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ORIGINAL ARTICLE
Year : 2022  |  Volume : 35  |  Issue : 1  |  Page : 1-7

The effect of different pacing modes on left ventricular global and regional longitudinal systolic strain by two-dimensional speckle-tracking echocardiography


1 Department of Cardiology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Cardiology and Electrophysiology, National Heart Institute, Cairo, Egypt

Date of Submission14-Oct-2021
Date of Decision21-Nov-2021
Date of Acceptance23-Nov-2021
Date of Web Publication18-Apr-2022

Correspondence Address:
Rehab I Yaseen
Department of Cardiology, Faculty of Medicine, Menoufia University, Abdelrahman Elsharkawey Street, Shebin Elkom, Menoufia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_205_21

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  Abstract 


Background
In spite of the fact that the quality of life improved for most patients with a cardiac pacemaker implant, the pacing-induced left bundle branch block pattern can result in changes of the structure, function, and hemodynamics of the heart.
Objectives
To study the effect of different pacing modes on left ventricular (LV) global and regional longitudinal systolic strain (LSS) by two-dimensional (2-D) speckle-tracking echocardiography.
Patients and methods
This study was performed on 30 patients with a history of dual-chamber pacemaker implantation of more than 6 months duration and 30 healthy volunteers as controls. Conventional and 2-D speckle-tracking echocardiographies were performed to evaluate the LV global and regional systolic longitudinal strain in different pacing modes.
Results
Pacemaker programming from atrial sensed ventricular paced mode to atrial paced ventricular paced mode showed a significant decrease in global LV LSS (P = 0.021). Moreover, programming with asynchronous ventricular pacing (VVI mode) demonstrated a further significant reduction of global LV LSS when compared with other pacing modes (P = 0.014).
Conclusion
Permanent right ventricular apical pacing leads to marked changes of LV systolic function. Moreover, atrial pacing and asynchronous ventricular pacing may cause more deterioration of LV global and regional systolic longitudinal strain detected by 2-D speckle-tracking echocardiography.

Keywords: two-dimensional speckle-tracking echocardiography, echocardiography, left ventricle, pacing, strain


How to cite this article:
Yaseen RI, Abdelaziz WF, Katta AA, Soliman AE. The effect of different pacing modes on left ventricular global and regional longitudinal systolic strain by two-dimensional speckle-tracking echocardiography. Menoufia Med J 2022;35:1-7

How to cite this URL:
Yaseen RI, Abdelaziz WF, Katta AA, Soliman AE. The effect of different pacing modes on left ventricular global and regional longitudinal systolic strain by two-dimensional speckle-tracking echocardiography. Menoufia Med J [serial online] 2022 [cited 2022 Aug 11];35:1-7. Available from: http://www.mmj.eg.net/text.asp?2022/35/1/1/343111




  Introduction Top


Pacemakers are considered an effective therapy for symptomatic bradyarrhythmia caused by atrioventricular nodal and sinoatrial nodal disease [1]. In spite of the fact that the quality of life improved for most patients with a cardiac pacemaker implant, the pacing-induced left bundle branch block pattern can result in changes of the structure, function, and hemodynamics of the heart [2],[3].

In cases with right ventricular apical (RVA) pacing, the electrical wavefront propagates in a slower manner and induces electrical heterogeneity in the activation of the myocardium similar, but not identical, to the changes that occur in patients having inherent left bundle branch block. The electrical wavefront starts to breakthrough across the interventricular septum and lastly activates the inferoposterior base of the left ventricular (LV) [4],[5]. This electrical pattern alters the mechanical activation of the LV during pacing of the RV apex. Not only the anatomic onset of myocardial activation changes but also the resulting mechanical pattern of contraction seems to be altered [6].

Badke et al. [7] explained the mechanism of a reduced rate of change of LV pressure (dP/dt) and the asynchronous pattern of contraction that occurred with apical pacing.

The early contraction of the paced area occurs at the time of low load, but then later in systole it is stretched as the final contraction occurs in the lateral wall [7]. Moreover, the stroke volume reduced significantly as the myocardium contracts in an asynchronous pattern, and this leads to a right shift of the LV end-systolic pressure–volume curve. Discrepancy between the relaxation of early and late stimulated areas shortens the filling time of LV. Thus, apical pacing of the RV apex causes ventricular dyssynchrony, impairment of both systolic and diastolic ventricular functions, elevated wall stress, and energetic inefficiency [8]. In this study, we aimed to study the effect of different pacing modes on LV global and regional longitudinal systolic strain (LSS) by two-dimensional (2-D) speckle-tracking echocardiography.


