Is dual-chamber programming inferior to single-chamber programming in an implantable cardioverter-defibrillator? Results of the INTRINSIC RV (Inhibition of Unnecessary RV Pacing With AVSH in ICDs) study

Pacing induced cardiomyopathy: recognition and management

Right ventricle (RV) apex continues to remain as the standard pacing site in the ventricle due to ease of implantation, procedural safety and lack of convincing evidence of better clinical outcomes from non-apical pacing sites. Electrical dyssynchrony resulting in abnormal ventricular activation and mechanical dyssynchrony resulting in abnormal ventricular contraction during RV pacing can result in adverse LV remodelling predisposing some patients for recurrent heart failure (HF) hospitalisation, atrial arrhythmias and increased mortality. While there are significant variations in the definition of pacing induced cardiomyopathy (PIC), combining both echocardiographic and clinical features, the most acceptable definition for PIC would be left ventricular ejection fraction (LVEF) of <50%, absolute decline of LVEF by ≥10% and/or new-onset HF symptoms or atrial fibrillation (AF) after pacemaker implantation. Based on the definitions used, the prevalence of PIC varies between 6% and 25% with overall pooled prevalence of 12%. While most patients undergoing RV pacing do not develop PIC, male sex, chronic kidney disease, previous myocardial infarction, pre-existing AF, baseline LVEF, native QRS duration, RV pacing burden, and paced QRS duration are the factors associated with increased risk for PIC. While conduction system pacing (CSP) using His bundle pacing and left bundle branch pacing appear to reduce the risk for PIC compared with RV pacing, both biventricular pacing and CSP may be used to effectively reverse PIC.

Selection and outcome of ICD and CRT-D patients - Comparison of 4384 patients from the German Device Registry to randomized controlled trials

BACKGROUND

Registry data adds important information to randomized controlled trials (RCT) on real-life aspects of implantable cardioverter-defibrillator (ICD) patients with and without cardiac resynchronization therapy (CRT-D). This analysis of the prospectively conducted German Device Registry aims at comparing mortality rates, comorbidities, complication rates to results from RCT.

METHODS

The German Device registry (DEVICE) prospectively collected data on ICD and CRT-D first implantations from 50 German centres. Demographic data, details on cardiac disease, electrocardiogram (ECG), medication, and data about procedure, complications and hospital stay were stored in electronic case report forms. One year after device implantation patients were contacted for follow-up.

RESULTS

DEVICE included n=4384 first ICD/CRT-D implantations (29.3% CRT-D devices). We found a strong adherence to guidelines with over 90% of patients being on ß-blocker and ACE-inhibitor medication and adequate QRS width in the majority of CRT-D patients. Patients receiving a CRT-D were older (67.6±11.0 years vs. 63.9±13.4 years, p<0.001) and had lower ejection fractions (mean 25% vs. 30%, p<0.001) compared to ICD patients. Dilated cardiomyopathy was the predominant underlying heart disease in CRT-D (53.3%), coronary artery disease in ICD patients (64.7%). Compared to RCT our DEVICE patients had more comorbidities (17.9% chronic kidney disease (CKD)) and higher one-year mortality rates (10.7% ICD group, 12.3% CRT group). In multivariate analysis, CKD patients had an almost 2-fold higher risk of 1-year mortality.

CONCLUSION

Despite relevant limitations of registry data, DEVICE highlights important differences between RCT and real-world registry data and the impact of comorbidities on mortality of ICD and CRT-D recipients. This article is protected by copyright. All rights reserved.

Heart rate score and outcomes in ICD patients: insights from the prospective randomized INTRINSIC RV trial

BACKGROUND

Heart rate score (HRSc), the percentage of atrial sensed and paced beats in the largest 10 beat/min bin of a device histogram and mean intrinsic heart rate (MIHR), predicted survival in nonrandomized studies of implantable defibrillator (ICD) patients. We evaluated whether HRSc and MIHR independently predicted mortality and heart failure (HF) hospitalization in the prospective, randomized, controlled INTRINSIC RV trial.

METHODS AND RESULTS

The INTRINSIC RV trial enrolled 1530 patients receiving dual-chamber ICDs. This analysis involves patients (n = 1471) for whom MIHR and HRSc data were available. Mean follow-up was 10.4 months. The relationship between pre-randomization MIHR and HRSc on the primary endpoint of all-cause mortality and HF hospitalization was assessed using multivariate regression and Cox modeling. As categorical variables, MIHR > 70 bpm and HRSc > 70% were considered high.

