Alternative Pacing Research Articles

Radiological and electrocardiographic characterization of right ventricular outflow tract pacing

The right ventricular outflow tract (RVOT) is used as an alternative pacing site, but its superiority to the RV apex remains to be established. This lack of proof may in part be explained by heterogeneity within the RVOT-paced group, due to poor definitions of the RVOT. The aim of the present study is to characterize the RVOT in terms of fluoroscopic and electrocardiographic parameters. One hundred and forty-three patients who underwent pacemaker implantation with a ventricular lead in the RVOT were included. Lead position was determined by fluoroscopy. The RVOT was divided into three areas: anterior, septal, and free wall (FW). On a 12-lead electrocardiogram (ECG) during forced ventricular pacing, QRS duration, configuration, and amplitude was determined. Lead position was judged to be anterior in 52 (36%), septal in 43 (30%), and FW in 48 (34%) patients, respectively. QRS duration is not significantly different between groups. QRS axis differs significantly between pacing sites (septal 79 ± 31°, anterior 60 ± 46°, FW 47 ± 38°, P < 0.05). QRS vector in lead I and QRS morphology and vector in lead aVL differ significantly between pacing sites. Precordial transition is earlier (towards V1) in septal pacing. This study demonstrates heterogeneity of pacing site and depolarization pattern within a cohort of patients paced form the RVOT. However, due to considerable overlap, we could not define clear cut-off point or devise flow-charts to match ECG and pacing site.

Performance of the Lumenless 4.1‐Fr Diameter Pacing Lead Implanted at Alternative Pacing Sites in Congenital Heart: A Chronic 5‐Year Comparison

United States approval of the Model 3830, 4.1-French (Fr) diameter, lumenless, pacing lead (Medtronic Inc., Minneapolis, MN, USA) in patients under 17 years of age, and those with congenital heart disease (CHD), was in 2005. To date, long-term performance at alternative pacing sites (APS) is limited and chronic efficacy comparisons with more established leads is lacking. The purpose of this study was to evaluate these factors. Implant and follow-up data on leads were compared: group 1 (non-3830 leads) and group 2 (Model 3830 leads). These included acute and chronic sensing and pacing, impedances, implant sites, and complications. Groups were compared using Fischer's exact test, paired, and nonpaired t-tests, with significance defined at P < 0.05. A total of 119 patients (ages 5-48 years) received 171 leads: group 1 (n = 80) and group 2 (n = 91). At implant, there were no differences in patient age, CHD, sensing, or pacing thresholds between groups. Implant lead impedances differed between groups but all were within normal values for each lead design. Chronic data showed no difference in sensing, pacing thresholds, or impedances. There were five (6%) early lead dislodgements in group 1 and one (1%) in group 2. APS were achieved in group 2 with mean 1.6 ± 1.3 minutes fluoroscopy time. The new 4.1-Fr lumenless lead shows similar performance indices to established leads even at APS, yet is thinner and achieves APS with technical ease, permitting more efficient chronic pacing in children and all patients with CHD.

Right Ventricular Septal Pacing: A Comparative Study of Outflow Tract and Mid Ventricular Sites

Prolonged right ventricle (RV) apical pacing is associated with left ventricle (LV) dysfunction due to dysynchronous ventricular activation and contraction. Alternative RV pacing sites with a narrower QRS compared to RV pacing might reflect a more physiological and synchronous LV activation. The purpose of this study was to compare the QRS morphology, duration, and suitability of RV outflow tract (RVOT) septal and mid-RV septal pacing. Seventeen consecutive patients with indication for dual-chamber pacing were enrolled in the study. Two standard 58-cm active fixation leads were passed to the RV and positioned in the RVOT septum and mid-RV septum using a commercially available septal stylet (model 4140, St. Jude Medical, St. Paul, MN, USA). QRS duration, morphology, and pacing parameters were compared at the two sites. The RV lead with less-satisfactory electrical parameters was withdrawn and deployed in the right atrium. Successful positioning of the pacing leads at the RVOT septum and mid-RV septum was achieved in 15 patients (88.2%). There were no significant differences in the mean stimulation threshold, R-wave sensing, and lead impedance between the two sites. The QRS duration in the RVOT septum was 151 ± 14 ms and in the mid-RV septum 145 ± 13 ms (P = 0.150). This prospective observational study shows that septal pacing can be reliably achieved both in the RVOT and mid-RV with active fixation leads using a specifically shaped stylet. There are no preferences in regard to acute lead performance or paced QRS duration with either position.

