier to wide scale penetration. Annualized sudden death rates are very low in certain primary prevention populations. Consequently, the potential for overtreatment is very large and the negative costs of ICD therapy are distributed equally among those patients who will have a life saving benefit and those who were "destined" never to require the therapy. The perception that these costs are acceptable if lives are saved is commonly cited as justification for expensive therapy on a population scale, but there is an important and practical difference between costs per unit life saved and costs among patients who really never needed the device. Until the a priori predictors of volumetric response to CRT are better understood, the use of CRTD in class IV patients should be discouraged since ICD therapy is unlikely to extend life in volumetric non-responders. Similarly, the use of CRTD in patients who are "destined" for significant volumetric response is probably unwise since their risk of sudden death is minimized due to favorable substrate modification. Clinical trials comparing conventional ICDs, CRTP and CRTD are necessary to rationalize use of expensive hardware resources among different patient populations. Additionally, the importance of patient preference regarding end of life care should receive greater emphasis. While CRTP may be considered palliative in terminal heart failure, the decision to offer CRTD must include a discussion with the patient regarding mode of death and the potential for the defibrillator to replace a sudden and peaceful death with a prolonged death from progressive pump failure.

Differentiation of ventricular and supraventricular tachycardias based on the analysis of the first postpacing interval after sequential anti-tachycardia pacing in implantable cardioverter-defibrillator patients

BACKGROUND

Current discrimination algorithms do not completely avoid inappropriate tachycardia detection.

OBJECTIVES

This study analyzes the discrimination capability of the changes of the first postpacing interval (FPPI) after successive bursts of anti-tachycardia pacing (ATP) trains in implantable cardioverter-defibrillator (ICD)-recorded tachycardias.

METHODS

We included 50 ICD patients in this prospective study. We hypothesized that the FPPI variability (FPPIV) when comparing bursts with different numbers of beats would be shorter in ventricular tachycardias (VTs) compared with supraventricular tachycardias (SVTs). The ATP (5-10 pulses, 91% of tachycardia cycle length) was programmed for tachycardias >240 ms.

RESULTS

Anti-tachycardia pacing was delivered during 37 sinus tachycardias (STs) in an exercise test, 96 induced VTs in an electrophysiological study, and 198 spontaneous episodes (144 VTs and 54 SVTs). The FPPI remained stable after all ATP bursts in VT but changed continuously in SVT; when comparing bursts of 5 and 10 pulses, the FPPIV was shorter in VT (34 +/- 65 vs.138 +/- 69, P<.0001, in all T and 12 +/- 20 vs. 138 +/- 69, P<.0001, in T>or=320 ms) than in SVT. In T>or=320 ms an FPPIV<or=50 ms between bursts of 5 and 10 pulses classified correctly 100% of VTs and 90% of SVTs. Anti-tachycardia pacing terminated 66% of induced VTs, 60% of spontaneous VTs, and 20% of spontaneous SVTs and induced no VT during spontaneous or exercise induced SVT. Five induced and two spontaneous VT episodes were accelerated.

CONCLUSIONS

Analysis of FPPIV after ATP discriminates ICD-detected T. Successive bursts (of ATP) trains at 91% of tachycardia cycle length are safe, despite being delivered before rhythm classification.

Incidence and Significance of Far-Field R Wave Sensing in a VDD-Implantable Cardioverter Defibrillator

BACKGROUND

A VDD-implantable cardioverter-defibrillator (ICD) provides atrioventricular (AV) synchronous stimulation when necessary and incorporates the advantages of dual chamber arrhythmia discrimination algorithms both at potentially lower costs and less periprocedural complications than a DDD-ICD system. A prerequisite for correct dual chamber ICD function is reliable atrial sensing.

METHODS

We evaluated atrial near- and ventricular far-field sensing and its impact on the dual-chamber detection algorithm in 106 patients with a single-lead VDD-ICD during a 12-month follow-up period.

