Dual chamber versus single chamber ventricular pacemakers for sick sinus syndrome and atrioventricular block

Dual-chamber pacing confers better myocardial performance and improves clinical outcomes compared to single-chamber pacing

The deleterious effects of long term right ventricular pacing are increasingly being recognized today. Current clinical practice favors the implantation of dual-chamber permanent pacemaker which maintains atrioventricular synchrony and is associated with better quality of life. However, despite the popular belief and common sense surrounding the superiority of dual-chamber pacing over single chamber pacing, the same has never been conclusively verified in clinical trials. Some observational evidence however, does exists which supports the improved cardiac hemodynamics, lower the rate of atrial fibrillation, heart failure and stroke in dual-chamber pacing compared to single-chamber pacing. In the index study by Haque et al, right ventricular pacing, particularly in ventricular paced, ventricular sensed, inhibited response and rate responsive pacemaker adversely impacted the left ventricular functions over 9-months compared to dual pacing, dual sensing, dual responsive and rate responsive pacemaker. Although there are key limitations of this study, these findings does support a growing body of evidence reinstating the superiority of dual chamber pacing compared to single chamber pacing.

Emergency pacemaker implantation in nonagenarians with CHB: single-versus dual-chamber pacing

In ambulatory patients with complete heart block (CHB), dual-chamber (DDD) pacing confers physiological benefits versus single-chamber (VVI) pacing, however, the impact on mortality is disputed. Nonagenarians constitute an expanding proportion of pacemaker recipients, yet data on device selection and outcomes are limited, especially in emergency situations. In nonagenarians with emergent CHB, we compared the clinical characteristics and outcomes of patients receiving VVI versus DDD pacemakers. Cox proportional-hazards analysis examined all-cause mortality and death from congestive cardiac failure (CCF). There were 168 consecutive patients followed-up for 30.6 ± 15.5 months. Of these, 22 patients (13.1%) received VVI pacemakers; when compared with DDD recipients, these patients had similar median age (93 vs. 91 years, p=0.15) and left ventricular (LV) systolic function (LV ejection fraction [EF] 49.2% ± 9.7 vs. 50.7% ± 10.1, p=0.71), but were more frail (Rockwood scale 5.2 ± 1.8 vs. 4.3 ± 1.1, p=0.004) and more likely to have dementia (27.3% vs. 8.9%, p=0.011). Post-implant, device interrogation demonstrated that VVI recipients had higher respiratory rates (21.3 ± 2.4 vs. 17.5 ± 2.6 breaths per minute, p=0.002), lower mean heart rates (65.5 ± 10.1 vs. 71.9 ± 8.6 bpm, p=0.002), and lower daily activity levels (0.57 ± 0.3 vs. 1.5 ± 1.1 hours of activity, p=0.016) than DDD recipients. Adjusting for age, frailty and dementia, VVI pacing was associated with an increased risk of all-cause mortality (adjusted hazard ratio [HR] 2.1, 95% confidence interval [CI] 1.08 to 4.1, p=0.03) and death from CCF (adjusted HR 7.1, 95%CI 2.5 to 20.6, p<0.001). In conclusion, in nonagenarians with emergent CHB, dual-chamber pacing was associated with improved symptomatic and prognostic outcomes versus singlechamber pacing.

Dual-chamber versus single chamber pacemakers, a systemic review and meta-analysis on sick sinus syndrome and atrioventricular block patients

Aims

The atrioventricular block (AVB) is a conduction system problem that results from the impairment in the transmission of an impulse from the atria to the ventricle, the disease has many etiologies. This article aimed to evaluate the efficacy and safety of dual and single-chamber pacemakers in patients with SSS and AVB.

Methods

An electronic search of PubMed (Medline), EMBASE, and Google Scholar was performed from 2000 till August 15th, 2022. Retrieved articles were exported to Endnote Reference Library Software, where duplicate studies were removed from the list, and only articles meeting the eligibility criteria of this study were selected. RevMan 5.4 and STATA 16 software were used for the analysis. The modified Cochrane Collaboration's risk of bias and New-castle Ottawa scale were used for quality assessment of RCTs and observational studies respectively.

