Left Ventricular Apical Pacing Research Articles

The Ventricular Hypokinesis at the Apical Pacing Site due to the Early Shortening and Rebound Stretch in a Case with Fontan Procedure.

The left ventricular (LV) apex is recommended as the first choice for positioning the epicardial pacing. We encountered a patient with congenital heart disease (CHD) showing hypokinesis of the LV apical pacing site after implantation of a pacemaker with epicardial leads. This phenomenon was revealed by the early shortening and systolic rebound stretch of the same lesion on two-dimensional speckle tracking echocardiography, which developed in the intraventricular dyssynchrony between the LV apex and base. Cardiac resynchronization therapy provided an excellent result around the hypokinetic lesion. It is wise to arrange detailed evaluations in each patient with complicated CHD, aiming at a successful treatment to enable ventricular synchronicity.

Is left ventricular superior to right ventricular pacing in children with congenital or postoperative complete heart block?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was 'Is left ventricular superior to right ventricular pacing in children with congenital or postoperative complete heart block?' Altogether, 19 papers were found using the reported search, of which 9 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. Two large multicentric showed that site of pacing was the major determinant of left ventricular (LV) function with LV pacing being superior to RV pacing, though the number of patients paced via LV was lesser in comparison to right ventricular (RV). There were 2 prospective, 2 retrospective and 1 cross-sectional studies with fewer patients that demonstrated superiority of LV over RV pacing in preserving LV function. Only 1 small-scale retrospective study showed similar results of LV and RV pacing on LV function. One cross-sectional study showed superiority of LV apical pacing on exercise tolerance. As per the existing literature, LV apex seems to be the most optimal site for epicardial pacing while RV free wall pacing has the highest risk of causing LV dysfunction over the long term. We conclude that LV pacing appears to be superior to RV pacing in terms of long-term effect on cardiac function and ventricular synchrony.

Left ventricular apical pacing in children: feasibility and long-term effect on ventricular function

Left ventricular apical pacing (LVAP) has been reported to preserve left ventricular (LV) function in chronically paced children with complete atrioventricular block (CAVB). We sought to evaluate long-term feasibility of LVAP and the effect on LV mechanics and exercise capacity as compared to normal controls. Thirty-six consecutive paediatric patients with CAVB and LVAP in the absence (N = 22) or presence of repaired structural heart disease (N = 14, systemic LV in all) and 25 age-matched normal controls were cross-sectionally studied after a median of 3.9 (interquartile range 2.1-6.8) years of pacing using echocardiography and exercise stress testing. Pacemaker implantation was uneventful and there was no death. Probability of the absence of pacemaker-related surgical revision (elective generator replacement excluded) was 89.0% at 5 years after implantation. Left ventricular apical pacing patients had lower maximum oxygen uptake (P = 0.009), no septal to lateral but significant apical to basal LV mechanical delay (P < 0.001) which correlated with decreased LV contraction efficiency (P = 0.001). Left ventricular ejection fraction and global longitudinal LV strain were, however, not different from controls. Results were similar in both the presence and absence of structural heart disease. Left ventricular apical pacing is technically feasible with a low reintervention rate. Mechanical synchrony between LV septum and free wall is maintained at the price of an apical to basal mechanical delay associated with LV contraction inefficiency as compared to healthy controls. Global LV systolic function is, however, not negatively affected by LVAP.

P496Mid-term results of left ventricular apical pacing in pediatric patients with complete atrio-ventricular block

P496Mid-term results of left ventricular apical pacing in pediatric patients with complete atrio-ventricular block

Key Role of Pacing Site as Determinant Factor of Exercise Testing Performance in Pediatric Patients with Chronic Ventricular Pacing.