RESULTS

Six hundred and thirty-nine follow-ups were included. Mean near-field amplitude was 3.82 +/- 1.76 mV; mean far-field amplitude was 0.31 +/- 0.15 mV. 46% of patients had far-fields >0.35 mV and 35% of patients showed atrial EGM markers corresponding to a ventricular far-field in at least one follow-up. Six hundred and forty-five tachycardia episodes were evaluated. Due to far-field sensing, three of 66 episodes (4.5%) of sinus tachycardia were misclassified as ventricular tachycardia (VT), leading to antitachycardia therapies. Delayed detection of VT was seen in a 12 of 323 episodes (3.7%) in five of 62 patients (8%) having VT events (delay 6.4 +/- 6.0 seconds (range 2-24 seconds)). Stable far-field amplitudes <0.2 mV in a follow-up had a high negative predictive value for the occurrence of malfunction during tachycardia-conversely, high far-field amplitudes or a high incidence of far-field markers are only moderately correlated with malfunction.

CONCLUSIONS

Ventricular far-field sensing in a VDD-ICD is not uncommon, however, tachycardia detection by the dual chamber algorithm is not seriously impaired by far-field sensing.

The Rhythm ID Going Head to Head Trial (RIGHT): Design of a Randomized Trial Comparing Competitive Rhythm Discrimination Algorithms in Implantable Cardioverter Defibrillators

BACKGROUND

The implantable cardioverter defibrillator (ICD) has become primary therapy for the prevention of sudden death. One of the major morbidities of ICD use remains inappropriate therapy for supraventricular arrhythmias (SVA). Detection enhancements have increased therapy specificity, but their impact on inappropriate therapy is not well studied. Moreover, ICD manufacturers have developed unique algorithms to meet this goal, with no previous clinical direct comparisons. RIGHT is a randomized, prospective study that will assess the differential efficacy of ICDs from two different manufacturers. It is the first trial to compare directly competitive ICD rhythm discrimination algorithms on a large scale.

OBJECTIVE

The primary objective of this study is to assess arrhythmia discrimination in Guidant versus Medtronic ICDs by comparing the time to first inappropriate therapy after the predischarge visit.

METHODS

The study will enroll approximately 2,000 patients in 100 centers. Patients will be randomized to Guidant or Medtronic using a permuted block design, stratified by center and by single/dual chamber device types. Patients will receive a commercially available Guidant VITALITY 2 family ICD with Rhythm ID or a Medtronic ICD using the Enhanced PR Logic or Wavelet discrimination algorithms, and will be followed according to the schedule shown until a common closing date with a minimum follow-up of 12 months. All events will be reviewed by an independent committee to determine the appropriateness of rhythm classification and therapy delivery.

CONCLUSION

RIGHT is the first randomized, large scale, head-to-head comparison of ICD discrimination algorithms.

Dual-Chamber Versus Single-Chamber Detection Enhancements for Implantable Defibrillator Rhythm Diagnosis

BACKGROUND

Delivery of inappropriate shocks caused by misdetection of supraventricular tachycardia (SVT) remains a substantial complication of implanted cardioverter/defibrillator (ICD) therapy. Whether use of optimally programmed dual-chamber ICDs lowers this risk compared with that in single-chamber ICDs is not clear.

METHODS AND RESULTS

Subjects with a clinical indication for ICD (n=400) at 27 participating centers received dual-chamber ICDs and were randomly assigned to strictly defined optimal single- or dual-chamber detection in a single-blind manner. Programming minimized ventricular pacing. The primary end point was the proportion of SVT episodes inappropriately detected from the time of programming until crossover or end of study. On a per-episode basis, 42% of the episodes in the single-chamber arm and 69% of the episodes in the dual-chamber arm were due to SVT. Mortality (3.5% in both groups) and early study withdrawal (14% single-chamber, 11% dual-chamber) were similar in both groups. The rate of inappropriate detection of SVT was 39.5% in the single-chamber detection arm compared with 30.9% in the dual-chamber arm. The odds of inappropriate detection were decreased by almost half with the use of the dual-chamber detection enhancements (odds ratio, 0.53; 95% confidence interval, 0.30 to 0.94; P=0.03).

CONCLUSIONS

Dual-chamber ICDs, programmed to optimize detection enhancements and to minimize ventricular pacing, significantly decrease inappropriate detection.