  Patients and methods Top


This study was performed on 30 patients with a history of dual-chamber pacemaker implantation (at RVA position) of more than 6 months duration and 30 healthy volunteers as controls. Patients were included in this study after obtaining their written informed consent and acquiring the approval of the local ethics committee.

The study included patients who were pacemaker dependent with an implanted dual-chamber pacemaker of more than 6 months duration with the ventricular lead placed in the apex of RV and LV ejection fraction (EF) more than 50%.

Patients with any of the following were excluded: position of the ventricular lead outside the apex of RV, pacemakers implanted of less than 6-month duration before enrollment, bad echocardiographic window, previous cardiac surgery (e.g., valve replacement, coronary artery bypass graft), history of ischemic heart disease or previous percutaneous coronary intervention, significant valvular lesions, and myocardial disease such as hypertrophic cardiomyopathy and restrictive cardiomyopathy.

The patients underwent detailed history taking, clinical examination, and 12-lead ECG. A transthoracic echocardiography was done using a Vivid E9, a General Electric health-care system (GE Vingmed, Horten, Norway) equipped with a harmonic M5S variable frequency (1.7–4 MHz) phased-array transducer with the patient in the left lateral position based on the American Society of Echocardiography recommendations [9].

Conventional echocardiographic examination: M-mode measurements included interventricular septal thickness in diastole, posterior wall thickness in diastole (PWd), the LV end-diastolic diameter, LV end-systolic diameter, LV EF %, and fractional shortening %. As this method is inaccurate due to that paradoxical septal motion caused by RV pacing, we assessed the EF using the modified biplane Simpson's method. The LVEDV and LVESV were calculated from the apical two-chamber and four-chamber views. The LV EF % was automatically calculated as follows [10]: EF %=(EDV − ESV)/EDV × 100.

2-D speckle-tracking echocardiography: apical views were adjusted at frame rates that range from 70 to 100 frame/s. The patients were asked to hold breath at the end of expiration and three cardiac cycles were taken consecutively. Images were stored on the hard drive digitally for off-line analysis later. Pulsed-wave Doppler was used to record mitral and aortic velocities to determine the timing of cardiac events.

The endocardial lining of these chambers was traced manually by the 2-D strain EchoPac software. Eventually, a region of interest involving the entire transmural wall was created automatically by the computer. The software divided each wall into three segments: basal, mid, and apical. Regional and global LV LSS values were calculated [11] [Figure 1], [Figure 2].
Figure 1: 2-D speckle tracking echocardiography in apical four-chamber view in patient during AS-VP mode (group I). 2-D, two dimensional; AS-VP, atrial sensed ventricular paced mode.

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Figure 2: 2-D speckle tracking echocardiography in apical long axis view in patient during AP-VP mode (group II). 2-D, two dimensional; Ap-VP, atrial paced ventricular paced mode.

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Pacemaker programming: all patients underwent different programming modes for their devices and were thereby represented as three groups: group I (AS-VP mode): in atrial sensing and ventricular paced mode, the devices sensed the intrinsic atrial activity and paced the ventricles accordingly to maintain A-V synchrony; group II (AP-VP mode): in atrial paced and ventricular paced mode, the device was programmed to initiate atrial pacing at a rate of 100 b/min, followed by ventricular pacing 'maintaining A-V synchrony;' and group III (VVI mode): in this mode, the atrial lead is switched off, and the device functions as a single-chamber pacemaker delivering ventricular pacing at 100 b/min dissociated from the intrinsic atrial activity, that is asynchronous ventricular pacing mode.

2-D speckle-tracking echocardiography was used to measure the global and segmental systolic longitudinal strain of the LV walls to compare them between controls and patients during the AS-VP mode (group I). We also compared LV LSS in patients in three pacing modes: group I (AS-VP mode), group II (AP-VP mode), and group III (VVI mode). The comparison of LV LSS between group (AS-VP) and group (AP-VP) was done to study the indirect effects of atrial pacing on LV LSS. The comparison of LV LSS between group AP-VP and group VVI was done to study the effects of A-V synchrony on LV LSS at the same heart rate of 100 b/min.

Statistical analysis

Results were statistically analyzed by the Statistical Package for the Social Sciences (SPSS, version 20; IBM Corp., Armonk, New York, USA). Student's t test was used to indicate the significance between two means. χ2 test was used for comparison regarding qualitative variables. P value was considered statistically significant if less than 0.05.


  Results Top


Our study enrolled 30 patients (18 females and 12 males) with a mean age of 62.60 ± 5.03 and 30 controls (16 females and 14 males) with a mean age of 59.63 ± 6.67. We did not observe any significant difference regarding age and sex between the patients and controls (P > 0.05).