Comparison of Effectiveness of Right Ventricular Septal Pacing Versus Right Ventricular Apical Pacing

Chronic right ventricular apical pacing (RVAP) has been associated with negative hemodynamic and clinical effects. The aim of the present study was to compare RVAP with right ventricular septal pacing (RVSP) in terms of echocardiographic features and clinical outcomes. A total of 93 patients without structural heart disease and with an indication for a permanent pacemaker were randomly assigned to receive a screw-in lead either in the RV apex (n = 46) or in the RV mid-septum (n = 47). The patients were divided into 3 subgroups according to the percentage of ventricular pacing: control group (n = 21, percentage of ventricular pacing < or =10%), RVAP group (n = 28), or RVSP group (n = 32; both latter groups had a percentage of ventricular pacing >10%). The RVAP group had more intraventricular dyssynchrony and a trend toward a worse left ventricular ejection fraction compared to the RVSP and control groups at 12 months of follow-up (maximal delay to peak systolic velocity between any of the 6 left ventricular basal segments was 57.8 +/- 38.2, 35.5 +/- 20.6, and 36.5 +/- 17.8 ms for RVAP, RVSP, and control group, respectively; p = 0.006; mean left ventricular ejection fraction 62.9 +/- 7.9%, 66.5 +/- 7.2%, and 66.6 +/- 7.2%, respectively, p = 0.14). Up to 48.1% of the RVAP patients showed significant intraventricular dyssynchrony compared to 19.4% of the RVSP patients and 23.8% of the controls (p = 0.04). However, no overt clinical benefits from RVSP were found. In conclusion, RVAP was associated with increased dyssynchrony compared to the RVSP and control patients. RVSP could represent an alternative pacing site in selected patients to reduce the harmful effects of traditional RVAP.

A Clinical Comparison Between a New Dual-Chamber Pacing Mode-AAIsafeR and DDD Mode

ObjectiveThe aim of this study was to compare the cross-follow-up results in DDD or AAISafeR mode and to describe the safety and effectiveness of this pacing mode. MethodsThe Symphony 2450/2550 cardiac pacemakers were implanted in 30 patients with sick sinus syndrome between February 2006 and September 2006. They were randomized to the DDD mode or AAISafeR mode for 3months and then crossed over to the alternate pacing modality for an additional 3months. ResultsNo AAISafeR-related adverse event was observed. All documented episodes of paroxysmal atrial ventricular block caused the immediate switch of the pacing mode from AAI to DDD. The cumulative percent ventricular pacing was significantly reduced in the AAISafeR mode compared with the DDD mode (0.9% [0%–3%] versus 51.3% [2%–91%] P=0.001; 2.94% [0%–18%] versus 41.18% [0%–65%] P=0.0001). After 3months in DDD mode, left atrial diameter, left ventricular enddiastolic diameter, and left ventricular end-systolic diameter increased significantly and left ventricular ejection fraction decreased. However, no obvious changes appeared in 3months of AAISafeR mode. Switches to DDD occurred during follow-up in 21 patients due to different-degree atrial ventricular block. ConclusionsThe AAISafeR mode substantially reduces the amount of unnecessary right ventricular pacing in the bradycardia population and effectively prevents the deleterious effects on cardiac performance. An international randomized study will further ascertain the efficacy of this new pacing mode specifically in the prevention of heart failure hospitalization and atrial fibrillation.

MRI assessment of pacing induced ventricular dyssynchrony in an isolated human heart

This study demonstrates the capabilities of MRI in the assessment of cardiac pacing induced ventricular dyssynchrony, and the findings support the need for employing more physiological pacing. A human donor heart deemed non-viable for transplantation, was reanimated using an MR compatible, four-chamber working perfusion system. The heart was imaged using a 1.5T MR scanner while being paced from the right ventricular apex (RVA) via an epicardial placed lead. Four-chamber, short-axis, and tagged short-axis cines were acquired in order to track wall motion and intramyocardial strain during pacing. The results of this study revealed that the activation patterns of the left ventricle (LV) during RVA pacing demonstrated intraventricular dyssynchrony; as the left ventricular mechanical activation proceeded from the septum and anterior wall to the lateral wall, with the posterior wall being activated last. As such, the time difference to peak contraction between the septum and lateral wall was approximately 125 msec. Likewise, interventricular dyssynchrony was demonstrated from the four-chamber cine as the time difference between the peak LV and RV free wall motion was 180 msec. With the ongoing development of MR safe and MR compatible pacing systems, we can expect MRI to be added to the list of imaging modalities used to optimize cardiac resynchronization therapy (CRT) and/or alternate site pacing.

