First worldwide clinical experience with a new dual chamber implantable cardioverter defibrillator. Advantages and complications. The Ventak AV II DR investigators

Atrial electrograms improve the accuracy of tachycardia interpretation from ICD and pacemaker recordings: The RATE Registry

BACKGROUND

Tachycardia diagnoses from implantable device recordings ultimately depend on the analysis of captured electrograms (EGMs). The degree to which atrial EGMs improve tachycardia discrimination, dependent on the level of expertise of the medical professional involved, remains uncertain.

OBJECTIVE

The purpose of this article was to determine whether atrial EGM recordings improve tachycardia discrimination and whether this improvement, if any, varies for professionals with different levels of training.

METHODS

Expert-adjudicated supraventricular tachycardia (SVT) and ventricular tachycardia (VT) dual-chamber EGMs (DEGMs) from the Registry of Atrial Tachycardia and Atrial Fibrillation Episodes in the Cardiac Rhythm Management Device Population were provided to electrophysiology specialists, electrophysiology fellows (EPF), and nurse practitioners or physician assistants (NPPA). Each participant diagnosed 112 EGM episodes presented in random sequence (61 VTs and 51 SVTs) and independently categorized each as "SVT," "VT," or "uncertain" in 2 stages. First, participants analyzed ventricular EGMs (VEGMs) alone (atrial channel covered). Second, the tracings were randomized and reanalyzed with atrial EGMs exposed. The diagnostic accuracy of VEGMs alone vs DEGMs was assessed for each group.

RESULTS

For all 3 groups, diagnostic accuracy improved significantly (>20% for VTs and >15% for SVTs; P < .01 for all) when DEGMs were provided. Electrophysiology specialists diagnosed VTs more accurately than did EPF and NPPA (VEGM: 73.1%±7.6% vs 58.7%±15.5% and 56.1%±14.1%; P < .01; DEGM: 98.0%±2.7% vs 90.8%±16.0% and 80.3%±7.4%; P < .01). EPF diagnosed VTs more accurately than did NPPA only when DEGMs were provided. There was no significant intergroup difference in SVT diagnoses.

CONCLUSION

DEGMs are superior to VEGMs alone for tachycardia discrimination at all levels of expertise. The level of training affects diagnostic accuracy with and without atrial EGMs.

A new method to investigate the response to the morphology discrimination algorithm in patients with ICD

BACKGROUND

Inappropriate therapy for supraventricular tachyarrhythmia is still a major problem in implantable cardioverter defibrillators (ICD). The morphology discrimination algorithm compares the morphology of a tachycardia electrogram with a stored template on a beat-to-beat basis. However, algorithm responders could not yet be identified prior to the occurrence of first tachycardia episodes. We analyzed whether rapid atrial pacing and/or exercise testing can be used for identification of responders and compared the results with ICD detected tachycardia.

METHODS

22 patients (16 male, 61+/-14 years) with dual-chamber ICDs have been enrolled. Patients underwent a standardized bicycle exercise testing and an atrial pacing protocol. For both tests, morphology match scores of 8 consecutive beats were analyzed for each 10-bpm-step increment above sinus rhythm. Patients were categorized as responders, if morphology match was > or = 90% of tested heart rates. During follow-up, ICD stored episodes with morphology discrimination activated were evaluated.

RESULTS

There were no significant differences between morphology match (85+/-29% vs. 84+/-27%) and linear regression slope B (-0.19+/-0.87 vs. -0.20+/-0.48) during exercise testing and atrial pacing. 16 patients (73%) were classified as responders. During follow-up (739+/-338 days) 121 sustained supraventricular (n=88) and ventricular tachycardia (n=33) were detected in 10 patients (45%). Specificity for tachycardia discrimination was 78% overall, 100% in responders and 22% in non-responders.

CONCLUSION

Exercise testing and atrial pacing were equally suitable for identification of patients who seem to respond to the morphology discrimination algorithm with a high specificity for ventricular tachycardia discrimination. Thus, morphology match tests are suggested to optimize tachycardia discrimination and to reduce inadequate therapies.

