Journal Of Indian College Of Cardiology

ORIGINAL ARTICLE
Year
: 2020  |  Volume : 10  |  Issue : 3  |  Page : 116--120

Comparing long-term effect of right ventricular septal versus apical pacing on left ventricular function


Akhlaque Ahmed, Ankit Kumar Sahu, Pravin K Goel 
 Department of Cardiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India

Correspondence Address:
Prof. Pravin K Goel
Department of Cardiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow - 226 014, Uttar Pradesh
India

Abstract

Background: Right ventricular (RV) apical pacing is the standard technique for permanent pacemaker implantation and is known to cause detrimental effects on left ventricular (LV) function in long term. Limited data are available on alternative pacing sites which may help preserve LV function. We aimed to compare the long-term effect of RV septal versus apical pacing on LV function. Materials and Methods: A total of 93 consecutive patients were enrolled, of whom 52 received RV apical pacing and 41 RV septal pacing over a period of 2 years. LV assessment was done at regular follow-up including measurement of LV ejection fraction (LVEF), left atrial volume index (LAVi), and 2D LV longitudinal strain. Clinical outcomes included all-cause mortality and heart failure-related hospitalization. Results: Over a median follow-up was 6 years with interquartile range of 4–9 years, LVEF in the apical and septal pacing group was 48.1% ± 10.3% and 51.5% ± 10.2%, respectively (P = 0.112). However, RV septal pacing was significantly better than RV apical pacing with respect to global longitudinal strain (−17.2 ± 2.0 vs. −15.1 ± 2.9; P < 0.001) and LAVi (in RV apical group and 35.5 ± 5.8 ml/m2 vs. 42.7 ± 5.8 ml/m2; P < 0.001). Clinical endpoints, however, did not differ between the two groups. Conclusions: Long-term RV septal pacing was associated with fairly preserved LV function and lesser adverse LA remodeling as compared to RV apical pacing. Larger randomized studies are required to demonstrate the beneficial effect of septal pacing on clinical cardiovascular outcomes.



How to cite this article:
Ahmed A, Sahu AK, Goel PK. Comparing long-term effect of right ventricular septal versus apical pacing on left ventricular function.J Indian coll cardiol 2020;10:116-120


How to cite this URL:
Ahmed A, Sahu AK, Goel PK. Comparing long-term effect of right ventricular septal versus apical pacing on left ventricular function. J Indian coll cardiol [serial online] 2020 [cited 2021 Oct 22 ];10:116-120
Available from: https://www.joicc.org/text.asp?2020/10/3/116/304379


Full Text



 Introduction



The right ventricular (RV) apex has been the traditional site for the ventricular lead implantation for permanent ventricular pacing. However, long-term RV apical pacing may induce or worsen left ventricular (LV) mechanics through distorted longitudinal shortening and torsion, leading to LV dysfunction.[1],[2] This is because during RV apical pacing, the electrical wave front propagates through the myocardium instead of His-Purkinje conduction system, resulting in the slower propagation of electrical wave front and heterogeneity in activation within the myocardium similar to that seen in left bundle branch (LBB) block. This abnormal electrical activation sequence is characterized by wave front breakthrough at the interventricular septum and earliest activation at the inferoposterior basal part of the left ventricle.[3],[4]

The ideal pacing mode for improving cardiac function requires the conduction through Purkinje fibers. Alternative site pacing incorporates: physiologic pacing including His-bundle pacing, para-Hisian pacing, direct LBB pacing, LBB area pacing, and deep septal pacing followed by septal pacing (mid and high septal pacing) and RV outflow tract (RVOT) pacing. Although these strategies are standardized but still not very well popular because of the technical difficulties in lead implantation (accessibility) and lead stability at these sites, yet the most practiced alternative pacing site is the inferior portion of septal RVOT or the septal (not free wall) zone bounded by the supraventricular crest, and septo-marginal trabeculation, the so-called “septal pacing.”

Clinical evidence to support septal pacing is still limited. Although studies have shown that RV septal pacing reduces interventricular conduction delay characterized by shortened paced QRS complex duration and a more synchronous LV contraction than RV apical pacing,[1],[5] yet its beneficial effect on the prevention of cardiac remodeling and preserving LV systolic function is highly variable.[2] In addition, limited studies have focused on the effect of different pacing sites on size and function of the left atrium, which is crucial for the development of atrial arrhythmias that may be effected secondary to latent LV dysfunction in long term.[6] We therefore sought to compare the effect of RV septal versus RV apical permanent pacing on LV function indices including the LV ejection fraction (LVEF), left atrial volume index (LAVi), and global longitudinal strain (GLS) on long-term follow-up.

