Exploring a New Systematic Route for Left Ventricular Pacing in Cardiac Resynchronization Therapy.

BACKGROUND: Frequency and distribution of left ventricular (LV) venous collaterals were studied in vivo to evaluate the ease and feasibility of implanting a new ultra-thin LV quadripolar microlead for cardiac resynchronization therapy (CRT).Methods and Results:Evaluable venograms were analyzed to define the prevalence of venous collaterals (>0.5 mm diameter) between: (1) different LV segments; and (2) different major LV veins in: unselected patients who underwent CRT from 2008 to 2012 at Rouen Hospital, France (retrospective); and CRT patients from the Axone Acute pilot study in 2018 (prospective). In prospective patients with evaluable venograms, LV microlead implantation was attempted. Thirty-six (21/65 retrospective, 15/20 prospective) patients had evaluable venograms with ≥1 visible venous collaterals. Collaterals were found between LV veins in all CRT patients with evaluable venograms. Regionally, prevalence was highest between: the apical inferior and apical lateral (42%); and mid inferior and mid inferolateral (42%) segments. Collateral connections were most prevalent between: the inferior interventricular vein (IIV) and lateral vein (64% [23/36]); and IIV and infero-lateral vein (36% [13/36]). Cross-vein microlead implantation was possible in 18 patients (90%), and single-vein implantation was conducted in the other 2 patients (10%). CONCLUSIONS: Venous collaterals were found in vivo between LV veins in all CRT patients with evaluable venograms, making this network an option for accessing multiple LV sites using a single LV microlead.

Improvement of electrical synchrony in cardiac resynchronization therapy using dynamic atrioventricular delay programming and multipoint pacing.

BACKGROUND: Optimization of cardiac resynchronization therapy (CRT) is often time-consuming and therefore underused in a clinical setting. Novel device-based algorithms aiming to simplify optimization include a dynamic atrioventricular delay (AVD) algorithm (SyncAV, Abbott) and multipoint pacing (MPP, Abbott). This study examines the acute effect of SyncAV and MPP on electrical synchrony in patients with newly and chronically implanted CRT devices. METHODS: Patients with SyncAV and MPP enabled devices were prospectively enrolled during implant or scheduled follow-up. Blinded 12-lead electrocardiographic acute measurements of QRS duration (QRSd) were performed for intrinsic QRSd (Intrinsic), bi-ventricular pacing (BiV), MPP, BiV with SyncAV at default offset 50 ms (BiVSyncAVdef ), BiV with SyncAV at patient-specific optimised offset (BiVSyncAVopt ), MPP with SyncAV at default offset 50 ms (MPPSyncAVdef ), and MPP with SyncAV at patient-specific optimised offset (MPPSyncAVopt ). RESULTS: Thirty-three patients were enrolled. QRSd for Intrinsic, BiV, MPP, BiVSyncAVdef , BiVSyncAVopt , MPPSyncAVdef , MPPSyncAVopt were 160.4 ± 20.6 ms, 141.0 ± 20.5 ms, 130.2 ± 17.2 ms, 121.7 ± 20.9 ms, 117.0 ± 19.0 ms, 121.2 ± 17.1 ms, 108.7 ± 16.5 ms respectively. MPPSyncAVopt led to greatest reduction of QRSd relative to Intrinsic (-31.6 ± 11.1%; p < .001), showed significantly shorter QRSd compared to all other pacing configurations (p < .001) and shortest QRSd in every patient. Shortening of QRSd was not significantly different between newly and chronically implanted devices (-51.6 ± 14.7 ms vs. -52.7 ± 21.9 ms; p = .99). CONCLUSION: SyncAV and MPP improved acute electrical synchrony in CRT. Combining both technologies with patient-specific optimization resulted in greatest improvement, regardless of time since implantation. Whats new Novel device-based algorithms like a dynamic AVD algorithm (SyncAV, Abbott) and multipoint pacing (MPP, Abbott) aim to simplify CRT optimization. Our data show that a combination of patient tailored SyncAV optimization and MPP results in greatest improvement of electrical synchrony in CRT measured by QRS duration, regardless if programmed in newly or chronically implanted devices. This is the first study to our knowledge to examine a combination of these device-based algorithms. The results help understanding the ideal ventricular excitation in heart failure.

