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European Journal of Heart Failure 2004 6(2):203-212; doi:10.1016/j.ejheart.2003.10.008
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© 2003 European Society of Cardiology

Improvement of left ventricular wall synchronization with multisite ventricular pacing in heart failure: a prospective study using Doppler tissue imaging{star}

Stephane Lafittea,*, Stephane Garrigueb, Jean-Marie Perrona, Pierre Bordacharb, Sylvain Reuterb, Pierre Jaïsb, Michel Haïssaguerreb, Jacques Clementyb and Raymond Roudauta

a Echocardiography Laboratory Hopital Cardiologique du Haut-Leveque, Pessac Cedex 33600, France
b Clinical Electrophysiology and Cardiac Pacing Department Hopital Cardiologique du Haut-Leveque, Pessac Cedex 33600, France

* Corresponding author. Present address: Department of Echocardiography, Hôpital Cardiologique du Haut-Lévêque, 19, Avenue de Magellan, Pessac Cedex 33604, France. Tel.: +33-5-57-65-65-65x75516; fax: +33-5-57-65-50-12. E-mail address: stephane.lafitte{at}chu-bordeaux.fr


   Abstract
Top
 Notes
 Abstract
1. Introduction
 2. Methods
 3. Results
 4. Discussion
 5. Conclusion
 References
 
We sought to assess right, left and biventricular pacing effects on myocardial function by using pulsed-Doppler tissue imaging (DTI) and automated border detection (ABD) techniques which provide electromechanical delay (EMD) assessment of the different left ventricular walls.

Methods: 15 patients (67±7 years) with drug-resistant primitive dilated cardiomyopathy and QRS≥140 ms received a pacemaker for multisite ventricular pacing. Echocardiography was performed after 1 month of biventricular pacing (BVP). Echocardiographic measurements were recorded during spontaneous rhythm (SpR), right ventricular pacing (RVP), left ventricular pacing (LVP) and BVP.

Results: LV ejection fraction was statistically similar between the four rhythms. BVP showed a significant EMD decrease for the lateral LV wall vs. SpR, RVP and even LVP. LVP resulted in significantly longer aortic pre-ejection time vs. BVP while the EMD temporal dispersion (time between the shortest regional EMD and the longest one) was similar in the two modes.

Conclusions: BVP and LVP substantially reduce the EMD temporal dispersion of the four LV walls, but with a longer aortic pre-ejection time for LVP. In RVP, LVP and BVP, the septal LV wall is always activated later than during SpR. BVP and LVP are associated with a mitral regurgitation reduction.

Key Words: Cardiac resynchronization therapy • Left ventricular pacing • Tissue Doppler imaging • Heart failure • Ventricular asynchrony

Received June 26, 2003; Revised July 31, 2003; Accepted October 13, 2003


   1. Introduction
Top
 Notes
 Abstract
 1. Introduction
2. Methods
 3. Results
 4. Discussion
 5. Conclusion
 References
 
Biventricular pacing (BVP) is a novel and promising therapy for patients with dilated cardiomyopathy. Recently, several acute prospective studies [1–5] sought to quantify the benefits of left or left and right ventricular pacing for hemodynamic improvement in heart failure patients. BVP mode was shown to acutely reduce the pulmonary capillary wedge pressure and to increase the cardiac output [1,3] which might be due to shortening of the ventricular electrical activation (QRS complex narrowing), improving mechanical synchronization of the left ventricular (LV) wall segments. However, standard investigative tools cannot provide clear information on the effects of myocardial wall synchronization.

Conventional two-dimensional echocardiography is an effective but limited tool for measuring systolic and diastolic left ventricular wall thickness and performance [6–8]. Similarly, Doppler flow data which provide indices of global function, strongly depends on cardiac workload with a significant inter-measurement variability. New echocardiographic modalities allowing regional electromechanical assessment have recently become available [9]. In this context, Doppler tissue imaging (DTI) provides a Doppler spectrum of segmental myocardial mechanics, which allows reliable and reproducible quantification of local ventricular velocity and respective electromechanical delay [10,11]. Automated Border Detection mode by radio-frequency analysis allows continuous measurement of left ventricular volume during the cardiac cycle [12,13].

This prospective study was designed to assess the degree of synchronization associated with the systolic shortening amplitude of the myocardial LV segments in heart failure patients by using DTI and ABD during multisite ventricular pacing.


