Biventricular Function is Impaired in Right Ventricular Septal Pacing-A Prospective Study Using Myocardial Strain Imaging

BACKGROUND

Left ventricular (LV) dysfunction is known to occur after right ventricular (RV) pacing; the effect on RV function is less well studied. The aim of this study was to assess the impact of RV mid-septal pacing upon RV function using the novel parameters of speckle-tracking derived RV global longitudinal strain (RV GLS) and RV free wall strain (RV FWS), as well as the conventional parameters RV fractional area change (FAC), tricuspid annular plane systolic excursion (TAPSE), and tricuspid annular systolic velocity (RV S').

METHODS

Thirty-two (32) consecutive patients with normal baseline LV and RV function requiring permanent pacemaker insertion (for high-grade AV block or sinus node dysfunction) were prospectively recruited. Echocardiography was performed prior to implantation, at 1 day, 1 month and 1 year after implantation, with 29 patients completing follow-up.

RESULTS

After 1 year, three patients (10%) with otherwise normal RV parameters developed abnormal RV strain patterns. Compared to 1 day after implantation, at 1 year significant reductions were observed in mean RV GLS (-24.8 to -21.8%) RV S' (15.1 to 12.2 cm/s), TAPSE (24.2 to 21.9 mm), RV GLS (-24.8 to -21.8%), left ventricular ejection fraction (LVEF) (66.0 to 57.9%), LV GLS (-19.9 to 17.0), all p<0.01. There was a non-significant reduction for RV FWS (-29.0 to -26.7%, p=0.06) and there was no change in RV FAC (49.1 to 46.9%, p=0.24).

CONCLUSION

We report abnormalities of RV strain developing 1 year after pacemaker insertion. Measurement of myocardial strain is emerging as an additional method to detect patients at risk of RV dysfunction in those who have undergone pacemaker implantation.

Exploratory use of intraprocedural transesophageal echocardiography to guide implantation of the leadless pacemaker

Background

Fluoroscopy is the standard tool for transvenous implantation of traditional and leadless pacemakers (LPs). LPs are used to avoid complications of conventional pacemakers, but there still is a 6.5% risk of major complications. Mid-right ventricular (RV) septal device implantation is suggested to decrease the risk, but helpful cardiac landmarks cannot be visualized under fluoroscopy. Transesophageal echocardiography (TEE) is an alternative intraprocedural imaging method.

Objective

The purpose of this study was to explore the spatial relationship of the LP to cardiac landmarks via TEE and their correlations with electrocardiographic (ECG) parameters, and to outline an intraprocedural method to confirm mid-RV nonapical lead positioning.

Methods

Fifty-six patients undergoing implantation of LP with TEE guidance were enrolled in the study. Device position was evaluated by fluoroscopy, ECG, and TEE. Distances between the device and cardiac landmarks were measured by TEE and analyzed with ECG parameters with and without RV pacing.

Results

Mid-RV septal positioning was achieved in all patients. TEE transgastric view (0°-40°/90°-130°) was the optimal view for visualizing device position. Mean tricuspid valve-LP distance was 4.9 ± 0.9 cm, mean pulmonary valve-LP distance was 4.2 ± 1 cm, and calculated RV apex-LP distance was 2.9 ± 1 cm. Mean LP paced QRS width was 160.8 ± 28 ms and increased from 117.2 ± 34 ms at baseline. LP RV pacing resulted in left bundle branch block pattern on ECG and 37.8% QRS widening by 43.5 ± 29 ms.

Conclusion

TEE may guide LP implantation in the nonapical mid-RV position. Further studies are required to establish whether this technique reduces implant complications compared with conventional fluoroscopy.

Influence of the right ventricular septum/free-wall boundary (hinge) on differentiation of the ventricular lead implantation site

BACKGROUND

The prognosis associated with right ventricular (RV) free-wall pacing is worse than that of septal pacing. Identification of the pacing site using a 12‑lead electrocardiogram (ECG) is controversial and may be influenced by ECG changes within the same septal or free-wall area. The relationship between the diagnostic capabilities of ECG and pacing sites has previously been qualitatively evaluated. However, in this study, this relationship was analyzed quantitatively, and accurate evaluation of the pacing site was determined using computed tomography (CT).