Feasibility of cathodic-anodal left ventricular stimulation for alternative multisite pacing.

BACKGROUND: Simultaneous cathodic-anodal capture by a bipole of a cardiac resynchronization therapy (CRT) left-ventricular (LV) catheter may depolarize a larger LV area than conventional multipoint pacing. We evaluated the feasibility of cathodic-anodal LV stimulation. METHODS: In 30 patients undergoing CRT with a quadripolar LV lead, we evaluated the cathodic and anodal capture threshold for each LV pole and compared QRS on electrocardiogram (ECG) during single-point cathodic biventricular stimulation (S-BS), multipoint BS (M-BS), and cathodic-anodal BS (CA-BS). RESULTS: Anodal capture was obtained by three poles in 23/30 patients, by two poles in five, and was not feasible in two. The mean single-point anodal threshold was 3.93 V versus single-point cathodic threshold of 1.95 V. On comparing ECGs, M-BS and CA-BS produced similar QRS wavefront activation in 90% of patients. CONCLUSIONS: CA-BS is feasible and may be used in LV pacing to achieve a different wavefront of electrical activation. Further prospective studies are needed in order to verify the clinical impact of this kind of stimulation.

Occurrence of simultaneous cathodal-anodal capture with left ventricular quadripolar leads for cardiac resynchronization therapy: an electrocardiogram evaluation.

AIMS: The occurrence of left ventricular (LV) anodal activation during pacing with modern multipolar cardiac resynchronization therapy (CRT) systems has never been reported. The aim of our study was to demonstrate, by means of electrocardiogram (ECG) analysis, the occurrence of simultaneous cathodal-anodal LV capture with quadripolar LV leads. METHODS AND RESULTS: We studied 10 first-time recipients of a CRT device equipped with a quadripolar LV lead. During follow-up, standard supine 12-lead ECGs were obtained in available cathode-to-anode LV pacing configurations with a pulse amplitude equal to twice the pacing threshold. The occurrence of simultaneous cathodal-anodal LV capture was defined as the presence of variations in electrocardiographic ventricular activation (EVA) when the distal tip (cathode)-to-device can (anode) pacing configuration was compared with the distal tip (cathode)-to-proximal ring (anode) configuration. In eight patients, we found differences in EVA when different LV sites were paced through the unipolar LV tip and unipolar LV ring configurations. In these patients, a difference in EVA was detected in 61.5% (59 of 96) of the ECG leads (marked difference in 31.3%, slight difference in 30.2%). Changes in EVA between unipolar tip-to-can and bipolar tip-to-ring pacing that were suggestive of cathodal-anodal LV capture were found in six patients. In these patients, a total of 30 (41.7%) ECG leads showed a difference in EVA (marked difference in 20.8%, slight difference in 20.8%). CONCLUSION: In our experience, additional anodal capture by the proximal LV ring during LV pacing is provable in most recipients of a resynchronization device equipped with a multipolar LV lead.

Updates in Cardiac Resynchronization Therapy for Chronic Heart Failure: Review of Multisite Pacing.