Right Ventricular Outflow Tract Pacing: An Alternative, Safe, and Effective Pacing Site

The right ventricular apex (RVA) has traditionally been preferred for the insertion of permanent cardiac pacemaker leads because of vast experience with their use, their ease of implantation, and the stability of passive fixation leads in the RVA trabeculae. However, prolonged RVA pacing is associated with progressive left ventricular dysfunction due to dysynchronous ventricular activation, and often results in substantial functional, hemodynamic, electrical, and structural changes, as previously demonstrated in many studies. Only in recent years has interest in the use of alternate pacing sites developed. The right ventricular outflow tract (RVOT) is now the preferred site of pacing because of potential advantages such as ease of application, better hemodynamics, synchronous activation, fewer myocardial perfusion defects, and a narrower QRS complex compared with RVA pacing. This review article comprehensively discusses this novel technique in terms of its beneficial effects, long-term safety, and performance measures compared with RVA pacing, and as an alternative method for biventricular pacing.

Biventricular pacing in paced patients with normal hearts

Right ventricular apical (RVA) stimulation, although beneficial in the treatment of symptomatic bradycardia, has proven detrimental in a substantial percentage of pacemaker recipients, leading to iatrogenic deterioration of left ventricular structure and function. Alternative right ventricular pacing sites appeared advantageous but their superiority has not been proven. Biventricular stimulation is effective in reducing ventricular dyssynchrony in subgroups of heart failure patients, improving their functional capacity, morbidity, and mortality. Therefore, it seems logical that this pacing strategy, by eliminating ventricular dyssynchrony, could play an important role in preventing the deleterious effects of chronic RVA stimulation in patients with normal hearts who undergo cardiac pacing for bradycardia indications. Preliminary investigations have yielded encouraging results, but further studies with harder endpoints such as quality of life, morbidity, and mortality are necessary to clarify the potentially advantageous effect of biventricular stimulation in paced patients with normal hearts.

Lead positioning for cardiac resynchronization therapy: techniques and priorities

Although cardiac resynchronization therapy (CRT) has demonstrated to be an effective treatment for heart failure patients, up to 30-40% of the patients do not show a favourable response. Implantation of the left ventricular (LV) pacing lead is one of the determinants of CRT response. This procedure includes several challenging technical issues and strongly depends on the highly variable anatomy of the coronary sinus and tributaries. In addition, the final position of the LV pacing lead may target the latest activated areas of the left ventricle in order to obtain effective resynchronization. Furthermore, the presence of transmural myocardial scar at the region targeted by the LV lead may also determine the response to CRT. This review discusses all the issues related to LV lead implantation and the role of multimodality imaging to anticipate the implantation strategy. Finally, alternative LV pacing sites and their effect on clinical outcome and LV performance will be discussed.

Intrathoracic and Ventricular Impedances are Associated with Changes in Ventricular Volume in Patients Receiving Defibrillators for CRT

Some implantable cardioverter defibrillators (ICD) are able to monitor intrathoracic impedance to detect pulmonary fluid overload. This is achieved by measuring impedance between the ICD case and the right ventricular (RV) lead. We hypothesized that the measured impedance would rise with improvement in left ventricular (LV) volumes during cardiac resynchronization therapy (CRT), and that such impedance changes would be more apparent when measured with an alternative pacing vector. We analyzed echocardiographic and impedance data from heart failure patients implanted with a CRT-ICD capable of intrathoracic impedance measurement for fluid accumulation diagnosis, and LV pacing impedance recording for lead integrity monitoring. In 127 out of 170 patients that received de novo CRT implantation, the LV end-systolic volume (LVESV) decreased at 6-month follow-up (LVESV at 6 month-LVESV at baseline <0: group A). For the remaining 43 patients (group B) the change was > or = 0. Despite comparable values at baseline (P = 0.262), the impedances of groups A and B gradually diverged soon after the implant, resulting in significant difference between the two groups at the 6-month visit (P = 0.001). The changes in LV dimensions produced larger differences between groups in the impedance measured between the LV and the RV leads (P < 0.001). The regression analysis demonstrated an inverse correlation between paired changes of volume and intrathoracic impedance. Higher correlation coefficient was obtained using the LV-to-RV measurement vector (r =-0.635, P < 0.001). The changes in ICD-measured impedance seem associated with the LV volume changes induced by CRT. Specifically, the LV-to-RV impedance estimations seem to better correlate with paired changes of ventricular volumes.