Results

This study is composed of 8953 patients with sick-sinus syndrome and atrioventricular block. A total of thirteen outcomes are included in this meta-analysis, out of which atrial fibrillation significantly favored dual chamber [OR = 1.29; 95 % CI = 1.05-1.59; P = 0.01 I2 = 29 %] and overall complications [OR = 0.48; 95 % CI = 0.29-0.77; p = 0.03 I2 = 0 %] and pneumothorax [OR = 0.31; 95 % CI = 0.10-0.93; p = 0.04, I2 = 0 %] were satisfied by single-chamber pacing.

Conclusion

This study concluded that neither single-chamber nor dual-chamber pacemakers are superior to each other, but they are unique in their own ways as the results of this study manifest remarkable reduction in atrial fibrillation rates and pneumothorax using dual-chamber and single-chamber pacemakers respectively.

Comparison of Global Longitudinal Strain in Dual-chamber versus Ventricular Pacemaker in Complete Heart Block

Context

Bradycardia caused by total atrioventricular block (TAVB) is treated by implantation of permanent pacemakers (PPMs) in either dual-chamber (DDD) versus ventricular (VVI) pacing modes. DDD is considered a more physiological pacing mode than VVI as it avoids atrioventricular dyssynchrony. However, previous trials have failed to demonstrate the superiority of DDD in improving quality of life and morbidity.

Aims

This study aims to provide postpacemaker function of the left ventricle (LV) measured with global longitudinal strain (GLS), in TAVB patients.

Settings and Design

This is a comparative study; samples included in the study are adult TAVB patients undergoing PPM implantation, without significant heart function, and structural abnormality. Echocardiographic parameters are obtained before, after 1 month, and after 3 months post-PPM.

Subjects and Methods

A total of 98 TAVB patients undergoes PPM implantation during the study period, 55 patients were excluded, and in the end, only 43 patients fulfill the inclusion criteria.

Statistical Analysis Used

Baseline data between DDD and VVI are compared using unpaired t-test. Statistical significance 1 month post-PPM and 3 months post-PPM is analyzed using paired t-test.

Results

There were no significant differences between both groups at baseline. However, significant GLS changes are observed 1 month after PPM in the VVI group (P = 0.002), but no significant change was observed in the DDD group even after 3 months (P = 0.055).

Conclusions

In our study, we conclude that DDD is superior in maintaining LV function in the short term in TAVB patients after PPM implantation.

Evolution of Pacemakers and Implantable Cardioverter Defibrillators (ICDs) in Cardiology

Pacemakers and implantable cardioverter defibrillators (ICDs) have revolutionized cardiology by providing life-saving interventions for patients with cardiac rhythm disturbances. Pacing the heart is an effective treatment for people suffering from bradycardia caused by sinus node dysfunction or atrioventricular (AV) block, and electronic pacing has saved countless lives since its introduction into clinical practice. AV synchronization is the typical cycle of atrial depolarization and contraction followed by ventricular depolarization and contraction. The continuation of this cycle leads to appropriate ventricular filling and cardiac output. By contrast, the failure of the cycle results in AV asynchrony, which may result in heart failure. Cardiac resynchronization treatment (CRT) involves using customized pacemakers with or without implantable cardioverter defibrillators and tries to resynchronize the failing heart by enhancing myocardial contraction without increasing energy consumption. This review delves into the extensive journey of pacemakers and ICDs in the field of cardiology. It highlights the transformative impact of these devices on patient care and quality of life, emphasizing technological advancements, clinical applications, and prospects. This comprehensive review aims to provide insights into the dynamic landscape of cardiac rhythm management.