RESULTS

The median baseline MIHR and HRSc were 74 (IQR = 16) and 50% (IQR = 20) respectively. As a continuous variable, for every 1% increase in HRSc, death/HF hospitalization increased by 1% (95%CI: 1.002-1.017; p = 0.01). Regression analysis showed baseline MIHR was associated with HRSc (p = 0.01); for every 1 beat/min increase in MIHR, HRSc increased by 1.8%. A MIHR > 70 bpm and HRSc ≥ 70% predicted, but were independently associated with, the primary endpoint (HR: 1.39; 95%CI: 1.10-1.76, p = 0.005 for MIHR and HR: 1.654; 95%CI: 1.11-2.46, p = 0.01 for HRSc). Male gender (HR: 0.75), history of HF (HR: 1.29), and atrial fibrillation (HR: 1.37) also predicted death/hospitalization in the Cox model.

CONCLUSIONS

In this large, prospectively studied ICD population, HRSc was a robust and independent predictor of death/HF hospitalization. High MIHR and high HRSc were associated but each predicted outcomes independently.

Single vs. dual chamber implantable cardioverter-defibrillators or programming of implantable cardioverter-defibrillators in patients without a bradycardia pacing indication: systematic review and meta-analysis

Aims

Implantable cardioverter-defibrillators (ICDs) are key in the prevention of sudden cardiac death, but outcomes may vary by type of device or programming [single chamber (SC) vs. dual chamber (DC)] in patients without a bradycardia pacing indication. We sought to meta-analyse patient outcomes of randomized trials of SC vs. DC devices or programming.

Methods and results

We searched PubMed, Embase, Scopus, Web of Science, and Cochrane trials databases for relevant studies excluding those published before 2000, involving children, or not available in English. Endpoints included mortality, inappropriate ICD therapies, and implant complications. Endpoints with at least three reporting studies were meta-analysed. We identified eight studies meeting inclusion criteria representing 2087 patients with 16.1 months mean follow-up. Mean age was 62.7 years (SD 1.92); in six studies reporting sex, most patients were male (85%). Comparing patients with a SC or DC ICD or programming, we found similar rates of mortality [odds ratio (OR) 0.95, 95% confidence interval (CI) 0.54-1.68; P = 0.86] and inappropriate therapies (OR 1.46, 95% CI 0.97-2.19; P = 0.07) in five and six studies, respectively. In three studies of SC vs. DC ICDs (but not programming) rates of pneumothorax and lead dislodgement were not different (OR 2.12, 95% CI 0.18-24.72; P = 0.55 and OR 0.87, 95% CI 0.32-2.47; P = 0.83, respectively).

Conclusion

In this meta-analysis of randomized controlled trials comparing SC vs. DC ICD device or programming, there was no significant difference in inappropriate therapies, mortality, pneumothorax, or lead dislodgement. Future studies should compare these devices over longer follow-up and in specific patient populations.

Adverse Consequences of Right Ventricular Apical Pacing and Novel Strategies to Optimize Left Ventricular Systolic and Diastolic Function

Several studies have focused on the deleterious consequences of Right Ventricular Apical (RVA) pacing on Left Ventricular (LV) function, mediated by pacing-induced ventricular dyssyn-chrony. Therapeutic strategies to reduce the detrimental consequences of RVA pacing have been pro-posed, that includes upgrading of RVA pacing to Cardiac Resynchronization Therapy (CRT), alterna-tive Right Ventricular (RV) pacing sites, minimal ventricular pacing strategies, as well as atrial-based pacing. In developing countries, single chamber RV pacing still constitutes a majority of cases of permanent pacing, and assessment of the optimal RV pacing site is of paramount importance. In chronically-paced patients, it is crucial to maintain as close and normal LV physiological function as possible, by minimizing ventricular dyssynchrony, reducing the chances for heart failure and other complications to develop. This review provides an analysis of the deleterious immediate and long-term consequences of RVA pacing, and the most recent available evidence regarding improvements in pacing options and strategies to optimize LV diastolic and systolic function. Furthermore, the place of advanced echocardiography in the identification of patients with pacing-induced LV dysfunction, the potential role of a new predictor of LV dysfunction in RV-paced subjects, and the long- term out-comes of patients with RV septal pacing will be explored

Very long-term prognosis in patients with right ventricular apical pacing for sick sinus syndrome

Objective

The impact of right ventricular (RV) apical pacing on very long-term cardiac prognosis is little known. In this study, we retrospectively evaluated the relationship between RV apical pacing and cardiovascular events (CEs) in patients with sick sinus syndrome (SSS) and left ventricular ejection fraction (LVEF) >35%.

Methods

Total of 532 consecutive pacemaker recipients with SSS and LVEF >35% were divided into two groups according to the mean cumulative per cent RV apical ventricular pacing (mean %VP) (<50%; non-VP group vs ≥50%; VP group) and occurrence of CE was compared using Kaplan-Meier analysis between two groups. Cox hazard model was used to assess predictors of CE after adjusting explanatory variables such as age, atrial fibrillation (AF) and structural heart disease (SHD).

