Real World Evaluation of Dual-Zone ICD and CRT-D Programming Compared to Single-Zone Programming: The ALTITUDE REDUCES Study

The fatal consequence of inappropriate therapy in a single VF zone primary prevention defibrillator

We report a case of inappropriate implantable cardioverter defibrillator (ICD) therapy due to single ventricular fibrillation (VF) zone programming leading to patient death. A remote transmission was received from a patient with a cardiac resynchronization therapy-defibrillator showing sinus tachycardia in the VF detection zone initiating inappropriate shocks and resulting in shock refractory VF. This case report highlights the importance of manufacturer specific ICD programming. In devices without discrimination in the VF zone, a higher rate single VF detection zone and/or addition of a ventricular tachycardia zone with supraventricular tachycardia discrimination should be considered.

Strategies to Reduce Recurrent Shocks Due to Ventricular Arrhythmias in Patients with an Implanted Cardioverter-Defibrillator

Ventricular arrhythmias are a therapeutic challenge, owing to their relatively unpredictable and deadly nature. Many patients are treated with an implantable cardioverter-defibrillator for either primary or secondary prevention of ventricular arrhythmias, meaning those who are at high risk of versus those who have experienced ventricular arrhythmias or sudden cardiac arrest, respectively. Despite the life-saving benefit, ICD comes with the risk of recurrent shocks for both appropriate and inappropriate rhythms. Patients with recurrent shocks have a poor quality of life and increased mortality rates. In this article, we review data for optimal device settings, medical management and radiofrequency ablation strategies to minimise the frequency of ICD shock, with a focus on treatment of ventricular arrhythmias, to reduce patient morbidity and mortality, and to maximise wellbeing and quality of life.

Subcutaneous Implantable Cardioverter Defibrillators: An Overview of Implantation Techniques and Clinical Outcomes

Sudden Cardiac Death (SCD) is a significant health problem worldwide. Multiple randomized controlled trials have shown that Implantable Cardioverter Defibrillators (ICDs) are effective life-saving management option for individuals at risk of SCD in both primary and secondary prevention. Although the conventional transvenous ICDs (TV-ICDs) are safe and effective, there are potential complications associated with its use, including localized pocket or wound infection or systematic infection, a vascular access related complication such as pneumothorax, and venous thrombosis, and lead related complications such as dislodgement, malfunction, and perforation. Furthermore, transvenous leads placement may not be feasible in certain patients like those with venous anomaly or occlusion, or with the presence of intracardiac shunts. Transvenous leads extraction, when needed, is associated with considerable morbidity & mortality and requires significant skills and costs. Totally subcutaneous ICD (S-ICD) is designed to afford the same life-saving benefit of the conventional TV-ICDs while avoiding the shortcomings of the TV-leads and to simplify the implant techniques and hence expand the use of ICDs in clinical practice. It becomes commercially available after receiving CE mark in 2009, and its use increased significantly after its FDA approval in 2012. This review aims to give an overview of the S-ICD system components, implantation procedure, clinical indications, safety, efficacy, and future directions.

Ventricular tachycardia prediction in patients with implantable cardioverter-defibrillators for primary prevention of sudden cardiac death

Clinical data analysis of 83 patients with implantable cardioverter-defibrillators (ICDs) for sudden cardiac death (SCD) primary prevention has been done. We revealed 5 parameters associated with the detection of life-threatening ventricular arrhythmias. These parameters formed the basis for constructing a logistic regression model. The model makes it possible to obtain the probability of occurrence of a specific event depending on the severity of the predictive parameters and the degree of its influence (risk of true ventricular arrhythmias detection). Estimating the potential risk of the life-threatening arrhythmias, individual programming options are required in implantable cardioverter-defibrillators (ICDs) to reduce the amount of unnecessary electrotherapy, as well as more accurate monitoring of the patient's drug therapy.