PURPOSE OF REVIEW: Cardiac resynchronization therapy (CRT) reduces the morbidity and mortality of patients with left ventricular (LV) systolic dysfunction and intra-ventricular conduction delay. However, its clinical outcomes are heterogeneous and not all patients show a beneficial response. Multisite pacing (MSP), by stimulating the myocardium from more than one locations, is a potential therapeutic option in patients requiring CRT. This article provides a current update in the methods and outcomes of MSP, as well as in challenges in this field and opportunities for further research and development. RECENT FINDINGS: MSP can be delivered either with multiple leads or with quadripolar LV leads which can stimulate the LV from two separate sites. Initial results are promising but not always consistent across studies. Larger patient subgroups and longer follow-up duration are required for more conclusive evaluation of MSP. Routine use of MSP in clinical practice cannot be advocated at present. In selected patient subgroups, however, MSP could be considered. Newer devices and expanding knowledge are expected to facilitate the more widespread implementation of MSP and the assessment of its effects in the clinical outcomes of CRT.

The use of multisite left ventricular pacing via quadripolar lead improves acute haemodynamics and mechanical dyssynchrony assessed by radial strain speckle tracking: initial results.

AIMS: The objective of the present study was to evaluate the effect of multipoint pacing (MPP) on acute haemodynamics, cardiac contractility, and left ventricle (LV) dyssynchrony, in comparison with conventional cardiac resynchronization therapy (CRT). METHODS AND RESULTS: An open-label, non-randomized, single-centre, prospective study was designed. Twenty-seven consecutive patients were included. Evaluation of pacing configurations was performed in a random order. Transthoracic echocardiography was used to obtain haemodynamic and dyssynchrony parameters. Left ventricular ejection fraction (LVEF) was significantly superior in MPP compared with baseline (38.4 ± 1.8% vs. 26.1 ± 2.2%; P < 0.001), and in conventional pacing configuration compared with baseline (33.2 ± 1.8% vs. 26.1 ± 2.2%; P = 0.007). Cardiac index (CI) was increased by 21.8 ± 5.4% and 34.7 ± 5.1% in conventional and MPP configurations, respectively (P = 0.19). Percentage of acute responders (CI increase ≥10%) was 62.9 and 85.2% in conventional and MPP, respectively (P < 0.001). LV dyssynchrony was defined by radial strain rate parameters. Baseline anteroseptal-to-posterior wall time delay was 168 ± 21 ms. It was reduced until 70.4 ± 29 ms in conventional and -6.6 ± 11 ms in MPP (conventional vs. baseline P = 0.04; MPP vs. conventional P = 0.05). Standard deviation of the time-to-peak radial strain of the 6 LV basal segments was 101 ± 9.7, 80.3 ± 9.2, and 66 ± 8.03 ms in baseline, conventional, and MPP configurations, respectively (MPP vs. basal P = 0.012). Finally, we observed a positive correlation (r = 0.69) between reduction in dyssynchrony and CI increase (P < 0.0001). CONCLUSION: MPP showed a further reduction in LV dyssynchrony compared with conventional biventricular pacing. Moreover, MPP resulted in an additional improvement in LVEF and in CI, and this was translated into a higher number of acute responders to CRT.

Multisite Pacing for Cardiac Resynchronization Therapy: Promise and Pitfalls.

Cardiac resynchronization therapy (CRT) reduces the morbidity and mortality of patients with symptomatic heart failure and intraventricular conduction delay. However, its clinical outcomes are non-uniform and up to one third of treated patients are subsequently classified as non-responders. Multisite pacing (MSP), i.e. stimulating the myocardium from multiple locations, has emerged as a potential therapeutic option in patients requiring CRT. The rationale for MSP is based on the hypothesis that increasing the pacing locations in the left ventricle results in a more physiologic and coordinated myocardial systole. MSP can be achieved by additional leads in the right or left ventricle but this can lead to high battery drain and more frequent generator replacements. Multipolar left ventricular leads can deliver pacing at multiple sites, and therefore, a single lead can be used for MSP. However, the optimal programming settings and the outcomes of this approach remain yet to be determined.

A review of multisite pacing to achieve cardiac resynchronization therapy.