Results

Mean %VP was 86.0% and 8.2% in VP and non-VP groups, respectively (p<0.001). During mean follow-up of 13.4±7.0 years, CE occurred in 131 patients and more frequently in VP than non-VP group (p<0.001). However, the VP group was no longer associated with CE after taking into account other variables in multivariate analysis, which revealed AF (HR (HR)=2.08), SHD (HR=4.97), low LVEF (HR=0.98 for every 1% increase) and high age (HR=1.03 for every year of age) were independent predictors for CE. Regarding patients with SHD and/or AF and those aged ≥75 years, Kaplan-Meier curves showed both groups had similar prognosis.

Conclusions

Cardiac prognosis of patients with RV apical pacing was poor, but after adjusting for other predictors of CE, RV apical pacing was not a prognostic factor in patients with SSS with LVEF >35%.

Important Parameters for Implantable Cardioverter Defibrillator Selection

The efficacy of implantable cardioverter defibrillators in reducing the risk of sudden cardiac death has been well established by several clinical trials. Several factors relating to device characteristics, patient attributes, and comorbidities should be considered when selecting the appropriate implantable cardioverter defibrillators for each patient. This review examines some of these issues.

Prognostic Significance of PR Interval Prolongation in Adult Patients With Total Correction of Tetralogy of Fallot

BACKGROUND

Several studies have demonstrated the importance of mechanoelectrical interaction in patients with surgically corrected tetralogy of Fallot. However, the significance of atrioventricular conduction disturbance, that is PR interval prolongation, on adverse cardiac events in those patients remains to be elucidated.

METHODS

We examined electrocardiograms at baseline and their temporal change in a total of 176 patients with repaired tetralogy of Fallot (49% men; median age, 17.4 years). Then, we evaluated their correlation with right ventricular volume and function measured by cardiac magnetic resonance and the significance as a risk factor of adverse cardiac events: lethal ventricular arrhythmias, atrial arrhythmias, heart failure hospitalization, complete atrioventricular block (AVB), and all-cause death.

RESULTS

First-degree AVB was noted in 25 patients (14%). During a median follow-up of 10.0 (5.0-14.2) years, there was a progressive prolongation of PR interval (2.00±3.99 ms/y). Importantly, there were significant correlations between PR interval prolongation and right ventricular enlargement or right ventricular dysfunction. In contrast, in patients who underwent pulmonary valve replacement (n=23), significant shortening of PR interval by pulmonary valve replacement was noted (204±32 versus 176±34 ms; P=0.007). Cox regression analysis showed that first-degree AVB was an independent risk factor for lethal ventricular arrhythmias (hazard ratio, 5.479; 95% CI, 1.181-25.42; P=0.030) and complete AVB (hazard ratio, 27.67; 95% CI, 4.152-184.3; P<0.001) and had a tendency for heart failure hospitalization (hazard ratio, 3.301; 95% CI, 0.864-11.80; P=0.069). In addition, PR interval prolongation >2 ms/y was also a significant risk factor for lethal ventricular arrhythmias, regardless of the presence or absence of first-degree AVB at enrollment (hazard ratio, 24.18; 95% CI, 2.080-281.1; P=0.011).

CONCLUSIONS

These results indicate that progressive atrioventricular conduction disturbance is correlated with right ventricular enlargement and could be a useful predictor for increased risk of lethal ventricular arrhythmias in patients with repaired tetralogy of Fallot.

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.

Heart failure and right ventricular pacing - how to avoid the need for cardiac resynchronization therapy

INTRODUCTION

Heart failure (HF) is a common finding in patients with pacemakers implanted for bradycardia, with cross-sectional and longitudinal studies contributing to the growing consensus that right ventricular pacing can cause adverse cardiac remodeling and left ventricular systolic dysfunction increasing the risk of hospitalization and death. An unselected approach using cardiac resynchronization therapy from the time of first implant in patients with heart block has produced equivocal results. Contemporary research has therefore begun to focus on the stratification of patients' risk of pacemaker-associated impairment to permit focused, personalized management.

AREAS COVERED

The present review will describe the incidence and relevance of HF in the pacemaker population and discuss current management options for such patients.

EXPERT COMMENTARY

At present there are few contemporary data to guide the identification of patients with and at risk of pacemaker-associated cardiac remodeling and dysfunction. Emphasis must be placed on precise and personalized treatment approaches which currently remain under-investigated due to a number of challenges, for example, small sample sizes, limited clarity on programmed settings, and short follow-up periods.

The Italian subcutaneous implantable cardioverter-defibrillator survey: S-ICD, why not?