Right Ventricular Septal Pacing: The Success of Stylet-Driven Active-Fixation Leads

The detrimental effects of right ventricular (RV) apical pacing on left ventricular function has driven interest in alternative pacing sites and in particular the mid RV septum and RV outflow tract (RVOT). RV septal lead positioning can be successfully achieved with a specifically shaped stylet and confirmed by the left anterior oblique (LAO) fluoroscopic projection. Such a projection is neither always used nor available during pacemaker implantation. The aim of this study was to evaluate how effective is the stylet-driven technique in septal lead placement guided only by posterior-anterior (PA) fluoroscopic view. One hundred consecutive patients with an indication for single- or dual-chamber pacing were enrolled. RV septal lead positioning was attempted in the PA projection only and confirmed by the LAO projection at the end of the procedure. The RV lead position was septal in 90% of the patients. This included mid RV in 56 and RVOT in 34 patients. There were no significant differences in the mean stimulation threshold, R-wave sensing, and lead impedance between the two sites.In the RVOT, 97% (34/35) of leads were placed on the septum, whereas in the mid RV the value was 89% (56/63). The study confirms that conventional active-fixation pacing leads can be successfully and safely deployed onto the RV septum using a purposely-shaped stylet guided only by the PA fluoroscopic projection.

Global electrophysiological and hemodynamic assessment of ventricular pacing employing non-contact mapping

Right ventricular (RV) pacing has been associated with abnormal cardiac electrical and mechanical dyssynchrony, resulting in impaired global and regional ventricular pump function. This study aimed to characterize the relative effects of pacing site on left ventricular (LV) activation patterns and associated hemodynamic performances. Acute pacing was performed in anesthetized swine (n=10) instrumented for RV and LV pressure, noncontact mapping (NCM) of endocardial unipolar electrograms, surface ECG, aortic flow, and sonomicrometry. Bipolar endocardial pacing leads were positioned in the right atrial appendage (RAA), RV apex (RVA), and RV outflow tract (RVOT), while bipolar epicardial leads were positioned on the LV-free wall (LVFW) and LV apex (LVA). LVFW and RVA pacing induced the largest increase in intraventricular electrical dyssynchrony (IVED; 32.2+/-10 ms, 21.7+/-4.1 ms, respectively; both p<0.01), whereas pacing from all sites increased QRS and total endocardial LV activation durations (p<0.01). The largest impairment of LV and RV contractility (dP/dtmax) and relaxation (dP/dtmin) was observed during RVA pacing (p= ns). Synchronous electrical activation patterns were observed on NCM during RVOT and LVA pacing. LVFW pacing was the only site that significantly increased tau values as compared to RAA pacing (approximately 25%), whereas LVA pacing elicited only slight increases (approximately 1%). In swine with preserved ventricular conduction, in vivo pacing of the RVOT and LVA was associated with preserved, physiologically similar electrical activation sequences and LV function relative to RAA pacing. In contrast, RVA pacing caused widespread electrical dyssynchrony of the LV and prolonged activation durations, thereby impairing associated cardiac performance. Such insights into alternate site cardiac pacing, which employed the combination of high-resolution electrical mapping with real-time hemodynamic assessments, may further increase acute and long-term benefits in patients requiring permanent pacemaker support.

Atrial antitachycardia pacing: do we still need to talk about it?