Non-response to cardiac resynchronization therapy remains a significant problem in up to 30% of patients. Multisite stimulation has emerged as a way of potentially overcoming non-response. This may be achieved by the use of multiple leads placed within the coronary sinus and its tributaries (dual-vein pacing) or more recently by the use of multipolar (quadripolar) left ventricular pacing leads which can deliver pacing stimuli at multiple sites within the same vein. This review covers the role of multisite pacing including the interaction with the underlying pathophysiology, the current and planned studies, and the potential pitfalls of this technology.

Acute hemodynamic effects of single- and dual-site left ventricular pacing employing a dual cathodal coronary sinus lead.

BACKGROUND: We studied the acute hemodynamic effect of left ventricular (LV) pacing from a dual cathodal coronary sinus (CS) lead in a both single- and dual-site electrode configuration. METHODS: In 17 patients who underwent implantation of a cardiac resynchronization therapy-defibrillator system with dual cathodal CS leads, LV stimulation was performed from the distal and proximal electrode separately and from both electrodes simultaneously. The acute hemodynamic response was evaluated by invasive measurement of LVdP/dtmax. Timing of LV electrical activation time measured from onset QRS to LV sense during intrinsic rhythm at both electrodes were determined from simultaneous intracardiac recordings. The latter results were compared to those of an additional group of 26 patients in whom no hemodynamic effects were evaluated. RESULTS: Baseline LVdP/dtmax was 897 ± 222 mm Hg/s. Single-site LV pacing resulted in a rise of LVdP/dtmax to 1,053 ± 266 mm Hg/s (+17.4%) taking the best of the two sites and 1,020 ± 254 mm Hg (+13.7%) at the worst site (P = 0.0001). In the dual-site pacing configuration LVdP/dtmax was 1,026 ± 243 mm Hg/s (+14.1%). P value for single best versus dual site was 0.005, and for dual site versus worst single site was 0.18 (n.s.). CONCLUSION: Even with a relatively small distance of 20-21 mm between stimulation electrodes, there is a significant difference in acute hemodynamic effect from the single best and worst site. Dual-site LV pacing offers no hemodynamic benefit over the best single pacing site. The short electrode distance may have been a limitation and results may not be applicable to other forms of multisite pacing.

A comparison of left ventricular endocardial, multisite, and multipolar epicardial cardiac resynchronization: an acute haemodynamic and electroanatomical study.

AIMS: Alternative forms of cardiac resynchronization therapy (CRT), including biventricular endocardial (BV-Endo) and multisite epicardial pacing (MSP), have been developed to improve response. It is unclear which form of stimulation is optimal. We aimed to compare the acute haemodynamic response (AHR) and electrophysiological effects of BV-Endo with MSP via two separate coronary sinus (CS) leads or a single-quadripolar CS lead. METHODS AND RESULTS: Fifteen patients with a previously implanted CRT system received a second temporary CS lead and left ventricular (LV) endocardial catheter. A pressure wire and non-contact mapping array were placed into the LV cavity to measure LVdP/dtmax and perform electroanatomical mapping. Conventional CRT, BV-Endo, and MSP were then performed (MSP-1 via two epicardial leads and MSP-2 via a single-quadripolar lead). The best overall AHR was found using BV-Endo pacing with a 19.6 ± 13.6% increase in AHR at the optimal endocardial site over baseline (P < 0.001). There was an increase in LVdP/dtmax with MSP-1 and MSP-2 compared with conventional CRT, but this was not statistically significant. Biventricular endocardial pacing from the optimal site was significantly superior to conventional CRT (P = 0.039). The AHR achieved when BV-Endo pacing was highly site specific. Within individuals, the best pacing modality varied and was affected by the underlying substrate. Left ventricular activation times did not predict the optimal haemodynamic configuration. CONCLUSION: Biventricular endocardial pacing and not MSP was superior to conventional CRT, but was highly site specific. Within individuals, however, different methods of stimulation are optimal and may need to be tailored to the underlying substrate.

Acute effects of multisite left ventricular pacing on mechanical dyssynchrony in patients receiving cardiac resynchronization therapy.