Aims

A recommendation for a subcutaneous-implantable cardioverter-defibrillator (S-ICD) has been added to recent European Society of Cardiology Guidelines. However, the S-ICD is not ideally suitable for patients who need pacing. The aim of this survey was to analyse the current practice of ICD implantation and to evaluate the actual suitability of S-ICD.

Methods and results

The survey ‘S-ICD Why Not?’ was an independent initiative taken by the Italian Heart Rhythm Society (AIAC). Clinical characteristics, selection criteria, and factors guiding the choice of ICD type were collected in consecutive patients who underwent ICD implantation in 33 Italian centres from September to December 2015. A cardiac resynchronization therapy (CRT) device was implanted in 39% (369 of 947) of patients undergoing de novo ICD implantation. An S-ICD was implanted in 12% of patients with no CRT indication (62 of 510 with available data). S-ICD patients were younger than patients who received transvenous ICD, more often had channelopathies, and more frequently received their device for secondary prevention of sudden death. More frequently, the clinical reason for preferring a transvenous ICD over an S-ICD was the need for pacing (45%) or for antitachycardia pacing (36%). Nonetheless, only 7% of patients fulfilled conditions for recommending permanent pacing, and 4% of patients had a history of monomorphic ventricular tachycardia that might have been treatable with antitachycardia pacing.

Conclusion

The vast majority of patients needing ICD therapy are suitable candidates for S-ICD implantation. Nevertheless, it currently seems to be preferentially adopted for secondary prevention of sudden death in young patients with channelopathies.

Comparison of Inappropriate Shocks and Other Health Outcomes Between Single- and Dual-Chamber Implantable Cardioverter-Defibrillators for Primary Prevention of Sudden Cardiac Death: Results From the Cardiovascular Research Network Longitudinal Study of Implantable Cardioverter-Defibrillators

BACKGROUND

In US clinical practice, many patients who undergo placement of an implantable cardioverter-defibrillator (ICD) for primary prevention of sudden cardiac death receive dual-chamber devices. The superiority of dual-chamber over single-chamber devices in reducing the risk of inappropriate ICD shocks in clinical practice has not been established. The objective of this study was to compare risk of adverse outcomes, including inappropriate shocks, between single- and dual-chamber ICDs for primary prevention.

METHODS AND RESULTS

We identified patients receiving a single- or dual-chamber ICD for primary prevention who did not have an indication for pacing from 15 hospitals within 7 integrated health delivery systems in the Longitudinal Study of Implantable Cardioverter-Defibrillators from 2006 to 2009. The primary outcome was time to first inappropriate shock. ICD shocks were adjudicated for appropriateness. Other outcomes included all-cause hospitalization, heart failure hospitalization, and death. Patient, clinician, and hospital-level factors were accounted for using propensity score weighting methods. Among 1042 patients without pacing indications, 54.0% (n=563) received a single-chamber device and 46.0% (n=479) received a dual-chamber device. In a propensity-weighted analysis, device type was not significantly associated with inappropriate shock (hazard ratio, 0.91; 95% confidence interval, 0.59-1.38 [P=0.65]), all-cause hospitalization (hazard ratio, 1.03; 95% confidence interval, 0.87-1.21 [P=0.76]), heart failure hospitalization (hazard ratio, 0.93; 95% confidence interval, 0.72-1.21 [P=0.59]), or death (hazard ratio, 1.19; 95% confidence interval, 0.93-1.53 [P=0.17]).

CONCLUSIONS

Among patients who received an ICD for primary prevention without indications for pacing, dual-chamber devices were not associated with lower risk of inappropriate shock or differences in hospitalization or death compared with single-chamber devices. This study does not justify the use of dual-chamber devices to minimize inappropriate shocks.

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.

Optimal Implantable Cardioverter Defibrillator Programming

Optimal programming of implantable cardioverter defibrillators (ICDs) is essential to appropriately treat ventricular tachyarrhythmias and to avoid unnecessary and inappropriate shocks. There have been a series of large clinical trials evaluating tailored programming of ICDs. We reviewed the clinical trials evaluating ICD therapies and detection, and the consensus statement on ICD programming. In doing so, we found that prolonged ICD detection times, higher rate cutoffs, and antitachycardia pacing (ATP) programming decreases inappropriate and painful therapies in a primary prevention population. The use of supraventricular tachyarrhythmia discriminators can also decrease inappropriate shocks. Tailored ICD programming using the knowledge gained from recent ICD trials can decrease inappropriate and unnecessary ICD therapies and decrease mortality.

Longitudinal changes in quality of life following ICD implant and the impact of age, gender, and ICD shocks: observations from the INTRINSIC RV trial

PURPOSE

ICDs can improve survival in at-risk patients but no consensus exists with respect to their impact on health-related quality of life (QOL). Moreover, the data are unclear on QOL benefits in specific patient subgroups. We sought to analyze, in the INTRINSIC RV ICD trial population, health-related QOL longitudinally following ICD implant and consider impact of age, gender, and ICD shocks on QOL by employing a global measure of health-related QOL.