Two-year Outcomes of Ventricular-demand Leadless Pacemaker Therapy for Heart Block After Transcatheter Aortic Valve Replacement

Ventricular-demand leadless pacemakers (VVI-LPMs) have often been used as an alternative to atrioventricular (AV) synchronous transvenous pacemakers (DDD-TPMs) in patients with high-grade AV block following transcatheter aortic valve replacement (TAVR). However, the clinical outcomes of this unusual usage are not elucidated. Patients who received permanent pacemakers (PPMs) owing to new-onset high-grade AV block after TAVR from September 2017 to August 2020 at a high-volume center in Japan were included in the analysis, and the clinical courses of VVI-LPM and DDD-TPM implants through 2 years of follow-up were compared retrospectively. Out of 413 consecutive patients who underwent TAVR, 51 (12%) patients received a PPM. After excluding 8 patients with chronic atrial fibrillation (AF), 3 with sick sinus syndrome, and 1 with incomplete data, 17 VVI-LPMs and 22 DDD-TPMs were included in our final cohort. The VVI-LPM group had lower serum albumin levels (3.2 ± 0.5 vs. 3.9 ± 0.4 g/dL, P < .01) than the DDD-TPM group. Follow-up revealed no significant differences between the 2 groups in terms of the incidence of late device-related adverse events (0% vs. 5%, log-rank P = .38) and new-onset AF (6% vs. 9%, log-rank P = .75); however, there were increases in the rates of all-cause death (41% vs. 5%, log-rank P < .01) and heart failure rehospitalization (24% vs. 0%, log-rank P = .01) in the VVI-LPM group. This small retrospective study reveals favorable post-procedural complication rates but higher all-cause mortality with VVI-LPM compared to DDD-TPM therapy for high-grade AV block after TAVR at 2 years of follow-up.

Clinical Outcomes of Non-Atrial Fibrillation Bradyarrhythmias Treated With a Ventricular Demand Leadless Pacemaker Compared With an Atrioventricular Synchronous Transvenous Pacemaker - A Propensity Score-Matched Analysis

BACKGROUND

Implanting a ventricular demand leadless pacemaker (VVI-LPM) for patients with non-atrial fibrillation (AF) bradyarrhythmias such as sick sinus syndrome (SSS) or high-grade (i.e., second- or third-degree) atrioventricular (AV) block is not recommended unless they have limited vascular access or a high infection risk; nevertheless, an unexpectedly high number of VVI-LPM implantations have been performed. This study investigated the clinical outcomes of these unusual uses.

METHODS AND RESULTS

This study retrospectively analyzed 193 patients who were newly implanted with a VVI-LPM or an atrioventricular synchronous transvenous pacemaker (DDD-TPM) for non-AF bradyarrhythmias at a high-volume center in Japan from September 2017 to September 2020. Propensity score-matching produced 2 comparable cohorts treated with a VVI-LPM or DDD-TPM (n=58 each). Each group had 20 (34%) patients with SSS and 38 (66%) patients with high-grade AV block. During a median follow up of 733 (interquartile range 395-997) days, there were no significant differences between the VVI-LPM and DDD-TPM groups regarding late device-related adverse events (0% vs. 4%, log-rank P=0.155), but the VVI-LPM group had a significantly increased readmission rate for heart failure (HF) (29% vs. 2%, log-rank P=0.001) and a tendency to have higher all-cause mortality (28% vs. 4%, log-rank P=0.059).

CONCLUSIONS

The implantation of a VVI-LPM for non-AF bradyarrhythmias increased the incidence of HF-related rehospitalization at the mid-term follow up compared to the use of a DDD-TPM.

Permanent epicardial pacing in neonates and infants less than 1 year old: 12-year experience at a single center

BACKGROUND

Permanent epicardial pacing is the primary choice for neonates and infants with bradyarrhythmia. We reviewed mid-term outcomes after epicardial permanent pacemaker (EPPM) implantation in this age group.

METHODS

From Dec 1, 2008 to Dec 1, 2019, children who underwent EPPM implantation within the first year of life were included in our study. Patients were followed up for as long as 12 years, until Jun 11, 2021, for all-cause mortality and pacemaker reoperation. Kaplan-Meier and log-rank tests were used for analysis.