BACKGROUND: A novel quadripolar left ventricular (LV) pacing lead has the ability to deliver multisite LV pacing (MSLV). We set out to characterize the safety and changes in acute mechanical dyssynchrony with MSLV in cardiac resynchronization therapy (CRT) patients. METHODS AND RESULTS: Prospective multicenter study in 52 patients receiving CRT. An acute pacing protocol comprising 8 MSLV configurations covering a range of delays was compared with conventional CRT (baseline). Transthoracic tissue Doppler imaging (TDI) was used to measure the standard deviation of time to peak contraction of 12 LV segments (Ts-SD) and delayed longitudinal contraction. No ventricular arrhythmia occurred in any of the 52 patients. Complete TDI datasets were collected in 41 patients. Compared with baseline: 1) The mean Ts-SD was significantly lower for the optimal MSLV configuration (35.3 ± 36.4 vs 50.2 ± 29.1 ms; P < .001); 2) at least 1 MSLV configuration exhibited a significant dyssynchrony improvement in 63% of patients; and 3) the mean number of LV segments with delayed longitudinal contractions was significantly reduced with the optimal MSLV configuration (0.37 ± 7.99 vs 2.20 ± 0.19; P < .001). CONCLUSIONS: Acute MSLV was acutely safe, and a proportion of MSLV vectors resulted in a significant reduction in echocardiographic dyssynchrony compared with conventional CRT.

Acute haemodynamic comparison of multisite and biventricular pacing with a quadripolar left ventricular lead.

AIMS: Pacing from multiple sites in the left ventricle (LV) may bring about further resynchronization of the diseased heart compared with biventricular (BiV) pacing. We compared acute haemodynamic response (LV dP/dtmax) of multisite and BiV pacing using a quadripolar LV lead. METHODS AND RESULTS: In 21 patients receiving cardiac resynchronization therapy, a quadripolar LV lead and conventional right atrial and ventricular leads were connected to an external pacing system. A guidewire pressure sensor was placed in the LV for continuous dP/dt measurement. Four multisite pacing configurations were tested three times each and compared with BiV pacing using the distal LV electrode. Nineteen patients had useable haemodynamic data. Median increase in LV dP/dtmax with BiV vs. atrial-only pacing was 8.2% (interquartile range 2.3%, 15.7%). With multisite pacing using distal and proximal LV electrodes, median increase in LV dP/dtmax was 10.2% compared with atrial-only pacing (interquartile range 6.1%, 25.6%). In 16 of 19 patients (84%), two or more of the four multisite pacing configurations increased LV dP/dtmax compared with BiV pacing. Overall, 72% of all tested configurations of multisite pacing produced greater LV dP/dtmax than obtained with BiV pacing. Pacing from most distal and proximal electrodes was the most common optimal configuration, superior to BiV pacing in 74% of patients. CONCLUSION: In the majority of patients, multisite pacing improved acute systolic function further compared with BiV pacing. Pacing with the most distal and proximal electrodes of the quadripolar LV lead most commonly yielded greatest LV dP/dtmax.

Acute Hemodynamic Effect of a Novel Dual-Vein, Multisite Biventricular Pacing Configuration.