METHODS

One thousand five hundred thirty patients had an ICD implanted. One week after implant (n = 1461), 988 patients were randomized to DDDR with AV search hysteresis (n = 502) or VVI (n = 486) programming. QOL data, using the SF-36 short form, were obtained for the 1461 patient cohort, irrespective of randomization status, at baseline and prospectively for 1 year following ICD implant.

RESULTS

Longitudinal mixed-effect analyses revealed significant improvements from baseline across all SF-36 subscales and component scores for the overall study cohort. Women had a substantially lower QOL at baseline, although their improvement after implant was similar to men. Patients <50 years scored consistently worse at baseline but experienced the greatest QOL improvement versus other age groups. Patients with higher NYHA class, angina, and diabetes had greater QOL improvements. There was no significant difference in QOL between patients with and without ICD shocks.

CONCLUSIONS

Our findings indicate that QOL was reportedly better post-implant and suggest that benefits associated with ICD implantation go beyond the direct treatment of arrhythmias, with benefits seen across genders and different age groups. These results further highlight that ICD implantation, in and of itself, does not reduce QOL.

Survival After Rate-Responsive Programming in Patients With Cardiac Resynchronization Therapy-Defibrillator Implants Is Associated With a Novel Parameter

Background—

Rate-responsive pacing (DDDR) versus nonrate-responsive pacing (DDD) has shown no survival benefit for patients undergoing cardiac resynchronization therapy defibrillator (CRT-D) implants. The heart rate score (HRSc), an indicator of heart rate variation, may predict survival. We hypothesized that high-risk HRSc CRT-D patients will have improved survival with DDDR versus DDD alone.

Methods and Results—

All CRT-D patients in LATITUDE remote monitoring (2006–2011), programmed DDD, had HRSc calculated at first data upload after implant (median 1.4 months). Patients subsequently reprogrammed to DDDR 7.6 median months later were compared with a propensity-matched DDD group and followed for 21.4 median months by remote monitoring. Data were adjusted for age, sex, lower rate limit, percent atrial pacing, percent biventricular pacing, and implant year. The social security death index was used to identify deaths. Remote monitoring provided programming and histogram data. DDDR programming in CRT-D patients was associated with improved survival (adjusted hazard ratio =0.77; P <0.001). However, only those with baseline HRSc ≥70% (2308/6164) had improved HRSc with DDDR (from 88±9% to 78±15%; P <0.001) and improved survival (hazard ratio =0.74; P <0.001). Patients with a high baseline HRSc and significant improvement over time were more likely to survive (hazard ratio =0.63; P =0.006). For patients with HRSc <70%, DDDR reprogramming increased the HRSc from 46±11% to 50±15% ( P <0.001); survival did not change. The HRSc did not change with DDD pacing over time.

Conclusions—

In CRT-D patients with HRSc ≥70%, DDDR reprogramming improved the HRSc and was associated with survival. Patients with lower HRSc had no change in survival with DDDR programming.

"Two for the Price of One": A Single-Lead Implantable Cardioverter-Defibrillator System with a Floating Atrial Dipole

In patients known to be a high risk for sudden cardiac arrest, implantable cardioverter defibrillators (ICD) are a proven therapy to reduce risk of death. However, in patients without conventional indications for pacing, the optimal strategy for type of device, dual- versus single-chamber, remains debatable. The benefit of prophylactic pacing in this category of patients has never been documented. Although available atrial electrograms in a dual chamber system improve interpretation of stored arrhythmia events, allow monitoring of atrial fibrillation and may potentially reduce the risk of inappropriate shocks by enhancing automated arrhythmia discrimination, the use of dual-chamber ICDs has a number of disadvantages. The addition of an atrial lead adds complexity to implantation and extraction procedures, increases procedural cost and is associated with a higher risk of periprocedural complications. The single lead pacing system with ability to sense atrial signals via floating atrial electrodes (VDD) clinically became available in early 1980's but did not gain much popularity due to inconsistent atrial sensing and concerns about the potential need for an atrial lead if sinus node fails. Most ICD patients do not have indications for pacing at implantation and subsequent risk of symptomatic bradycardia seems to be low. The concept of atrial sensing via floating electrodes has recently been revitalized in the Biotronik DX ICD system (Biotronik, SE & Co., Berlin, Germany) aiming to provide all of the potential advantages of available atrial electrograms without the risks and incremental cost of an additional atrial lead. Compared to a traditional VDD pacing system, the DX ICD system uses an optimized (15 mm) atrial dipole spacing and improved atrial signal processing to offer more reliable atrial sensing. The initial experience with the DX system indicates that the clinically useful atrial signal amplitude in sinus rhythm remains stable over time. Future studies are needed to determine reliability of atrial sensing during tachyarrhythmias, particularly atrial fibrillation as well as clinical utility and cost-effectiveness of this technology in different populations of patients.