RESULTS

Of 31 consecutive patients [18 boys (58.1%) and 2 neonates (6.5%)] included in this study, 30 (96.8%) were discharged alive and assessed at a median follow-up of 3.9 years [interquartile range (IQR) 4.7]. The median age and weight of the patients were 156 days (IQR 217) and 5.3 kg (IQR 3.5), respectively, at the time of their operation. Twenty-five (80.6%) patients had congenital heart disease, and the main indication for pacing was postoperative atrioventricular block (AVB) in 21 (67.7%) patients. During follow-up, 3 (9.7%) patients died and there were a total of 9 pacing lead failures in 7 (22.6%) patients. The median longevity of leads (unipolar steroid-eluting) was 2.9 years (IQR 3.6). Freedom from lead reoperation was 90.3%, 72.0%, 65.5% and 49.1% at 1, 3, 5, and 8 years, respectively. The median longevity of the pacing generators was 3.3 years (IQR 2.8). Freedom from generator reoperation was 90.3%, 75.6%, 52.4% and 43.6% at 1, 3, 5 and 6 years, respectively.

CONCLUSIONS

The mid-term outcome of EPPM implantation in neonates and infants was acceptable. Neonates and infants with EPPM implants face the risk of repeated reoperations and all-cause death. A patient's prognosis can depend on regular follow-up, type of pacing lead and the presence of congenital heart malformations, especially complex congenital heart disease.

Optimizing mechanically sensed atrial tracking in patients with atrioventricular-synchronous leadless pacemakers: A single-center experience

Background

Atrioventricular (AV)-synchronous single-chamber leadless pacing using a mechanical atrial sensing algorithm produced high AV synchrony in clinical trials, but clinical practice experience with these devices has not yet been described.

Objective

To describe pacing outcomes and programming changes with AV-synchronous leadless pacemakers in clinical practice.

Methods

Consecutive patients without persistent atrial fibrillation who received an AV-synchronous leadless pacemaker and completed follow-up between February 2020 and April 2021 were included. We evaluated tracking index (atrial mechanical sense followed by ventricular pace [AM-VP] divided by total VP), total AV synchrony (sum of AM-ventricular sense [AM-VS], AM-VP, and AV conduction mode switch), use of programming optimization, and improvement in AV synchrony after optimization.

Results

Fifty patients met the inclusion criteria. Mean age was 69 ± 16.8 years, 24 (48%) were women, 24 (48%) had complete heart block, and 17 (34%) required ≥50% pacing. Mean tracking index was 41% ± 34%. Thirty-five patients (70%) received ≥1 programming change. In 36 patients with 2 follow-up visits, tracking improved by +9% ± 28% (P value for improvement = .09) and +18% ± 19% (P = .02) among 15 patients with complete heart block. Average total AV synchrony increased from 89% [67%, 99%] to 93% [78%, 100%] in all patients (P = .22), from 86% [52%, 98%] to 97% [82%, 99%] in those with complete heart block (P = .04), and from 73% [52%, 80%] to 78% [70%, 85%] in those with ≥50% pacing (P = .09).

Conclusion

In patients with AV-synchronous leadless pacemakers, programming changes are frequent and are associated with increased atrial tracking and increased AV synchrony in patients with complete heart block.

