Variable left ventricular activation pattern in patients with heart failure and left bundle branch block

Electrocardiographic Predictors of Complete Heart Block During Right Ventricular Lead Implantation in Patients Who Underwent Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) device procedures have their own complications in addition to the complications associated with standard pacemaker implantations. This study aimed to analyze the predictors of the right bundle branch injury resulting in complete heart block (CHB) during right ventricular (RV) lead implantation in patients who underwent CRT with defibrillator. We conducted an observational study of consecutive 790 patients who underwent CRT with defibrillator device implantation at our institution from 2010 to 2022. Relevant clinical information and complete data regarding the echocardiographic data, implantation procedure, and clinical follow-up were collected into a computerized database. A total of 29 patients (3.7%) had CHB during RV lead implantation. In multivariate analysis, left axis deviation (odds ratio [OR] 2.408, 95% confidence interval [CI] 1.025 to 5.658, p = 0.044), QRS width (OR 1.022, 95% CI 1.001 to 1.043, p = 0.035) and QRS alternans (OR 4.214, 95% CI 1.788 to 9.930, p = 0.001) were found independently related to right bundle branch injury resulting in CHB development during RV lead implantation. In conclusion, left axis deviation, QRS width, and QRS alternans were associated with a higher rate of CHB, and these findings provide insight into optimal and safe CRT device implantation strategies based on preprocedural characteristics.

Cardiac Resynchronization Therapy and Left Atrial Remodeling: A Novel Insight?

Cardiac resynchronization therapy (CRT) restores ventricular dyssynchrony, improving left ventricle (LV) systolic function, symptoms, and outcome in patients with heart failure, systolic dysfunction, and prolonged QRS interval. The left atrium (LA) plays tremendous roles in maintaining cardiac function, being often inflicted in various cardiovascular diseases. LA remodeling implies structural-dilation, functional-altered phasic functions, and strain and electrical-atrial fibrillation remodeling. Until now, several important studies have approached the relationship between LA and CRT. LA volumes can predict responsiveness to CRT, being also associated with improved outcome in these patients. LA function and strain parameters have been shown to improve after CRT, especially in those who were positive responders to it. Further studies still need to be conducted to comprehensively characterize the impact of CRT on LA phasic function and strain, and, also, in conjunction with its impact on functional mitral regurgitation and LV diastolic dysfunction. The aim of this review was to provide an overview of current available data regarding the relation between CRT and LA remodeling.

Vectorcardiography-derived index allows a robust quantification of ventricular electrical synchrony

Alteration of muscle activation sequence is a key mechanism in heart failure with reduced ejection fraction. Successful cardiac resynchronization therapy (CRT), which has become standard therapy in these patients, is limited by the lack of precise dyssynchrony quantification. We implemented a computational pipeline that allows assessment of ventricular dyssynchrony by vectorcardiogram reconstruction from the patient’s electrocardiogram. We defined a ventricular dyssynchrony index as the distance between the voltage and speed time integrals of an individual observation and the linear fit of these variables obtained from a healthy population. The pipeline was tested in a 1914-patient population. The dyssynchrony index showed minimum values in heathy controls and maximum values in patients with left bundle branch block (LBBB) or with a pacemaker (PM). We established a critical dyssynchrony index value that discriminates electrical dyssynchronous patterns (LBBB and PM) from ventricular synchrony. In 10 patients with PM or CRT devices, dyssynchrony indexes above the critical value were associated with high time to peak strain standard deviation, an echocardiographic measure of mechanical dyssynchrony. Our index proves to be a promising tool to evaluate ventricular activation dyssynchrony, potentially enhancing the selection of candidates for CRT, device configuration during implantation, and post-implant optimization.

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.

Differentiation between left bundle branch block (LBBB) preceded dilated cardiomyopathy and dilated cardiomyopathy preceded LBBB by cardiac magnetic resonance imaging

BACKGROUND

Dilated cardiomyopathy (DCM) may be a result of or the cause of left bundle branch block (LBBB) in patients with DCM and LBBB. It is almost impossible from the history alone to know which came first in clinical work.