Clinical Results of an Advanced SVT Detection Enhancement Algorithm

INTRODUCTION

Supraventricular tachycardia (SVT) has many characteristics that are similar to ventricular tachycardia (VT). This presents a significant challenge for the SVT-detection algorithms of an implantable cardioverter defibrillator (ICD). A newly developed ICD, which utilizes a Vector Timing and Correlation algorithm as well as interval-based conventional SVT discrimination algorithms (Rhythm ID), was evaluated in this study.

MATERIALS AND METHODS

This study was a prospective, multicenter trial that evaluated 96 patients implanted with an ICD at 21 U.S. centers. All patients were followed at 2 weeks, 1 month, and every 3 months post implant. A manual Rhythm ID reference vector was acquired prior to any arrhythmia induction. During testing, atrial tachyarrhythmias were induced first, followed by ventricular arrhythmia induction. Induced and spontaneous SVT and VT/ventricular fibrillation (VF) episodes recorded during the trial were annotated by physician investigators.

RESULTS

The mean age of the patients implanted with an ICD was 67.3 +/- 10.8 years. Eighty-one percent of patients were male. The primary cardiovascular disease was coronary artery disease, and the primary tachyarrhythmia was monomorphic VT. Implementation of the Rhythm ID algorithm did not affect the VT/VF detection time. There were a total of 370 ventricular tachyarrhythmias (277 induced and 93 spontaneous) and 441 SVT episodes (168 induced and 273 spontaneous). Sensitivity for ventricular tachyarrhythmias was 100%, and specificity for SVT was 92% (94% and 91% for induced and spontaneous SVT, respectively). All patients had a successful manual Rhythm ID acquisition prior to atrial tachyarrhythmia induction. At the 1-month follow-up, the Rhythm ID references were updated automatically an average of 167.8 +/- 122.7 times. Stored Rhythm ID references correlated to patients' normally conducted rhythm 100% at 2 weeks, and 98% at 1 month.

CONCLUSIONS

The Rhythm ID algorithm achieved 100% sensitivity for VT/VF, and 92% specificity for SVT. The manual and automatic Rhythm ID update algorithms successfully acquired references, and the updated references were highly accurate.

Optimal Combination of Discriminators for Differentiating Ventricular from Supraventricular Tachycardia by Dual-Chamber Defibrillators

Discriminators for ventricular/supraventricular tachycardia.

INTRODUCTION

Dual-chamber implantable cardioverter defibrillators (ICDs) use discriminators to differentiate between supraventricular tachycardias (SVTs) and ventricular tachycardias (VT), the accuracy of which may depend on the type and method used. ICDs can combine rate branching of tachyarrhythmias according to their A:V relationship with two SVT-VT discriminators in each rate branch, using ANY (either) or ALL (both) logic. Our goal was to determine the optimal discriminator combination.

METHODS

Stored electrogram data from 596 spontaneous tachyarrhythmias from 203 patients with Photon DR ICDs were analyzed. Arrhythmias are first classified by the relationship of atrial and ventricular rates (rate branches V<A, V=A, and V>A) followed by additional discriminators: morphology and/or sudden onset if V=A; morphology and/or interval stability if V<A. Data were analyzed for all combinations of ANY and ALL logic.

RESULTS

Sensitivity and specificity were calculated for all spontaneous episodes in each analysis. V=A branch: ALL logic produced unacceptably low sensitivity, whereas morphology provided only similar sensitivity but better specificity than ANY logic. A>V branch: ANY logic provided adequate sensitivity. The combination of morphology only in V=A with interval stability or morphology (ANY logic) in V<A, provided the optimal result with sensitivity, specificity, positive, and negative predictive values of 99%, 79%, 87%, and 98%, respectively.

CONCLUSION

SVT-VT combined discriminators strongly influence dual-chamber SVT-VT discrimination performance. In our study, optimal programming is morphology only in the V=A branch and morphology or interval stability (ANY) in the V<A branch. ALL logic should be used with caution due to loss of sensitivity.

Appropriate and Inappropriate Ventricular Therapies, Quality of Life, and Mortality Among Primary and Secondary Prevention Implantable Cardioverter Defibrillator Patients

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. β-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.

Clinical variables predicting inappropriate use of implantable cardioverter-defibrillator in patients with coronary heart disease or nonischemic dilated cardiomyopathy

Inappropriate therapy is a common clinical problem in recipients of implantable cardioverter-defibrillators (ICDs). The present study evaluated whether clinical characteristics could predict inappropriate ICD therapy due to atrial tachyarrhythmias in a series of 260 patients.