   2. Methods
Top
 Notes
 Abstract
 1. Introduction
 2. Methods
3. Results
 4. Discussion
 5. Conclusion
 References
 
2.1. Inclusion criteria
Patients with idiopathic cardiomyopathy were considered for inclusion if they presented with severe cardiac heart failure, as defined by: class III or IV according to the New York Heart Association (NYHA), despite medical treatment including diuretics and ACE inhibitors at optimal doses for every patient, a left ventricular ejection fraction (LVEF) assessed by radionuclide angiography of less than 35%, left ventricular end-diastolic diameter ≥60 mm, a QRS duration ≥140 ms and a PR interval >150 ms measured in three leads at least of the surface ECG during spontaneous rhythm. They were also required to have a suitable acoustic window for reliable echocardiographic analysis. All patients received a pacemaker providing biventricular pacing after written informed consent approved by our local and national Ethics Committee.

2.2. Exclusion criteria
Patients were excluded if they were less than 18 or more than 80 years of age, and if they had history of unstable angina pectoris, acute myocardial infarction, percutaneous coronary angioplasty or coronary artery bypass grafts.

2.3. Biventricular pacing implantation procedure
Fifteen patients (14 males, one female, mean age: 67±7 years) formed the study group. Their clinical characteristics are presented in Table 1. All patients received a three lead-cardiac pacemaker: one lead screwed in the right atrial appendage and the right ventricular lead placed at the apex. The left ventricular lead was placed in a lateral vein at the middle portion in 10 patients (66%) whereas five patients (33%) had their left ventricular lead placed at the mid segment of an antero-lateral vein through the coronary sinus. The atrial lead was connected to the atrial channel of a dual-chamber pacemaker and the two ventricular leads were connected to the pacemaker ventricular channel all together via a Y connector. Bipolar ventricular stimulation allows biventricular pacing while the unipolar mode permits left ventricular stimulation.


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  		Table 1 Clinical, echocardiographic and hemodynamic characteristics of patients

 
2.4. Evaluation of the parameters
One month after implant, echocardiographic examination was performed by an independent observer (an echocardiographer) in spontaneous rhythm (SpR), right ventricular pacing (RVP), left ventricular pacing (LVP) and BVP in random order. The three studied pacing modes were assessed in VDD pacing configuration, so that the spontaneous sinus rate was similar in each patient for every pacing configuration. For each pacing mode, the atrio-ventricular delay was echocardiographically optimized so that it provided the longest filling time for completion of the end-diastolic filling flow prior to left ventricular contraction [14]. Furthermore, in order to ensure complete capture during RVP, LVP and BVP, the morphology and the QRS width of the QRS complex were verified to be similar between the VVI and VDD pacing mode.

The first part of the echocardiographic study was a conventional examination performed with a VIVID SEVEN (GENERAL ELECTRIC) equipped with a 2–3 MHz transducer. For all rhythm modes, measurements of end-diastolic, end-systolic diameters and shortening percentage calculation were obtained from a parasternal long axis view with criteria recommended by the American Society of Echocardiography. The aortic Doppler flow was recorded in pulsed mode from the apical four chamber view. The maximal aortic velocity was measured as well as the time-velocity integer and the aortic ejection delay defined as the delay between the start of the electrocardiographic QRS and the start of the aortic spectrum. On the same view, we also measured the mitral regurgitation area using color Doppler without gain modification during the stimulation mode changes (maximum 10 s). Mitral Doppler flow was also recorded to measure both E and A wave maximal velocities and the total diastolic filling time.

Left ventricular real time cavity dimensions were obtained by automated border detection (ABD) on a Sonos 2500 Hewlett-Packard system equipped with the acoustic quantification mode. An apical four chamber view was used. Depth gain and lateral gain were adjusted for each patient as well as the dynamic range and filters. Exclusion criteria for the ABD validation were endocardial detection less than 80% and intra-cavity artefact area more than 1 cm2.

In order to avoid any measurement variation from the transducer position, the probe was kept in the same place on the chest by the echocardiographer, while an other physician changed the pacemaker settings from SpR to RVP, LVP and BVP stimulation modes in random order. Left ventricular volume was extrapolated automatically by the system from the cavity area using the disc method. End-diastolic volume, end-systolic volume, ejection fraction and global time–volume curve were recorded during brief apnea. The time–volume curve was digitized off line to measure the systolic time, the relaxation time, the diastasis time, the systolic slope and the relaxation slope.