METHODS

Patients with LBBB and DCM who had cardiac magnetic resonance (CMR) examination were analyzed. Occurrence sequence of DCM and LBBB was determined by chart reviewing. Diastolic lateral/septal wall thickness ratio (DLSWTR) and lateral wall thickening (LWT) were compared between patients with different time sequences. Response to CRT was analyzed according to medical history and CMR manifestation.

RESULTS

Sixty-three patients were divided into two groups by cluster analysis. DLSWTR and LWT were significantly higher in group 1 (preserved lateral wall thickness and function), compared to those in group 2 (reduced lateral wall thickness and function) (1.06 ± 0.13 vs. 0.8 ± 0.12, 34.57 ± 11.48% vs. 11.18 ± 5.56%, respectively, both P < .001). Occurrence sequence was clear in 14 patients and further analyzed. In group 1, seven patients were clearly having no evidence of DCM when LBBB was first diagnosed (defined as LBBB-precede-DCM) and in group 2, seven patients did not have LBBB when DCM was diagnosed (defined as DCM-precede-LBBB). Among 10 patients who received CRT therapy, all seven patients in group 1 responded well whereas none of three patients in group 2 responded well.

CONCLUSIONS

Occurrence sequence of DCM and LBBB can be discriminated by CMR. Preserved lateral wall morphology and function in CMR suggested LBBB preceded to DCM. Such features may be predictors of good response to CRT.

The Temporal Relation between Cardiomyopathy and LBBB and Response to Cardiac Resynchronization Therapy: Case Series and Literature Review

Background: Left bundle branch block (LBBB)-induced cardiomyopathy has been proposed, but the association between LBBB and cardiac resynchronization therapy (CRT) response remains unclear and practical criteria for selecting CRT candidates are needed.Methods: One hundred and seventeen consecutive heart failure patients were reviewed, 24 of whom received CRT. Only two patients had a clear temporal relation between cardiomyopathy and LBBB.Results: Compared with the patient with “cardiomyopathy-induced LBBB,” the patient with “LBBB-induced cardiomyopathy” had higher left ventricular (LV) wall thickness, higher LV wall thickening rate, higher peak circumferential strain, and longer peak circumferential strain delay. The LV deformation patterns in the two patients were obviously distinct on cardiovascular magnetic resonance tissue tracking. During follow-up, the patient with LBBB-induced cardiomyopathy had a good response to CRT (LV ejection fraction 23 before CRT vs. 30% at 6 months vs. 29 at 12 months vs. 32% at 18 months; LV end-diastolic diameter 77 mm before CRT vs. 66 mm at 6 months vs. 62 mm at 12 months vs. 63 mm at 18 months), and the other patient had no response to CRT (LV ejection fraction 29 before CRT vs. 29% at 6 months vs. 26 at 12 months vs. 22% at 24 months; LV end-diastolic diameter 85 mm before CRT vs. 88 mm at 6 months vs. 85 mm at 12 months vs. 84 mm at 24 months).Conclusion: The temporal relation between cardiomyopathy and LBBB could be a determinant for CRT response. Cardiovascular magnetic resonance tissue tracking may be a useful tool to identify the chronological order and a principal consideration for selecting candidates for CRT. Larger prospective clinical trials are needed to study the prevalence of, time course of, and risk factors for LBBB-induced cardiomyopathy.

[Resynchronization Therapy for Chronic Heart Failure: Diagnostic and Therapeutic Approaches]

Chronic heart failure (CHF) remains one of the most important problems of modern cardiology. One of the effective treatment methods is resynchronization therapy (RT). The article presents an analysis of literature data on the effectiveness of RT in improving the quality of life, reducing the number of hospitalizations and mortality in patients with heart failure with severe left ventricular systolic dysfunction and expanding QRS complex, and also discusses key methods for optimizing RT.

CRT Optimization: What Is New? What Is Necessary?

