Pacing the Right Ventricular Septum: Time to Abandon Apical Pacing

The Australian and New Zealand Cardiac Implantable Electronic Device Survey, Calendar Year 2021: 50-Year Anniversary

BACKGROUND

A cardiac implantable electronic device (CIED) survey was undertaken in Australia and New Zealand for calendar year 2021. The survey involved pacemakers (PMs) and implantable cardioverter-defibrillators (ICDs). The survey was conducted on the 50^th anniversary of the first survey for both Australia and New Zealand in 1972; that initial survey being conducted by two of the current authors.

RESULTS AND CONCLUSIONS

For 2021, there were 19,410 PMs (17,971 in 2017) sold in Australia for new implants and 2,282 (1,811 in 2017) sold in New Zealand. The number of new PM implants per million population was 755 for Australia (745 in 2017) and 446 for New Zealand (384 in 2017). Unlike previous recent surveys, the percentage of PM replacements compared to total sales in both Australia and New Zealand rose. Pulse generator types implanted were predominantly dual chamber; Australia 77% (73% in 2017) and New Zealand 70% (68% in 2017). There were 1,509 biventricular PMs implanted in Australia (1,247 in 2017) and 172 in New Zealand (118 in 2017). Transvenous pacing leads were >90% active fixation in the atrium and ventricle. There was an increase in ICD usage with Australia 4,519 new implants (4,212 in 2017) and New Zealand 449 (396 in 2017). New ICD implants per million population were 187 for Australia (175 in 2017) and 88 for New Zealand (90 in 2017). For the first time the survey included implantable event monitors with 6,933 being implanted in Australia. However, for proprietary reasons, survey figures for subcutaneous implantable defibrillators, leadless pacemakers and conduction system pacing have not been included. Both Australia and New Zealand have high PM and ICD implant numbers compared to the rest of the Asia Pacific region.

The usefulness of right ventriculography to aid anchoring a pacing lead to the right ventricular septum

Aims

Although right ventricular septal pacing is thought to be more effective in minimizing pacing-induced left ventricular dysfunction, the accurate way to anchor the lead to the right ventricular septum (RVS) has not been established. Our aim was to clarify the usefulness of right ventriculography (RVG) to aid accurate anchoring of the lead to the RVS.

Methods and results

Eighty-four patients who underwent pacemaker implantation were enrolled. We anchored the lead to the RVS by using an RVG image obtained at a 30° right anterior oblique view as a reference. We confirmed the actual lead position by performing computed tomography after the procedure and examined the characteristics of the paced QRS complex. Of the 81 patients, except 3 patients whose leads were anchored to the apex due to high pacing thresholds in the RVS, the leads were successfully anchored to the RVS in the 79 (98%) patients, and the number of leads placed in the high-, mid-, and low-RVS was 3 (4%), 58 (73%), and 18 (23%), respectively. The paced QRS duration in these 79 patients was 140 ± 13 ms. The paced QRS duration from mid-RVS was considerably narrower than that from high- or low-RVS (137 ± 12 ms vs. 146 ± 12 ms; P = 0.012).

Conclusion

Right ventriculography was very useful in aiding accurate anchoring of the lead to the RVS. Further, pacing from mid-RVS may be more effective in minimizing the QRS duration than pacing from other RVS sites.

The Australian and New Zealand Cardiac Implantable Electronic Device Survey: Calendar Year 2017

BACKGROUND

A cardiac implantable electronic device (CIED) survey was undertaken in Australia and New Zealand for calendar year 2017 and involved pacemakers (PMs) and implantable cardioverter-defibrillators (ICDs).

RESULTS AND CONCLUSIONS

For 2017, there were 17,971 (15,203 in 2013) new PMs sold in Australia and 1,811 (1,641 in 2013) implanted in New Zealand. The number of new PM implants per million population was 745 for Australia (652 in 2013) and 384 for New Zealand (367 in 2013). In both Australia and New Zealand, the number of PM replacements fell as a result of improved power source service life. Pulse generator types implanted were predominantly dual chamber; Australia 73% (74% in 2013) and New Zealand 68% (59% in 2013). There were 1,247 biventricular PMs implanted in Australia (661 in 2013) and 118 in New Zealand (83 in 2013). Transvenous pacing leads were overwhelmingly active fixation in both the atrium and ventricle. In Australia there was an increase in ICD usage with 4,212 new implants (3,904 in 2013), but a small fall in New Zealand to 396 (423 in 2013). The new ICD implants per million population were 175 for Australia (167 in 2013) and 90 for New Zealand (95 in 2013). There was a small reduction in biventricular ICDs in both Australia (2,195) and New Zealand (111).