 Materials and Methods



This was a single center, retrospective, case–control, comparative follow-up study that enrolled consecutive patients undergoing permanent pacemaker implantation (PPI) from 2010 to 2012. One set of operators performed septal pacing on routine basis, whereas during the same time period, the other set of operators performed standard RV apical pacing. We excluded patients who presented with a history of atrial fibrillation and/or heart failure (HF), severe tricuspid valve disease, or history of tricuspid valve surgery, prior pacemaker implant, documented coronary artery disease, pulmonary disease, or those having any contraindication to endocardial permanent pacing.

Procedure protocol

The decision on the mode of permanent pacing (dual vs. single chamber) was made at the discretion of the operating cardiologist on the basis of patient's clinical profile, electrocardiogram (ECG) findings, and patient preference. A written informed consent was obtained before the procedure in all patients as per institutional protocol. PPI was performed with the patient in a conscious state under local anesthesia with all aseptic precautions. In the RVA pacing group, leads were positioned at the RV apex as per standard technique [Figure 1]a and [Figure 1]b and in RV septal pacing group, the pacing leads were positioned on septal side of the RVOT about half way along the length of the septum. The septal location was confirmed with the tip of the electrode pointing posteriorly in LAO or left lateral view [Figure 2]a and [Figure 2]b. The posterior lead direction was reached using the hand-made Mond's curve on the stylet once the lead was floating toward RVOT. The tip was fixed at halfway along septal length and position was confirmed by fluoroscopic image in LAO view. Various electrocardiographic criteria were used to document the septal position of ventricular pacing lead including a negative or isoelectric vector in lead I, qR pattern in lead aVL (30% sensitivity and 74% specificity),[7] positive deflection in leads II, III, AVF, V6, and paced QRS duration ≤145 ms (85.1% sensitivity and 78.9% specificity).[8] Surface 12 lead ECG postprocedure showing RV apical [Figure 1]c and septal pacing [Figure 2]c respectively. In addition, transthoracic echocardiography in parasternal short axis and apical 4-chamber view was employed to verify the same.{Figure 1}{Figure 2}

Follow-up

All data related to the procedure, patient's clinical presentation, and follow-up were retrieved from a predefined software where the data was recorded on day-to-day basis as a routine part of the departmental protocol. Post PPI, patients were subjected to clinical follow-up, routine echocardiography, and device interrogation during outpatient visits at 1-year interval.

Echocardiographic examination protocol

Imaging was performed with patients in the left lateral decubitus position using a 3.5-MHz transducer on Vivid™ E9 cardiovascular ultrasound system (GE healthcare, Chicago, IL, USA) using standard American society of echocardiography protocols. All gray-scale images were with depth and sector width adjusted to achieve frame rates >70 frames/s. Two dimensional images of apical four-chamber, two-chamber and apical long-axis view were recorded. The imaging sector was modified for optimal visualisation of the structure under consideration. A minimum of 3 consecutive cardiac cycles was recorded for each image. LV end-diastolic and end-systolic volumes were measured from apical 4-and 2-chamber images and global LVEF was calculated using Simpson's biplane method. LV strain profiles were derived by speckle-tracking by manual tracing of the endocardial border and adjustment of region of interest width to encompass the LV myocardium. Strain versus time curves were obtained for 18 segments from 3 apical views. The peak systolic strain was measured from the 18 segments and averaged to obtain global LV longitudinal strain score. LA volume was estimated from apical 4-chamber and 2-chamber images at end-systole using biplane area-length method (0.85 × A1× A2)/L) (where A1= LA area from 2 orthogonal views, L = LA length measured from the mitral annular plane to the posterior wall). LA volume was divided with body surface area to derive LAVi.

Statistical analysis

Continuous data were expressed as mean ± standard deviation. Categorical data were summarized as frequencies and percentages, which were analysed using the Chi-square test. Unpaired Student's t-test was used for comparing nominal data between the two groups. A P < 0.05 was deemed statistically significant. The data was entered in an excel chart and analysed using SPSS® statistical analysis software (IBM SPSS statistics for windows (2011), version 20.0, IBM corp., Armonk, NY, USA).