Apical versus Non-Apical Lead: Is ICD Lead Position Important for Successful Defibrillation?

INTRODUCTION

We aim to compare the acute and long-term success of defibrillation between non-apical and apical ICD lead position.

METHODS AND RESULTS

The position of the ventricular lead was recorded by the implanting physician for 2,475 of 2,500 subjects in the Shockless IMPLant Evaluation (SIMPLE) trial, and subjects were grouped accordingly as non-apical or apical. The success of intra-operative defibrillation testing and of subsequent clinical shocks were compared. Propensity scoring was used to adjust for the impact of differences in baseline variables between these groups. There were 541 leads that were implanted at a non-apical position (21.9%). Patients implanted with a non-apical lead had a higher rate of secondary prevention indication. Non-apical location resulted in a lower mean R-wave amplitude (14.0 vs. 15.2, P < 0.001), lower mean pacing impedance (662 ohm vs. 728 ohm, P < 0.001), and higher mean pacing threshold (0.70 V vs. 0.66 V, P = 0.01). Single-coil leads and cardiac resynchronization devices were used more often in non-apical implants. The success of intra-operative defibrillation was similar between propensity score matched groups (89%). Over a mean follow-up of 3 years, there were no significant differences in the yearly rates of appropriate shock (5.5% vs. 5.4%, P = 0.98), failed appropriate first shock (0.9% vs. 1.0%, P = 0.66), or the composite of failed shock or arrhythmic death (2.8% vs. 2.3% P = 0.35) according to lead location.

CONCLUSION

We did not detect any reduction in the ICD efficacy at the time of implant or during follow-up in patients receiving a non-apical RV lead.

Accelerated graft dysfunction in heart transplant patients with persistent atrioventricular conduction block

AIMS

Bradyarrhythmia following heart transplantation is common-∼7.5-24% of patients require permanent pacemaker (PPM) implantation. While overall mortality is similar to their non-paced counterparts, the effects of chronic right ventricular pacing (CRVP) in heart transplant patients have not been studied. We aim to examine the effects of CRVP on heart failure and mortality in heart transplant patients.

METHODS AND RESULTS

Records of heart transplant recipients requiring PPM at St Vincent's Hospital, Sydney, Australia between January 1990 and January 2015 were examined. Patient's without a right ventricular (RV) pacing lead or a follow-up time of <1 year were excluded. Patients with pre-existing abnormal left ventricular function (<50%) were analysed separately. Patients were grouped by pacing dependence (100% pacing dependent vs. non-pacing dependent). The primary endpoint was clinical or echocardiographic heart failure (<35%) in the first 5 years post-PPM. Thirty-three of 709 heart transplant recipients were studied. Two patients had complete RV pacing dependence, and the remaining 31 patients had varying degrees of pacing requirement, with an underlying ventricular escape rhythm. The primary endpoint occurred significantly more in the pacing-dependent group; 2 (100%) compared with 2 (6%) of the non pacing dependent group (P < 0.0001 by log-rank analysis, HR = 24.58). Non-pacing-dependent patients had reversible causes for heart failure, unrelated to pacing. In comparison, there was no other cause of heart failure in the pacing-dependent group.

CONCLUSIONS

Permanent atrioventricular block is rare in the heart transplant population. We have demonstrated CRVP as a potential cause of accelerated graft failure in pacing-dependent heart transplant patients.

Minimizing right ventricular pacing in pacemaker patients with intact and compromised atrioventricular conduction : Results from the EVITA Trial

INTRODUCTION

Unnecessary ventricular pacing is associated with increased morbidity and mortality. Over the years different algorithms have been developed to reduce right ventricular pacing.

OBJECTIVES

Goal of the present study was to test the efficacy of the ventricular intrinsic preference (VIP) algorithm in patients with atrioventricular intact (AVi) and atrioventricular compromised (AVc) AV-conduction.

METHODS

Evaluation of VIP feature in pacemaker patients (EVITA) was a multicenter, prospective, randomized trial (Trials.gov Identifier: NCT00366158). In total, 389 patients were randomized to AVc group: n = 140/132 VIP OFF/VIP On, AVi group: n = 54/63 VIP OFF/VIP ON). One-month post-implantation AV conduction testing (AVc: PR/AR interval > 210 ms) was performed. Follow-up visits occurred 6 and 12 months after DDD-pacemaker implantation.