Haemodynamic Alterations Induced By Cardiac Pacing: Is Clinical Evaluation Sufficient Or Do We Need Long-Term Device Monitoring?

Cardiac pacing may induce haemodynamic alterations. RV pacing may have deleterious effects including a decrease of LV function as well as an increase of heart failure hospitalizations and mortality. Biventricular pacing is established in patients with heart failure and left bundle branch block or chronic AV block to improve haemodynamics. In the future, device optimization employing quadripolar leads or multisite pacing may further increase the rate of responders. However, cinical evaluation represents the most important tool to recognize the necessity for device optimization. Device algorithms are not yet successfully established to replace clinical and echocardiographic evaluation.

Risk of heart failure- and cardiac death gradually increases with more right ventricular pacing

BACKGROUND

Right ventricular pacing (RVP) is associated with an increased risk of heart failure (HF) events. However, the extent and shape of this association is hardly assessed.

OBJECTIVE

We quantified whether the undesired effects of RVP are confirmed in an unselected population of first bradycardia pacemaker recipients. Furthermore, we studied the shape of the association between RVP and HF death and cardiac death.

METHODS

Cumulative percentage RVP (%RVP) was measured in 1395 patients. Using multivariable Cox regression analysis with %RVP as time-dependant co-variate we evaluated the association between %RVP and HF- and cardiac death, both unadjusted and adjusted for confounders, including age, gender, pacemaker-indication, cardiac disease, HF at baseline, diabetes, hypertension, atrio-ventricular synchrony, usage of beta-blocking drugs, anti-arrhythmic medication, HF medication, and prior atrial fibrillation/flutter. Non-linear associations were evaluated with restricted cubic splines.

RESULTS

During a mean follow-up of 5.8 (SD 1.1) years 104 HF deaths and 144 cardiac deaths were observed. %RVP was significantly associated with HF- and cardiac death in both unadjusted (p<0.001 and p<0.001, respectively) and adjusted analyses (p=0.046 and p=0.009, respectively). Our results show a linear association between %RVP and HF- and cardiac death. We observed a constant increase of 8% risk of HF death per 10% increase in RVP. A model incorporating various non-linear transformations of %RVP using restrictive cubic splines showed no improved model fit over linear associations.

CONCLUSION

This long-term, prospective study observed a significant, though linear association between %RVP and risk of HF death and/or cardiac death in unselected bradycardia pacing recipients.

Separated right and left ventricular excitation during right ventricular septal pacing in a patient with narrow QRS wave: a case report

Introduction

Right ventricular septal pacing is thought to be better than right ventricular apical pacing for shortening the QRS duration and for preserving left ventricular function. However, right ventricular septal pacing may not be effective in all cases. In this case report, we present a rare case in which right ventricular septal pacing induced thoroughly separated right and left ventricular excitation despite the presence of a relatively narrow QRS wave during atrium-only pacing.

Case presentation

We report a case of 63-year-old Japanese man with cardiomyopathy with an implantable cardioverter defibrillator placement for ventricular tachycardia. Three years after implantation, he developed second-degree atrio-ventricular block. Therefore, atrio-ventricular sequential pacing was started; then his heart failure was much worsened. His electrocardiogram showed a dissociated biphasic QRS wave during right ventricular high-septal pacing, despite the presence of a non-fragmented QRS morphology during atrium-only pacing. An activation map during right ventricular high-septal pacing showed that right ventricular conduction started at the pacing site and ended at the right ventricular basal inferior site. Subsequently after a 10ms interval, left ventricular conduction started at the left ventricular posteroseptum and ended at the left ventricular lateral wall. These data indicate that during right ventricular high-septal pacing, the first component of the QRS wave supposedly reflects only right ventricular excitation and the second component only left ventricular excitation. Also due to the intracardiac electrograms, it was assumed that this phenomenon was caused by transversely limited severe transseptal conduction disturbance.

Conclusion

It should be noted that even ventricular septal pacing could evoke harmful interventricular dyssynchrony due to transversely limited severe septal conduction disturbance, despite the presence of a relatively narrow QRS wave.

The insufficiency of left anterior oblique and the usefulness of right anterior oblique projection for correct localization of a computed tomography-verified right ventricular lead into the midseptum

BACKGROUND

The aim of the study was to verify the correct anchoring location for the tip of the right ventricular lead using cardiac computed tomography and to assess the best fluoroscopic and ECG criteria associated with the correct location of the electrode into the midseptum.