Sex Differences and Long-Term Outcome in Patients With Pacemakers

Introduction: Evidence of sex-related differences in patients with pacemakers regarding comorbidities is insufficiently investigated. The aim of this study was to determine the relationship of cardiovascular comorbidities and sex category with properties of pacemaker implantation, pacemaker follow-up, and long-term survival. Methods: This retrospective, single-center cohort study consisted of 6,362 pacemaker-patients (39.7% female) enrolled between May 2000 and April 2015. Functional pacemaker parameters were registered at regular pacemaker controls. Survival status and cause of death were analyzed in relation to comorbidities, implanted pacing devices, and echocardiography. Survival analyses were plotted for a 10-year follow-up. Results: Patients with hypertension or hyperlipidemia had higher rates of implantations due to sick sinus syndrome (28.6 vs. 25.5% without hypertension, P < 0.001; 30.7 vs. 25.7% without hyperlipidemia, P < 0.001), while endocarditis was associated with higher rates of implantations due to AV block (46.7 vs. 33.4%, P < 0.001). Patients with valvular heart disease had higher rates of pacemaker implantation due to bradycardic atrial fibrillation (24.9 vs. 21.0% without valvular heart disease, P < 0.001). Ventricular pacing threshold increased in both sexes during the follow-up and was higher in women in the final follow-up (0.94 vs. 0.91 V in men, P = 0.002). During the 10-years follow-up, 6.1% of women and 8.6% of men underwent lead replacement (P = 0.054). Device and lead replacement rates were increased if the comorbidities coronary artery disease, heart failure, hypertension, hyperlipidemia, valvular heart disease, previous stroke/TIA, atrial arrhythmias, chronic kidney disease, or endocarditis were present. Diabetes and previous CABG increase the rates of device replacement, but not the rate of lead replacement. Severe tricuspid regurgitation after implantation of pacemaker was present in more men than women (14.4 vs. 6.1%, P < 0.001). In a multivariate COX regression, the following variables were associated with independent decrease of 10-year survival: hypertension (HR 1.34, 95% CI 1.09-1.64), chronic kidney disease (HR 1.83, 95% CI 1.53-2.19), tricuspid regurgitation after pacemaker implantation (HR 1.48, 95% CI 1.26-1.74). Survival was independently increased in female sex (HR 0.83, 95% CI 0.70-0.99) and hyperlipidemia (HR 0.81, 95% CI 0.67-0.97). Conclusions: Cardiovascular comorbidities influenced significantly pacemaker implantations and long-term outcome. Trial Registration: ClinicalTrials.gov Unique identifier: NCT03388281.

Evaluating and managing bradycardia

Bradycardia is a commonly observed arrhythmia and a frequent occasion for cardiac consultation. Defined as a heart rate of less than 50-60 bpm, bradycardia can be observed as a normal phenomenon in young athletic individuals, and in patients as part of normal aging or disease (Table 1). Pathology that produces bradycardia may occur within the sinus node, atrioventricular (AV) nodal tissue, and the specialized His-Purkinje conduction system. Given the overlap of heart rate ranges with non-pathologic changes, assessment of symptoms is a critical component in the evaluation and management of bradycardia. Treatment should rarely be prescribed solely on the basis of a heart rate lower than an arbitrary cutoff or a pause above certain duration. In the 2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients with Bradycardia and Cardiac Conduction Delay (referred to hereafter as the 2018 Bradycardia Guideline), there was a significant shift in emphasis from prior guidelines that emphasized device-based implantation recommendations to a focus on evaluation and management of disease states [1,2]. In this review, we will highlight the changes in the new guideline as well as describe the key elements in evaluation and management of patients presenting with bradycardia.

Statistics on the use of cardiac electronic devices and interventional electrophysiological procedures in Africa from 2011 to 2016: report of the Pan African Society of Cardiology (PASCAR) Cardiac Arrhythmias and Pacing Task Forces

Aims

To provide comprehensive information on the access and use of cardiac implantable electronic devices (CIED) and catheter ablation procedures in Africa.

Methods and results

The Pan-African Society of Cardiology (PASCAR) collected data on invasive management of cardiac arrhythmias from 2011 to 2016 from 31 African countries. A specific template was completed by physicians, and additional information obtained from industry. Information on health care systems, demographics, economics, procedure rates, and specific training programs was collected. Considerable heterogeneity in the access to arrhythmia care was observed across Africa. Eight of the 31 countries surveyed (26%) did not perform pacemaker implantations. The median pacemaker implantation rate was 2.66 per million population per country (range: 0.14–233 per million population). Implantable cardioverter-defibrillator and cardiac resynchronization therapy were performed in 12/31 (39%) and 15/31 (48%) countries respectively, mostly by visiting teams. Electrophysiological studies, including complex catheter ablations were performed in all countries from Maghreb, but only one sub-Saharan African country (South Africa). Marked variation in cost (up to 1000-fold) was observed across countries with an inverse correlation between implant rates and the procedure fees standardized to the gross domestic product per capita. Lack of economic resources and facilities, high cost of procedures, deficiency of trained physicians, and non-existent fellowship programs were the main drivers of under-utilization of interventional cardiac arrhythmia care.

Conclusion

There is limited access to CIED and ablation procedures in Africa. A quarter of countries did not have pacemaker implantation services, and catheter ablations were only available in one country in sub-Saharan Africa.

