Ventricular Epicardial Pacing Research Articles

Kardiyak Resenkronizasyon Tedavisinin Ventriküler Repolarizasyon Parametreleri ve Ventriküler Aritmiler Üzerindeki Etkisi

Objective: Cardiac resynchronization therapy (CRT) is commonly used in patients with heart failure (HF) along with left ventricular mechanic and electrical dyssencrony. Left ventricular epicardial pacing in CRT patients changes the normal myocardial activation and increases the transmural dispersion of repolarization. We aimed to investigate the impact of CRT on repolarization parameters and reveal its consequences on arrhythmic events.
 Materials and Methods: The study consisted of 54 patients treated with CRT. Repolarization parameters; QT, T peak-to-T end and JT, Tpe/QT, QT dispersion and Tpe dispersion were measured. The patients were also investigated in two subgroups according to the presence of ventricular arrhythmias at the end of follow-up. Subgroups were compared in terms of repolarization parameters.
 Results The change in repolarization parameters according to baseline values were also compared in the whole group.In the whole study group, all of the repolarization parameters significantly increased in the acute phase. In the chronic phase, these abnormalities were significantly diminished. The comparison of the two subgroups did not show any significant difference in respect of repolarization parameters. 
 Conclusion: Epicardial pacing prolongs myocardial repolarization time and increases transmural dispersion of repolarization. However, these abnormalities were transient and were not associated with ventricular arrhythmias.

Under-sensing by a temporary pacemaker after cardiac surgery and ventricular fibrillation

An 80-year-old man with a 6-month-history of shortness of breath on minimal exertion and fatigue was admitted to our unit for a planned operation to replace his stenotic aortic valve. The surgery was uneventful and a temporary ventricular epicardial pacing lead was placed on the free wall of the right ventricle. The patient remained haemodynamically stable in sinus rhythm post-surgery and was extubated 8 h later. The following day he was transferred from intensive care to our high dependency unit with the temporary epicardial pacemaker in VVI mode: stimulation amplitude 10 V, sensitivity 1 mV, and back-up pacing rate of 44 beats per min. A pacing check at that time showed no problems.

Magnetic resonance imaging safety in patients with abandoned or functioning epicardial pacing leads.

The European Society of Cardiology Guidelines on cardiac pacing from 2021 allow magnetic resonance imaging (MRI) in patients with cardiac implantable electronic devices (CIEDs) but do not recommend MRI in patients with epicardial pacing leads. The clinical dilemma remains whether performing an MRI in patients with CIED and epicardial leads is safe. We aimed to evaluate the safety of performing an MRI in patients with CIED and abandoned or functioning epicardial pacing leads. We included all adult patients who underwent clinically indicated MRIs with CIED and functioning or abandoned epicardial leads in a single tertiary hospital between November 2011 and October 2019. The data were retrospectively collected. Twenty-six MRIs were performed on 17 patients with functioning or abandoned epicardial pacing leads. Sixty-nine percent of the MRI scans (18/26) were conducted on patients with functioning epicardial pacing leads. A definite adverse event occurred in one MRI scan. This was a transient elevation of the pacing threshold in a patient with a functioning epicardial ventricular pacing lead implanted 29years previously. An irreversible atrial pacing lead impedance elevation was detected 6months after the MRI in another patient; the association with the previous MRI remained unclear. No adverse events were detected in MRIs performed on patients with modern (implanted in 2000 or later) functioning epicardial leads. MRIs in patients with CIED and modern functioning epicardial pacing leads were performed without detectable adverse events. Further large-scale studies are necessary to confirm MRI safety in patients with epicardial pacing leads. • Currently, MRI in patients with cardiac implantable electronic devices (CIEDs) and functioning or abandoned epicardial pacing leads is not recommended. • MRIs in patients with CIED and modern functioning epicardial leads (implanted in 2000 or later) were performed without detectable adverse events in our patient cohort. • Allowing MRI in patients with epicardial pacing leads may significantly improve the diagnostic work-up, especially in specific patient groups, such as patients with congenital heart disease.