Since first described in 1968,1 sick sinus syndrome (SSS) has become one of the most frequent indications for pacemaker implantation. Although in early days, the presence of atrial fibrillation (AF) limited the use of pacemakers in patients with SSS, nowadays pacemakers play an important role in the management of AF in patients with SSS. Highly sophisticated devices have been developed with increased Holter capabilities allowing continuous rhythm monitoring. Although the prevalence of AF prior to pacemaker implantation has been found in the range of 40–45%,2 AF detection during follow-up using pacemaker Holter data is reported in 50–65% of patients with SSS.3,4 In the Mode Selection Trial (MOST), pacemaker-detected paroxysmal AF was a strong independent predictor of stroke, death, and persistent AF, whereas symptoms as a clinical comparator could not reliably predict AF recurrence.4 The known limited success rate of drug therapy for rhythm control and the overwhelming number of pacemaker patients with paroxysmal AF prompted interest in using pacing therapy to treat AF. Therapy options developed included alternative single-site atrial pacing, multisite atrial pacing, pacing algorithms to prevent AF by increasing the amount of atrial pacing suppressing triggers of AF, and atrial antitachycardia pacing (ATP) to terminate AF. Many clinical trials have been conducted over the past 10 years studying the efficacy of pacing algorithms for AF prevention and termination. The present paper by Gillis et al. 5 reports the first long-term data on atrial ATP. Neither ATP alone nor ATP in combination with preventive pacing algorithms could successfully suppress atrial tachycardia (AT)/AF during a follow-up period of 3 years. The trial was early terminated due to phasing out of the AT500/501 pacemaker and study results may have been underpowered to detect any differences. However, the results correlate well with other ATP studies like … *Corresponding author. Tel: +49 89 9270 2071, Fax: +49 89 9270 2683, Email: ellen.hoffmann{at}klinikum-muenchen.de

P-109 Mitral Valve Motion and Mitral Inflow Dynamics in Aortic Regurgitation, with Reference to the Relation with Regurgitant Jet Direction

(2.6±0.9 vs. 3.4±0.9 cm/s, P= 0.028) and longer interatrial time delay (33±25 vs. 12±19ms, P= 0.022). However, there were no differences in Va of RA and intra-atrial synchronicity between two groups. The lower mitral A velocity and prolonged inter-atrial time delay (OR, 95%CI: 1.12, 1.01 1.24 p = 0.025; 1.08, 1.01 1.16 p = 0.020 resp.) were the strongest predictors on presence of PAF. Conclusion: Compared to these without AF, pts with SND and PAF had worsening of LA mechanical function. The occurrence of inter-atrial dyssychrony may have implications to the mechanical benefit of alternative atrial pacing.

DDDR pacing results in left ventricular asynchrony with preservation of ejection fraction and NT-proBNP: A prospective study in sick sinus syndrome and normal ventricular function

Desynchronization induced by right ventricular pacing may increase the risk for heart failure. We aimed to compare left ventricular (LV) function, synchrony and left atrial size along with NT-proBNP levels, in 2 different modes of pacing: AAIR versus DDDR. This was a prospective study of 60 patients with sick sinus syndrome, preserved LV function and normal atrioventricular conduction. Each pacing mode lasted at least 2months, in every patient, after which period every patient was switched to the alternate pacing mode. Intraventricular asychrony was assessed by: 1) M-Mode septal-to-posterior wall motion delay (SPWMD), and 2) Tissue Doppler imaging (TDI) septal to lateral delay. NT-proBNP was measured at the end of each pacing mode. LV ejection fraction and left atrial diameter were not different in the 2 pacing modes, although asynchrony was induced in the DDDR arm (p<0.001 for TDI). NT-proBNP was lower in the DDDR compared to the AAIR mode (p=0.003, F=9.64). The NT-proBNP was inversely correlated to LV ejection fraction in the DDDR mode (p=0.0001, R=-0.75), whilst it was significantly correlated to the TDI septal-lateral delay and SPWMD (p=0.007, R=0.4 and p=0.002, R=0.5) in the AAIR mode. In conclusion in sick sinus syndrome with preserved LV function the DDDR mode does not compromise LV systolic function although it causes asynchrony. The NT-proBNP is lower when the right ventricle is paced, is inversely related to LV function and it is related to the degree of LV synchronization in the AAIR mode.

The Role of Speckle Tracking Strain Imaging in Cardiac Pacing

In recent years, concerns have been raised about possible harmful effects of long-term right ventricular (RV) apical pacing. These detrimental effects may be related to changes in left ventricular (LV) mechanics during RV apical pacing. As a consequence, alternative RV pacing sites have been proposed, and in selected patients an upgrade from RV to biventricular pacing may be considered. Novel two-dimensional (2D) speckle tracking strain imaging allows detailed evaluation of LV mechanics, including LV mechanical dyssynchrony, LV strain and LV torsion. In this review, the role of speckle tracking strain imaging in the evaluation of LV function in patients with RV apical pacing will be reviewed. The effects of RV apical pacing on LV mechanical dyssynchrony, LV strain and LV torsion will be discussed. In addition, the role of speckle tracking strain imaging in the selection of the optimal (alternative) RV pacing site and in the selection of patients who may benefit from an upgrade from RV apical pacing to biventricular pacing will be reviewed.