Influence of patients' age at implantation on mortality and defibrillator shocks

Aims

Patients have increasing comorbidities and competing causes of death with advancing age, raising questions about the effectiveness of the implantable cardioverter defibrillators (ICD) in older age. We therefore investigated the effect of patients' age at initial device implantation on all-cause mortality and on the risk of ICD shocks in single-chamber (V-ICD), dual-chamber (D-ICD), and cardiac resynchronization therapy defibrillator (CRT-D) recipients.

Methods and results

We reviewed de-identified records of 67 128 ICD recipients enrolled in the Boston Scientific ALTITUDE database of remote monitored patients [V-ICD (n = 11 422), D-ICD (n = 23 974), and CRT-D (n = 31 732)]. Over a mean follow-up of 2.3 ± 1.4 years, patients in all ICD groups had increased all-cause mortality but decreased risk of defibrillator shocks and/or anti-tachycardia pacing per 10 year increase in age. Compared with the youngest age group (<50 years), patients in the oldest age group (≥80 years) had a 6.8-fold, 5.9-fold, and 3.4-fold increase in all-cause mortality (P < 0.001 for all comparisons) and a 31, 45, and 53% decrease in the risk of ICD shock (P ≤ 0.002 for all comparisons) for the V-ICD, D-ICD, and CRT-D groups, respectively.

Conclusion

Older recipients of standard and CRT defibrillators have higher mortality but fewer ICD shocks and/or therapies compared with younger patients. These data highly suggest less benefit of ICD therapy with increasing age, presumably because of competing risks of non-arrhythmic mortality. The role of defibrillator therapy in older patients may need to be evaluated with randomized controlled trials.

Long-term incidence of inappropriate shocks in patients with implantable cardioverter defibrillators in clinical practice-an underestimated complication?

BACKGROUND

Implantable cardioverter defibrillators (ICD) are life-saving device therapy, and patients often carry devices for decades with interim pulse generator exchanges. Inappropriate shocks are associated with impaired quality of life and increased mortality, but available data on their incidence and etiology outside of clinical trials is limited and usually restricted to the lifespan of a singular device. We hypothesized that the incidence in clinical practice is underestimated and aimed this study to retrospectively assess the long-term incidence and etiology of inappropriate shocks in a real-world cohort of patients with multiple ICDs over a long follow-up period.

METHODS

Patients with ICDs implanted between 1998 and 2012 in two Swiss cardiology departments and at least one device exchange in the same department thereafter were included in this cohort. Retrospective analysis with follow-up until 2016 was conducted to assess incidence and etiology of inappropriate ICD shocks.

RESULTS

Two hundred forty-nine ICDs were implanted in 100 patients (mean age: 60.1 ± 11.7; 80% male). Over a mean follow-up time of 11.2 (± 3.6) years, 555 shocks occurred in 55 patients. One hundred twenty-three (22%) shocks in 23 (23%) patients were inappropriate. Supraventricular arrhythmia and oversensing were the most frequent causes of inappropriate shock. Patients with younger age or previous supraventricular arrhythmias were at increased risk of inappropriate shocks. Patients with inappropriate shocks during the lifespan of their first ICD were at increased risk for inappropriate shocks in subsequent devices.

CONCLUSIONS

Inappropriate shocks are an underestimated and frequent problem in clinical practice with an incidence that may exceed numbers of previously reported clinical trials with shorter follow-up periods. Patients at increased risk for inappropriate shocks need careful evaluation of potential therapeutic optimization strategies including pharmacological treatment, device programming, electrophysiological ablation, device downgrading, and telemonitoring.

Right Ventricular Pacing Increases Risk of Appropriate Implantable Cardioverter-Defibrillator Shocks Asymmetrically: An Analysis of the ALTITUDE Database

BACKGROUND

Right ventricular pacing (RVP) increases risk of atrial fibrillation in patients with implantable cardioverter-defibrillators (ICDs), but ventricular proarrhythmia is less clear. We analyzed a large remote monitoring database to assess this question.