Abstract 11452: Full 3D Single Heartbeat Electromechanical Wave Imaging of the Heart in Vivo with Coherent Compounding of Diverging Waves

Introduction: Electromechanical wave imaging (EWI) is a new ultrasound-based technique that can noninvasively map myocardial activation of all four chambers at high temporal resolution (500-2000 frames per second). Localization of atrial and ventricular arrhythmias with 3D-rendered EWI maps has been demonstrated and validated in heart rhythm disorders using multiple 2D echocardiographic views at different heartbeats. Objective: The objective of this study was to assess the in vivo performance of single heartbeat 3D EWI using coherent compounding of high volume-rate 3D anatomical echocardiography. Methods: A 32x32-element matrix array (Vermon, France) was connected to four synchronized research ultrasound scanners (Vantage 256, Verasonics, WA). High volume rate acquisitions were performed with diverging wave imaging at a compounded imaging rate of 840 volumes per second. Three healthy volunteers were imaged during normal sinus rhythm and one open chest canine was imaged during left ventricular pacing. Timing of zero-crossing of temporal inter-volume axial strain curves, corresponding to local onset of contraction, was determined for EWI activation. Results: A normal activation sequence was consistently observed in all volunteers (Figure 1). Early activation was mapped in the right atrium, followed by the left atrium, followed by the ventricles. Epicardial ventricular pacing was performed alternatively in the basal anterior-lateral region and in the apical anterior-septal region. The earliest activated region with 3D EWI was observed in the same location as the pacing electrode (Figure 1). Good agreement between 3D EWI and electro-anatomical mapping was obtained. Conclusions: Ultrasound-based full 3D EWI is capable of consistently mapping myocardial activation of the full heart in a single heartbeat in healthy volunteers noninvasively and is capable of identifying early activation during epicardial ventricular pacing in an open-chest canine.

Left ventricular epicardial pacing achieved hyper-responsiveness in young children with dilated cardiomyopathy with left bundle branch block.

AimsThe management of heart failure (HF) in young children is challenging. The present study aimed to clarify the effect of left univentricular epicardial pacing on dilated cardiomyopathy with left bundle branch block (LBBB) in children.Methods and resultsA total of five cases (30.86 ± 16.39 months, three female) of children weighing 5.8–15 kg with dilated cardiomyopathy and LBBB were included in this study. LBBB in one child occurred after device closure of peri‐membranous ventricular septal defects, and the remaining four were idiopathically discovered early after birth. Before implantation, all children suffered from refractory HF and cardiac dilatation; the left ventricular ejection fraction was 33.48 ± 5.84% with Ross Heart Failure Classification III–IV. Electrical and mechanical dyssynchrony were observed in all children with QRS duration >140 ms and prolonged septal‐to‐left posterior wall motion delay. Left univentricular epicardial pacing was successfully implanted via left axillary minithoracotomy in the five children. Sensed atrioventricular delays (83 ± 15 ms) were optimized by velocity time integral of aortic blood flow before discharge. During the follow‐up period (10.8 ± 2.68 months), the dilated failing heart was reversed significantly in terms of decreased left ventricular dimension (55.62 ± 3.46 vs. 38.94 ± 3.69 mm, P = 0.005), while the left ventricular ejection fraction improved to 60.18 ± 8.78% (P = 0.006).ConclusionsIn young children with low body weight, if HF is caused by or related to LBBB, left ventricular epicardial pacing still has an excellent effect.