Chronic right ventricular (RV) apical pacing has been associated with deterioration of functional capacity and chronotropic incompetence during exercise testing in children. The effects of alternative pacing site on exercise performance in pediatric population remain unknown. We evaluated the influence of ventricular pacing site on exercise capacity in pediatric patients with complete congenital atrioventricular block requiring permanent pacemaker therapy. Sixty-four children paced from RV apex (n=26), RV midseptum (n=15) and left ventricular (LV) apex (n=23) were studied cross-sectionally. Treadmill exercise stress testing was performed according to modified Bruce protocol. LV apical pacing was associated with greater exercise capacity. In comparison with the other study groups, children with RV apical pacing showed significantly lower VO2peak (37±4.11; p=0.003), O2 pulse (8.78±1.15; p=0.006), metabolic equivalents (7±0.15; p=0.001) and exercise time (6±3.28; p=0.03). Worse values in terms of maximum heart rate (139±8.83bpm; p=0.008) and chronotropic index (0.6±0.08; p=0.002) were detected in the RV apical pacing group although maximal effort (respiratory exchange ratio) did not differ among groups (p=0.216). Pacing from RV apex (odds ratio 9.4; confidence interval 2.5-18.32; Wald 4.91; p=0.0036) and low peak heart rate achieved (odds ratio 3.66; confidence interval 0.19-7.4; Wald 4.083; p=0.015) predicted significantly decrease in exercise capacity. Duration of pacing, gender, VVIR mode, baseline heart rate and QRS duration had not significant impact on exercise capacity. The site of ventricular pacing has the major impact on exercise capacity in children requiring permanent pacing. Among the sites assessed, LV apex is related to the better exercise performance.

Differential Effects of Left Ventricular Pacing Sites on Regional Contraction Patterns and Global Performance.

To define the differential effect of site-specific ventricular counterpacing efficacy during cardiac resynchronization therapy (CRT) to identify the most informative imaging views to quantify it. Cross-sectional and long-axis views commonly are used to assess left ventricular (LV) contractility. The effects of LV apical (LVa) and free-wall (LVfw) pacing during CRT on long- and short-axis contraction, cardiac output, and stroke work were assessed in an open-chested acute canine model to determine whether LVa and LVfw would induce earlier apical than basilar LV radial contraction and earlier free-wall than septal contraction, respectively. Apical (CRTa) and free-wall (CRTfw) using right ventricular (RV) pacing-induced dyssynchrony also were examined. University large animal research laboratory. Ten acutely anesthetized and instrumented open-chested purpose-bred dogs. RV pacing served as the model of cardiac dyssynchrony. Selective LVfw and LVa pacing alone or with RV (CRTfw and CRTa, respectively) were studied relative to right atrial pacing (RA) as the control. Two pairs of 3 ultrasonic crystals were place along the LV longitudinal axis-apex and mid-to-base pairs along septal and free wall lines. Conductance catheter-defined longitudinal LV segmental volumes and pressure-volume data were collected. RV decreased cardiac output and stroke work compared with RA (2.0±0.3 v 1.4±0.1 L/min; 137±22 v 60±14 mJ; p<0.05, respectively). LVfw but not LVa decreased stroke work (130±35 mJ), and CRTa but not CRTfw improved both (2.1±0.2 L/min; 113±13 mJ; p<0.01 v RV pacing). No difference in time to minimal length free wall-to-septal crystal was seen with pacing. Both LVa and CRTa displayed increased apical-to-basilar shortening delay compared with RA, RV, and LVfw (42±47, 9±105, and 1±46 msec, respectively; p<0.05). No matching regional LV volume changes were seen during LVa. LV functional analysis from only a cross-sectional plane may be insufficient to characterize improved LV contraction synchrony during multisite CRT.

Right or Left Ventricular Pacing in Young Minipigs With Chronic Atrioventricular Block

Background— Left ventricular (LV) dyssynchrony may occur as a result of right ventricular (RV) pacing and is a known risk factor for the development of heart failure. In children with complete atrioventricular block, pacing-induced dyssynchrony lasting for decades might be especially deleterious for LV function. To determine the hemodynamic and ultrastructural remodeling after either RV free wall or LV apical pacing, we used a chronic minipig model. Methods and Results— Fourteen piglets 8 weeks of age underwent atrioventricular node ablation and were paced from either the RV free wall or the LV apex at 120 bpm for 1 year (7 age-matched minipigs served as controls with spontaneous heart rates of 104±5 bpm). Echocardiographic examinations, pressure-volume loops, patch-clamp investigations, and examinations of connexin43, calcium-handling proteins, and histomorphology were carried out. RV free wall–paced minipigs exhibited significantly more LV dyssynchrony than LV apex–paced animals, which was accompanied by worsening of LV function (maximum LV mechanical delay/LV ejection fraction: RV free wall pacing, 154±36 ms/28±3%, LV apical pacing, 52±19 ms/45±2%, control 47±14 ms/62±1%; P =0.0001). At the cellular level, both pacemaker groups exhibited a significant reduction in L-type calcium and peak sodium current, shortening of action potential duration and amplitude, increased cell capacity, and alterations in the calcium-handling proteins that were similar for RV free wall– and LV apex–paced animals. Conclusions— The observed molecular remodeling seemed to be more dependent on heart rate than on dyssynchrony. LV apical pacing is associated with less dyssynchrony, a more physiological LV contraction pattern, and preserved LV function as opposed to RV free wall pacing.