DTI examination was performed using the pulsed Doppler mode. Acoustic power, gain, dynamic range and filters were set for each myocardial area analyzed with all available stimulation modes (SpR, RVP, LVP, BVP) as performed during ABD acquisition. The Doppler window was only changed after complete recordings were obtained for all four modes in a random order, to analyze exactly the same myocardial segment with the different pacing modes. The explored areas were, respectively, the basal septum, the basal lateral wall, the basal inferior wall and the basal anterior wall. From the Doppler spectrum, the electro-mechanical delay (EMD-defined as the delay between the onset of the QRS complex on the surface ECG and the onset of the systolic DTI wave) were measured as well as the maximal peak velocity of the S wave during SpR, RVP, LVP and BVP [11,15,16]. The intra-observer correlation for the DTI parameters quantification was assessed in 10 patients and reached 0.92, which shows high reproducibility.

2.5. Statistics
Quantitative variables were assessed by using the analysis of variance design with repeated measurements according to the SpR, RVP, LVP and BVP modes for the same patient. The exact Fisher test was performed for qualitative variables. The Spearman coefficient (non-parametric test) was used to quantify and to assess the correlations between quantitative variables. A P-value<0.05 was considered as significant. All data are presented as mean±S.D. or %.


   3. Results
Top
 Notes
 Abstract
 1. Introduction
 2. Methods
 3. Results
4. Discussion
 5. Conclusion
 References
 
Clinical and hemodynamic characteristics of the 15 patients are given in Table 1. LVEF assessed by radionuclide ventriculography was 26.4±4.7% and the mean echocardiographic LV end-diastolic diameter was 70±8 mm. Biventricular pacing provided a mean reduction of the QRS duration of 25% (from 163±17 to 139±37 ms, P<0.05). After 1 month of BVP, all patients observed a significant functional improvement. The 5 patients in NYHA class IV improved to class III and the 10 class III patients changed to class II, without any modification of drug therapy.

3.1. Standard echocardiography
Data are shown in Table 2. No significant difference was observed between SpR, RVP, LVP and BVP for the aortic VTI parameter (Table 2). The aortic ejection delay was the shortest during BVP compared with the other pacing modes and SpR (P<0.01), whereas LVP provided the longest one (P<0.01). A significant decrease of the area of mitral regurgitation was seen during BVP (4.6±3.5 cm2) compared with SpR (9.6±5.2 cm2, P<0.01) and RVP (8.7±3.7 cm2, P<0.05). The reduction in the area of mitral regurgitation with LVP (6.4±3.4 cm2) compared with SpR almost reached significance (P=0.069). There was no significant difference in terms of mitral flow parameters (E and A waves) but a tendency to the increase of the flow duration with BVP (Table 2).


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  		Table 2 Doppler flow parameters with the four modes of pacing

 
3.2. Real time left ventricular dimensions variations obtained with the ABD modality
Analysis of left ventricular area changes by ABD permitted the identification and measurement of the different phases of the cardiac cycle. No significant difference was observed for the LV end-diastolic volume, the LV systolic volume between spontaneous rhythm and two stimulation modes (SpR, LVP, BVP) (Table 1). In contrast, the time–volume curves were modified with BVP and LVP. The relaxation time interval was significantly reduced with BVP compared with SpR and LVP (respectively, 26±8% vs. 43±4% and 41±7%, P<0.05). The diastasis time duration was significantly increased with BVP (BVP: 38±6%, SpR: 18±8%, LVP: 23±6%, P<0.05). The systolic slope was significantly higher with BVP (59±7°) and LVP (64±9°) compared with SpR (49±8°; P<0.01). The relaxation slope was significantly steeper with BVP compared with LVP and SpR (BVP: 66±5° vs. SpR: 47±5°, P<0.05, and vs. LVP: 59±8°, P=0.05) (Fig. 1).


Figure 1
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  		Fig. 1 This figure shows the results of Automated Border Detection (ABD) analysis: The top panel shows the 5 parameters obtained with ABD: 3 time phases, the systole, relaxation and diastasis phases and 2 slopes, the systolic slope and the relaxation slope [12,13]. The bottom panel exhibits the different mean values (as a percentage of the cardiac cycle duration) of each phase and slope with BVP, SpR, and LVP. BVP provided a significant decrease of the relaxation duration allowing a significant increase of the diastasis time. Both LVP and BVP provided a significant increase of the relaxation and systolic slope compared with those observed during SpR. *P<0.05 compared with SpR.