METHODS AND RESULTS

Patients indicated to pacemaker implantation were prospectively enrolled. The right ventricular lead was implanted into the midseptum according to standard criteria in left anterior oblique 40 view. The cardiac shadow on the right anterior oblique 30 was divided into 4 quadrants perpendicular to the lateral cardiac silhouette and the position of the lead tip was analyzed. The exact position of the lead tip was assessed using computed tomography. Of 51 patients, the right ventricular lead was anchored midseptum in 21 (41.2%; MS group). In 30 patients (58.8%; non-MS group), the lead was anchored in the adjacent anterior wall. The angle between the lead and horizontal axis on the left anterior oblique was similar in both groups. The non-MS group was associated with shorter distances between the tip and the cardiac contours in the right anterior oblique 30 (96.7% of leads in the non-MS group were in the outer quadrant versus 9.6% in the MS group; P<0.001). The presence of the lead in the middle or inferior quadrants was independently associated with correct midseptum placement with positive predictive value of 94.7%.

CONCLUSIONS

Despite the optimal shape of the left anterior oblique, substantial numbers of leads were not anchored in the midseptum. Knowing the right anterior oblique 30 lead position can ensure proper midseptal placement.

Effects of right ventricular nonapical pacing on cardiac function: a meta-analysis of randomized controlled trials

BACKGROUND

A meta-analysis of randomized controlled trials (RCTs) was conducted to compare the effects of right ventricular nonapical (RVNA) and right ventricular apical (RVA) pacing on cardiac function.

METHODS

A systematic literature search was performed using MEDLINE, EMBASE, and the Cochrane Library to identify RCTs comparing RVNA pacing with RVA pacing with follow-up ≥2 months. Twenty RCTs involving 1,114 patients were included.

RESULTS

Compared with RVA pacing, RVNA (mainly right ventricular septum [RVS]) pacing exhibited not only excellent pacing threshold and R-wave amplitude but also higher impedance. RVNA pacing showed a significant increase in left ventricular ejection fraction (LVEF) at the end of follow-up (weighted mean difference = 3.58, 95% confidence interval = 1.80-5.35), and the effects were observed in the following subgroups: 6-month follow-up, ≤12-month follow-up, >12-month follow-up, baseline LVEF ≤45%, and baseline LVEF >45%. RVS and RVA pacing significantly differed in improving LVEF (weighted mean difference = 4.82, 95% confidence interval = 2.78-6.87). In addition, RVNA pacing resulted in a narrower QRS duration, a smaller left ventricular end-systolic volume, and a lower New York Heart Association functional class.

CONCLUSIONS

This meta-analysis found that RVNA (mainly RVS) pacing exhibited satisfactory long-term lead performance compared with RVA pacing and demonstrated beneficial effects in improving LVEF after the 6-month follow-up. Furthermore, it proved superior to RVA pacing in terms of interventricular synchrony and cardiac function.

Electrocardiographic diagnosis of biventricular pacing in patients with nonapical right ventricular leads

BACKGROUND

Assessment of left ventricular (LV) capture is of paramount importance in patients with biventricular (BiV) pacing. Our goal was to identify electrocardiographic features that differentiate between BiV and right ventricular (RV)-only pacing in patients with nonapical RV leads.

METHODS

The study enrolled 300 consecutive patients with BiV devices and nonapical RV leads, and obtained from them 558 electrocardiograms with either BiV pacing (n = 300) or RV-only pacing (n = 258). RV pacing served as a surrogate for loss of LV capture. Electrocardiograms from the first 150 patients were used to identify BiV-specific features, and to construct an algorithm to differentiate between BiV and RV-only pacing. Electrocardiograms from the second 150 patients were used to validate the algorithm.

RESULTS

The following electrocardiographic features typical of BiV pacing were identified: QS in lead V6 (specificity = 98.7%, sensitivity = 54.7%), dominant R in lead V1 (specificity = 100%, sensitivity = 23.3%), q in lead V6 (specificity = 96%, sensitivity = 22.7%), and a QRS < 160 ms (specificity = 100%, sensitivity = 66.0%). The algorithm based on those features was found to have an overall diagnostic accuracy of 95.0%, a specificity of 96.0%, and a sensitivity of 93.5%.

CONCLUSIONS

The study identified QRS features that were very specific for BiV pacing in patients with nonapical RV leads. Sequential arrangement of those features resulted in an algorithm that was very accurate for differentiating between BiV pacing and loss of LV capture.