Inappropriate ICD Therapy: Does Device Configuration Make a Difference

INTRODUCTION

Inappropriate implantable cardioverter defibrillator (ICD) therapy (IT) is a common complication in patients with ICD. IT is commonly triggered by supraventricular tachycardias (SVT). Dual chamber ICDs (D-ICDs) may distinguish SVT from ventricular tachycardia/ventricular fibrillation better than single chamber ICDs (S-ICDs) and may be associated with a smaller incidence of IT.

METHODS

We reviewed the charts of 386 patients who had an ICD implanted for an AHA class I indication. Intracardiac electrograms were used to classify shocks as either appropriate or inappropriate.

RESULTS

Of 295 patients with an S-ICD, 66 (22.3%) received IT, compared to 5 (5.4%) of 91 patients with a D-ICD. The likelihood of being event-free at 1, 2, 3, and 4 years was 96.1%, 96.1%, 96.1%, and 89% for patients with D-ICD and 80.7%, 72.7%, 69.6%, and 66.4%, respectively, for patients with S-ICD (P < 0.001). Multivariate analysis showed no significant association with age, sex, history of atrial fibrillation, history of hypertension, or ejection fraction. SVTs were the commonest cause of IT in our patients.

CONCLUSION

Patients with D-ICD are less likely to receive IT as compared to patients with S-ICD.

Simultaneous Atrial and Ventricular Anti-Tachycardia Pacing as a Novel Method of Rhythm Discrimination

OBJECTIVE

To evaluate a new discrimination algorithm for supraventricular (SVT) and ventricular (VT) tachycardias, based on the response to simultaneous (A+V) atrial (A) and ventricular (V) anti-tachycardia pacing (ATP).

METHODS

Patients undergoing electrophysiological testing or dual-chamber implantable cardioverter-defibrillator (ICD) implantation were enrolled (N = 32) and underwent A+V ATP through a Marquis ICD with investigational software. If persisting after ATP, the rhythm was classified as VT if the first electrical event was sensed on the V channel and as an SVT otherwise.

RESULTS

Arrhythmia sequences (N = 275; 53 VT; 222 SVT) were analyzed in 26 patients (age = 51 +/- 17 years, 13 men, LVEF = 0.49 +/- 0.14). In response to A+V ATP, 55% of SVT versus 41% of VT episodes were terminated (P = NS). Termination of VT but not of SVT was more likely with faster (50% at ATP/arrhythmia cycle length (CL) = 0.81 vs 8% at ATP/arrhythmia CL = 0.88, P = 0.02) but not with longer ATP bursts (P = NS). Of the 115 arrhythmias that persisted after A+V ATP, the algorithm correctly classified 24 of 24 VT (GEE-adjusted sensitivity = 100%) and 85 of 91 SVT (GEE-adjusted specificity = 93%). Proarrhythmia was noted after two A+V ATP, in the form of atrial fibrillation induction and VT acceleration.

CONCLUSIONS

We describe a new algorithm that can discriminate between SVT and VT with a high sensitivity and specificity. This form of ATP can terminate 55% of SVT sequences. The performance of this new algorithm merits further testing in a large population of dual-chamber ICD patients.

What are the professional and logistic demands to appropriately follow patients with an implantable cardioverter-defibrillator?

OBJECTIVES

To determine events during follow-up of patients with implantable cardioverter-defibrillators (ICD) and the specific experience cardiologists need for trouble-shooting.

DESIGN

Prospective evaluation of all patient visits in an outpatient clinic.

SETTING

University hospital, single centre performing ICD controls in a region of 1.5 Mio inhabitants.

SUBJECTS

A total of 351 patients with 1118 consecutive visits during 14 months.

INTERVENTIONS

Classification of events according to predefined training levels.

MAIN OUTCOME MEASUREMENTS

Skill levels A: simple visit, e.g. for switching the device 'off'. B: normal visit, no further measures taken (no device reprogramming), even though the patient might have experienced ICD interventions. C: complex visit, electrophysiologist actively involved. Correlation of these levels with timing (routine, emergency on/off office hours) and reason of visits.