METHODS

Of 779 consecutive outpatients, 65 who underwent pacemaker implantation and thoracic CT were prospectively included and classified into the following groups according to the lead tip position: free-wall, septal, or septum/free-wall boundary (hinge) group. The hinge was used as an anatomical marker, and the distance from the hinge to the lead tip was measured. Under RV pacing, a 12‑lead ECG was obtained. ECG findings were evaluated using three criteria (including lead I, II, and aV_L and precordial leads V₅ and V₆) previously reported to be useful in differentiating pacing sites.

RESULTS

The lead tips were anchored at the free-wall in 10 patients, the septal wall in 19 patients, and the hinge in 32 patients. Paced QRS duration correlated with the distance from the hinge to the lead tip for the free-wall and septum (r = 0.47 and - 0.68, respectively). Estimation of the lead tip implantation site using the ECG algorithm was useful; however, the algorithm's accuracy decreased around the hinge.

CONCLUSIONS

ECG is useful in differentiating pacing sites but is less accurate around the hinge, which may be the reason that the identification of the RV pacing site using ECG remains controversial.

Anatomy for atrial lead implantation

Positioning and fixation of pacemaker leads in the right atrium depends on advanced anatomic knowledge in order to correctly interpret information from fluoroscopy and electrograms. Particularly the inability to reach a certain position or to achieve lead stability requires familiarity with right atrial structures such as the Eustachian ridge or areas of trabeculated versus smooth myocardium. Only a good understanding of right atrial anatomy makes it possible to replace electrophysiologically suboptimal atrial pacing sites such as right atrial appendage or high lateral wall by electrophysiologically better septal atrial pacing sites.

Clinical outcomes in patients with atrioventricular block undergoing pacemaker: 3-year follow-up

PURPOSE

Left ventricular function can be affected by chronic ventricular pacing. Different right ventricular (RV) pacing sites have shown heterogeneous clinical outcomes. We investigated these factors in patients receiving permanent pacemaker (PPM) implants.

METHODS

This multicenter, retrospective analysis of PPM use in South Korea, included all patients undergoing de novo transvenous PPM implantation for atrioventricular block from 2017 to 2019. Clinical characteristics, 12-lead electrocardiograms, echocardiography, and laboratory parameters were evaluated. Composite outcomes are defined by two coprimary endpoints: (1) hospitalizations and (2) cardiac death by heart failure during follow-up period.

RESULTS

There were 167 patients (66 males; overall mean age 75.3 ± 11.9 years), divided into two groups according to the pacing site: 83 apical RV (RVA) vs. 84 septal RV (RVS). There were no significant baseline differences. Paced QRS duration (pQRSd) increased with RVA (168.5 ± 20.1 vs. 159.1 ± 16.3 ms; p < 0.001). Over a median 31-month follow-up, there were 15 hospitalizations and 2 deaths. More patients with RVA were hospitalized or died (16% vs. 5%, respectively; p = 0.049). In Cox proportional regression analysis, pQRSd (hazard ratio [HR] 1.046; 95% confidence interval [CI] 1.004-1.091; p = 0.033), and diastolic dysfunction (HR 7.343; 95% CI 2.035-26.494; p = 0.002) were independent predictors of composite clinical outcomes.

CONCLUSIONS

RVS placement shortened the pQRSd and improved clinical outcomes. However, the determinants of these were pQRSd and diastolic dysfunction. Therefore, clinicians should try to shorten the pQRSd when implanting a PPM, and patients with diastolic dysfunction should be monitored intensively.

Can QRS morphology be used to differentiate between true septal vs. apparently septal lead placement? An analysis of ECG of real mid-septal, apparent mid-septal, and apical pacing