METHODS AND RESULTS

Patients with single- or dual-chamber ICDs, engaged in remote monitoring for at least 6 months and with unchanged tachycardia programming, were included. %RVP was derived for each weekly transmission. ICD electrograms preceding the first shock were adjudicated. Among 425 625 transmissions received from 8435 patients, 389 appropriate shocks occurred over a mean follow-up of 15.0±8.8 months. In a time-dependent Cox proportional hazards model, transmissions with 80% to 98% RVP were associated with a hazard ratio of 1.56 for an appropriate shock in the subsequent week compared with <1% RVP (95% CI, 1.01-2.41; P=0.04). By contrast, ≥98% RVP trended toward a lower risk of an appropriate shock (hazard ratio, 0.61; 95% CI, 0.33-1.12; P=0.108). Lifetime cumulative %RVP was closely correlated with weekly %RVP (R²=0.907) and was similarly associated with increased risk of appropriate shocks at 80% to 98% RVP (hazard ratio, 1.57; 95% CI, 1.01-2.44; P=0.046) but not at ≥98% RVP (hazard ratio, 0.49; 95% CI, 0.24-1.01; P=0.052). These results were driven by dual-chamber devices, but unaffected by PVC counts or programming. Male sex and age were also associated with appropriate ICD shocks.

CONCLUSIONS

Increasing frequency of RVP is associated with a progressively increased risk of appropriate ICD shocks until ≥98% RVP. RVP may have ventricular proarrhythmia because of competition of paced and intrinsic rhythm in ICD patients.

How implantable cardioverter-defibrillators work and simple programming

Following the sudden death of a friend in 1966, Dr Michel Mirowski began pioneering work on the first implantable cardioverter-defibrillator. By 1969 he had developed an experimental model and performed the first transvenous defibrillation. In 1970 he reported on the use of a "standby automatic defibrillator" that was tested successfully in dogs. He postulated that such a device "when adapted for clinical use, might be implanted temporarily or permanently in selected patients particularly prone to develop ventricular fibrillation and thus provide them with some degree of protection from sudden coronary death". In 1980 he reported on the first human implants of an "electronic device designed to monitor cardiac electrical activity, to recognise ventricular fibrillation and ventricular tachyarrhythmias … and then to deliver corrective defibrillatory discharges". Through innovations in circuitry, battery, and capacitor technologies, the current implantable cardioverter-defibrillator is 10 times smaller and exponentially more sophisticated than that first iteration. This article will review the inner workings of the implantable cardioverter-defibrillator and outline several features that make it the wonder in technology that it has become.

Very high rate programming in primary prevention patients with reduced ejection fraction implanted with a defibrillator: Results from a large multicenter controlled study

BACKGROUND

Programming implantable cardioverter-defibrillators (ICDs) with a high-rate therapy strategy has proven to be effective in reducing shocks and is associated with a reduced mortality.

OBJECTIVE

We sought to determine the impact of a very high rate cutoff programming strategy on outcomes in patients with a primary indication for an ICD due to reduced left ventricular ejection fraction.

METHODS

Using data from the multicenter French DAI-PP registry, this cohort-controlled study compared outcomes in 500 patients programmed with a very high rate cutoff (VH-RATE group: monitor zone 170-219 beats/min; ventricular fibrillation zone ≥220 beats/min with 13 ± 4 detection intervals) with 1500 matched control patients programmed with 1 or 2 therapy zone. All ICDs were implanted for primary prevention in patients with systolic dysfunction. Risks of events were compared after propensity score matching of sex, age, ejection fraction, New York Heart Association class, cardiomyopathy, atrial fibrillation, and type of device.