Prevention of inappropriate therapy in implantable cardioverter-defibrillators

OBJECTIVES

The purpose of this randomized study was to investigate the performance of single- and dual-chamber tachyarrhythmia detection algorithms.

BACKGROUND

A proposed benefit of dual-chamber implantable cardioverter-defibrillators (ICDs) is improved specificity of tachyarrhythmia detection.

METHODS

All ICD candidates received a dual-chamber ICD and were randomized to programmed single- or dual-chamber detection. Of 60 patients (47 male, age 58 +/- 14 years, left ventricular ejection fraction 30%), 29 had single-chamber and 31 had dual-chamber settings. The detection results were corrected for multiple episodes within a patient with the generalized estimating equations method.

RESULTS

A total of 653 spontaneous arrhythmia episodes (39 patients) were classified by the investigators; 391 episodes were ventricular tachyarrhythmia (32 patients). All episodes of ventricular tachyarrhythmias were appropriately detected in both settings. In 25 patients, 262 episodes of atrial tachyarrhythmias were recorded. Detection was inappropriate for 109 atrial tachyarrhythmia episodes (42%, 18 patients). Rejection of atrial tachyarrhythmias was not significantly different between both groups (p = 0.55). Episodes of atrial flutter/tachycardia were significantly more misclassified (p = 0.001). Overall, no significant difference in tachyarrhythmia detection (atrial and ventricular) between both settings was demonstrated (p = 0.77).

CONCLUSIONS

The applied detection criteria in dual-chamber devices do not offer benefits in the rejection of atrial tachyarrhythmias. Discrimination of atrial tachyarrhythmias with a stable atrioventricular relationship remains a challenge.

Randomized controlled study of detection enhancements versus rate-only detection to prevent inappropriate therapy in a dual-chamber implantable cardioverter-defibrillator

OBJECTIVES

The purpose of this study was to compare rate-only detection to enhanced detection in a dual-chamber implantable cardioverter-defibrillator (ICD), to discriminate ventricular tachycardia from supraventricular tachycardia.

BACKGROUND

ICDs are highly effective in treating ventricular tachycardia (VT) or ventricular fibrillation (VF). However, they frequently deliver inappropriate therapy during supraventricular tachycardia (SVT).

METHODS

We conducted a randomized clinical trial of detection enhancements in a dual-chamber ICD compared to control (rate-only) detection to discriminate VT from SVT. Detection enhancements included a specific standardized protocol identical for all patients for programming rate stability, sudden onset, atrial-to-ventricular relationship (sudden onset = 9% and rate stability = 10 ms; V > A "on"), and "sustained rate duration" (3 minutes). The primary endpoint was the time to first inappropriate therapy classified by a blinded events committee.

RESULTS

One hundred forty-nine patients had a history of sustained VT or VF. Mean age (+/- SD) was 60 +/- 13 years; 83% were male, and mean ejection fraction was 35 +/- 15%. Control (n = 70) and "enhanced" (n = 79) groups did not differ with regard to age, sex, ejection fraction, or primary arrhythmia. The proportion of patients free of inappropriate therapy over time was significantly higher in the enhanced versus the control group (hazard ratio = 0.47, P = .011). High-energy shocks were reduced from 0.58 +/- 4.23 shocks/patient/month in the control group to 0.04 +/- 0.15 shocks/patient/month in the enhanced group (P = .0425). No patient programmed per protocol failed to receive therapy for VT detected by the ICD (422 VT episodes).

CONCLUSIONS

Standardized programming in a dual-chamber ICD leads to a significant and clinically important reduction in inappropriate therapies compared to rate-only detection and does not compromise safety with respect to appropriate treatment of VT.

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.