MRI safety wih abandoned or functional epicardial pacing leads

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): HUS Medical Imaging Center research grant Background The Heart and Rhythm Society’s consensus statement 2017 approves magnetic resonance imaging (MRI) with cardiac implantable electronic devices (CIED), but excludes patients with epicardial and abandoned leads. Potential safety hazards of an MRI with epicardial pacing leads include heating of the tip of the lead and induction of current in the pacing lead resulting in inappropriate cardiac stimulation. Only a few small studies of MRI safety with epicardial pacing leads have been published and adverse events have been rare. The clinical dilemma remains, whether performing an MRI on a patient with CIED and epicardial pacing leads is safe. We have performed MRIs on patients with CIED and epicardial pacing leads when benefits have been considered to outweigh the risks after careful case-by-case evaluation following our institutional MRI with CIED safety protocol. Purpose The aim of this study was to evaluate the safety of performing an MRI scan on patients with CIED and abandoned or functional epicardial pacing leads. Methods All the clinically indicated MRI examinations conducted on adult patients with CIED and functional or abandoned epicardial leads (n = 24) performed in our hospital between November 2011 and October 2019 were included in this observational retrospective study. The data were retrospectively collected from electronic medical records. Results Altogether 24 MRIs were performed to 16 patients with functional or abandoned epicardial pacing leads (Table). 93.8% (15/16) patients had congenital heart disease. Cardiac MRI was the most frequent examination (21/24, 91.7%). 66.7% of the MRI scans (16/24) were conducted on patients with functional epicardial pacing leads. In 5/24 (20.8%) MRIs, the patient was pacemaker-dependent. A clinically significant event occurred in one MRI scan. This was transient elevation of the pacing lead threshold in a patient with functional epicardial ventricular pacing lead, that was implanted 29 years prior to the MRI. In another patient with 30-year-old functional epicardial pacing leads, clinically significant irreversible elevation in atrial pacing lead impedance was detected 6 months after the MRI and unlikely related to previous MRI examination. None of the patients experienced sensations leading to cessation of the MRI scans. No clinically significant pacing lead parameter changes were detected after MRIs performed on patients with modern (implanted year 2000 or later) functional epicardial pacing leads or functional endocardial leads and abandoned epicardial leads. Conclusions MRI examinations in patients with CIED and modern functional epicardial pacing leads were performed without detectable adverse events. Performing an MRI with old functional epicardial pacing leads may involve more risks.

Endocardial pacing is not haemodynamically superior to trans-coronary sinus epicardial pacing in cardiac resynchronization therapy: the Endo-Epi CRT study

Abstract Funding Acknowledgements Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Medtronic Background Cardiac resynchronization therapy (CRT) conventionally involves trans-coronary sinus, epicardial left ventricular (LV) pacing. Some studies have suggested that endocardial LV pacing may be superior to epicardial LV pacing. Objectives To compare the acute haemodynamic effects of CRT when delivered from endocardial (Endo-CRT) and epicardial LV stimulation sites (Epi-CRT). Methods and results Sixteen CRT recipients (aged 70.4 ± 10.1 years [mean ± SD], 62.5% male, QRS: 156.5 ± 16.1 ms, LBBB in 13 [81.3%]) in sinus rhythm underwent intra-procedural measurements of the rate of rise of LV pressure (dP/dtmax) during Endo- and Epi-CRT (RADI pressure wire). Epi-CRT was delivered in basal, mid and apical positions. The Endo-CRT pacing site was chosen using iterative, biplane fluoroscopic views, to target the same position as the Epi-CRT site on the endocardium (see Figure A). Compared to AAI pacing (10 beats per minute above intrinsic rate), both Endo-CRT and Epi-CRT led to an increase in LV dP/dtmax (6.52 ± 8.90% and 6.15 ± 7.97% respectively, both p < 0.001). There were no significant differences in the change in LV dP/dtmax (ΔLV dP/dtmax) between Endo-CRT and Epi-CRT at basal (p = 0.54), mid (p = 0.78) or apical LV stimulation sites (p = 0.12) [Figure B]. Conclusions Endo-CRT is not haemodynamically superior to Epi-CRT. Abstract Figure.

Left Ventricular Enlargement, Cardiac Resynchronization Therapy Efficacy, and Impact of MultiPoint Pacing.