RESULTS

After a mean follow-up of 3.6 ± 2.3 years, VH-RATE programming was associated with a reduction of appropriate therapy risk (hazard ratio [HR] 0.40; 95% confidence interval [CI] 0.31-0.51; P < .0001) and inappropriate shock (HR 0.42; 95% CI 0.27-0.63; P < .0001). It was also associated with a decreased risk of sudden cardiac death (HR 0.43; 95% CI 0.17-0.99; P = .04) as compared with patients programmed with 2 therapy zones. There was no significant difference in overall survival between the groups.

CONCLUSION

In patients implanted with an ICD in primary prevention with left ventricular dysfunction, very high rate cutoff programming (single therapy zone ≥220 beats/min) was associated with a 60% reduction of appropriate therapies as well as inappropriate shocks, without affecting mortality.

Relation between detection rate and inappropriate shocks in single versus dual chamber cardioverter-defibrillator--an analysis from the OPTION trial

The programming of implantable cardioverter-defibrillators (ICDs) influences inappropriate shock rates. The aim of the study is to analyse rates of patients with appropriate and inappropriate shocks according to detection zones in the OPTION trial. All patients received dual chamber (DC) ICDs randomly assigned to be programmed either to single chamber (SC) or to DC settings including PARAD+ algorithm. In a post-hoc analysis, rates of patients with inappropriate and appropriate shocks were calculated for shocks triggered at heart rates ≥170 bpm (ventricular tachycardia zone) and at rates ≥200 bpm (ventricular fibrillation zone). In the SC group, higher rates of patients with total and inappropriate shocks were delivered at heart rates ≥170 bpm than at rates ≥200 bpm (total shocks: 21.1% vs. 16.6%; p = 0.002; inappropriate shocks: 7.6% vs. 4.5%, p = 0.016; appropriate shocks: 15.2% vs. 13.5%; p = n.s.). No such differences were observed in the DC group (total shocks: 14.3% vs. 12.6%; p = n.s.; inappropriate shocks: 3.9% vs. 3.6%; p = n.s.; appropriate shocks: 12.2% vs. 10.4%; p = n.s.). The higher frequency of patients with total shocks with SC settings than with DC settings that benefit from PARAD+ was driven by a higher percentage of patients with inappropriate shocks in the VT zone (170–200 bpm) in the SC population.

Programming implantable cardioverter/defibrillators and outcomes

Implantable cardioverter-defibrillators are complex technical devices with a multitude of programming options for the physician. In recent years, numerous randomized trials have been performed to define the optimal programming strategies and have provided valuable insights, especially in primary prevention patients. This article provides an actual overview on the existing evidence on the most important programming features for accurate detection and therapy of ventricular arrhythmias.

Worldwide experience with a totally subcutaneous implantable defibrillator: early results from the EFFORTLESS S-ICD Registry

Aims

The totally subcutaneous implantable-defibrillator (S-ICD) is a new alternative to the conventional transvenous ICD system to minimize intravascular lead complications. There are limited data describing the long-term performance of the S-ICD. This paper presents the first large international patient population collected as part of the EFFORTLESS S-ICD Registry.

Methods and results

The EFFORTLESS S-ICD Registry is a non-randomized, standard of care, multicentre Registry designed to collect long-term, system-related, clinical, and patient reported outcome data from S-ICD implanted patients since June 2009. Follow-up data are systematically collected over 60-month post-implant including Quality of Life. The study population of 472 patients of which 241 (51%) were enrolled prospectively has a mean follow-up duration of 558 days (range 13–1342 days, median 498 days), 72% male, mean age of 49 ± 18 years (range 9–88 years), 42% mean left ventricular ejection fraction. Complication-free rates were 97 and 94%, at 30 and 360 days, respectively. Three hundred and seventeen spontaneous episodes were recorded in 85 patients during the follow-up period. Of these episodes, 169 (53%) received therapy, 93 being for Ventricular Tachycardia/Fibrillation (VT/VF). One patient died of recurrent VF and severe bradycardia. Regarding discrete VT/VF episodes, first shock conversion efficacy was 88% with 100% overall successful clinical conversion after a maximum of five shocks. The 360-day inappropriate shock rate was 7% with the vast majority occurring for oversensing (62/73 episodes), primarily of cardiac signals (94% of oversensed episodes).

