Alternate Site Biventricular Pacing:. Bi-V in the RV-Is There a role?

Right ventricular septal pacing as alternative for failed left ventricular lead implantation in cardiac resynchronization therapy candidates

AIMS

To compare the effects on left ventricular (LV) function of right ventricular (RV) septal pacing vs. cardiac resynchronization therapy (CRT) in patients with an indication for the latter. Cardiac resynchronization therapy is an effective therapy in patients with drug-refractory heart failure. Despite advances in implantation techniques, LV lead placement can be impossible in up to 10% of cases. We, therefore, assessed the effects of RV septal pacing from mid septum (RVmIVS) and outflow tract (RVOT) on cardiac performance, in comparison with CRT.

METHODS AND RESULTS

Twenty-two patients scheduled for CRT underwent dual-chamber temporary pacing. The ventricular lead was placed at the RV apex (RVA), RVmIVS, and RVOT in random order. Comprehensive echocardiography was performed in a baseline AAI mode and then at each RV position in dual chamber pacemaker function (D pacing, D sensing, D dual responses) mode and repeated on the next day following CRT implantation. Right ventricular apex pacing did not change any of the assessed echocardiography parameters. Both RVmIVS and RVOT pacing increased LV ejection fraction (EF): 29 ± 7% at baseline vs. 32 ± 6% (P = 0.02) and 32 ± 5% (P = 0.04) with RVmIVS and RVOT pacing, respectively. Similarly, the dyssynchrony index (Ts-SD) decreased: 50 ± 19 ms at baseline vs. 39 ± 17 ms (P = 0.04) and 37 ± 17 ms (P = 0.006) with RVmIVS and RVOT pacing, respectively. Cardiac resynchronization therapy further improved LVEF and Ts-SD to 36 ± 7% and 34 ± 15 ms, respectively, however, only LVEF was significantly higher compared with RVmIVS and RVOT pacing (P = 0.03 and P = 0.01 respectively). There were no significant differences in either LVEF or Ts-SD between RVmIVS and RVOT.

CONCLUSION

Right ventricular septal pacing from mid septum or RVOT pacing improves LVEF and LV synchrony in CRT candidates. Further improvement in LVEF was achieved by CRT, which remains the 'gold standard' therapy in these patients. However, RV septal pacing is worthy of further study as an alternative strategy when LV lead implantation fails.

Bifocal right ventricular pacing: an alternative way to achieve resynchronization when left ventricular lead insertion is unsuccessful

PURPOSE

Bifocal pacing in the right ventricle is an option for patients with end-stage heart failure in whom biventricular pacing is not possible, due to failure in left ventricular (LV) lead insertion. The purpose of this prospective study was to document the clinical response of these patients, after bifocal pacing.

METHODS

From the patients referred for cardiac resynchronization therapy (CRT), from 2009 to 2010, 13 cardiac CRT candidates who underwent unsuccessful LV lead implantation were included. The bifocal system's leads were implanted in the right atrium, the right ventricular (RV) apex, and the RV outflow tract. Initial patient assessment and follow-up evaluation after 6 months included clinical criteria, echocardiographic indices, and biochemical parameters.

RESULTS

From 13 patients (age 68 ± 9 years, nine male), 10 improved clinically. New York Heart Association classification was reduced by one grade (from 3.6 ± 0.5 to 2.8 ± 0.8, p < 0.005 and respectively), while hospitalizations in 6-month time were reduced from three to one (p < 0.001). Six-minute walk test (in meters) increased from 176 ± 86 to 297 ± 91 (p < 0.001) and quality of life improved (EQ-VAS scale changed from 42 ± 12.5 % to 70.8 ± 20.3 %, p < 0.001). Mean shortening in QRS duration was 31.3 ms (from 165.1 ± 16.3 to 133.8 ± 12.7, p < 0.001) and B-type natriuretic peptide (in picograms per milliliter) dropped from 834 ± 350 to 621 ± 283 (p < 0.001). Ejection fraction (in percent) increased from 27.5 ± 4.6 to 33.3 ± 4.4 (p < 0.001), and mitral regurgitation severity decreased by one grade (from 2.7 ± 0.9 to 1.8 ± 0.7, p < 0.05).

CONCLUSION

RV bifocal pacing seems to offer a substantial clinical benefit to heart failure patients with traditional CRT indications and could be an alternative option when LV access is unsuccessful.

Right ventricular apical pacing: the unwanted model of cardiac stimulation?

Despite having a huge benefit in enabling heart rate control, cardiac pacing by stimulating the right ventricular apex causes an artificial iatrogenic left bundle-branch block-like syndrome. As a result, QRS widening and cardiac wall desynchronization occurs. The problems caused by this undesirable pacemaker side effect have been ignored, as they are counteracted by the great benefit of cardiac rate correction. However, the compelling evidence about its harmful effect presented in this article cannot be disregarded and should start an attitude change toward alternate sites of ventricular pacing and preclusion of the right ventricular apex stimulation.

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 ven- tricular 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 bifo- cal or biventricular modes. Pacing from the right ven- tricular 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.