Severe Bradycardia Prior to Coronary Artery Bypass Graft Surgery: A Case Report

Intraventricular conduction abnormalities following cardiac surgery have been thoroughly described, especially after valvular surgery. It is also widely known that several anesthetic factors can cause autonomic disturbances resulting in the unmasking of sinus node dysfunction, significant bradycardia, and cardiovascular collapse during the intraoperative period. However, little is known about asymptomatic episodes, especially those occurring prior to coronary artery bypass grafting (CABG). We report a rare occurrence of an intraventricular conduction defect that presented in an asymptomatic patient following non-ST-elevation myocardial infarction prior to urgent CABG. Our patient presented with sudden-onset chest pain, and following coronary angiography he was found to have triple-vessel coronary disease. During anesthetic induction for inpatient CABG surgery, he developed episodes of acute sinus tachy-brady episodes, requiring a stat dose of adrenaline to maintain the heart rate prior to the establishment of cardiopulmonary bypass. The arrhythmia persisted postoperatively, necessitating the insertion of a permanent dual-chamber pacemaker for complete heart block. The patient was later discharged without further complications, and upon follow-up 12 months later, he remains in good health.

Single chamber permanent epicardial pacing for children with congenital heart disease after surgical repair

Background

To analyze the 10-year experience of single chamber permanent epicardial pacemaker placement for children with congenital heart diseases (CHD) after surgical repair.

Methods

Between 2002 and 2014, a total of 35 patients with CHD (age: 26.9 ± 23.2 months, weight: 9.7 ± 5.6 kg) received permanent epicardial pacemaker placement following corrective surgery. Echocardiography and programming information of the pacemaker, as well as major adverse cardiac events (MACE) as heart failure or sudden death, were recorded during follow-up (46.8 ± 33.8 months).

Results

Acute ventricular stimulation threshold was 1.34 ± 0.72 V and no significant increase was observed at the last follow-up as 1.37 ± 0.81 V (p = 0.93). Compared with initial pacemaker implantation, the last follow-up didn’t show significant increases in impedance (p = 0.327) or R wave (p = 0.635). Four patients received pacemaker replacement because of battery depletion. 7/35 (20 %) of patients experienced MACE. Although the age and body weight were similar between patients with and without MACE, the patients with MACE were with complex CHD (100 % vs.55.6 %, p = 0.04).

Conclusion

High-degree iatrogenic atrioventricular block was the primary reason for placement of epicardial pacemaker for patients with CHD after surgical repair. Pacemaker placement with the steroid-eluting leads results in acceptable outcomes, however, the pacemaker type should be optimized for the children with complex CHD.

The role of cardiac pacing in carotid sinus syndrome: a meta-analysis

PURPOSE

Cardiac pacing can be used to treat carotid sinus syndrome (CSS), but clinical studies have shown conflicting results. We conducted a systematic review and meta-analysis to evaluate the role of pacing for CSS.

METHODS

A systematic search of publications in PubMed, Embase, and the Cochrane Library without language restriction was performed. Prospective randomized studies that compared cardiac pacing with standard therapy or pacing with different algorithms were included if the recurrence of syncope or the number of falls was observed.

RESULTS

Eight studies enrolling 540 patients were identified. In open-label studies, the recurrence of syncope was reduced significantly by cardiac pacing compared with standard therapy. The recurrence of syncope was not different between single- and dual-chamber pacing, but a lower rate of patients with pre-syncope was observed in the group with dual-chamber pacing. Double-blind clinical studies failed to observe the role of cardiac pacing for preventing falls in patients with CSS.

CONCLUSION

The results of meta-analysis supported the use of cardiac pacing for patients with dominant cardioinhibitory CSS.

Sick sinus syndrome in a dog: treatment with dual-chambered pacemaker implantation

A 2-year-old male castrated boxer dog was presented because of a history of syncope. Electrocardiogram tracings obtained with a cardiac event monitor showed bradycardia culminating in asystole. Sick sinus syndrome was diagnosed and treated with transvenous implantation of a dual-chambered permanent pacemaker.