Adverse response to cardiac resynchronisation therapy in patients with septal scar on cardiac MRI preventing a septal right ventricular lead position

PURPOSE

Myocardial scar is an adverse factor when considering which patients are likely to respond to cardiac resynchronisation therapy (CRT). We hypothesized that septal scarring on magnetic resonance imaging (MRI) may be associated with a poor outcome from CRT, which may relate to the inability to place the right ventricular (RV) lead in the septum.

METHODS

Fifty patients (ejection fractions, 25 ± 8%; 45 men, 62.8 ± 14 years; 26 dilated cardiomyopathy; and 24 ischaemic cardiomyopathy (ICM)) receiving CRT underwent delayed enhancement cardiac MRI to assess location and burden of myocardial scar. Acute hemodynamic response (AHR) was evaluated at implant with a pressure wire in the left ventricular (LV) cavity. LV remodelling was determined by reduction in LV end-systolic volume at 6 months.

RESULTS

The presence of ICM with septal scar was associated with a poor acute and chronic response to CRT. This was predominantly due to a worse response in patients with septal scar. Patients without septal scar had a better AHR with a 26.7 ± 28.9% rise in LV dP/dt (max) from baseline vs. -2.8 ± 14.5% for patients with septal scar (P = 0.01) with Biventricular (BIV) pacing. A greater proportion remodelled (56% vs. 20% (P = 0.02)). Furthermore, only 33% of patients with septal scar had an RV septal lead compared with 66% with no septal scar (P = 0.03).

CONCLUSIONS

The presence of septal scar was associated with a poor acute and chronic response to CRT. This may relate to the inability to achieve a RV septal lead placement.

[Advances in cardiac pacing]

This article contains a review of the current status of remote monitoring and follow-up involving cardiac pacing devices and of the latest developments in cardiac resynchronization therapy. In addition, the most important articles published in the last year are discussed.

Acute left ventricular dysfunction secondary to right ventricular septal pacing in a woman with initial preserved contractility: a case report

Introduction

Right ventricular apical pacing-related heart failure is reported in some patients after long-term pacing. The exact mechanism is not yet clear but may be related to left ventricular dyssynchrony induced by right ventricular apical pacing. Right ventricular septal pacing is thought to deteriorate left ventricular function less frequently because of a more normal left ventricular activation pattern.

Case presentation

We report the case of a 55-year-old Tunisian woman with preserved ventricular function, implanted with a dual-chamber pacemaker for complete atrioventricular block. Right ventricular septal pacing induced a major ventricular dyssynchrony, severe left ventricular ejection fraction deterioration and symptoms of congestive heart failure. Upgrading to a biventricular device was associated with a decrease in the symptoms and the ventricular dyssynchrony, and an increase of left ventricular ejection fraction.

Conclusion

Right ventricular septal pacing can induce reversible left ventricular dysfunction and heart failure secondary to left ventricular dyssynchrony. This complication remains an unpredictable complication of right ventricular septal pacing.

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.

Current concepts in pacing 2010-2011: the right and wrong way to pace

OPINION STATEMENT

Over five decades have passed since the first permanent cardiac pacemakers were introduced into clinical medicine. Evolving technology and falling costs have demanded adaptation to clinical practice and implantation trends and, with the advent of evidenced-based medicine, the specific roles and benefits of individual pacemaker technologies have never been so carefully scrutinized. Pacing mode choice continues to be a subject of great controversy, and there are great regional variations in practice. We believe that single chamber atrial pacing use (AAI/R) has become an anachronism that should generally be abandoned (obviously with rare exceptional cases) and be replaced by dual chamber pacemakers (DDD/R) equipped with modern pacing algorithms that minimize patient exposure to ventricular pacing. Also, in patients with atrioventricular (AV) block, randomized clinical trials have failed to show improvement in clinically relevant outcomes such as mortality, stroke, and heart failure, particularly in the elderly, which has led some to advocate that DDD/R devices should never be offered to elderly AV block patients. However, we believe that the elderly, like the young, come in many "shapes and sizes" and individualized medicine compels us to consider each pacemaker candidate as unique. Implanting DDD/R devices in chronologically older, yet physiologically younger, patients is justifiable and good medical practice. Where right ventricular (RV) pacing is necessary and unavoidable, physicians should consider routinely placing RV leads on the RV mid- or outflow tract septum because these location are as good, if not better, for patients than the current practice of RV apical lead placement. In patients with AV block and asymptomatic yet moderate to severely depressed left ventricular systolic function, primary cardiac resynchronization therapy (CRT) should be strongly considered. Compelling clinical trial evidence does not yet exist to indicate that CRT should be the standard of care in patients with AV block and intact left ventricular systolic function. Right ventricular septal lead placement remains a reasonable option.