High Incidence of Appropriate and Inappropriate ICD Therapies in Children and Adolescents with Implantable Cardioverter Defibrillator

Appropriate and inappropriate therapies of implantable cardioverter defibrillators have a major impact on morbidity and quality of life in ICD recipients, but have not been systematically studied in children and young adults during long-term follow-up. ICD implantation was performed in 20 patients at the mean age of 16 +/- 6 years, 11 of which had prior surgical repair of a congenital heart defect, 9 patients had other cardiac diseases. Implant indications were aborted sudden cardiac death in six patients, recurrent ventricular tachycardia in 9 patient, and syncope in 5 patients. Epicardial implantation was performed in 6 and transvenous implantation in 14 patients. Incidence, reasons and predictors (age, gender, repaired congenital heart disease, history of supraventricular tachycardia, and epicardial electrode system) of appropriate and inappropriate ICD therapies were analyzed during a mean follow-up period of 51 +/- 31 months range 18-132 months. There were a total 239 ICD therapies in 17 patients (85%) with a therapy rate of 2.8 per patient-years of follow-up. 127 (53%) ICD therapies in 15 (75%) patients were catagorized as appropriate and 112 (47%) therapies in 10 (50%) patients as inappropriate, with a rate of 1.5 appropriate and 1.3 inappropriate ICD therapies per patient-years of follow-up. Time to first appropriate therapy was 16 +/- 18 months. Appropriate therapies were caused by ventricular fibrillation in 29 and ventricular tachycardia in 98 episodes. Termination was successful by antitachycardia pacing in 4 (3%) and by shock therapy in 123 episodes (97%). Time to first inappropriate therapy was 16 +/- 17 months. Inappropriate therapies were caused by supraventricular tachycardia in 77 (69%), T wave oversensing in 19 (17%), and electrode defect in 16 episodes (14%). It caused shocks in 87 (78%) and only antitachycardia pacing in 25 episodes (22%). No clinical variable could be identified as predictor of either appropriate or inappropriate ICD therapies. There is a high rate of ICD therapies in young ICD recipients, the majority of which occur during early follow-up. The rate of inappropriate therapies is as high as 47% and is caused by supraventricular tachycardia and electrode complications in the majority of cases. Prospective trials are required to establish preventative strategies of ICD therapies in this young patient population.

Clinical Experience with a New Detection Algorithm for Differentiation of Supraventricular from Ventricular Tachycardia in a Dual-Chamber Defibrillator

INTRODUCTION

Inadequate therapy for supraventricular tachyarrhythmias (SVT) is a frequent problem of implantable cardioverter defibrillators (ICD). Dual-chamber ICDs have been developed to improve discrimination of SVT from ventricular tachycardia (VT). We investigated the positive predictivity, sensitivity, and specificity of a new algorithm, the SMART detection trade mark algorithm, incorporated in the Phylax AV (Biotronik) dual-chamber ICD.

METHODS AND RESULTS

Two hundred nine patients (185 men, age 64 +/- 11 years) received a Phylax AV ICD with SMART detection trade mark activated. In 138 of these patients, 1,245 sustained tachycardia episodes with a detailed electrogram were stored in the device during a follow-up period of 10 +/- 6 months. Episodes were correctly classified as ventricular fibrillation (VF, n = 178) in 52 patients, VT (n = 641) in 98 patients, and SVT (n = 385) in 48 patients by the algorithm. Forty-one true SVT episodes (3.3%) were misclassified as VT: atrial fibrillation (n = 7) and flutter (n = 1), sinus tachycardia (n = 12), and other SVT (n = 21). The positive predictivity for VF/VT was 94.5% (95% CI 92.7-95.8) uncorrected and 94.5% (95% CI 92.9-95.8%) corrected with the generalized equation estimation (GEE) method. The positive predictivity for SVT was 100%. The specificity was 88.9% (95% CI 85.6-91.6%) uncorrected and 89.0% (95% CI 85.6-91.6%) corrected with the GEE method with a sensitivity of 100%.

CONCLUSION

The SMART detection trade mark algorithm was safe and reliable for the detection of all ventricular tachycardias. Although its specificity was high, it should be improved with regard to SVT to avoid inappropriate ICD therapies.

Analysis of implantable cardioverter defibrillator therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial

INTRODUCTION

The implantable cardioverter defibrillator (ICD) is commonly used to treat patients with documented sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Arrhythmia recurrence rates in these patients are high, but which patients will receive a therapy and the forms of arrhythmia recurrence (VT or VF) are poorly understood.