Contemporary pacemakers: what the primary care physician needs to know

Pacemaker therapy is most commonly initiated because of symptomatic bradycardia, usually resulting from sinus node disease. Randomized multicenter trials assessing the relative benefits of different pacing modes have made possible an evidence-based approach to the treatment of bradyarrhythmias. During the past several decades, major advances in technology and in our understanding of cardiac pathophysiology have led to the development of new pacing techniques for the treatment of heart failure in the absence of bradycardia. Left ventricular or biventricular pacing may improve symptoms of heart failure and objective measurements of left ventricular systolic dysfunction by resynchronizing cardiac contraction. However, emerging clinical data suggest that long-term right ventricular apical pacing may have harmful effects. As the complexity of cardiac pacing devices continues to grow, physicians need to have a basic understanding of device indications, device function, and common problems encountered by patients with devices in the medical and home environment.

Treatment Crossovers Did Not Affect Randomized Treatment Comparisons in the Mode Selection Trial (MOST)

OBJECTIVES

We evaluated the impact of treatment crossovers on study results in the Mode Selection Trial (MOST).

BACKGROUND

The MOST study, a 2,010-patient, 6-year trial comparing dual-chamber pacing (DDDR) and ventricular pacing (VVIR) in sinus node dysfunction, demonstrated no difference in death or stroke and modest reductions in heart failure hospitalization (HFH) and atrial fibrillation (AF) with DDDR pacing. However, a moderate proportion of VVIR-randomized patients were temporarily or permanently crossed over to DDDR pacing.

METHODS

Intent-to-treat (ITT) analyses compared treatment arms by randomized pacing mode. On-treatment analyses used time-dependent covariates to account for all crossovers. All analyses used Cox proportional hazards models and included covariates prespecified in the study design: age, gender, Charlson index, and prior stroke, heart failure, myocardial infarction, supraventricular tachyarrhythmia, and ventricular tachycardia or fibrillation.

RESULTS

Of 996 VVIR-randomized patients, 375 (38%) were DDDR paced at some time, accounting for 27% of follow-up days among all VVIR-randomized patients. Of 1,014 DDDR-randomized patients, 53 (5%) were VVIR paced at some time, accounting for 1.5% of follow-up days among all DDDR-randomized patients. On-treatment analyses showed slightly lower hazard ratios favoring DDDR versus VVIR compared with ITT: death or stroke 0.88 (on-treatment) versus 0.91 (ITT); death 0.94 versus 0.95; stroke 0.74 versus 0.81; HFH 0.72 versus 0.73; and AF 0.72 versus 0.77. Interpretation of treatment effects was unchanged.

CONCLUSIONS

Although treatment crossovers accounted for >25% of follow-up time in the VVIR-randomized group, this did not affect study results. End point comparisons between randomized modes are accurate reflections of DDDR versus VVIR pacing in this study population.

Modelling the health benefits and economic implications of implanting dual-chamber vs. single-chamber ventricular pacemakers in the UK

AIMS

To estimate the consequences of managing bradycardia due to sinoatrial node disease or atrioventricular block with dual-chamber vs. single-chamber ventricular pacemakers.

METHODS AND RESULTS

A discrete-event simulation was conducted to predict outcomes over 5 years. Patients could develop post-operative complications, clinically relevant pacemaker syndrome leading to replacement of single-chamber with dual-chamber, atrial fibrillation (AF; which if chronic might require anticoagulants) or stroke. Survival, quality-adjusted life years (QALYs), complications, and associated direct medical costs were estimated (2003 British Pounds pounds sterling). Identical patients were simulated after receiving a single-chamber device or a more expensive dual-chamber pacemaker. Probabilities of conditions were obtained from clinical trials. Benefits were discounted at 1.5% and costs at 6%. Post-operative complications increased from 6.4% with single-chamber to 7.7% with dual-chamber but AF decreased (22 vs. 18%) as did clinically relevant pacemaker symptoms (16.8 vs. 0%). Approximately 4300 pounds sterling were accrued per patient over 5 years. Additional health benefits with dual-chamber are achieved at a mean net cost of 43 pounds sterling per patient, leading to 0.09 QALY with a cost-effectiveness ratio of 477 pounds sterling/QALY.