By comparing conventional echocardiographic parameters between the studied groups, LV end-diastolic diameter and LV end-systolic diameter did not show any significant difference between the controls and the patients during the AS-VP mode (group I) (P > 0.05) [Table 1].
Table 1: Comparison of conventional echocardiographic parameters between the controls and patients during the atrial sensed ventricular paced mode (group I)

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When we measured the LV EF by M-mode, we did not observe any statistical difference between the controls and the patients during the AS-VP mode (group I) (P > 0.05). On the contrary, we found that LV EF measured by the biplane 2D Simpson's technique was significantly lower in patients during the AS-VP mode (group I) than the controls (P < 0.05) [Table 1].

By 2-D speckle-tracking echocardiography, the patients during the AS-VP mode (group I) had statistically significant lower global LV LSS when compared with the control (P < 0.001) [Table 2].
Table 2: Comparison between the controls and patients during the atrial sensed ventricular paced mode (group I) regarding regional and global left ventricular longitudinal systolic strain

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As regards regional LV LSS, most LV segments had significantly lower LSS in the patients during the AS-VP mode (group I) when compared with the controls. Moreover, the apical segments had the lowest values (P < 0.001) [Table 2].

Programming the pacemakers from the AS-VP mode (group I) to AP-VP mode at a rate of 100 b/min in (group II) showed a significant decrease in both global and regional LV LSS. Moreover, the programming of asynchronous ventricular pacing (VVI mode) at a rate of 100 b/min in group III demonstrated a further reduction of both global and regional LV LSS when compared with both groups (P < 0.05) [Table 3] and [Figure 3].
Figure 3: Linear comparison between the patients during the AS-VP mode (group I), AP-VP mode (group II), and during the VVI mode (group III) regarding global LV longitudinal systolic strain. 2-D, two dimensional; AP-VP, atrial paced ventricular paced mode; AS-VP, atrial sensed ventricular paced mode; LV, left ventricular.

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Table 3: Comparison between patients during the atrial sensed ventricular paced mode (group I), atrial paced ventricular paced mode (group II), and VVI mode (group III) regarding regional and global left vetricular longitudinal systolic strain

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  Discussion Top


The use of pacemakers was shown to have a marked effect on the quality of life of patients with bradyarrhythmia [12]. However, serious clinical consequences may occur due to myocardial dysfunction caused by apical pacing [13]. Pacing with implantable cardiac devices had a slower electrical conduction velocity than normal conduction as well as abnormal sequences of myocardial activation [14].

One of the serious consequences of RV pacing is the development of pacing-induced cardiomyopathy (PICM), which is known as a significant drop in LV EF in a patient with high pacing percentage of RV when no other possible cause is detected [15],[16].

Dyssynchrony is considered one of the several mechanisms that RV pacing can cause myocardial dysfunction. Pacing of RV apex leads to both interventricular and intraventricular dyssynchrony, which in turn reduces LV systolic function and leads to adverse clinical outcomes [17]. Long-term studies suggested that more than 40% of RV pacing in modulated dual-chamber pacemaker with rate modulation mode is predictive of unfavorable events such as heart failure hospitalization [3],[18].

Moreover, restoration of ventricular synchrony by cardiac resynchronization therapy resulted in improved systolic function of LV and improved clinical outcomes [19]. This suggests that the abnormal ventricular activation pattern during pacing may be the cause of LV function deterioration [20].

Based on the aforementioned studies regarding the consequences of RVA pacing on the heart and their effect on clinical outcomes, our study investigated the effect of pacing of RV on global and regional LV function using 2-D speckle-tracking echocardiographic strain techniques in comparison to controls. In addition, we evaluated the change in global LV longitudinal strain upon programming the DDD pacemaker from the AS-VP mode to AP-VP mode and to VVI mode.

When we measured the LV EF by M-mode, we did not observe any statistical difference between the controls and the patients during the AS-VP mode (group I). On the contrary, we found that LV EF measured by the biplane 2-D Simpson's technique was significantly lower in patients during the AS-VP mode (group I) than the controls. This can be explained as the EF in M-mode is measured across the basal, septal, and posterior walls and is limited by excessive geometric simplification leading to inaccurate values when abnormal wall motion is present, especially in the apical regions [9]. Simpson's method is based on the summation of smaller volumes to obtain the overall LV volume, which can provide a better evaluation of LV function especially in the presence of abnormal motion of the septum during the activation by RVA pacing [9].

Our results coincided with Burns et al. [21], who provided evidence that mechanical dyssynchrony induced by RVA pacing was associated with reduced LV function even when LV function was normal before pacing. Pacing of RV acutely increases intramural dyssynchrony in normal hearts. After chronic pacing, intramural dyssynchrony persists and intraventricular dyssynchrony may become evident. Pacing-induced LV dysfunction may be caused by intramural dyssynchrony [22].