Conclusion

The first large cohort of real-world data from an International patient S-ICD population demonstrates appropriate system performance with clinical event rates and inappropriate shock rates comparable with those reported for conventional ICDs. Clinical trial registration URL: http://www.clinicaltrials.gov. Unique identifier NCT01085435.

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.

Telemedicine and cardiac implants: what is the benefit?

Cardiac implantable electronic devices are increasing in prevalence. The post-implant follow-up is important for monitoring both device function and patient condition. However, practice is inconsistent. For example, ICD follow-up schedules vary from 3 monthly to yearly according to facility and physician preference and availability of resources. Recommended follow-up schedules impose significant burden. Importantly, no surveillance occurs between follow-up visits. In contrast, implantable devices with automatic remote monitoring capability provide a means for performing constant surveillance, with the ability to identify salient problems rapidly. Remote home monitoring reduces the volume of device clinic visits and provides early detection of patient and/or system problems.

Survival after shock therapy in implantable cardioverter-defibrillator and cardiac resynchronization therapy-defibrillator recipients according to rhythm shocked. The ALTITUDE survival by rhythm study

OBJECTIVES

This study sought to determine if the risk of mortality associated with inappropriate implantable cardioverter-defibrillator (ICD) shocks is due to the underlying arrhythmia or the shock itself.

BACKGROUND

Shocks delivered from ICDs are associated with an increased risk of mortality. It is unknown if all patients who experience inappropriate ICD shocks have an increased risk of death.

METHODS

We evaluated survival outcomes in patients with an ICD and a cardiac resynchronization therapy defibrillator enrolled in the LATITUDE remote monitoring system (Boston Scientific Corp., Natick, Massachusetts) through January 1, 2010. First shock episode rhythms from 3,809 patients who acutely survived the initial shock were adjudicated by 7 electrophysiologists. Patients with a shock were matched to patients without a shock (n = 3,630) by age at implant, implant year, sex, and device type.

RESULTS

The mean age of the study group was 64 ± 13 years, and 78% were male. Compared with no shock, there was an increased rate of mortality in those who received their first shock for monomorphic ventricular tachycardia (hazard ratio [HR]: 1.65, p < 0.0001), ventricular fibrillation/polymorphic ventricular tachycardia (HR: 2.10, p < 0.0001), and atrial fibrillation/flutter (HR: 1.61, p = 0.003). In contrast, mortality after first shocks due to sinus tachycardia and supraventricular tachycardia (HR: 0.97, p = 0.86) and noise/artifact/oversensing (HR: 0.91, p = 0.76) was comparable to that in patients without a shock.

CONCLUSIONS

Compared with no shock, those who received their first shock for ventricular rhythms and atrial fibrillation had an increased risk of death. There was no significant difference in survival after inappropriate shocks for sinus tachycardia or noise/artifact/oversensing. In this study, the adverse prognosis after first shock appears to be more related to the underlying arrhythmia than to an adverse effect from the shock itself.

Clinical outcome endpoints in heart failure trials: a European Society of Cardiology Heart Failure Association consensus document

Endpoint selection is a critically important step in clinical trial design. It poses major challenges for investigators, regulators, and study sponsors, and it also has important clinical and practical implications for physicians and patients. Clinical outcomes of interest in heart failure trials include all-cause mortality, cause-specific mortality, relevant non-fatal morbidity (e.g., all-cause and cause-specific hospitalization), composites capturing both morbidity and mortality, safety, symptoms, functional capacity, and patient-reported outcomes. Each of these endpoints has strengths and weaknesses that create controversies regarding which is most appropriate in terms of clinical importance, sensitivity, reliability, and consistency. Not surprisingly, a lack of consensus exists within the scientific community regarding the optimal endpoint(s) for both acute and chronic heart failure trials. In an effort to address these issues, the Heart Failure Association of the European Society of Cardiology (HFA-ESC) convened a group of expert heart failure clinical investigators, biostatisticians, regulators, and pharmaceutical industry scientists (Nice, France, 12-13 February 2012) to evaluate the challenges of defining heart failure endpoints in clinical trials and to develop a consensus framework. This report summarizes the group's recommendations for achieving common views on heart failure endpoints in clinical trials.

