Reduction of right ventricular pacing in patients with sinus node dysfunction using an enhanced search AV algorithm

Newer algorithms in bradycardia management

Permanent cardiac pacemakers (PPM) are effective in the treatment of bradycardia in a growing number of clinical scenarios. An appreciation of the capacity of PPMs to result in negative hemodynamic and proarrhythmic effects has grown alongside clinical experience with permanent pacing. Such experience has necessitated the development of algorithms aimed at optimizing device functionality across a broad spectrum of physiologic and pathologic conditions. This review highlights recent device-based algorithms used in automated threshold testing, reduction of right ventricular pacing, prevention and treatment of pacemaker-mediated tachycardia, mode switching for atrial tachyarrhythmias, rate-modulated pacing, and advances in arrhythmia storage and remote monitoring.

Clinical evaluation of pacemaker automatic capture management and atrioventricular interval extension algorithm

AIMS

The present study was to assess the accuracy of automatic atrial and ventricular capture management (ACM and VCM) in determining pacing threshold and the performance of a second-generation automatic atrioventricular (AV) interval extension algorithm for reducing unnecessary ventricular pacing.

METHODS AND RESULTS

A total of 398 patients at 32 centres who received an EnPulse dual-chamber pacing/dual-chamber adaptive rate pacing pacemaker (Medtronic, Minneapolis, MN, USA) were enrolled. The last amplitude thresholds as measured by ACM and VCM prior to the 6-month follow-up were compared with manually measured thresholds. Device diagnostics were used to evaluate ACM and VCM and the percentage of ventricular pacing with and without the AV extension algorithm. Modelling was performed to assess longevity gains relating to the use of automaticity features. Atrial and ventricular capture management performed accurately and reliably provided complete capture management in 97% of studied patients. The AV interval extension algorithm reduced the median per cent of right ventricular pacing in patients with sinus node dysfunction from 99.7 to 1.5% at 6-month follow-up and in patients with intermittent AV block (excluding persistent 3° AV block) from 99.9 to 50.2%. On the basis of validated modelling, estimated device longevity could potentially be extended by 1.9 years through the use of the capture management and AV interval extension features.

CONCLUSION

Both ACM and VCM features reliably measured thresholds in nearly all patients; the AV extension algorithm significantly reduced ventricular pacing; and the use of pacemaker automaticity features potentially extends device longevity.

Left ventricular performance during para-His pacing in patients with high-grade atrioventricular block: an acute study

AIM

To compare changes in left ventricular (LV) performance and mechanical synchrony between atrial-based pacing with intrinsic conduction (AAI), dual-chamber para-His Pacing (DDD-PHP) and dual-chamber right ventricular septal pacing (DDD-RVS) in patients with high-grade atrioventricular block (AVB).

METHODS AND RESULTS

Patients with high-grade AVB and QRS <120 ms, who had temporary intrinsic atrioventricular (AV) conduction the day after the implantation were included in the study. All patients received a biventricular pacemaker with a para-His lead in the LV port, and a RVS lead in the right ventricular port. Left ventricular three-dimensional echocardiograms, LV outlet tract-velocity time integrals (LVOT-VTI), and LV synchrony with tissue Doppler imaging were recorded during AAI, DDD-PHP, and DDD-RVS. Eleven patients were included. The mean LVOT-VTI was significant lower during DDD-RVS (19.2 ± 5.5 cm) as compared with DDD-PHP (21.4 ± 5.5 cm), P = 0.006 and AAI (21.6 ± 6.8 cm), P = 0.016. The LVEF was higher during AAI than during DDD-PHP (P= 0.02) and DDD-RVS (P< 0.01). The maximal time to peak velocity between basal segments was significant longer with DDD-RVS (95 ± 26 ms) than with AAI (72 ± 30 ms), P = 0.028, whereas no difference was observed between AAI and DDD-PHP (81 ± 42 ms), P = 0.20.

CONCLUSIONS

Acutely, DDD-PHP preserves LV systolic performance and mechanical synchrony as compared with DDD-RVS.

His and para-His pacing in AV block: feasibility and electrocardiographic findings

PURPOSE

Right ventricular apical pacing induces a dyssynchronous activation of the left ventricle and is associated with adverse clinical outcome. We aimed to establish permanent His-bundle pacing or para-His pacing in patients with high-grade atrioventricular (AV) block.

METHOD

We included patients with pacemaker indication due to second- or third-degree AV block, left ventricular ejection fraction >0.40, QRS duration <120 ms, and sinus rhythm. All patients received a pacemaker with one atrial lead, one right ventricular mid-septal lead, and one lead in the His bundle or in the para-His position. Pacing from apex was performed temporarily. Patients were followed for 12 months.

RESULTS

Thirty-eight patients were included (mean age, 67 ± 10 years; 30 (79%) male). Mean implantation time was 85 ± 31 min, mean fluoroscopy time was 23 ± 13 min, and mean position attempts of the His bundle lead was 8 ± 5. In four patients, we established direct His-bundle pacing with a mean QRS of 100 ± 19 ms, and in 28 patients, para-His pacing was achieved with a mean QRS of 112 ± 18 ms, and in six patients, neither direct His-bundle pacing or para-His pacing could be achieved. The mean QRS duration was 153 ± 12 ms with mid-septal pacing and 161 ± 15 ms with apical pacing.