 
3.3. DTI parameters
3.3.1. Electromechanical delays
Fig. 2 shows in a patient the EMD calculation for the septal and the lateral LV wall with SpR. The temporal dispersion between the two EMDs was 73 ms. Fig. 3 illustrates in the same patient the respective EMDs calculation with BVP. Although the EMD for the septal wall goes from 100 ms with SpR to 140 ms with BVP, the EMD for the lateral wall was shortened from 173 ms with SpR to 160 ms with BVP. This resulted in a substantial reduction of the temporal time-dispersion between the two EMDs with BVP. For this patient, when the pacemaker was switched to left ventricular pacing, the EMD calculation for the septal LV wall was 170 ms whereas the EMD for the lateral LV wall reached 213 ms, i.e. data better than spontaneous rhythm but worse than BVP.


Figure 2
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  		Fig. 2 The top panel shows in a patient with sinus rhythm and spontaneous atrio-ventricular conduction the value of the EMD calculated for the septal LV wall (100 ms) whereas the QRS duration reaches 165 ms. The EMD was calculated as defined in the methods. The bottom panel shows a much longer calculated EMD for the lateral LV wall (173 ms), revealing a highly heterogeneous LV systolic sequence.

 


Figure 3
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  		Fig. 3 The top panel shows in the same patient as Fig. 1 but with BVP the value of the EMD calculated for the septal LV wall (140 ms). This value is higher than that obtained with spontaneous rhythm (Fig. 1) although the QRS duration was reduced with BVP (130 ms). This can be explained by the EMD of the lateral LV wall shown on the bottom panel with a noticeable time shortening (160 ms). With BVP, the time difference between the septal and the lateral LV walls was reduced to 20 ms instead of 73 ms observed in Fig. 1.

 
Fig. 4 summarizes all the data of all 15 patients. There was a significant increase in terms of EMD for the anterior LV wall during BVP, LVP and RVP compared with SpR (P=0.02) and same tendency was observed for the septal LV wall (Fig. 4). In contrast, BVP showed a significant decrease of EMD for the lateral LV wall compared with the three other rhythm modes, P<0.01 (BVP: 195±36 ms, SpR: 235±44 ms, RVP: 248±45 ms, LVP: 239±46 ms). Concerning the inferior LV wall, BVP significantly shortened the EMD only when compared with LVP (respectively, 194±41 vs. 248±43 ms, P<0.05).


Figure 4
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  		Fig. 4 The electromechanical delay (EMD) was defined as the delay between the onset of the QRS and that of the S wave in regard of the lateral, septal, inferior and anterior walls. The spontaneous rhythm (SpR) is the reference for comparisons with right ventricular pacing (RVP), left ventricular pacing (LVP) and biventricular pacing (BVP). The EMD was significantly shorter with BVP compared with SpR for the lateral wall. In contrast, LVP provided longer EMDs for the inferior and anterior LV walls compared with SpR. *P<0.05.

 
Fig. 5 depicts on a time scale the mean values of the four LV wall EMDs for each pacing configuration and SpR. The longest EMD was observed for the lateral LV wall and the shortest for the septal LV wall. The maximum difference between EMDs was the largest during spontaneous rhythm (65±8 ms) while it was the smallest with BVP (29±6 ms, P=0.01). RVP and LVP resulted in larger EMD differences compared with BVP but significantly smaller compared with SpR (respectively, 44±8 ms and 38±9 ms; P=0.01). The EMD temporal dispersion was finally the shortest in BVP compared to SpR, RVP and LVP.


Figure 5
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  		Fig. 5 The mean values (15 patients) of the EMDs related to each of the four studied LV walls are represented on a time scale. The EMD is defined as the time delay between the onset of the QRS and the onset of the S wave of a given LV wall segment obtained with the DTI technique. EMD temporal dispersion represents the time duration between the shortest LV wall EMD and the longest one. The longer the EMD temporal dispersion, the more important would be the heterogeneity of the LV systolic sequence. High heterogeneity is observed with SpR and RVP compared with LVP and BVP for which the EMD temporal dispersion is significantly reduced (see text for details). Notice that the degree of dispersion was statistically comparable between LVP and BVP, although earlier systolic motion was observed with BVP for each LV wall. (S: septal LV wall. A: anterior LV wall. I: inferior LV wall. L: lateral LV wall).

