Selective site ventricular pacing

Interpreting the Normal Pacemaker Electrocardiograph

Modern cardiac pacing systems have sophisticated software to document, evaluate and record intrinsic and paced rhythms as well as correct pacing abnormalities and rhythm disturbances by applying algorithms, which are generally company specific. To the cardiologist and technologist, these algorithms may be difficult to interpret on both the 12-lead electrocardiograph (ECG) and Holter ambulatory monitoring recordings, which are usually performed because of patient symptoms or physician concern. The tracings may appear bewildering and mimic pacemaker malfunction, thus leading to unnecessary tests or even surgery. This review will define the common programmed pacemaker modes and describe a range of ECG appearances of normal pacemaker function during the application of testing, correcting or therapy algorithms.

Selective site pacing from the right ventricular mid-septum. Follow-up of lead performance and procedure technique

Pacing from the right ventricular (RV) apex is associated with adverse effects such as heart failure and atrial fibrillation. We attempted pacing from the RV mid-septum, which is theoretically a more physiological pacing site. A total of 172 consecutive patients with indications for permanent pacemaker implantation were studied. A screw-in lead and a curved stylet were used for lead positioning on the RV mid-septum. Pacemaker indices were evaluated at implantation and one year later. As an electrocardiographic parameter, QRS duration was measured in lead II. These data were compared to those of 66 patients subjected to conventional RV apical pacing. Lead placement was successful in all patients of RV mid-septal pacing. There were no technical problems during or after the procedure. The cumulative percentage of ventricular pacing at one year postimplantation was 85 ± 24 % in the SSP group. Sensing, pacing threshold, and lead impedance in the SSP group remained clinically stable over one year. When these measurements were compared between the SSP and AP groups, the pacing threshold and the lead impedance at one year postimplantation in the SSP group were higher (P < 0.05) and lower (P < 0.01), respectively, than those of the AP group. The mean QRS duration was markedly shorter (123 ± 16 versus 150 ± 18 msec, P < 0.0001). Selective site pacing from the RV mid-septum is feasible and results in less conduction delay compared to conventional RV apical pacing, and its procedure seems to be more physiological in permanent pacemaker implantation.

Beneficial effects of right ventricular non-apical vs. apical pacing: a systematic review and meta-analysis of randomized-controlled trials

AIMS

Previous studies have suggested that right ventricular apical (RVA) pacing may have deleterious effects on left ventricular function. Whether right ventricular non-apical (RVNA) pacing offers a better alternative to RVA pacing is unclear. We aimed to conduct a systematic review and meta-analysis of randomized-controlled trials (RCTs) in order to compare the mid- and long-term effects of RVA and RVNA pacing.

METHODS AND RESULTS

We systematically searched the Cochrane library, EMBASE, and MEDLINE databases for RCTs comparing RVA with RVNA pacing over >2 months follow-up. Data were pooled using random-effects models. Fourteen RCTs met our inclusion criteria involving 754 patients. Compared with subjects randomized to RVA pacing, those randomized to RVNA pacing had greater left ventricular ejection fractions (LVEF) at the end of follow-up [13 RCTs: weighted mean difference (WMD) 4.27%, 95% confidence interval (CI) 1.15%, 7.40%]. RVNA had a better LVEF at the end of follow-up in RCTs with follow-up ≥12 months (WMD 7.53%, 95% CI 2.79%, 12.27%), those with <12 months of follow-up (WMD 1.95%, 95% CI 0.17%, 3.72%), and those conducted in patients with baseline LVEF ≤40-45% (WMD 3.71%, 95% CI 0.72%, 6.70%); no significant difference was observed in RCTs of patients whose baseline LVEF was preserved. Randomized-controlled trials provided inconclusive results with respect to exercise capacity, functional class, quality of life, and survival.

CONCLUSIONS

While RCTs suggest that LVEF is higher with RVNA than with RVA pacing, there remains a need for large RCTs to compare the safety and efficacy of RVNA and RVA pacing.

Left Ventricular Septal and Left Ventricular Apical Pacing Chronically Maintain Cardiac Contractile Coordination, Pump Function and Efficiency

Background— Conventional right ventricular (RV) apex pacing can lead to adverse clinical outcome associated with asynchronous activation and reduced left ventricular (LV) pump function. We investigated to what extent alternate RV (septum) and LV (septum, apex) pacing sites improve LV electric activation, mechanics, hemodynamic performance, and efficiency over 4 months of pacing.

Methods and Results— After AV nodal ablation, mongrel dogs were randomized to receive 16 weeks of VDD pacing at the RV apex, RV septum, LV apex, or LV septum (transventricular septal approach). Electric activation maps (combined epicardial contact and endocardial noncontact) showed that RV apical and RV septal pacing induced significantly greater electric desynchronization than LV apical and LV septal pacing. RV apex and RV septal pacing also significantly increased mechanical dyssynchrony, discoordination (MRI tagging) and blood flow redistribution (microspheres) and reduced LV contractility, relaxation, and myocardial efficiency (stroke work/myocardial oxygen consumption). In contrast, LV apical and LV septal pacing did not significantly alter these parameters as compared with the values during intrinsic conduction. At 16 weeks, acute intrasubject comparison showed that single-site LV apical and LV septal pacing generally resulted in similar or better contractility, relaxation, and efficiency as compared with acute biventricular pacing.