Echocardiographic study of left ventricular 3-dimension displacement during different ventricular pacing in vivo:a canine model

Objective To evaluate the changes of left ventricular(LV) 3-dimension peak displacement (3D-D) during different cardiac pacing patterns. To provide a reliable mechanical data base for the optimization cardiac pacing. Methods Cardiac pacings in open-chest Beagle canine models( n = 10) were performed using three patterns[I, e. , right ventricular apical pacing (RVA-P), LV lateral pacing (LVL-P)and LV apical pacing(LVA-P)],3D full volumetric real-time imaging were acquired in a completed cardiac cycle. The 3D-D,3D-D peak time (3D-DTc) and the standard deviation of TC(3D-DTSD) were calculated and analyzed in different pacing patterns for difference and spatial correlationship. Results ① The 3D-D of LVL-P and LVA-P state decreased compared with BASE and RVA-P state, there were significant 3D-D difference of mid anterior,mid anteriorspetal, mid interior,mid posterior, mid lateral between LVL-P and BASE, RVA-P patterns( P ＜0.05). There were significant 3D-D difference of mid anterior,mid lateral,mid posterior between LVA-P and RVA-P patterns groups( P ＜0.05). There were significant 3D-D difference of all segments in apical level between LVL-P,LVA-P and BASE, RVA-P states( P ＜0.05). ② Corrected by the heart rate,the 3D-DTC of different cardiac pacing patterns were shorter than BASE state. ③ There were no significant 3D-DTSD difference between different cardiac pacings and BASE patterns. There were significant 3D-DTSD difference between RVA-P and LVA-P patterns (P ＜ 0.05). Conclusions LV mechanical activation and synchronization could be maintained during RVA-P rather than LVA-P and LVL-P. Echocardiographic study of left ventricular 3D-D can actually reveal myocardial mechanical state during different cardiac pacings and BASE patterns. Key words: Echocardiography; three-dimensional; Cardiac pacing, artificial; Ventricular function, left

Differential effects of the site of permanent epicardial pacing on left ventricular synchrony and function in the young: implications for lead placement

To analyse left ventricular (LV) synchrony and function with respect to the epicardial pacing site in the young. Left ventricular function and synchrony (M-mode, speckle tracking) were evaluated during mid-term follow-up in 32 children with complete non-surgical (n = 15) or surgical (n = 17) atrioventricular block (structural heart disease in 21/32) paced from LV apex (n = 19), right ventricular (RV) apex (n = 7), and RV free wall (n = 6), respectively. Data are in the following order: LV apical, RV apical, and RV free wall pacing. Septal to posterior wall motion delay (SPWMD) = median 0, 69, and 136 ms (P < 0.001), septal to lateral mechanical delay = 54 +/- 29, 73 +/- 24, and 129 +/- 70 ms (P = 0.001), apical to basal mechanical delay = 96 +/- 37, 106 +/- 50, and 79 +/- 18 ms (P NS), and LV ejection fraction (LVEF) = 57 +/- 9, 49 +/- 12, and 33 +/- 10% (P < 0.001), respectively. Left ventricular ejection fraction correlated negatively with SPWMD (R(2) = 0.454, P < 0.001) and septal to lateral mechanical delay (R(2) = 0.320, P < 0.001) but not with apical to basal mechanical delay. Right ventricular free wall pacing (P = 0.014) and SPWMD (P = 0.044) were negative multivariable predictors of LVEF. Compared with other sites, LV apical pacing preserves septal to lateral LV synchrony and systolic function and may be the preferred epicardial pacing site in the young.