Cardiac resynchronization therapy (CRT) has proven to improve quality of life, reduce heart failure hospitalization, and prolong life in selected heart failure patients with reduced ejection fraction, on optimal medical therapy and with electrical dyssynchrony. To ensure maximal benefit for CRT patients, optimization of care should be implemented. This begins with appropriate referring as well as selecting patients, knowing that the presence of left bundle branch block and QRS ≥ 150 ms is associated with the greatest reverse remodeling. The LV lead, preferably quadripolar, is best targeted in a postero-lateral position. After implantation, optimal device programming should aim for maximal biventricular pacing and in selected cases further electrical delay optimization might be of use. Even as important, is the implementation of thorough multidisciplinary heart failure care with medication uptitration, remote monitoring, rehabilitation, and patient education. The role of newer pacing strategies as endocardial or His-bundle pacing remains the subject of ongoing investigation.

[Assessment of myocardial electrical dissynchrony by noninvasive activation mapping and its role in achieving the success of cardiac resynchronization]

PURPOSE

To assess and to compare the ventricular myocardium activation patern obtained by non-invasive epi- and endocardial mapping (NIEEM), as well as electrocardiographic (ECG) variants of lef bundle branch block (LBBB) and to estimate the value of these data for the success of cardiac resynchronization therapy (CRT).

MATERIALS AND METHODS

Te study included 23 patients (mean age 59,6±9,9 years) with LBBB, QRS duration ≥ 130 ms, lef ventricular ejection fraction (LVEF) ≤ 35%, heart failure (HF) NYHA II-IV despite optimal pharmacological therapy during 3 month. All patients had undergone CRT-D implantation. Depending on presence or absence of LBBB ECG-criteria, proposed by Strauss D.G. et. al, patients were divided into 2 groups: 1group - strict LBBB, proposed by Strauss D.G. et. al. (n=14) and 2 group - other ECG morphologies of LBBB (n=9). NIEEM by the Amycard 01C system with an analysis of epi- and endocardial ventricular electrical activation was performed in all patients and 5 healthy volunteers (mean age 29±1,0years). Response to CRT was estimated by echo and was defned as decrease in lef ventricular (LV) end-systolic volume by &gt; 15% afer 6 months of follow-up.

RESULTS

LBBB ECG-criteria, proposed by Strauss D.G. et. al, was detected in 14 patients (61% of all included). According to the results of NIEEM, these patients had more pronounced ventricular electrical uncoupling (VEU) (р=0,002). Most ofen the line of block was detected in the anteroseptal or posterolateral region of the LV. Te zone of late LV activation, which is the most optimal position for the LV pacing electrode, was located in the basal and middle segments of the lateral and posterior walls. Afer 6 months of CRT 15 patients (65%) were included in the "response" group, the remaining 8 patients (35%) formed the "non-response" group according to echo criteria. In the "response" group the morphology of the QRS complex more frequently met the criteria, proposed by Strauss D.G. et al, than other ECG variants of LBBB (12 vs. 3 respectively, p = 0.023). Initially, VEU was more pronounced in the "response" group (VEU 55 [51, 64] ms in the "response" group vs 22 [8, 38] ms in the "non-response" group).Сonclusions. LBBB ECG criteria, proposed by Strauss D.G., identify patients with delayed transseptal interventricular conduction due to complete LBBB, what is a good target for CPT. Identifcation of individual ventricular activation properties may help to reveal responders to CRT in patients with LBBB.

Surface electrogram-guided left ventricular lead placement improves response to cardiac resynchronization therapy

OBJECTIVE

Failure to select the optimal left ventricular (LV) segment for lead implantation is one of the most important causes of unresponsiveness to the cardiac resynchronization therapy (CRT). In our study, we aimed to investigate the echocardiographic and clinical benefits of LV lead implantation guided by an intraoperative 12-lead surface electrocardiogram (ECG) in patients with multiple target veins.

METHODS

We included 80 [42 (62.5%) male] heart failure patients who successfully underwent CRT defibrillator (CRT-D) implantation. Patients were divided into two groups. In group 1, LV lead was positioned at the site with the shortest biventricular-paced (BiV-paced) QRS duration (QRSd), as intraprocedurally measured using surface ECG. In group 2 (control), we included patients who underwent the standard unguided CRT. ECG, echocardiogram, and functional status were evaluated before and 6 months after CRT implantation in all patients.