Conclusions— Acute and chronic LV apical and LV septal pacing maintain regional cardiac mechanics, contractility, relaxation, and efficiency near native levels, whereas RV apical or RV septal pacing diminish these variables. Acute LV apical and LV septal pacing tend to maintain or improve contractility and efficiency compared with biventricular pacing.

Atrial fibrillation in congestive heart failure: current management

Atrial fibrillation (AF) and congestive heart failure are common conditions and each predisposes to the development of the other. Basic research using animal models of the two conditions continues to yield insights that may improve therapies. The role of medical therapies aimed at the underlying structural changes in AF continues to be a subject of ongoing studies. Cardiac resynchronization therapy is effective in appropriately selected patients with both sinus rhythm and AF. Catheter ablation is emerging as a potential alternative to antiarrhythmic drug therapy, but large randomized trials will be needed to assess its role.

Implantation of lumenless pacing leads at the inter-atrial septum and right ventricular outflow tract with deflectable catheter-sheath

Current permanent right ventricular and right atrial endocardial pacing leads are implanted utilizing a central lumen stylet. Right ventricular apex pacing initiates an abnormal asynchronous electrical activation pattern, which results in asynchronous ventricular contraction and relaxation. When pacing from right atrial appendage, the conduction time between two atria will be prolonged, which results in heterogeneity for both depolarization and repolarization. Six patients with Class I indication for permanent pacing were implanted with either single chamber or dual chamber pacemaker. The SelectSecure 3830 4-French (Fr) lumenless lead and the SelectSite C304 8.5-Fr steerable catheter-sheath (Medtronic Inc., USA) were used. Pre-selected pacing sites included inter-atrial septum and right ventricular outflow tract, which were defined by ECG and fluoroscopic criteria. All the implanting procedures were successful without complication. Testing results (mean atrial pacing threshold: 0.87 V; mean P wave amplitude: 2.28 mV; mean ventricular pacing threshold: 0.53V; mean R wave amplitude: 8.75 mV) were satisfactory. It is concluded that implantation of a 4-Fr lumenless pacing lead by using a streerable catheter-sheath to achieve inter-atrial septum or right ventricular outflow tract pacing is safe and feasible.

Impact of Different Pacing Modes on Left Ventricular Contractility Following Cardiopulmonary Bypass

BACKGROUND

Acute left ventricular (LV) dysfunction after cardiopulmonary bypass (CBP) is a serious complication in cardiac surgery. The aim of this study was to investigate the effect of different epicardial pacing modes on LV contractility and changes of myocardial oxygen extraction (MVO(2)) following CPB in an animal model. The utility of conductance catheter measurement versus left ventricular outflow tract mean systolic acceleration (LVOT(Acc)) for quantification of LV function was evaluated.

METHODS

Fourteen piglets underwent median sternotomy and CPB for 90 minutes, myocardial ischemia for 60 minutes, and reperfusion for 30 minutes. Different pacing modes were obtained before and after CPB to investigate changes in LV function. LV Function was quantified by end-systolic-pressure-volume relationships (ESPVR) as measured by the conductance catheter method and by LVOT(Acc) obtained from transepicardial echocardiographic studies.

RESULTS

LV contractility improved significantly by biventricular and atrial pacing compared with natural sinus rhythm (SR). MVO(2) remained stable or even decreased with biventricular pacing after surgery compared with SR. Right ventricular pacing resulted in poor LV-function with a rise of MVO(2). LVOT(Acc) showed a strong correlation to invasively measured ESPVR.

CONCLUSION

Postoperative biventricular pacing was associated with an improved LV contractility without rise of MVO(2) compared with SR and atrial pacing. At termination of CPB, this appears to facilitate the management of LV failure and potentially may reduce the need for inotropic support, additionally protecting myocardial metabolism. The echocardiographic assessment of LVOT(Acc) was a simple and reliable as well as effective method to quantify LV contractility and showed a good correlation with the more invasive conductance catheter.

New concepts in physiologic cardiac pacing

Physiologic pacing is an evolving term used to describe different concepts and technologic developments in implantable devices (including pacemakers and defibrillators) over the past several decades. Currently much of the discussion about optimal physiologic pacing involves fairly recently appreciated deleterious effects of traditional right ventricular pacing. Technologic solutions to the goal of avoiding unnecessary ventricular pacing appear to be available and successful. Although much work is being done to find more physiologic ways to pace the ventricles when necessary, the solutions for this goal are less clear.

The Right Ventricular Outflow Tract: The Road to Septal Pacing

BACKGROUND

Pacing from the right ventricular apex is associated with long-term adverse effects on left ventricular function. This has fuelled interest in alternative pacing sites, especially the septal aspect of the right ventricular outflow tract (RVOT). However, it is a common perception that septal RVOT pacing is difficult to achieve.

METHODS AND RESULTS

In this article, we will review the anatomy of the RVOT and discuss the importance of standard radiographic views and the 12-lead electrocardiogram in aiding lead placement. We will also describe a method utilizing a novel stylet shape, whereby a conventional active-fixation, stylet-driven lead can be easily and reliably deployed onto the RVOT septum.