Analysis of Ventricular Performance as a Function of Pacing Site and Mode

Emerging data from experimental and clinical studies have shown that right ventricular (RV) apical pacing led to abnormalities of ventricular activation and contraction, and impairment of myocardial perfusion with adverse left ventricular (LV) remodeling, which was associated with increased risk of cardiac morbidity and mortality. As a result, there is a growing interest in searching for methods to minimize unnecessary RV pacing and preserving normal ventricular activation with alternative ventricular pacing sites. The risk of developing heart failure (HF) after RV apical pacing depends on the interactions between patient-specific factors (baseline atrial rhythm, intrinsic atrioventricular and ventricular conduction, LV ejection fraction, and the presence of HF and myocardial infarction) and pacing-related factors (mode of pacing, site of ventricular pacing, paced QRS duration, and percentage and duration of pacing). In patients with intact atrioventricular conduction, atrial-based pacing should be used to avoid unnecessary ventricular pacing. In patients requiring ventricular pacing, the potential benefits of alternate ventricular pacing sites, such as RV or LV septa, or even biventricular pacing in different patient populations remain unclear and warrant further long-term prospective clinical trial evaluations especially in those patients who are at a higher risk of developing HF after RV apical pacing.

Alternate Site Pacing in Patients at Risk for Heart Failure

Cardiac pacing from the right ventricular apex is the most common site of cardiac pacing. During the last decade, several studies demonstrated the harmful effects of the iatrogenic left bundle branch block, which is observed in cardiac pacing from the right ventricular apex. These observations led to an interest in alternative right ventricular pacing sites aiming to achieve a more "physiological" pattern of ventricular activation. Alternate site pacing may involve His bun- dle, other right ventricular sites (outflow or septal sites), or left ventricular sites in either unifocal or bifocal or biventricular modes. Pacing from the right ventricular outflow tract has been studied extensively. Several studies showed that right ventricular outflow tract pacing has better hemodynamic effects and less harmful influence. Bifocal right ventricular (apical and outflow tract) pacing has been proposed for patients with heart failure where the coronary sinus approach to effect biventricular pacing turns out to be unsuccessful because of various reasons. Some studies examined left ventricular pacing alone as an alternative mode of pacing, and the results were quite encouraging but not conclusive. Finally, in heart failure patients not responding to biventricular pacing, the triple site pacing mode has been recently proposed. In triple site pacing, the leads are inserted in the right ventricular apex and outflow tract in conjunction with lateral left ventricular pacing. Improvement of exercise capacity and increased ejection fraction were observed with this triventricular pacing. Although more data from specifically designed randomized studies are needed, there are many alternative pacing sites, especially for patients at high risk of heart failure, which seems to be less harmful and better tolerated by the patients.

ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities

ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities

Biventrikuläre Stimulation bei AV-Block

Since the establishment of cardiac resynchronization therapy in left bundle branch block and mechanical asynchrony, the adverse effects of right ventricular apical pacing have gained increasing scientific interest. The sequelae of "iatrogenic desynchronization" on cardiac structure and function as well as on patients' prognosis could be well documented. "Minimally desynchronizing" stimulation strategies could be an alternative for patients needing ventricular pacing. The search for hemodynamically more advantageous alternative right ventricular pacing sites has failed so far to deliver well validated results, and due to the somewhat higher lead dislodgment rates pure left ventricular pacing cannot be recommended, at least not in pacemaker-dependent patients. Hence there is the question for primary biventricular stimulation in patients with AV block. The results of several biventricular studies with limited numbers of patients have been promising with respect to structural and functional surrogate endpoints. Two major controlled prospective and prognostically orientated studies, the BIOPACE study and the BLOCK-HF study, are currently underway and will report results in the next few years. According to the actual guidelines of the European Society of Cardiology (ESC) the implantation of a biventricular system is recommended in patients with AV block even without left bundle branch block (Class IIa, evidence level C) if they fulfill the remaining criteria that justify the implantation of a biventricular system. According to the guidelines for pacemaker therapy of the German Cardiac Society (GCS) biventricular pacing can be considered in these patients. Both societies do expressly permit the implantation of biventricular systems with ICD backup if indicated.