BACKGROUND: Biventricular pacing (BVP) from multiple left ventricular (LV) sites could enhance the efficacy of cardiac resynchronization therapy (CRT) by engaging a greater myocardial mass. OBJECTIVES: The goal of this study was to evaluate the acute hemodynamic effect of various multisite pacing (MSP) configurations against conventional BVP. METHODS: Twenty patients with nonischemic dilated cardiomyopathy and left bundle branch block (mean age: 59 ± 14 years; LV ejection fraction: 27% ± 6%; native QRS: 171 ± 16 milliseconds) were investigated during a routine CRT implant procedure. In addition to conventional right atrial and right ventricular leads, 2 quadripolar leads were placed in the distant coronary venous branches. LV hemodynamics was evaluated by using a micromanometer-tipped catheter during atrioventricular BVP with 4 LV lead configurations: single-lead conventional BVP; single-lead multipoint pacing; triventricular pacing from distal dipoles of 2 LV leads; and maximum MSP (MSP-Max) from 4 dipoles of 2 LV leads. RESULTS: Compared with right atrial pacing, any BVP configuration produced a significant increase in the maximal LV diastolic pressure rise (LVdP/dTMax) (a median relative increase of 28% [IQR: 8%-45%], 25% [IQR: 18%-46%], 36% [IQR: 18%-54%], and 38% [IQR: 28%-58%], respectively; all, P < 0.001). MSP-Max but no other multisite BVP generated a significant increase of the maximal LVdP/dTMax than conventional BVP (P = 0.041). Increased LVdP/dTMax during MSP-Max was associated with greater LV diameter and lower LV ejection fraction, independently of the QRS width. CONCLUSIONS: The study shows the hemodynamic advantage of a novel dual-vein MSP-Max configuration that could be useful for CRT in patients with advanced LV remodeling.

Multisite Left Ventricular Pacing in Cardiac Resynchronization Therapy.

Cardiac resynchronization therapy (CRT) is an established treatment of patients with heart failure with reduced ejection fraction and prolonged ventricular depolarization on surface electrocardiogram. Although patients' characteristics, such as their type of cardiomyopathy and the morphology and width of their baseline QRS complex, have been associated with CRT response, these features are not modifiable. Left ventricular multisite pacing has been proposed and tested as a tool to improve response to CRT and positively impact patient outcomes. This article reviews the published literature on left ventricular multisite pacing, with focus on the results of recently presented or published clinical trials.

Pacing Optimized by Left Ventricular dP/dtmax.

Left ventricular (LV) dP/dtmax provides a sensitive measure of the acute hemodynamic response to cardiac resynchronization therapy (CRT) and can predict reverse remodeling on echocardiography. Its use to guide LV lead placement has been shown to improve outcomes in a multicenter randomized trial. Given the invasive protocol required for measurement, it is unlikely to be universally beneficial for patients undergoing CRT but may be useful for patients who do not respond to conventional CRT, or in those who have borderline indications or risk factors for non-response. In such cases, LV dP/dtmax may help guide LV lead placement, optimize device programming, and select the best alternative method of delivering CRT, such endocardial LV pacing or conduction system pacing.

Anodal Capture for Multisite Pacing with a Quadripolar Left Ventricular Lead: A Feasibility Study.

BACKGROUND: Up to 40% of patients are CRT non-responders. Multisite pacing, using a unique quadripolar lead, also called multipoint/multipole pacing (MPP), is a potential alternative. We sought to determine the feasibility of intentional anodal capture using a single LV quadripolar lead, to reproduce MPP without the need of a specific algorithm (so-called "pseudo MPP"). METHODS: Consecutive patients implanted with a commercially available CRT device and a quadripolar LV lead in our department were prospectively included. The electric charge (Q, in Coulomb) of RV and LV pacing spikes were calculated for all available LV pacing configurations at the threshold. The best MPP was defined as the configuration with the lowest consumption (QRV + Qbest LV1 + Qbest LV2). The best "pseudo MPP" (QRV + QLV1-LV2 with anodal capture) and best BVp (QRV + Qbest LV) were also calculated. A theoretical longevity was estimated for each configuration at the threshold without a safety margin. RESULTS: A total of 235 configurations were tested in 15 consecutive patients. "Pseudo-MPP" was feasible in 80% of patients with 3.1 ± 2.6 vectors available per-patient and LVproximal-LVdistal (most distant electrodes) vectors were available in 47% of patients. Each MPP pacing spike electrical charge was comparable to "pseudo-MPP" (18,428 ± 6863 µC and 20,528 ± 5509 µC, respectively, p = 0.15). Theoretical longevity was 6.2 years for MPP, 5.6 years for "pseudo-MPP" and 13.7 years for BVp. CONCLUSIONS: "Pseudo MPP" using intentional anodal capture with a quadripolar left ventricular lead, mimicking conventional multisite pacing, is feasible in most of CRT patients, with comparable energy consumption. Further studies on their potential clinical impact are needed.