Left ventricular (LV) epicardial pacing results in slowly propagating paced wavefronts. We postulated that this effect might limit cardiac resynchronization therapy efficacy in patients with LV enlargement using conventional biventricular pacing with single-site LV pacing, but be mitigated by LV stimulation from 2 widely spaced sites using MultiPoint pacing with wide anatomic separation (MPP-AS: ≥30 mm). We tested this hypothesis in the multicenter randomized MPP investigational device exemption trial. Following implant, quadripolar biventricular single-site pacing was activated in all patients (n=506). From 3 to 9 months postimplant, among patients with available baseline LV end-diastolic volume (LVEDV) measures, 188 received biventricular single-site pacing and 43 received MPP-AS. Patients were dichotomized by median baseline LVEDV indexed to height (LVEDVIMedian). Outcomes were measured by the clinical composite score (primary efficacy end point), quality of life, LV structural remodeling (↑EF >5% and ↓ESV 10%) and heart failure event/cardiovascular death. LVEDVIMedian was 1.1 mL/cm. Baseline characteristics differed in patients with LVEDVI>Median versus LVEDVI≤Median. Among patients with LVEDVI>Median, biventricular single-site pacing was less efficacious compared to patients with LVEDVI≤Median (clinical composite score, 65% versus 79%). In contrast, MPP-AS programming generated greater clinical composite score response (92% versus 65%, P=0.023) and improved quality of life (-31.0±29.7 versus -15.7±22.1, P=0.038) versus biventricular single-site pacing in patients with LVEDVI>Median. Reverse remodeling trended better with MPP-AS programming. In patients with LVEDVI>Median, heart failure event rate increased following the 3-month randomization point with biventricular single-site pacing (0.0150±0.1725 in LVEDVI>Median versus -0.0190±0.0808 in LVEDVI ≤Median, P=0.012), but no heart failure event occurred in patients with MPP-AS programming between 3 and 9 months in LVEDVI>Median. All measured outcomes did not differ in patients receiving MPP-AS and biventricular single-site pacing with LVEDVI≤Median. Conventional biventricular single-site pacing, even with a quadripolar lead, has reduced efficacy in patients with LV enlargement. However, the greatest response rate in patients with larger hearts was observed when programmed to MPP-AS pacing.

Left ventricular endocardial pacing is less arrhythmogenic than conventional epicardial pacing when pacing in proximity to scar

BackgroundEpicardial pacing increases risk of ventricular tachycardia (VT) in patients with ischemic cardiomyopathy (ICM) when pacing in proximity to scar. Endocardial pacing may be less arrhythmogenic as it preserves the physiological sequences of activation and repolarization.ObjectiveThe purpose of this study was to determine the relative arrhythmogenic risk of endocardial compared to epicardial pacing, and the role of the transmural gradient of action potential duration (APD) and pacing location relative to scar on arrhythmogenic risk during endocardial pacing.MethodsComputational models of ICM patients (n = 24) were used to simulate left ventricular (LV) epicardial and endocardial pacing 0.2–3.5 cm from a scar. Mechanisms were investigated in idealized models of the ventricular wall and scar. Simulations were run with/without a 20-ms transmural APD gradient in the physiological direction and with the gradient inverted. Dispersion of repolarization was computed as a surrogate of VT risk.ResultsPatient-specific models with a physiological APD gradient predict that endocardial pacing decreases VT risk (34%; P <.05) compared to epicardial pacing when pacing in proximity to scar (0.2 cm). Endocardial pacing location does not significantly affect VT risk, but epicardial pacing at 0.2 cm compared to 3.5 cm from scar increases it (P <.05). Inverting the transmural APD gradient reverses this trend. Idealized models predict that propagation in the direction opposite to APD gradient decreases VT risk.ConclusionEndocardial pacing is less arrhythmogenic than epicardial pacing when pacing proximal to scar and is less susceptible to pacing location relative to scar. The physiological repolarization sequence during endocardial pacing mechanistically explains reduced VT risk compared to epicardial pacing.

Outcome of patients with functional single ventricular heart after pacemaker implantation: What makes it poor, and what can we do?

Pacemaker implantation in patients with single ventricle is associated with poor outcomes. The purpose of this study was to determine the reasons for the poor outcomes of pacemaker implantation. We performed a retrospective chart review of patients with single ventricle who had undergone permanent pacemaker implantation. Patients were categorized into 3 groups based on the site of pacing and the proportion of ventricular pacing (VP) as follows: (1) atrial pacing group with atrial pacing only (n = 11); (2) low VP group with low daily VP proportion (<50%; n = 12); and (3) high VP group with high daily VP proportion (≥50%; n = 15). Pacing leads were placed at the epicardium in all patients. No patients in the atrial pacing or low VP groups died, whereas the survival rate in the high VP group was 58.9% and 39.3% at 10 and 20 years, respectively, after pacemaker implantation. Among the post-Fontan patients, plasma brain natriuretic peptide (BNP) levels significantly increased with the proportion of VP: 11.7, 20.3, and 28.4 pg/mL in the atrial pacing, low VP, and high VP groups, respectively (P = 0.04). In the high VP group, the plasma BNP level was significantly lower in patients with an apical pacing lead than in those with a nonapical pacing lead (27.0 pg/mL vs 82.8 pg/mL, respectively; P = .03). A higher proportion of VP was associated with poor outcome and higher plasma BNP levels, probably due to ventricular dyssynchrony. In epicardial ventricular pacing, apical pacing is better to avoid the increase in ventricular stress and plasma BNP level.