CONCLUSION

Implanting the costlier device increases the cost of the initial operation; however, this is expected to be offset by a reduction in costs associated with re-operations and AF.

Pacemaker selection: time for a rethinking of complex pacing systems?The opinions expressed in this article are not necessarily those of the Editors of the European Heart Journal or of the European Society of Cardiology

Evidence from randomized trials indicates that the clinical benefits of dual-chamber (DDD) pacing are modest: (i) no significant differences exist between physiological pacing and single-chamber pacing in mortality and stroke; (ii) ventricular desynchronization resulting from chronic right-ventricular pacing in DDD mode, induces a significantly increased incidence of atrial fibrillation (AF) and heart failure hospitalizations; (iii) AF pacing prevention and therapy algorithms have shown a modest to minimal or absent efficacy; (iv) the widespread use of physiological pacemakers is not an economically attractive strategy. Thus, these data provide a reliable body of evidence on which to make more rationale clinical decisions for individual patients and policy decisions for health costs saving. The cheaper single-chamber AAI(R) or VVI(R) has been shown to satisfy both conditions in most cases of sinus node disease and AV block.

Controversies in pacing: Indications and programming

This article reviews controversies in cardiac pacing in four areas: methods to prevent unnecessary right ventricular pacing and optimal ventricular pacing sites in the bradycardia population, pacing for prevention of atrial fibrillation (AF), a novel pacing technique for the treatment of heart failure, and pacing for the treatment of sleep apnea. Frequent right ventricular pacing has been reported to increase the incidence of AF and congestive heart failure. However, many patients with pacemakers for bradycardia have intrinsic atrioventricular conduction most of the time. Optimal programming of pacemakers and new algorithms designed to reduce unnecessary ventricular pacing are discussed. Pacing algorithms for prevention of AF have generally been shown to be ineffective. Atrial antitachycardia pacing has been shown to reduce the burden of atrial tachyarrhythmias in selected patients. Cardiac contractility modulation has recently been reported to be a promising new approach to the treatment of heart failure. Some pacing techniques may be effective in the treatment of sleep apnea but larger, long-term clinical trials are required to demonstrate a significant clinical benefit.

A simplified search strategy for identifying randomised controlled trials for systematic reviews of health care interventions: a comparison with more exhaustive strategies

BACKGROUND

It is generally believed that exhaustive searches of bibliographic databases are needed for systematic reviews of health care interventions. The CENTRAL database of controlled trials (RCTs) has been built up by exhaustive searching. The CONSORT statement aims to encourage better reporting, and hence indexing, of RCTs. Our aim was to assess whether developments in the CENTRAL database, and the CONSORT statement, mean that a simplified RCT search strategy for identifying RCTs now suffices for systematic reviews of health care interventions.

METHODS

RCTs used in the Cochrane reviews were identified. A brief RCT search strategy (BRSS), consisting of a search of CENTRAL, and then for variants of the word random across all fields (random$.af.) in MEDLINE and EMBASE, was devised and run. Any trials included in the meta-analyses, but missed by the BRSS, were identified. The meta-analyses were then re-run, with and without the missed RCTs, and the differences quantified. The proportion of trials with variants of the word random in the title or abstract was calculated for each year. The number of RCTs retrieved by searching with "random$.af." was compared to the highly sensitive search strategy (HSSS).

RESULTS

The BRSS had a sensitivity of 94%. It found all journal RCTs in 47 of the 57 reviews. The missing RCTs made some significant differences to a small proportion of the total outcomes in only five reviews, but no important differences in conclusions resulted. In the post-CONSORT years, 1997-2003, the percentage of RCTs with random in the title or abstract was 85%, a mean increase of 17% compared to the seven years pre-CONSORT (95% CI, 8.3% to 25.9%). The search using random$.af. reduced the MEDLINE retrieval by 84%, compared to the HSSS, thereby reducing the workload of checking retrievals.

CONCLUSION

A brief RCT search strategy is now sufficient to locate RCTs for systematic reviews in most cases. Exhaustive searching is no longer cost-effective, because in effect it has already been done for CENTRAL.