Right ventricular outflow tract pacing: practical and beneficial. A 9-year experience of 460 consecutive implants

BACKGROUND

Pacing from the right ventricular apex (RVA) in patients with ventricular dysfunction has been identified as a possible contributor to deterioration of ventricular function. Therefore, alternative pacing sites such as the right ventricular outflow tract (RVOT) are receiving intensified scrutiny. An unresolved question is whether technical, procedural, and stability issues are comparable for the RVA and the RVOT.

METHODS

This report details 460 consecutive ventricular pacing lead implants with the primary intended site in the RVOT. Patients were evaluated for success, complication rates, and followed-up for stability of pacing parameters. The total patient implant population included 300 male and 170 female patients with a mean age of 70.6 years. Ten patients were excluded from the analysis, since there was a primary indication and intention to implant in the RVA, leaving a total of 460 patients for analysis. The indications for pacing were symptomatic bradycardia due to any cause and/or Mobitz II or complete heart block. There was no clinical evidence of heart failure in 420 patients. In 40 patients with heart failure, the indication for pacing was cardiac resynchronization therapy using the RVOT as an alternate site when pacing from a branch vein of the coronary sinus was not possible. Outcome information was obtained from the implanter's clinic.

RESULTS

The overall success rate in the RVOT was 84% over the total 9-year period with a 92% success rate in the last 4(1/2) years, using the RVOT technique described. At 20 months in a subgroup comparison of RVOT and RVA implants, there was no significant difference in pacing threshold, R-wave sensing, or pacing lead impedance. Dislodgment occurred in only 1 of 460 patients. Reasons for failure to implant in the RVOT include inability to find a stable position with adequate pacing and sensing thresholds (related to anatomy, scarred myocardium, pulmonary hypertension, tricuspid regurgitation), hemodynamic instability limiting time for implant, and a learning curve. Long-term stability and lead performance were excellent, and certain acute and chronic complications of RV pacing did not occur.

The deleterious consequences of right ventricular apical pacing: time to seek alternate site pacing

BACKGROUND

The purpose of this article is to critically review the data accumulated to date from studies evaluating the hemodynamic and clinical effects of right ventricular apical pacing during conventional permanent cardiac pacing. The data from studies comparing the effects of right ventricular apical pacing and alternate site ventricular pacing are also reviewed.

METHODS

We conducted a MEDLINE and journal search of English-language reports published in the last decade and searched relevant papers.

RESULTS

Although intraventricular conduction delay in the form of left bundle branch block (LBBB) has traditionally been viewed as an electrophysiologic abnormality, it has now become abundantly clear that it has profound hemodynamic effects due to ventricular dyssynchrony, especially in patients with heart failure. These deleterious effects can be significantly ameliorated by cardiac resynchronization therapy effected by biventricular or left ventricular pacing. However, not only is spontaneous LBBB harmful, but the iatrogenic variety produced by right ventricular apical pacing in patients with permanent pacemakers may be equally deleterious. In this review new evidence from recent studies is presented, which strongly suggests a harmful effect of our long-standing practice of producing an iatrogenic LBBB by conventional right ventricular apical pacing in patients receiving permanent pacemakers. This emerging strong new evidence about the adverse hemodynamic and clinical effects of right ventricular apical pacing would dictate a reassessment of our traditional approach to permanent cardiac pacing and direct our attention to alternate sites of pacing, such as the left ventricle and/or the right ventricular outflow tract or septum, if not for all patients, at least for those with left ventricular dysfunction. Indeed, current convincing data on alternate site ventricular pacing are encouraging and this approach should be actively pursued and further investigated in future studies.

CONCLUSIONS

Not only is spontaneous permanent LBBB harmful to our patients, but the iatrogenic variety produced by right ventricular apical pacing during conventional permanent pacing may also be deleterious to some patients. The compelling evidence presented herein cannot be ignored; it may dictate a change of attitude toward right ventricular apical pacing directing our attention to alternate sites of ventricular pacing and avoidance of the right ventricular apex.

Biventricular Pacing Using Dual-Site Right Ventricular Stimulation: Is It Placebo Effect?

Alternate site lead placement in cardiac resynchronization therapy has been used successfully but remains to be validated. A 62-year-old heart failure patient in whom coronary sinus lead placement was not possible underwent implantation of the lead in the right ventricular outflow tract (RVOT) and demonstrated clinical improvement as measured by New York Heart Association class and noninvasive parameters. When heart failure recurred, it was determined that his RVOT electrode had been pulled back (Twiddler's syndrome). Repositioning again improved his clinical status and noninvasive hemodynamic measurements. With dual-site right ventricular (RV) pacing there was no echocardiographic measurable intraventricular dyssynchrony. Tissue Doppler imaging correlated with clinical improvement using dual-site RV pacing, providing evidence that this technique may represent a viable alternative in cardiac resynchronization therapy.

Cardiac resynchronization through selective His bundle pacing in a patient with the so-called InfraHis atrioventricular block

We present a case of infraHis AV block in which selective His bundle pacing with His-ventricular conduction through the conduction system was accomplished. While further investigations are developed, this approach may be an alternative for cardiac resynchronization in cases of difficult coronary sinus access.