 
3.3.2. Wall velocities
The systolic wall velocity was significantly increased for the lateral wall during BVP compared to SpR, RVP and LVP (BP: 8.2±2 cm/s, SpR: 6.2±1.4 cm/s, RP: 6.5±2 cm/s, LP: 6.8±1.4 cm/s, P<0.05). A wall velocity increase tendency was also observed for the inferior wall but without significant difference. No improvement of the LV wall velocity was observed for the anterior and septal LV walls (Fig. 6).


Figure 6
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  		Fig. 6 The myocardial wall velocity was obtained with the Pulsed-Doppler Tissue Imaging applied to the lateral, septal, inferior and anterior LV walls with the three pacing configurations and spontaneous rhythm. As a possible consequence of the EMD decrease for the lateral wall, the velocity in regard of this LV area was significantly increased. *P<0.05.

 

   4. Discussion
Top
 Notes
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
5. Conclusion
 References
 
This study shows that DTI can quantify the role of multisite ventricular pacing on regional contractility and electromechanical delays in patients with chronic heart failure. We deliberately chose the option to limit our investigations to non-invasive echocardiographic assessment of the LV function, since previous studies have already well characterized changes in conventional hemodynamic parameters with left, right and biventricular pacing modes [1–4,17]. Biventricular pacing was found to provide the best hemodynamic benefits compared with right or left ventricular pacing. Several investigators have hypothesized that biventricular pacing can provide a more coordinated pattern of contraction [16–23]. Although Kass et al. [4] demonstrated that ventricular systolic pressure changes relate primarily to direct improvement of LV systolic function, non-invasive tools such as the DTI are needed for better quantification and analysis of the phenomenon. Indeed, by calculating the regional electromechanical delays of the different LV walls and their respective systolic motion velocities, we could accurately estimate the local effect on the left ventricle of the three tested pacing modes. We demonstrated that the tendency of aortic VTI values enhancement is primarily due to better homogeneity of local electromechanical delays of the different LV walls and the increase in LV wall systolic motion velocities. Furthermore, this study characterizes the relationship between the shortening of the EMDs of the LV walls and a resulting longer diastolic phase. Since LV wall systolic motion is better synchronized, there is a steeper relaxation slope (with a shorter relaxation time-phase) permitting a much longer diastasis phase which results in better LV filling (Fig. 1). These data strongly suggest that biventricular pacing provides a steeper and more efficient relaxation phase and consequently, more time for more effective diastasis leading to better left ventricular filling (Fig. 1).

4.1. Mechanisms of biventricular pacing effects
We selected patients with major intraventricular conduction block in spontaneous rhythm. Leclercq et al. [3] and Alonso et al. [24] suggested that the wider the QRS complex, the greater would be the LV contraction time. Yet, several authors strongly suggested that left ventricular pacing alone could provide substantial acute hemodynamic improvement but with wider QRS complexes [2,4,17,25,26]. Prinzen et al. [18] and Wyman et al. [19] suggested that the sequence of electrical activation is a stronger determinant of ventricular function than the synchrony of activation. Accordingly, these controversies have led us to consider other parameters to better characterize the mechanisms of biventricular pacing in patients with wide QRS and severe heart failure.

If we compare data of SpR to those of BVP, BVP prolonged the EMD for septal and anterior LV walls although those of the lateral LV walls were significantly shortened. This resulted in better homogenization (and not overall EMDs shortening) of the four EMDs to which could be attributed the hemodynamic improvement. Furthermore, not only the EMDs were shorter for the lateral LV wall, but also higher systolic motion velocities were observed compared with spontaneous rhythm and also right and left ventricular pacing mode (Fig. 6). Fig. 7 clearly illustrates this tendency showing that shortening of the time difference between the septal and lateral EMDs is positively correlated to the systolic motion velocity of the lateral LV wall.


Figure 7
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  		Fig. 7 Correlation between the lateral LV wall systolic velocity and the degree of LV walls synchronization evaluated by the difference between the lateral and septal LV wall EMDs. The shorter this time difference, the greater the lateral LV wall systolic velocity with a highly significant correlation considering a parabolic curve shape (r2=0.53; P<0.0001).

 
Shortening the electromechanical delays leads to increasing the diastasis time (Fig. 6). Indeed, the contractile function of individual myocytes is predominantly determined by calcium release during the systolic phase and calcium re-uptake during the diastolic phase [27–29]. The calcium uptake by the sarcoplasmic reticulum is ensured by the calcium activated-ATPase within the sarcoplasmic reticulum. Accordingly, heart failure results from altered contractile function that is in part caused by a decreased calcium uptake during the diastolic phase. Resynchronization-induced diastasis time increase probably yields improvement in calcium uptake and consequently induces a better contractile function of myocytes as suggested from the increase in S waves amplitude characterized with the Tissue Doppler Imaging technique.