Multisite pacing and myocardial scars: a computational study.

Cardiac resynchronization therapy (CRT) is a frequently effective treatment modality for dyssynchronous heart failure, however, 30% of patients do not respond, usually due to suboptimal activation of the left ventricle (LV). Multisite pacing (MSP) may increase the response rate, but its effect in the presence of myocardial scars is not fully understood. We use a computational model to study the outcome of MSP in an LV with scars in two different locations and of two different sizes. The LV was stimulated from anterior, posterior and lateral locations individually and in pairs, while a septal stimulation site represented right ventricular (RV) pacing. Intraventricular pressures were measured, and outcomes evaluated in terms of maximum LV pressure gradient (dP/dtmax)- change compared to isolated RV pacing. The best result obtained using various LV pacing locations included a combination of sites remote from scars and the septum. The highest dP/dtmax increase was achieved, regardless of scar size, using MSP with one pacing site located on the LV free wall opposite to the scar and one site opposite to the septum. These in silico modelling results suggest that making placement of pacing electrodes dependent on location of scarring, may alter acute haemodynamics and that such modelling may contribute to future CRT optimization.

Multisite pacing via a quadripolar lead for cardiac resynchronization therapy.

Cardiac resynchronization therapy is challenging. Up to 40% of patients are non-responder. Multisite pacing via a quadripolar lead, also called multipoint/multipole pacing (MPP), is a debated alternative. In this review, we summarize evidence in the literature, tips and pitfalls related to MPP programming, and the different algorithms of MPP in different manufacturers.

Benefits of Multisite/Multipoint Pacing to Improve Cardiac Resynchronization Therapy Response.

This article provides a general overview of the underlying mechanisms that support pacing from more discrete points and/or a wider vector (multisite and multipoint pacing) to improve left ventricular resynchronization. We performed a critical overview of the current literature and to identify some remaining knowledge gaps to spur further research. It was not our goal to provide a systematic review with a comprehensive bibliography, but rather to focus on selected publications that, in our opinion, have either expertly reviewed a specific aspect of cardiac resynchronization therapy or have been landmark studies in the field.

Ventricular force-frequency relationships during biventricular or multisite pacing in congenital heart disease.

BACKGROUND: Traditional indices to evaluate biventricular (BiV) pacing are load dependent, fail to assess dynamic changes, and may not be appropriate in patients with congenital heart disease (CHD). We therefore measured the force-frequency relationship (FFR) using tissue Doppler-derived isovolumic acceleration (IVA) to assess the dynamic adaption of the myocardium and its variability with different ventricular pacing strategies. METHODS: This was a prospective pilot study of pediatric and young adult CHD patients with biventricular or multisite pacing systems. Color-coded myocardial velocities were recorded at the base of the systemic ventricular free wall. IVA was calculated at resting heart rate and with incremental pacing. FFR curves were obtained by plotting IVA against heart rate for different ventricular pacing strategies. RESULTS: Ten patients were included (mean: 22 ± 7 years). The FFR identified a best and worst ventricular pacing strategy for each patient, based on the AUC at baseline, submaximal, and peak heart rates (P < .001). However, there was no single best ventricular pacing strategy that was optimal for all patients. Additionally, the best ventricular pacing strategy often differed within the same patient at different heart rates. CONCLUSION: This novel assessment demonstrates a wide variability in optimal ventricular pacing strategy. These inherent differences may play a role in the unpredictable clinical response to BiV pacing in CHD, and emphasizes an individualized approach. Furthermore, the optimal ventricular pacing varies with heart rate within individuals, suggesting that rate-responsive ventricular pacing modulation may be required to optimize ventricular performance.