METHODS AND RESULTS

The therapy delivered by the ICD was examined in 449 patients randomized to ICD therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. Events triggering ICD shocks or antitachycardia pacing (ATP) were reviewed for arrhythmia diagnosis, clinical symptoms, activity at the onset of the arrhythmia, and appropriateness and results of therapy. Both shock and ATP therapies were frequent by 2 years, with 68% of patients receiving some therapy or having an arrhythmic death. An appropriate shock was delivered in 53% of patients, and ATP was delivered in 68% of patients who had ATP activated. The first arrhythmia treated in follow-up was diagnosed as VT (63%), VF (13%), supraventricular tachycardia (18%), unknown arrhythmia (3%), or due to ICD malfunction or inappropriate sensing (3%). Acceleration of an arrhythmia by the ICD occurred in 8% of patients who received any therapy. No physical activity consistently preceded arrhythmias, nor did any single clinical factor predict the symptoms of the arrhythmia.

CONCLUSION

Delivery of ICD therapy in AVID patients was common, primarily due to VT. Inappropriate ICD therapy occurred frequently. Use of ICD therapy as a surrogate endpoint for death in clinical trials should be avoided.

Diagnostic value of single versus dual chamber electrograms recorded from an implantable defibrillator

INTRODUCTION

The clinical utility of ventricular electrograms in comparison to atrial and ventricular electrograms in diagnosing the type of tachycardias recorded by an implantable defibrillator has not been addressed from the standpoint of a clinician's diagnostic accuracy and confidence in that diagnosis.

METHODS

Fifty-two tachycardia episodes recorded from dual chamber defibrillators were divided into two tests. The initial test contained only information from the ventricular electrogram and the second test contained information from both the atrial and ventricular electrograms. For each test, the reviewers were asked to provide the specific diagnosis, the originating chamber of origin of the tachycardia, and the confidence of their responses for each question. McNemar's test for matched pairs was used to determine accuracy and an analysis of variance to determine reviewer confidence.

RESULTS

The overall accuracy for both the specific diagnosis (61% vs. 79%; p < 0.001) and the chamber of origin (76% vs. 90%; p < 0.001) improved when both the atrial and ventricular electrograms were available for review. Reviewer confidence appeared to correlate with diagnostic accuracy.

CONCLUSIONS

The data clearly show the favorable impact of dual chamber defibrillators on the diagnostic accuracy and confidence of clinicians faced with a clinical tachycardia recorded from an implantable defibrillator. Such improvements may translate into more focused and appropriate therapeutic interventions.

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.

Clinical investigation of a new dual-chamber implantable cardioverter defibrillator with improved rhythm discrimination capabilities

INTRODUCTION

Despite continuing advances, inappropriate implantable cardioverter defibrillator (ICD) therapies in response to nonventricular tachyarrhythmias continue to cause patient discomfort and increased follow-up demands.

METHODS AND RESULTS

We investigated the performance of a new dual-chamber ICD (Photon DR, St. Jude Medical), with specific attention to its arrhythmia discrimination and detection capabilities. The system uses a hierarchical approach to tachyarrhythmia classification utilizing a new AV Rate Branch feature and subsequently utilizing morphology analysis, onset, and stability criteria. The arrhythmia discrimination results from this study group were compared to historical control group data from a recent clinical investigation of single-chamber Contour MD (Morphology Discrimination) and Angstrom MD ICDs without the Rate Branch feature. Rhythm discrimination was evaluated by comparing ventricular tachycardia diagnosis sensitivity and specificity between the two groups. To determine whether the new discrimination scheme affected detection speed, median ventricular fibrillation (VF) detection and redetection times also were compared. The study group consisted of 107 patients, and the control group consisted of 161 patients. Use of the AV Rate Branch feature was associated with significant improvements in both sensitivity (100% vs 97.9%, P < 0.0001) and specificity (84% vs 55.7%, P = 0.0002) of ventricular tachycardia diagnosis. Use of the new scheme slightly but significantly accelerated VF detection times (2.8 vs 3.0 sec, P < 0.0001) and redetection times (1.3 vs 1.4 sec, P < 0.0001). Adverse events were typical for this patient population.

CONCLUSION

Compared with earlier St. Jude Medical ICDs, the Photon DR ICD offers improved rhythm discrimination without compromising VF detection time.