Feasibility of RA-LV pacing in patients with symptomatic left bundle branch block: a pilot study.

Several studies have reported the adverse effects of right ventricular apical pacing. Permanent His bundle pacing is proved to be the most physiological. But it can be technically difficult sometimes. One recent large multicenter randomized trial showed that pacing from left ventricular apex or mid-lateral wall has the greatest potential to prevent pacing-induced reduction of cardiac pump function (by maintaining left ventricular mechanical synchrony) and, therefore, can be considered as physiological site. In our study, we have wanted to see the outcome of left ventricular pacing through coronary sinus branch with active fixation bipolar lead as a routine pacing technique in patients with symptomatic left bundle branch block. In our study we have recruited 27patients for left ventricular pacing through coronary sinus branch (as done in cardiac resynchronization therapy) with active fixation bipolar lead and 33 patients for right ventricular apical pacing (control) and compared left ventricular pacing with right ventricular apical pacing in patients with history of syncope with left bundle branch block in baseline electrocardiography who presented with atrio-ventricular block or prolonged HV interval (≥ 70ms) on electrophysiology study in term of procedure and fluoroscopy time and short-term lead performance and left ventricular function. The results of our study showed that left ventricular pacing through a tributary of coronary sinus is associated with shortened QRS duration (21.10 ± 3.92ms) and better LV function (higher left ventricular ejection fraction 64.00 ± 3.03 vs. 59.73 ± 6.73 and lower left ventricular diastolic internal diameter 4.58 ± 0.32 vs. 5.23 ± 0.40cm) in comparison to right ventricular apical pacing. However, the total procedure time and fluoroscopy time was significantly higher (73.75 ± 11.02 vs. 63.32 ± 6.06min and 7.08 ± 1.48 vs. 5.02 ± 1.39min, respectively) in left ventricular pacing group. The results of this study indicate that transvenous left ventricular epicardial pacing may be an option for physiological pacing in patients with symptomatic left bundle branch block.

Three-Dimensional Printed Biopatches With Conductive Ink Facilitate Cardiac Conduction When Applied to Disrupted Myocardium.

Reentrant ventricular arrhythmias are a major cause of sudden death in patients with structural heart disease. Current treatments focus on electrically homogenizing regions of scar contributing to ventricular arrhythmia with ablation or altering conductive properties using antiarrhythmic drugs. The high conductivity of carbon nanotubes may allow restoration of conduction in regions where impaired electrical conduction results in functional abnormalities. We propose a new concept for arrhythmia treatment using a stretchable, flexible biopatch with conductive properties to attempt to restore conduction across regions in which activation is disrupted. Carbon nanotube patches composed of nanofibrillated cellulose/single-walled carbon nanotube ink 3-dimensionally printed in conductive patterns onto bacterial nanocellulose were developed and evaluated for conductivity, flexibility, and mechanical properties. The patches were applied on 6 canines to epicardium before and after surgical disruption. Electroanatomic mapping was performed on normal epicardium, then repeated over surgically disrupted epicardium, and then finally with the patch applied passively. We developed a 3-dimensional printable carbon nanotube ink complexed on bacterial nanocellulose that was (1) expressable through 3-dimensional printer nozzles, (2) electrically conductive, (3) flexible, and (4) stretchable. Six canines underwent thoracotomy, and, during epicardial ventricular pacing, mapping was performed. We demonstrated disruption of conduction after surgical incision in all 6 canines based on activation mapping. The patch resulted in restored conduction based on mapping and assessment of conduction direction and velocities in all canines. We have demonstrated 3-dimensional custom-printed electrically conductive carbon nanotube patches can be surgically manipulated to improve cardiac conduction when passively applied to surgically disrupted epicardial myocardium in canines.