RESULTS

Seventy-six per cent of visits were scheduled routine visits, 5% performed within 24 h because of shocks, 19% performed for other reasons (shock tests; switching the device 'off/on'; reported dizziness, syncope, palpitations without ICD interventions). Required skill levels were A in 44 (4%), B in 796 (71%) and C in 278 (25%) visits. Emergency visits were more often classified as level C (60%) than regular visits (20%), Skill level C was more often encountered during emergency (30%) than during regular visits (6%) (both P = 0.001).

CONCLUSIONS

Our study suggests that for standard follow-up in patients without obvious problems, a cardiologist might be sufficient, whereas presentations due to/with clinical problems most likely will need the expertise of an electrophysiologist.

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.

Impact of Dual Chamber Pacing on the Incidence of Atrial and Ventricular Tachyarrhythmias in Recipients of Implantable Cardioverter Defibrillators

Recent observations suggest that frequent dual-chamber pacing in recipients of implantable cardioverter defibrillators (ICD) may adversely influence clinical outcomes. This prospective, multicenter study examined the relationship between the frequency of atrial (%AP) and ventricular pacing (%VP) and the incidence of atrial (AT) and/or ventricular tachyarrhythmias (VT) in a standard ICD population. A total of 141 consecutive patients with primary and secondary ICD indications were studied. Continuous arrhythmia detection with a dual-chamber ICD revealed paroxysmal AT in 60 (43%) and VT in 72 (51%) patients within 6 months of device implantation. Far-field oversensing of ventricular signals occurred in 13% of all "atrial tachy response" mode switches. Without adjustment for covariates, a higher %AP was associated with an increased incidence of AT (P < 0.05). However, this association remained only weakly significant after adjustment for covariates using a multivariate model. High New York heart failure functional classes correlated significantly with AT (P = 0.02) and VT (P = 0.007). Rate-modulated pacing, programmed in 1/3 of patients, correlated with occurrence of AT (P = 0.006), but not with occurrence of VT. With respect to dual-chamber pacing, a %AP >/= 48% combined with a %VP > 40% was associated with an increased probability for VT. In conclusion, AT and VT occurred frequently within 6 months after dual-chamber ICD implantation. High rates of DDD/R stimulation were associated with a trend toward higher incidence of AT, VT, or both.

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.

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.

Prevalence and incidence of arrhythmias and sudden death in heart failure

Patients with heart failure are prone to a variety of arrhythmias, symptomatic and asymptomatic, that are prognostically significant and have an important bearing on the management of these patients. However there are some inherent problems in assessing the frequency of these arrhythmias within a large patient population, due to a lack of uniformity in defining heart failure and the transient nature of these rhythms. Patients with heart failure commonly die suddenly. The causes of these deaths are difficult to ascertain accurately and are often presumed arrhythmic. With the advent of effective interventions to prevent sudden death, accurately defining the causal relationship between the arrhythmias and sudden death has assumed great importance to appropriately target therapy. Several attempts have been made to predict such deaths on the basis of non-invasive and invasive diagnostic investigations with variable success. In this article we review the incidence and prevalence of atrial and ventricular arrhythmias and sudden deaths in epidemiological studies, surveys and randomised control trials of patients with heart failure. We discuss the prognostic significance of these arrhythmias, the inherent problems in their diagnosis and whether their presence predicts the risk of sudden deaths and the mode of such deaths in the heart failure population. The role of various investigations in risk stratification of sudden death has also been discussed.

Algorithms for better arrhythmia discrimination in implantable cardioverter defibrillators

The discrimination of concomitant atrial tachyarrhythmias and sinus tachycardias in patients with malignant ventricular tachyarrhythmias is a major challenge for new defibrillator devices. Different algorithms have now been established to distinguish between atrial and ventricular tachyarrhythmias. Furthermore, new dual-chamber implantable defibrillators are capable of tiered atrial therapies for both regular and irregular atrial and ventricular tachyarrhythmias. The increasingly complex and subtle dual-chamber detection algorithms have proven to be safe and effective for the detection of ventricular tachycardia, and also in terms of an increase in specificity and a reduction in inappropriate ventricular therapies for supraventricular tachyarrhythmias. Stable electrode position, and a continuous and correct atrial signal quality, are prerequisites for atrial therapies and algorithms for arrhythmia discrimination.