RESULTS

In group 1, BiV-paced QRSd measurements were successfully performed in 112 of 120 coronary sinus branches during CRT and an LV lead was successfully placed at the optimal site in all patients. Compared with group 2, group 1 had a significantly higher rate (85% vs. 50%, p=0.02) of response (>15% reduction in LV end-systolic volume) to CRT as well as a shorter QRSd (p<0.001) and a greater QRS shortening (ΔQRS) associated with CRT compared with baseline (p<0.001). The mean New York Heart Association functional class was significantly improved in both groups, and no significant differences were found in clinical response to CRT (85% vs. 70%, p=0.181).

CONCLUSION

Surface ECG can be used to guide LV lead placement in patients with multiple target veins for improving response to CRT. Thus, it is a safe, feasible, and economic approach for CRT-D implantation.

Alternative left ventricular pacing approaches for optimal cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) improves mortality, morbidity, and quality of life in selected heart failure patients with severe left ventricular (LV) ejection fraction impairment. However, between 20% and 40% of device recipients do not benefit clinically from CRT. Indeed, some anatomic and technical difficulties are related to the coronary venous implantation site via the coronary sinus (CS). Additionally, electrical constraints have been described, and CS does not always correspond to the optimal LV lead position. In the last decade, engineers and physicians have worked together to overcome the challenging LV lead implantation, and various biventricular pacing alternatives have been developed to improve CRT response. In this review, we discuss the evolution from CS pacing to wireless LV stimulation and His-bundle pacing.

Understanding non-response to cardiac resynchronisation therapy: common problems and potential solutions

Heart failure is a complex clinical syndrome associated with a significant morbidity and mortality burden. Reductions in left ventricular (LV) function trigger adaptive mechanisms, leading to structural changes within the LV and the potential development of dyssynchronous ventricular activation. This is the substrate targeted during cardiac resynchronisation therapy (CRT); however, around 30-50% of patients do not experience benefit from this treatment. Non-response occurs as a result of pre-implant, peri-implant and post implant factors but the technical constraints of traditional, transvenous epicardial CRT mean they can be challenging to overcome. In an effort to improve response, novel alternative methods of CRT delivery have been developed and of these endocardial pacing, where the LV is stimulated from inside the LV cavity, appears the most promising.

Assessment of left ventricular contraction patterns using gated SPECT MPI to predict cardiac resynchronization therapy response

BACKGROUND

The U-shaped left ventricular (LV) contraction pattern, identified by MRI or echocardiography, is associated with improved CRT response. Gated SPECT MPI can measure both myocardial viability and mechanical dyssynchrony in a single scan. The aim of this study is to examine the relationship of the LV contraction pattern and the response of CRT in patients with left bundle branch block (LBBB).

METHODS

Fifty-eight patients who met CRT guidelines and who had pre-CRT MPI were enrolled. Myocardial segments with tracer uptake < 50% of maximum were considered as scar. The LV contraction pattern was considered as U-shaped or non-U-shaped (U-shaped has a block line in the direction of contraction propagation). CRT response was defined as an increase in left ventricular ejection fraction ≥ 5% after 6-month follow-up.

RESULTS

Twenty-eight patients (48%) had a U-shaped contraction pattern and thirty patients (52%) had a non-U-shaped contraction pattern. The U-shaped group showed a significantly higher response rate than the non-U-shaped group (90% vs. 57%; P = 0.005). By univariate and multivariate logistic regression analysis, the U-shaped pattern was an independent predictor of CRT response.

CONCLUSION

Non-invasive gated SPECT MPI can characterize LV mechanical contraction patterns. A U-shaped contraction pattern identified is associated with improved CRT response. This may prove useful for improved patient selection for CRT.