THE LEVEL OF THE CARDIAC BIOMARKER ST2 AND NT-PROBNP IN CHILDREN WITH PERMANENT RIGHTVENTRICULAR PACING

NT-proBNP and ST2 levels are important in diagnosing heart failure and determining cardiovascular risk. The&nbsp;study found that elevated levels of NT-proBNP were detected in patients with right ventricular epicardial pacing, which suggests the presence of this contingent of heart failure. The ST2 level in group did not exceed the threshold value.

Surgical placement of left ventricular lead for cardiac resynchronisation therapy after failure of percutaneous attempt.

SummaryObjectiveCardiac resynchronisation therapy has been shown to be an effective treatment to improve functional status and prolong survival of patients in advanced chronic heart failure. This study assessed the surgical outcomes of left anterior mini-thoracotomy for the implantation of left ventricular epicardial pacing leads in cardiac resynchronisation therapy.MethodsOur study consisted of 30 consecutive patients who underwent cardiac resynchronisation therapy with a left thoracotomy between November 2010 and April 2012 in our clinic. Postoperative follow up included the assessment of New York Heart Association (NYHA) functional class, electrocardiography and echocardiography.ResultsThere were 22 male and eight female patients with a mean age of 68 ± 5.04 years. All patients were in NYHA class III or IV. Pre-procedure mean left ventricular ejection fraction was 28.1 ± 4.5% and post-procedural ejection fraction improved to 31.7 ± 5.1%. The pre-operative QRS duration changed from 171.7 ± 10.8 to 156.2 ± 4.4 ms after the operation. Also there was a significant reduction in left ventricular end-diastolic dimension from 6.98 ± 0.8 to 6.72 ± 0.8 mm (p < 0 .05), but no change in left ventricular end-systolic dimension and severity of mitral regurgitation. All patients had successful surgical left ventricular lead placement. There was no procedure-related mortality. The mean follow-up time was 40.4 months.ConclusionSurgical epicardial left ventricular lead placement procedure is a safe and effective technique in patients with a failed percutaneous attempt.

PERSISTENT COMPROMISED HEMODYNAMIC FUNCTION, DUE TO SINGLE VENTRICULAR EPICARDIAL PACING, AFTER AORTIC VALVE REPLACEMENT SURGERY: A CASE REPORT

We report the case of a 69-year old woman, who was admitted to the cardiac surgery intensive care unit (ICU) of a tertiary hospital, after surgical aortic valve replacement, due to severe aortic stenosis. During the early postoperative period, the patient was hemodynamically stable and her cardiac rhythm was supported by temporary epicardial ventricular pacing. One hour after her ICU admission, the woman presented compromised hemodynamics, characterized by severe hypotension with poor response to aggressive inotropic, vasopressor and fluid therapy. After 15 minutes of her significant clinical worsening, the change of the pacing mode from single ventricular to single atrial effected immediate hemodynamic stabilization, improved arterial blood pressure and optimum patient cardiovascular function. This could be explained by the significantly reduced cardiac output in the absence of atrial contraction to assist ventricular preloading, which characterized some patients with impaired ventricular function, as those with severe aortic stenosis.

Getting the LV lead to the right spot.

Getting the LV lead to the right spot.

Immediate electrical storm of Torsades de Pointes after CRT-D implantation in an ischemic cardiomyopathy patient

Cardiac resynchronization therapy with an implantable cardioverter-defibrillator (CRT-D) is the preferred treatment for patients with severe heart failure, dyssynchrony, and an increased risk of sudden cardiac death or for primary ventricular arrhythmia survivors. Rarely, left ventricular epicardial pacing can induce ventricular tachyarrhythmia rather than a beneficial effect. We describe an ischemic cardiomyopathy patient who underwent CRT-D therapy and developed sustained torsades de pointes (TdP) immediately after switching to biventricular pacing (BVP) mode. Here, TdP possibly developed owing to the change in the dispersion of repolarization of the left ventricle myocardium. The diagnosis and management of BVP-induced ventricular arrhythmia is discussed.