Remote monitoring of cardiovascular implanted electronic devices: a paradigm shift for the 21st century

Traditional follow-up of cardiac implantable electronic devices involves the intermittent download of largely nonactionable data. Remote monitoring represents a paradigm shift from episodic office-based follow-up to continuous monitoring of device performance and patient and disease state. This lessens device clinical burden and may also lead to cost savings, although data on economic impact are only beginning to emerge. Remote monitoring technology has the potential to improve the outcomes through earlier detection of arrhythmias and compromised device integrity, and possibly predict heart failure hospitalizations through integration of heart failure diagnostics and hemodynamic monitors. Remote monitoring platforms are also huge databases of patients and devices, offering unprecedented opportunities to investigate real-world outcomes. Here, the current status of the field is described and future directions are predicted.

United Kingdom national experience of entirely subcutaneous implantable cardioverter-defibrillator technology: important lessons to learn

AIMS

The aim of this study was to describe the early phase United Kingdom (UK) clinical experience with a novel entirely subcutaneous implantable cardioverter-defibrillator (S-ICD).

METHODS AND RESULTS

A questionnaire was sent to all UK hospitals implanting S-ICDs. Nineteen of 25 (76%) hospitals responded with the details of 111 implanted patients [median 5/hospital (range 1-18)]. Mean duration of follow-up was 12.7 ± 7.1 months. Median patient age was 33 years (range 10-87 years). Underlying pathology was primary electrical disease in 43%, congenital heart disease 12%, hypertrophic cardiomyopathy 20%, ischaemic cardiomyopathy 14%, idiopathic dilated cardiomyopathy 5%, and other cardiomyopathies 7% patients. Nineteen (17%) patients required 20 re-operations, including permanent device explantation in 10 (9%). Twenty-four appropriate shocks were delivered in 13 (12%) patients, including 10 for ventricular fibrillation. One patient suffered arrhythmic death, but there were no failures to detect or terminate ventricular arrhythmias above the programmed detection rate. Fifty-one inappropriate shocks were delivered in 17 (15%) patients. Forty-one (80%) were for T-wave over-sensing and 1 (2%) for atrial flutter-wave over-sensing. The 11 patients who received inappropriate shocks due to T-wave over-sensing were significantly younger than patients who did not (24 ± 10 vs. 37 ± 19 years; P = 0.02).

CONCLUSION

The S-ICD is an important innovation in ICD technology. However, these data indicate that adverse event rates are significant during early clinical adoption. Important lessons in patient selection, implant technique, and device programming can be learnt from this experience.

Implantable cardioverter defibrillator harm?

Despite the general acceptance of implantable cardioverter defibrillator (ICD) therapy [including cardiac resynchronization therapy defibrillator (CRT-D)] among cardiologists, there has been some recent concern about potential harm associated with ICDs, particularly related to quality of life and possible adverse effects of ICD shocks. These and others undeniably constitute complications of ICD therapy paper. However, the evidence from multiple ICD/CRT-D trials, which take into account complications on the one side, and benefits on the other, speaks strongly in favour of patients receiving net benefit, rather than harm. And this is true for (i) prognosis, (ii) effects of shocks, and (iii) quality of life. Moreover--addressing specifically the complications aspects--there have been major advances, both in the technology of the systems and in physician practice, which have put major focus on minimizing shocks (appropriate and inappropriate) in favour of antitachycardia pacing. In addition, the tendency is that more and more of such patients receive devices incorporating cardiac resynchronization pacing, now proven to delay and/or minimize heart failure. There is now a large body of evidence, particularly in recent years with improved technology, that, rather than 'harm', the ICD/CRT-D provides substantial protection for appropriately selected patients.