The location of the pacemaker lead is based on the shape of the lead on fluoroscopy only, typically in the left and right anterior oblique positions. However, these fluoroscopy criteria are insufficient and many leads apparently considered to be in septum are in fact anchored in anterior wall. Periprocedural ECG could determine the correct lead location. The aim of the current analysis is to characterize ECG criteria associated with a correct position of the right ventricular (RV) lead in the mid-septum. Patients with indications for a pacemaker had the RV lead implanted in the apex (Group A) or mid-septum using the standard fluoroscopic criteria. The exact position of the RV lead was verified using computed tomography. Based on the findings, the mid-septal group was divided into two subgroups: (i) true septum, i.e. lead was found in the mid-septum, and (ii) false septum, i.e. lead was in the adjacent areas (anterior wall, anteroseptal groove). Paced ECGs were acquired from all patients and multiple criteria were analysed. Paced ECGs from 106 patients were analysed (27 in A, 36 in true septum, and 43 in false septum group). Group A had a significantly wider QRS, more left-deviated axis and later transition zone compared with the true septum and false septum groups. There were no differences in presence of q in lead I, or notching in inferior or lateral leads between the three groups. QRS patterns of true septum and false septum groups were similar with only one exception of the transition zone. In the multivariate model, the only ECG parameters associated with correct lead placement in the septum was an earlier transition zone (odds ratio (OR) 2.53, P = 0.001). ECGs can be easily used to differentiate apical pacing from septal or septum-close pacing. The only ECG characteristic that could help to identify true septum lead position was the transition zone in the precordial leads. ClinicalTrials.gov identifier: NCT02412176.

Surface ECG criteria can discriminate post-septal pacing cardiac memory from ischemic T wave inversions

Cardiac memory (CM) refers to transient T wave changes that appear after cessation of a period of abnormal ventricular activation, such as right ventricular (RV) pacing. ECG criteria for differentiating post-pacing CM from ischemia-induced T wave changes were previously published only for apical, but not for septal RV pacing.

AIM

To find ECG criteria for discriminating post-septal pacing CM from ischemic T wave inversions.

METHODS

ECGs were analyzed in 2 groups: CM (n = 23) and ischemia (n = 26). CM was induced by 2 weeks of DDD pacing with a short AV delay. Ischemic patients were grouped by culprit vessel: left anterior descending (LAD), circumflex (Cx), right coronary artery (RCA).

RESULTS

CM was visible on the ECG after 1 week of ventricular pacing, started to disappear in <1 week after pacing cessation and was completely reversible within 4 weeks of pacing cessation. T wave axis differed between CM (75.8 ± 18.5°) and Cx (-25.2 ± 25.5°, p < 0.01) and RCA (-18.3 ± 18.9°, p < 0.01) groups, but not compared to LAD group (96.4 ± 65.0°, p = 0.17). The combination of (1) positive T wave in aVF; and (2) (i) T wave amplitude in aVF ≥ the absolute value of the most negative precordial T wave, or (ii) positive T wave in V5 and positive or isoelectric T wave in lead I identified CM from all ischemia with a sensitivity of 91% and a specificity of 92%.

CONCLUSION

ECG criteria can discriminate post-septal RV pacing CM from ischemic changes with high sensitivity and specificity.

Hemodynamics of His Bundle Pacing

In addition to the His bundle, numerous other sites have been evaluated as more physiologic alternatives to pacing at the right ventricular apex. Several hemodynamic studies have shown the benefit of His bundle pacing and septal pacing in comparison with right ventricular apical pacing. This article summarizes this literature and presents acute hemodynamic data in an intrapatient study examining His bundle pacing, right ventricular septal pacing, and right ventricular apical pacing.

Atrial fibrillation septal pacing: translation of modelling results

AIMS

Atrial fibrillation (AF) septal pacing consists of rapid pacing from a ring of electrodes around the atrial septum, leading to local capture of both atria during AF. The present model-based study evaluated the impact of the number of stimulation electrodes in the septal ring on AF capture for different types of sustained AF dynamics.

METHODS AND RESULTS

Using a biophysical model of AF based on CT scans from an AF patient, models with different AF substrates (Cholinergic AF and Meandering Wavelets) were created by varying the atrial membrane kinetics. Rapid pacing was applied from the septum area with a ring of 1, 2, 3, 4, 6, 8, or 12 electrodes during 20 seconds at a pacing cycle lengths (PCLs) in the range 60-100% of AF cycle length (AFCL), in 4% steps. Percentage of captured tissue during rapid pacing was determined using 24 sensing electrode pairs evenly distributed on the atrial surface. Results were averaged over 10 AF simulations. For Cholinergic AF, the number of stimulation electrodes on the septal ring had no significant impact on AF capture independently of AF dynamics. For Meandering Wavelets, more electrodes were needed to achieve AF capture in the presence of complex AF.

CONCLUSION

Changes in AF substrate significantly impacted septal pacing outcomes and response to rapid AF pacing may similarly vary patient-to-patient. The number of stimulation electrodes had a lesser impact, suggesting that the design of a ring with 3-4 electrodes around the septum would be sufficient for most AF dynamics.