4.2. Left ventricular pacing
We did not find any difference in terms of LV ejection fraction compared with spontaneous rhythm or right or biventricular pacing mode. In contrast, the anterior wall systolic motion velocity looked to be greater in left ventricular compared with that of the other rhythm modes. The temporal time-dispersion between the shortest EMD and the longest one was observed to be still significantly smaller than with RVP and SpR. This new data is in accordance with that of Blanc et al. [2] and Auricchio et al. [5] who suggested that activation of the left ventricle, rather than activation of both ventricles simultaneously, may be the most important factor in achieving benefit from pacing therapy in heart failure patients. In our case, the LV epicardial lead was advanced to a tributary of the great cardiac vein over the proximal (or mid-) part of the antero-lateral or lateral left ventricular wall. Another lead location would have certainly provided different results, which is in accordance with other studies [20–22,30,31]. Indeed, location of the fibrosis areas in patients with primitive cardiomyopathy might play an important role in the sequence of electromechanical activation by creating unidirectional conduction blocks. Due to the high inter-individual variation of this parameter (degree of ventricular fibrosis), it is difficult to gather a truly harmonious population representative of the entire population of patients with dilated primitive cardiomyopathy. It is likely that many other propagation patterns exist without any doubt.

LVP is provided from an epicardial lead so that the electrical activation time is substantially prolonged compared to endocardial stimulation, i.e. RVP or BVP [30,32–34]. Consequently, electro-mechanical activation is also prolonged even if it is harmonious. Then, although the systolic aortic ejection phase is delayed from the onset of the QRS, the EMD temporal dispersion is reduced compared to spontaneous rhythm and RVP (Fig. 4). It is likely that the further the LV lead is from the septum, the longer the LV pre-ejection time. Indeed, in every pacing mode (BVP, RVP and LVP), the septal wall was the first electromechanically activated (Fig. 4). It is conceivable that it takes much more time to activate the septum from a remote epicardial LV lead than from a RV endocardial lead, which explains why the LV pre-ejection time was shorter with RVP as well as BVP compared to LVP.

However, our study suggests that the left ventricle is more homogeneously activated with two stimulation sites than a single one from the left ventricle. This confirms that the apical right ventricular lead is responsible for an important part of left ventricular activation, which might be activated later by the left ventricular pacing lead [30].

4.3. Limitations
This is an acute non-invasive hemodynamic study so that these short-term results may not reflect long-term responses. Our patients sample was small due to the severity of our inclusion criteria as well as the necessity of a very good acoustic echocardiographic window for suitable and reliable measurements. Our results strongly depend on the location of the left coronary sinus ventricular lead which was placed, as far as possible, in regard of the same left ventricular area for all the patients. One month of biventricular pacing might already have induced changes in LVEDD, mitral regurgitation and LV filling [21]. Yet, we could observe significant differences between spontaneous rhythm (after 1 month of BVP) and the three pacing modes. This indicates that despite the 1-month period of BVP, changing the pacing mode still substantially and acutely modifies electromechanical and hemodynamic parameters. Accordingly, we probably underestimated those differences that are likely to be more marked without the 1-month period of BVP. However, we had some important ethical concerns about turning off BVP after implant since those patients were symptomatic; the local ethical committee would not permit us to design such a protocol. In addition, we wanted to wait 1 month in order to perform the study with a stable position of the pacing leads.


   5. Conclusion
Top
 Notes
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 5. Conclusion
References
 
Biventricular pacing can hemodynamically improve patients with end-stage heart failure and complete left bundle branch block. For that purpose, we propose a non-invasive echocardiographic procedure allowing analysis and measurement of the regional electromechanical delays as well as the amplitude of the systolic motion velocities for the different left ventricular walls. The underlying mechanism of BVP-induced clinical improvement might be related to better homogeneity of the respective regional electromechanical delays resulting in shorter ejection phase and longer left ventricular filling time. Left single-site ventricular pacing has also been shown as providing better LV wall systolic synchronization even if delayed compared with BVP.


   Notes
Top
 Notes
Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 5. Conclusion
 References
 
{star} The first two authors contributed equally to this work. Back


   References
Top
 Notes
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 5. Conclusion
 References
 

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