Left Ventricular Septal and Left Ventricular Apical Pacing Chronically Maintain Cardiac Contractile Coordination, Pump Function and Efficiency

Conventional right ventricular (RV) apex pacing can lead to adverse clinical outcome associated with asynchronous activation and reduced left ventricular (LV) pump function. We investigated to what extent alternate RV (septum) and LV (septum, apex) pacing sites improve LV electric activation, mechanics, hemodynamic performance, and efficiency over 4 months of pacing. After AV nodal ablation, mongrel dogs were randomized to receive 16 weeks of VDD pacing at the RV apex, RV septum, LV apex, or LV septum (transventricular septal approach). Electric activation maps (combined epicardial contact and endocardial noncontact) showed that RV apical and RV septal pacing induced significantly greater electric desynchronization than LV apical and LV septal pacing. RV apex and RV septal pacing also significantly increased mechanical dyssynchrony, discoordination (MRI tagging) and blood flow redistribution (microspheres) and reduced LV contractility, relaxation, and myocardial efficiency (stroke work/myocardial oxygen consumption). In contrast, LV apical and LV septal pacing did not significantly alter these parameters as compared with the values during intrinsic conduction. At 16 weeks, acute intrasubject comparison showed that single-site LV apical and LV septal pacing generally resulted in similar or better contractility, relaxation, and efficiency as compared with acute biventricular pacing. Acute and chronic LV apical and LV septal pacing maintain regional cardiac mechanics, contractility, relaxation, and efficiency near native levels, whereas RV apical or RV septal pacing diminish these variables. Acute LV apical and LV septal pacing tend to maintain or improve contractility and efficiency compared with biventricular pacing.

The ultrasonic research of left ventricular systolic volume and pressure in different electro-mechanical patterns:a canine model

Objeetive To evaluate the changes of left ventricular(LV) global and segmental volume, LV outlet pressure and their co-relationship, and to access LV global and segmental systolic function and mechanical asynchrony in different LV electro-mechanical patterns using full volume three-dimensional echocardiography(3DE). Methods Nineteen open-chest canine models were employed for the acquirement of LV full volume dynamic 3DE imaging during right atrial appendage (RAA), right ventricular apical (RVA), LV lateral wall(LVL) and LV apical(LVA). LV outlet end-systolic pressure(ESP) was recorded simultaneously. End-systolic volume (ESV), end-diastolic volume (EDV), global and segmental ejection fraction(EF) and systolic dyssynchrony index(SDI) of LV were measured and calculated using a dedicated workstation. The average ascending rate of LV pressure during systole(+ dp/dt) and the average descending systolic pressure(ESP), + dp/dt and - dp/dt during RVA pacing were lower than those during RAA pacing (P <0.05). SDI during RVA pacing was higher than that during RAA pacing(P<0.05). ESP, + dp/dtand - dp/dt during LVL and LVA pacing were lower than those during RAA pacing (P <0.05). There and LVA pacing was higher than that during RVA pacing (P <0.05),SD1 during LVL pacing was lower than that during RVA pacing (P <0.05), there was no significant difference of SDI between RVA and LVA and LVL pacing. Segmental EF of septum and apex during LVI. pacing were higher than those during LVA pacing (P <0.05). @Segmental EF of anterior and post septum and all apical segments (except lateral wall) during RVA pacing were lower than those during RAA pacing (P <0.05). Segmental EF of lateral and anterior wall during I.VI. pacing were lower than those during RAA pacing (P <0.05). Segmental EF of anterior wall and anterior septum during LVA pacing were lower than those during RAA parameters. Conclusions The global and minority segmental systolic function of LV during RAA pacing could be reduced compared with normal sinus rhythm. All the ventricular pacing worsen LV systolic and diastolic function compared with RAA pacing. LV systolic function during LVL pacing was superior to RVA pacing. During ventricular pacing,the systolic function at nearby segments of the pacing site was depressed. Key words: Echocardiography; Cardiac pacing,artificial; Ventricular function,left

Reversal of Pacing-Induced Heart Failure by Left Ventricular Apical Pacing

To the Editor: Children with congenital complete atrioventricular block often require lifelong pacemaker therapy. Although such therapy restores a normal heart rate, it also results in dyssynchrono...