CONCLUSION

Stable direct His-bundle pacing or para-His pacing is feasible in 85% of patients with narrow QRS and high-grade AV block and leads to a normal or near-normal ventricular activation pattern.

Simulation of AV hysteresis pacing using an integrated dual chamber heart and pacer model

Long term right ventricular apical pacing has been known to have adverse effects in cardiac function. The AV hysteresis (AVH) is a feature existing in many dual-chamber cardiac pacemakers that aims to minimize the right ventricular pacing, but its clinical efficacy remains inconclusive due to conflicting evidence from different studies. We have recently developed a novel integrated dual-chamber heart and pacer (IDHP) model, which can simulate various interactions between intrinsic heart activity and extrinsic cardiac pacing. In this study, we use the IDHP model to simulate various atrio-ventricular (AV) conduction pathologies, and to investigate the effects of an AVH algorithm on reducing right ventricular pacing. Our results show that the efficacy of AVH is dependent on the underlying cardiac conditions. While it can preserve intrinsic conduction during minor or moderate first degree AV block, its efficacy is reduced at higher degree AV block conditions. This pilot study further supports using the IDHP model to design and evaluate more advanced pacemaker algorithms for therapeutic interventions.

[Avoidance of ventricular pacing in patients with sinus node disease or intermittent AV block]

In patients with frequent right ventricular stimulation, worsening of heart failure and atrial fibrillation may occur. Avoidance of unnecessary right ventricular pacing is a major requirement for pacemaker selection and programming in patients with sinus node disease or intermittent AV block. In dual chamber pacemakers this goal can be achieved by programming a long AV delay or an AV delay hysteresis. Algorithms that allow AAI pacing in a dual chamber pacing mode and change to DDD mode in case of high degree AV block are a new attempt to avoid unnecessary right ventricular pacing. The article describes various strategies to avoid unnecessary ventricular pacing and discusses their advantages and disadvantages.

Minimizing ventricular pacing to reduce atrial fibrillation in sinus-node disease

BACKGROUND

Conventional dual-chamber pacing maintains atrioventricular synchrony but results in high percentages of ventricular pacing, which causes ventricular desynchronization and has been linked to an increased risk of atrial fibrillation in patients with sinus-node disease.

METHODS

We randomly assigned 1065 patients with sinus-node disease, intact atrioventricular conduction, and a normal QRS interval to receive conventional dual-chamber pacing (535 patients) or dual-chamber minimal ventricular pacing with the use of new pacemaker features designed to promote atrioventricular conduction, preserve ventricular conduction, and prevent ventricular desynchronization (530 patients). The primary end point was time to persistent atrial fibrillation.

RESULTS

The mean (+/-SD) follow-up period was 1.7+/-1.0 years when the trial was stopped because it had met the primary end point. The median percentage of ventricular beats that were paced was lower in dual-chamber minimal ventricular pacing than in conventional dual-chamber pacing (9.1% vs. 99.0%, P<0.001), whereas the percentage of atrial beats that were paced was similar in the two groups (71.4% vs. 70.4%, P=0.96). Persistent atrial fibrillation developed in 110 patients, 68 (12.7%) in the group assigned to conventional dual-chamber pacing and 42 (7.9%) in the group assigned to dual-chamber minimal ventricular pacing. The hazard ratio for development of persistent atrial fibrillation in patients with dual-chamber minimal ventricular pacing as compared with those with conventional dual-chamber pacing was 0.60 (95% confidence interval, 0.41 to 0.88; P=0.009), indicating a 40% reduction in relative risk. The absolute reduction in risk was 4.8%. The mortality rate was similar in the two groups (4.9% in the group receiving dual-chamber minimal ventricular pacing vs. 5.4% in the group receiving conventional dual-chamber pacing, P=0.54).

CONCLUSIONS

Dual-chamber minimal ventricular pacing, as compared with conventional dual-chamber pacing, prevents ventricular desynchronization and moderately reduces the risk of persistent atrial fibrillation in patients with sinus-node disease. (ClinicalTrials.gov number, NCT00284830 [ClinicalTrials.gov].).

Physiologic Pacing: New Modalities and Pacing Sites

Right ventricular (RV) apical pacing impairs left ventricular function by inducing dys-synchronous contraction and relaxation. Chronic RV apical pacing is associated with an increased risk of atrial fibrillation, morbidity, and even mortality. These observations have raised questions regarding the appropriate pacing mode and site, leading to the introduction of algorithms and new pacing modes to reduce the ventricular pacing burden in dual chamber devices, and a shift of the pacing site away from the RV apex. However, further investigations are required to assess the long-term results of pacing from alternative sites in the right ventricle, because long-term results so far are equivocal. The potential benefit of prophylactic biventricular, mono-chamber left ventricular, and bifocal RV pacing should be explored in selected patients with a narrow QRS complex, especially those with impaired left ventricular function. His bundle pacing is a promising and evolving technique that requires improvements in lead technology.