RESULTS

In AVi and AVc-patients initiation of the VIP feature significantly reduced incidence of ventricular pacing (AVi: 53 ± 38 vs. 9 ± 21%, p = 0.0001; AVc: 79 ± 31 vs. 28 ± 35%, p = 0.0001). DDD-pacemaker implantation per se significantly reduced incidence of AF in VIP ON (AVi 27 vs. 0%, p < 0.0001; AVc 29 vs. 3%, p < 0.0001) and VIP OFF patients (AVi 43 vs. 4%, p < 0.0001; AVc 33 vs. 3, p < 0.0001), without significant differences between VIP ON and OFF groups (p > 0.05). In the AVc group activation of VIP significantly reduced incidence of adverse events (AE). All-cause mortality was not significantly different in VIP ON (n = 5) and VIP OFF (n = 4, p > 0.05) patients.

CONCLUSION

AV search hysteresis (VIP) markedly reduces ventricular pacing both in patients with normal AV conduction and in patients with prolonged PR interval or intermittent AV block.

Future Research Prioritization: Implantable Cardioverter-Defibrillator Therapy in Older Patients

BACKGROUND

Although the implantable cardioverter-defibrillator (ICD) is highly effective therapy for preventing sudden cardiac death, there is considerable uncertainty about its benefits and harms in older patients, especially in the presence of factors, other than old age, that increase the risk of death.

OBJECTIVE

To develop a prioritized research agenda for the Patient-Centered Outcomes Research Institute as informed by a diverse group of stakeholders on the use and outcomes of the ICD in older patients.

DESIGN

The existing literature was reviewed to identify evidence gaps, which were then refined by engaged stakeholders. Using a forced-ranking prioritization method, the stakeholders ranked evidence gaps by importance. For the highest-ranked evidence gaps, relevant recent studies were identified using PubMed, and relevant ongoing trials were identified using ClinicalTrials.gov.

PARTICIPANTS

Eighteen stakeholders, including clinical experts and researchers in the prevention of sudden cardiac death and ICD therapy, representatives from federal and non-governmental funding agencies, representatives from relevant professional societies, health care decision-makers and policymakers, and representatives from related consumer and patient advocacy groups

KEY RESULTS

The top 12 evidence gaps prioritized by stakeholders were related to the safety and effectiveness of ICDs in older patient subgroups not well represented in clinical trials, predictors of SCD, the impact of the ICD on quality of life, the use of shared decision-making, disparities in ICD use, risk stratification strategies, patient preferences, and distribution of modes of death in older patients.

CONCLUSIONS

In this paper, we identify evidence gaps of high priority for current and future investigations of ICD therapy. Addressing these gaps will likely resolve many of the uncertainties surrounding the use and outcomes of the ICD in older patients seen in clinical practice.

Honing in on optimal ventricular pacing sites: an argument for his bundle pacing

OPINION STATEMENT

Frequent ventricular pacing is often or completely unavoidable in patients with high-grade or complete heart block. Over time, patients with high-burden RV pacing are at risk for developing symptomatic cardiomyopathy due to pacing-induced ventricular dyssynchrony. Growing awareness of this concern has generated interest in alternative pacing sites like the septum and outflow tract, the thinking being that these sites will more closely mimic His-Purkinje-mediated ventricular activation. Numerous studies have met with mixed results likely due to the fact that-to quote Marvin Gaye-there ain't nothing like the real thing. Herein lies the advantage of His bundle pacing (HBP), as it is the only pacing modality capable of physiological ventricular activation. HBP has been demonstrated to be safe and reliable in various forms of AV block with minimal drawbacks, namely modestly higher pacing thresholds when compared with other RV sites. Additionally, HBP is a truly physiologic alternative to biventricular pacing to effect cardiac resynchronization therapy (CRT), a concept supported by small observational and prospective studies. In our view, His bundle pacing should be considered in nearly all patients requiring ventricular pacing.

[Right ventricular septal stimulation would produce similar bi-ventricular dyssynchrony as does apical stimulation in patients with normal ejection fraction]

OBJECTIVE

To determine in patients with normal ejection fraction, undergoing permanent VVI pacing, if medial septal stimulation has lower dyssynchrony than apical stimulation assessed by echocardiography.

METHOD

A prospective trial, 19 patients>70 years old, scheduled for VVI pacemaker implantation for complete degenerative atrioventricular block, ventricular frequency<50beat per minute and ejection fraction≥45%. Patients with atrial fibrillation, heart failure, left bundle branch block and QRS durations longer than 120milliseconds in surface electrocardiogram with sinus rhythm were excluded. Patients were randomized to apical implantation group A: 47% and septal implantation group B: 53%. Echocardiographic parameters were measured previous to the implant, 48h, 5 and 48 months after implantation.