 Results



93 patients (52 RVA pacing patients and 41 RV septal pacing patients) were included in this comparative analysis. Median follow-up duration was 6 years with an inter-quartile range of 4–9 years. As shown in [Table 1], there was no statistical difference between the two groups with respect to age, sex, and prevalence of risk factors like diabetes or hypertension. Procedural success rate was 100%. No major complication occurred during peri-procedural period or during follow-up. In the RVA pacing group, 27 patients (51.9%) were implanted dual-chamber pacemaker (DDD) and 25 patients (48.1%) with single chamber pacemaker (VVI). In the RV septal pacing group, 24 patients (58.5%) were implanted a dual-chamber pacemaker (DDD) and 17 patients (41.5%) with a single chamber pacemaker (VVI) (P = 0.525). As shown in [Table 2], there was no significant difference in mean global LVEF between two groups (P = 0.112). However, with respect to GLS, RV septal pacing (−17.24 ± 2.01) was significantly better as compared to RVA pacing (−15.10 ± 2.93) (P < 0.001). Also, LAVi was noted to be significantly higher with RV apical pacing (42.73 ± 5.76 ml/m2) as compared to RV septal pacing (35.54 ± 5.78 ml/m2) (P < 0.001). This improvement in LAVi with RV septal pacing was noted in both single-chamber paced and dual-chamber paced patients [Table 3]. Although the study was not powered for clinical outcomes, yet all-cause mortality was similar in the two groups, but HF related hospitalization rates demonstrated a higher trend in patients with RV apical pacing (9.6%) as compared to RV septal pacing (4.9%) (P = 0.130).{Table 1}{Table 2}{Table 3}

 Discussion



The main observation from our study was the better LV function at follow up in patients of RV septal pacing as compared to RV apical pacing, as observed by a trend to higher global LVEF and significantly better GLS and LAVi.

Chronic RVA pacing has been associated with deleterious effects. These deleterious effects are due to abnormal electrical activation of LV myocardium leading to dyssynchronous left ventricle (LV) contraction mechanics. Chronic RV apical pacing also carries the risks of several short and long-term complications including pain, tamponade from perforation, clinically significant far-field over-sensing or stimulation of extra-cardiac structures e.g., phrenic or intercostal stimulation. Thambo et al.[9] studied patients with complete congenital atrioventricular block paced long-term from the RV apex. They found that RVA pacing was associated with intraventricular dyssynchrony, adverse LV remodelling, and reduced functional capacity. In long-term follow-up of young patients permanently paced from the RV apex, a detrimental effect on LV systolic function was also noted by Tantengco et al.[10] Several other studies have also shown that RV apical pacing is associated with a reduction in LVEF.[2],[10],[11],[12]

Alternative pacing sites with a more synchronous ventricular activation pattern have thus been explored.[5] Earlier studies by Nikoo et al.[13] and Zou et al.[14] have shown beneficial effect of RV septal pacing on plasma natriuretic peptide levels and echocardiographic equivalent of atrial electrical activity in the form of LA function and LV filling pressures, respectively. In contrast to the above-mentioned studies, Bai et al.[15] in a small randomized study involving 96 patients with high-grade atrioventricular block showed no difference between the two pacing sites with respect to echocardiographic or biochemical markers of ventricular dysfunction at 6 months follow-up. However, at 12 month of follow-up a trend towards intraventricular dyssynchrony in the form of worsened LVEF was observed in patients with RV apical pacing when compared to RV mid-septal pacing. Similarly, in our study it was seen that RV septal pacing group showed a trend towards better LV systolic function as compared to RV apical pacing group, although not reaching statistically significant which could be probably due to small sample size (P = 0.112). This may be because LVEF as such is a less refined parameter and significance may not be observed because of smaller number of patients. More sensitive parameters of LV functional assessment like GLS is a more sensitive marker which in our study, was as such noted to be significantly better in the septal pacing group.

LA size is an indirect predictor of diastolic LV dysfunction and has been shown to have prognostic value in a variety of cardiac conditions.[16] Little is known to date about the effects of permanent pacing on LA structure and function. Our study showed that LAVi in RV septal pacing group was significantly lower than the RV apical pacing group. This also suggests that RV septal pacing possibly has more favourable effect on LV function shown by reverse remodelling of left atrium when compared to RV apical pacing.

Study limitations

There were a few lacunae in this study. Firstly, this was a single centre and nonrandomized study. Also, the sample size was not large enough. Secondly, patient data regarding baseline echocardiographic LVEF and other parameters of LV function were not available for analysis but this is equalized by comparing the final outcomes between the two groups in absolute. Also, several parameters of diastolic LV dysfunction have not been assessed in this study which could have been done. Thirdly, definitive confirmation of the septal lead position could have been done with multimodality imaging including computed tomography which have been shown to accurately verify the screwing lead position.[17] Fourthly, in patients with dual-chamber pacing, the frequency of atrial high rate episodes was not accounted for in both the groups. In addition, the percentage of ventricular pacing required by the patients was not taken into account. Finally, effect of various pacing modes on study outcomes and comparison between screwing and passive fixation leads was not done.

 Conclusions



We conclude that RV septal pacing is superior to RV apical pacing at preserving LV function with significantly improved GLS, less adverse LA remodelling and trend towards better global LVEF at follow-up. A larger, randomized, controlled study powered to detect differences in clinical endpoints between respective pacing sites may be warranted in future.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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