By 2-D speckle-tracking echocardiography, the patients during the AS-VP mode (group I) had statistically significant lower global LV LSS when compared with the control. As regards regional LV LSS, most LV segments had significantly lower LSS in patients during the AS-VP mode (group I) when compared with the controls. Moreover, the apical segments showed the most significant difference in reduction.

Similarly, Burns et al. [21] observed that LV longitudinal shortening decreased acutely in a significant pattern in the pacing of RV apex. Affections of longitudinal strain were even more evident than circumferential strains. Moreover, differences in strain were most evident when measured at the apex and midventricle, rather than at the LV base. Interestingly, the degree of shortening in the early-activated regions of LV was lower than in the other regions, causing a decrease in the global LV strain in pacing [23]. Liu et al. [24] studied the acute effects of RVA on LV function using real-time 3-D echocardiography in patients who had sick sinus syndrome, and they found that RVA pacing-induced interventricular and intraventricular mechanical delays that led to a reduction of LV systolic function.

Our results aligned with a study by Liang et al. [25] which showed that RVA pacing resulted in a decrease in longitudinal strain values near pacing sites (apical segments) compared with remote regions (middle and base segments), indicating that RV apex pacing has an unfavorable impact on LV strain. Chin et al. [26] used global LSS as a predictor of RVA PICM. In their study, PICM was defined as an LV EF decrease more than or equal to 10% from the preimplant EF that results in an LV EF less than 50%. They concluded that PICM was evidenced by reduced global longitudinal strain values in patients with subclinical LV systolic dysfunction. These patients warrant a closer follow-up with a lower threshold for biventricular pacing.

In our study, programming the pacemakers from AS-VP mode (group I) to AP-VP mode at a rate of 100 b/min in group II showed a significant decrease in both global and regional LV LSS.

Hettrick et al. [27] observed that atrial pacing has been shown to reduce the overall LV stroke volume due to impaired filling caused by atrial dysfunction. In the Liang et al. [25] study, atrial pacing in DDD mode resulted in suboptimal ventricular diastolic filling and consequently stroke volume compared with intrinsic atrial-derived rhythm in VDD mode. In addition, they also demonstrated atrial mechanical dysfunction reflected by decreased active atrial strain caused by atrial pacing in DDD mode. In their study, although LV EF was not statistically different between VDD (ventricular-only pacing) and DDD (dual-chamber pacing) modes, the more sensitive strain measurements demonstrated statistically significant differences in the global strain of LV. This indicated that the LV systolic function is indeed lower in DDD mode due to the direct deleterious effect of atrial pacing on the atrium leading to indirect effects on the LV strain. Therefore, they concluded that atrial pacing in DDD mode led to atrial dysfunction causing decreased LV preload and consequently reduced LV systolic mechanics, resulting in suboptimal LV performance when compared with the VDD mode.

In our study, the programming of asynchronous ventricular pacing (VVI mode) at a rate of 100 b/min in group III demonstrated a further reduction of both global and regional LV LSS when compared with both groups.

Dual-chamber pacing during the AS-VP mode maintains physiological A-V synchrony. This is important as the atrial contribution to ventricular filling is extremely valuable as a result of LV diastolic and systolic pacing-induced dysfunction. Loss of A-V synchrony during the VVI mode has a deleterious impact on ventricular filling and may even lead to occasional simultaneous atrioventricular contractions, which can lead to pacemaker syndrome. A substudy of the mode selection trial (MOST) showed that pacing of RV was strongly associated with heart failure, hospitalization, and atrial fibrillation in both 'physiologic pacing' (dual-chamber pacing, n = 707) and ventricular pacing (single-chamber ventricular pacing, n = 632). They observed that ventricular pacing more than 40% in the DDD group and more than 80% in the VVI group was closely related to heart failure and hospitalization [3],[12].

Limitations

The sample size was relatively small, and the data resulting from this study should be considered as preliminary observations. Larger studies with a greater number of patients should be conducted to validate our results. Coronary angiography was not performed to rule out coronary artery disease as an additional cause that can affect strain values. This was due to the absence of indications for further coronary evaluation.


  Conclusion Top


Permanent RVA pacing leads to marked changes of LV systolic function. Moreover, atrial pacing and asynchronous ventricular pacing may cause more deterioration of LV global and regional systolic longitudinal strain detected by 2-D speckle-tracking echocardiography.

Acknowledgements

Authors' contributions: authors' contributions: equal sharing between authors as regards writing of the manuscript, collection and analysis of data and revision of the final manuscript; all authors have read and approved the manuscript.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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