RESULTS

No patients had diagnosis of ischemic cardiomyopathy or heart failure. Echocardiographic parameters for interventricular dyssynchrony between groups were A: 14.44±19.76msec vs. B: 9±36.45msec; A: 6.11±62.11msec vs. B: 13±38.31msec; A: 77±53.51msec vs. B: 24.29±80.90msec, P=NS). For interventricular dyssynchrony were A: 46.44±19.76msec vs. B: 42.20±29.56msec; A: 45.33±45.67msec vs. B: 29.80±44.66msec; A: 46,38±20 msec vs. B: 21±27.20msec, P=NS) at 48h, 5 and 48 months, respectively.

CONCLUSION

Apical site of stimulation does not increase ventricular dyssynchrony rate in patients with preserved ejection fraction. Septal stimulation showed decreased trend in interventricular dyssynchrony.

Chronic right ventricular apical pacing: adverse effects and current therapeutic strategies to minimize them

The permanent cardiac pacemaker is the only effective therapy for patients with symptomatic bradycardia and hundreds of millions are implanted worldwide every year. Despite its undisputed clinical benefits, the last two decades have drawn much attention to the negative effects associated with long-term pacing of the right ventricle (RV). Experimental and clinical studies have shown that RV pacing produces ventricular dyssynchrony, similar to that of left bundle branch block, with consequent detrimental effects on cardiac structure and function, with adverse clinical outcomes such as atrial fibrillation, heart failure and death. Although clinical evidence largely comes from subanalyses of pacemaker and implantable cardiac defibrillator studies, there is strong evidence that patients with reduced left ventricular function are at high risk of suffering from the detrimental effects of long-term RV pacing. Biventricular pacing in cardiac resynchronization therapy devices can prevent ventricular dyssynchrony and has emerged as an attractive option in this patient group with promising results and more clinical studies underway. Moreover, there is evidence that specific pacemaker algorithms that minimize RV pacing can reduce the negative effects of RV stimulation on cardiac function and may also prevent clinical deterioration. The extent of the long-term clinical effects of RV pacing in patients with normal ventricular function and how to prevent this are less clear and subject to future investigation.

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.

Is conventional cardiac pacing harmful in patients with normal ventricular function?

BACKGROUND

Right ventricular pacing may be deleterious in patients with left ventricular dysfunction, but in patients with normal function the impact of this stimulation triggering clinically relevant ventricular dysfunction is not fully established.

OBJECTIVES

To evaluate the clinical, echocardiographic findings of patients with previously normal left ventricular function underwent implantation of a pacemaker.

METHODS

Observational, cross-sectional study with 20 patients, who underwent implantation of pacemaker, prospectively followed-up, with the following inclusion criteria: normal left ventricular function defined by echocardiography and ventricular pacing higher than 90%. Were evaluated functional class (FC) (New York Heart Association), 6-minute walk test (6MWT), B-type natriuretic peptide (BNP), echocardiographic assessment (conventional and dyssynchrony parameters), and quality of life questionnaire (QLQ) (SF-36). The assessment was performed at ten days (t1), four months (t2), eight months (t3), 12 months (t4) and 24 months (t5).

RESULTS

Conventional echocardiographic parameters and dyssynchrony parameters showed statistically significant variation over time. The 6MWT, FC, and BNP showed worsening at the end of two years. QLQ showed initial improvement and worsening at the end of two years.

CONCLUSION

The implantation of conventional pacemaker was associated with worsening in functional class, worsening in walk test, increased BNP levels, increased duration of QRS, and worsening in some domains of the QLQ at the end of two years. There were no changes in echocardiography measurements (conventional and asynchrony measures).

The importance of avoiding unnecessary right ventricular pacing in clinical practice

Symptomatic bradycardia is effectively treated with the implantation of a cardiac pacemaker. Although a highly successful therapy, during recent years there has been a focus on the negative effects associated with long-term pacing of the apex of the right ventricle (RV). It has been shown in both experimental and clinical studies that RV pacing leads to ventricular dyssynchrony, similar to that of left bundle branch block, with subsequent detrimental effects on cardiac structure and function, and in some cases adverse clinical outcomes such as atrial fibrillation, heart failure and death. There is substantial evidence that patients with reduced left ventricular function (LVEF) are at particular high risk of suffering the detrimental clinical effects of long-term RV pacing. The evidence is, however, incomplete, coming largely from subanalyses of pacemaker and implantable cardiac defibrillator studies. In this group of patients with reduced LVEF and an expected high amount of RV pacing, biventricular pacing (cardiac resynchronization therapy) devices can prevent the negative effects of RV pacing and reduce ventricular dyssynchrony. Therefore, cardiac resynchronization therapy has emerged as an attractive option with promising results and more clinical studies are underway. Furthermore, specific pacemaker algorithms, which minimize RV pacing, can also reduce the negative effects of RV stimulation on cardiac function and may prevent clinical deterioration.