A new single chamber implantable defibrillator with atrial sensing: a practical demonstration of sensing and ease of implantation

Implantable cardioverter-defibrillators (ICDs) terminate ventricular tachycardia (VT) and ventricular fibrillation (VF) with high efficacy and can protect patients from sudden cardiac death (SCD). However, inappropriate shocks may occur if tachycardias are misdiagnosed. Inappropriate shocks are harmful and impair patient quality of life. The risk of inappropriate therapy increases with lower detection rates programmed in the ICD. Single-chamber detection poses greater risks for misdiagnosis when compared with dual-chamber devices that have the benefit of additional atrial information. However, using a dual-chamber device merely for the sake of detection is generally not accepted, since the risks associated with the second electrode may outweigh the benefits of detection. Therefore, BIOTRONIK developed a ventricular lead called the Linox(SMART) S DX, which allows for the detection of atrial signals from two electrodes positioned at the atrial part of the ventricular electrode. This device contains two ring electrodes; one that contacts the atrial wall at the junction of the superior vena cava (SVC) and one positioned at the free floating part of the electrode in the atrium. The excellent signal quality can only be achieved by a special filter setting in the ICD (Lumax 540 and 740 VR-T DX, BIOTRONIK). Here, the ease of implantation of the system will be demonstrated.

[Progress in cardiac electrophysiology and arrhythmias]

This article contains a review of the most important publications in the field of cardiac electrophysiology and arrhythmias that have appeared in the last year. Publications were selected because they reported important scientific developments or significant improvements in the devices or invasive techniques used for the treatment of arrhythmias.

Prospective comparison of discrimination algorithms to prevent inappropriate ICD therapy: primary results of the Rhythm ID Going Head to Head Trial

BACKGROUND

Inappropriate therapy for supraventricular arrhythmias remains a significant source of morbidity in implantable cardioverter-defibrillator (ICD) recipients.

OBJECTIVE

The Rhythm ID Goes Head to Head Trial (RIGHT) was designed to compare rhythm discrimination and inappropriate therapies among patients with ICDs from 2 manufacturers.

METHODS

Patients with standard ICD indications were randomized to receive a Guidant VITALITY 2 with Rhythm ID or selective Medtronic pulse generators using the Enhanced PR Logic or Wavelet discrimination algorithms. A single- or dual-chamber device was implanted based on clinical indications and programmed in 2 detection zones with detection enhancements enabled for rates between 150 and 200 bpm. Algorithm performance was compared between randomization groups, stratified by single or dual chamber, for the primary end point of first inappropriate therapy (shock or antitachycardia pacing) for supraventricular arrhythmias.

RESULTS

There were 1962 patients enrolled and followed for 18.3 ± 9.2 months, with no difference in all-cause mortality between groups. There were 3973 treated episodes where electrograms were available and adjudicated. The primary end point of inappropriate therapy occurred in 246 of 985 VITALITY 2 patients vs 187 of 977 specific Medtronic ICD patients (hazard ratio = 1.34; confidence interval = 1.11-1.62; P = .003). Differences in inappropriate therapy were confined to single-chamber ICDs. Inappropriate shocks were more frequent in VITALITY 2 ICDs (hazard ratio = 1.63; confidence interval = 1.29-2.06; P < .001), with most therapies and performance differences occurring at slower rhythms (rates < 175 bpm).

CONCLUSION

Rhythm discrimination performed better in the specific Medtronic than in VITALITY 2 ICDs evaluated, particularly for single-chamber devices. Inappropriate therapies, and differences in performance, may be reduced with the use of rate cutoff above 175 bpm.