Differential effects of left ventricular pacing sites in an acute canine model of contraction dyssynchrony

The goal of the present study was to assess the effects of left ventricular (LV) pacing sites (apex vs. free wall) on radial synchrony and global LV performance in a canine model of contraction dyssynchrony. Ultrasound tissue Doppler imaging and hemodynamic (LV pressure-volume) data were collected in seven anesthetized, opened-chest dogs. Right atrial (RA) pacing served as the control, and contraction dyssynchrony was created by simultaneous RA and right ventricular (RV) pacing to induce a left bundle-branch block-like contraction pattern. Cardiac resynchronization therapy (CRT) was implemented by adding simultaneous LV pacing to the RV pacing mode at either the LV apex (CRTa) or free wall (CRTf). A new index of synchrony was developed via pair-wise cross-correlation analysis of tissue Doppler radial strain from six midmyocardial cross-sectional regions, with a value of 15 indicating perfect synchrony. Compared with RA pacing, RV pacing significantly decreased radial synchrony (11.1 +/- 0.8 vs. 4.8 +/- 1.2, P < 0.01) and global LV performance (cardiac output: 2.0 +/- 0.3 vs. 1.4 +/- 0.1 l/min and stroke work: 137 +/- 22 vs. 60 +/- 14 mJ, P < 0.05). Although both CRTa and CRTf significantly improved radial synchrony, only CRTa markedly improved global function (cardiac output: 2.1 +/- 0.2 l/min and stroke work: 113 +/- 13 mJ, P < 0.01 vs. RV pacing). Furthermore, CRTa decreased LV end-systolic volume compared with RV pacing without any change in LV end-systolic pressure, indicating an augmented global LV contractile state. Thus, LV apical pacing appears to be a superior pacing site in the context of CRT. The dissociation between changes in synchrony and global LV performance with CRTf suggests that regional analysis from a single plane may not be sufficient to adequately characterize contraction synchrony.

Relief of Left Ventricular Outflow Tract Obstruction Following Inadvertent Left Ventricular Apical Pacing in a Patient with Hypertrophic Cardiomyopathy

Dual chamber (DDD) pacing improves symptoms and relieves left ventricular (LV) outflow obstruction in hypertrophic cardiomyopathy. The ventricular lead is usually positioned at the right ventricular apex (RVA). We report a patient in whom the ventricular lead had inadvertently penetrated the septum, resulting in DDD pacing from the LV apex. However, after 3 months, obstruction was reduced and symptoms were improved. Pacing from LV apex and RVA resulted in comparable hemodynamic improvement. This case suggests that the asynchronous wave of septal contraction, originating from the apex, irrespective of ventricular site, accounts for the reduction in LV outflow obstruction.

Endocardial pacing site affects left ventricular end-diastolic volume and performance in the intact anesthetized dog.

We investigated how pacing from different endocardial sites affects the left ventricular three-dimensional contraction pattern and performance in intact anesthetized dogs. We used data from the motion of radiopaque markers implanted in the left ventricular endocardium in an analysis based on the polar decomposition theorem to determine the left ventricle's three-dimensional principal directions and magnitudes of deformation, and its axis and angle of rotation during the cardiac cycle. This paper also derives a new procedure that permits statistical comparison of different left ventricular cavity deformation patterns. During normal sinus rhythm and pacing from the right atrium, left ventricular septum, left ventricular apex, and right ventricular apex, the principal directions of left ventricular deformation remained relatively fixed with respect to the left ventricle's anatomy, independent of heart rate and pacing site. These directions were oriented in septum-free wall, anterior-posterior, and apex-base directions. End-systolic pressure and volume did not vary significantly among pacing sites. End-diastolic volume varied significantly among pacing sites, with right ventricular apical pacing producing the smallest end-diastolic and stroke volume. These results reveal that beats produced by right ventricular apical pacing eject less blood compared with beats produced by right atrial, left ventricular septal, or left ventricular apical pacing.