Effects of Different Ventricular Pacing Modes on Ventricular Repolarisation in Patients Undergoing Cardiac Resynchronisation Therapy: A Single-centre Study

The aims of this study were to compare ventricular repolarisation parameters in patients who underwent cardiac resynchronisation therapy (CRT) at Sun Yat-sen University Memorial Hospital under different ventricular pacing modes and to understand effects of epicardial pacing on ventricular repolarisation. The study included 55 patients who underwent CRT. During follow-up outpatient visits three months after CRT implantation, the CRT devices were programmed to deliver no pacing (with the exception of patients with third-degree atrioventricular block), biventricular pacing (BivP), right ventricular endocardial pacing (RV-EndoP), and left ventricular epicardial pacing (LV-EpiP). Signals from the standard 12-lead ECG were recorded simultaneously to measure the QT interval, JT interval, and Tp-e interval, from which the heart rate-corrected QTc interval, JTc interval, and Tp-ec interval were determined. The JTc interval and Tp-ec interval were prolonged during LV-EpiP and BivP compared with those during spontaneous cardiac rhythm and RV-EndoP. The JTc dispersion and Tp-ec dispersion were not significantly different among the four pacing modes. Epicardial pacing prolongs myocardial repolarisation time and increases transmural dispersion of repolarisation. Epicardial pacing has no significant effect on the dispersion of regional ventricular repolarisation.

Atrioventricular Left Ventricular Apical Pacing Improves Haemodynamic, Rotational, and Deformation Variables in Comparison to Pacing at the Lateral Wall in Intact Myocardium: Experimental Study

Aim. To assess the effect on left ventricular (LV) function of atrioventricular (AV) and ventricular pacing at the LV apical or lateral wall and to compare the normal torsional and deformation pattern of the intact LV myocardium with those created by the aforementioned LV pacing modes and sites. Methods. Experiments were conducted in pigs (n = 21) with normal LV function to investigate the acute hemodynamic effects of epicardial AV and ventricular LV pacing at the LV apical or lateral wall. Torsional and deformation indices of LV function were assessed using speckle tracking echocardiography. Results. AV pacing at the apex revealed a significant reduction in the radial strain of the base (P < 0.03), without affecting significantly the ejection fraction and the LV torsion or twist. In contrast, AV pacing at the lateral wall produced, in addition to the reduction of the radial strain of the base (P < 0.01), significant reduction of the circumferential and the radial strain of the apex (both P < 0.01) as well as of the ejection fraction (P < 0.002) and twist (P < 0.05). Conclusions. In pig hearts with intact myocardium, LV function is maintained at sinus rhythm level when AV pacing is performed at the LV apex.

Acute electrical and hemodynamic effects of multisite left ventricular pacing for cardiac resynchronization therapy in the dyssynchronous canine heart

Multisite left ventricular (multi-LV) epicardial pacing has been proposed as an alternative to conventional single-site LV (single-LV) pacing to increase the efficacy of cardiac resynchronization therapy. To compare the effects of multi-LV versus single-LV pacing in dogs with left bundle branch block (LBBB). Studies were performed in 9 anaesthetized dogs with chronic LBBB using 7 LV epicardial electrodes. Each electrode was tested alone and in combination with 1, 2, 3, and 6 other electrodes, the sequence of which was chosen on the basis of practical real-time electrical mapping to determine the site of the latest activation. LV total activation time (LVTAT) and dispersion of repolarization (DRep) were measured by using approximately 100 electrodes around the ventricles. LV contractility was assessed as the maximum derivative of left ventricular pressure (LVdP/dtmax ). Single-LV pacing provided, on average, a -4.0% ± 9.3% change in LVTAT and 0.2% ± 13.7% change in DRep. Multi-LV pacing markedly decreased both LVTAT and DRep in a stepwise fashion to reach -41.3% ± 5% (P < .001 for overall comparison) and -14.2% ± 19.5% (P < .02 for overall comparison) in the septuple-LV pacing configuration, respectively. Single-LV pacing provided a mean increase of 10.7% ± 7.7% in LVdP/dtmax. LVdP/dtmax incrementally increased by the addition of pacing electrodes to 16.4% ± 8.7% (P < .001 for overall comparison). High response to single-LV pacing could not be improved further during multi-LV pacing. Compared with single-LV pacing, multi-LV pacing can considerably reduce both LVTAT and DRep in dogs with LBBB, but the improvement in contractility is limited to conditions where single-LV pacing provides suboptimal improvement. Further studies are warranted to determine whether these acute effects translate in antiarrhythmic properties and better long-term outcomes.