Effects of right ventricular pacing sites on blood pressure variation in upright posture: a comparison of septal vs. apical pacing sites

AIMS

Large variations in blood pressure (BP) in the upright position are a major cause of pacemaker syndrome, observed in up to 80% of patients paced non-physiologically at the right ventricular (RV) apex. We hypothesized that the magnitude of BP variations might be influenced by the RV pacing site. To assess this, we compared haemodynamic findings during supine and upright posture with RV apical vs. septal pacing.

METHODS AND RESULTS

The study population comprised a retrospective cohort of 24 dual-chamber pacemaker patients with advanced or complete atrioventricular block, in which 11 were randomly chosen from those with RV apical pacing, and 13 randomly chosen from those with septal pacing. Studies were performed during fixed rate VVI and DDD pacing modes with patients in both supine and passive head-up tilt positions. Continuous BP, stroke volume, cardiac index, and total peripheral resistance index were measured non-invasively. During RV apical pacing, there were significant differences of beat-to-beat BP variation after movement from supine to upright posture for both VVI and DDD pacing modes (P < 0.05); however, this was not the case for either mode during RV septal pacing. Further, comparing RV apical to RV septal pacing in the supine position, there were no BP variation differences for either DDD or VVI modes. Conversely, in the upright position BP variation was significantly greater during RV apical vs. RV septal VVI pacing (P = 0.017) but not during DDD pacing.

CONCLUSION

During VVI pacing, RV septal pacing exhibited lesser BP variation during upright posture compared with RV apical pacing.

Influence of atrial substrate on local capture induced by rapid pacing of atrial fibrillation

AIMS

Preliminary studies showed that the septum area was the only location allowing local capture of both the atria during rapid pacing of atrial fibrillation (AF) from a single site. The present model-based study investigated the influence of atrial substrate on the ability to capture AF when pacing the septum.

METHODS AND RESULTS

Three biophysical models of AF with an identical anatomy from human atria but with different AF substrates were used: (i) AF based on multiple wavelets, (ii) AF based on heterogeneities in vagal activation, (iii) AF based on heterogeneities in repolarization. A fourth anatomical model without Bachmann's bundle (BB) was also implemented. Rapid pacing was applied from the septum at pacing cycle lengths in the range of 50-100% of AF cycle length. Local capture was automatically assessed with 24 pairs of electrodes evenly distributed on the atrial surface. The results were averaged over 16 AF simulations. In the homogeneous substrate, AF capture could reach 80% of the atrial surface. Heterogeneities degraded the ability to capture during AF. In the vagal substrate, the capture tended to be more regular and the degradation of the capture was not directly related to the spatial extent of the heterogeneities. In the third substrate, heterogeneities induced wave anchorings and wavebreaks even in areas close to the pacing site, with a more dramatic effect on AF capture. Finally, BB did not significantly affect the ability to capture.

CONCLUSION

Atrial fibrillation substrate had a significant effect on rapid pacing outcomes. The response to therapeutic pacing may therefore be specific to each patient.

Focus on right ventricular outflow tract septal pacing

Experimental and clinical studies have shown that right ventricular apical pacing may result in long-term deleterious effects on account of its negative impact on left ventricular remodeling through desynchronization. This risk appears more pronounced in patients with even moderate left ventricular dysfunction and generally occurs after at least 1 year of pacing. As right ventricular apical pacing may be associated with the development of organic mitral insufficiency, other sites that allow for more physiological stimulation, such as right ventricular outflow tract septal pacing, have been developed, with good feasibility and reproducibility. However, the prospective randomized studies and meta-analyses to date have only demonstrated a modest effect on ejection fraction in the medium term, without any significant effect on quality of life and morbimortality. However, the absence of a favorable effect for right ventricular outflow tract septal pacing compared with right ventricular apical pacing in terms of clinical manifestations and patient prognosis appears to be more associated with the designs of these studies, which were not homogeneous with regard to methodology used, judgment criteria, follow-up and, especially, statistical power. Two randomized prospective multicentre studies are currently ongoing in order to evaluate the favorable effect of infundibular septal pacing, when considering the indirect negative effects of right ventricular apical pacing as reported in the literature.