[Coronary sinus mapping of the optimal LV electrode position]

Cardiac resynchronization therapy (CRT) is an established pillar of treatment for patients with chronic heart failure. However, 30% of patients do not respond adequately to this type of therapy. One possible reason for this is a nonoptimal left ventricular stimulation site. This review focuses on possibilities of visualization of the coronary vein anatomy and its role in the determination of the electrical and mechanical dyssynchrony to optimize the therapeutic success of the resynchronization therapy. In addition, the clinical implication and the perspectives of a dedicated mapping of the coronary vein are discussed. Finally, a brief outlook on current and future technologies for improving this form of therapy is given.

Comparison of triple-site ventricular pacing versus conventional cardiac resynchronization therapy in patients with systolic heart failure: A meta-analysis of randomized and observational studies

Background

Conventional cardiac resynchronization therapy (CRT, Bi‐V) is associated with no response in about 40% patients due to an insufficient resynchronization. Some studies showed triple‐site ventricular (Tri‐V) pacing had greater benefits compared with Bi‐V pacing, but the results of these studies were conflicting. We hypothesized that Tri‐V pacing had greater benefits on long‐term outcomes compared with Bi‐V pacing in patients with heart failure.

Methods

PubMed, EMBASE, and the Cochrane Library were searched for clinical studies with related outcomes. Weighted mean differences (WMD) and 95% confidence intervals (CIs) were calculated to compare the change in left ventricular ejection fraction (LVEF), left ventricular geometry, functional capacity, and quality of life between Tri‐V pacing group and control group.

Results

Five trials with 251 patients were included in the analysis. Patients in the Tri‐V pacing group had a greater improvement in LVEF (WMD 4.04; 95% CI 2.15‐5.92, P < .001) and NYHA classes (WMD −0.27; 95% CI −0.42 to −0.11, P = .001) compared with control group. However, there were no significant differences in left ventricular geometry, six‐min walk distance, or Minnesota Living With Heart Failure Questionnaire score between the two groups. The subgroup analyses showed there might be a greater improvement in LVEF in the Tri‐V pacing group in patients with QRS duration ≥ 155 ms (WMD 5.60; 95% CI 3.09‐8.10, P < .001).

Conclusions

The present analysis suggests that Tri‐V pacing has greater benefits in terms of an improvement in LVEF and functional capacity in patients with systolic heart failure, especially in patients with the duration of QRS ≥ 155 ms.

Absence of Rapid Propagation through the Purkinje Network as a Potential Cause of Line Block in the Human Heart with Left Bundle Branch Block

Background: Cardiac resynchronization therapy is an effective device therapy for heart failure patients with conduction block. However, a problem with this invasive technique is the nearly 30% of non-responders. A number of studies have reported a functional line of block of cardiac excitation propagation in responders. However, this can only be detected using non-contact endocardial mapping. Further, although the line of block is considered a sign of responders to therapy, the mechanism remains unclear.

Methods: Herein, we created two patient-specific heart models with conduction block and simulated the propagation of excitation based on a cellmodel of electrophysiology. In one model with a relatively narrow QRS width (176 ms), we modeled the Purkinje network using a thin endocardial layer with rapid conduction. To reproduce a wider QRS complex (200 ms) in the second model, we eliminated the Purkinje network, and we simulated the endocardial mapping by solving the inverse problem according to the actual mapping system.

Results: We successfully observed the line of block using non-contact mapping in the model without the rapid propagation of excitation through the Purkinje network, although the excitation in the wall propagated smoothly. This model of slow conduction also reproduced the characteristic properties of the line of block, including dense isochronal lines and fractionated local electrocardiograms. Further, simulation of ventricular pacing from the lateral wall shifted the location of the line of block. By contrast, in the model with the Purkinje network, propagation of excitation in the endocardial map faithfully followed the actual propagation in the wall, without showing the line of block. Finally, switching the mode of propagation between the two models completely reversed these findings.

Conclusions: Our simulation data suggest that the absence of rapid propagation of excitation through the Purkinje network is the major cause of the functional line of block recorded by non-contact endocardial mapping. The line of block can be used to identify responders as these patients loose rapid propagation through the Purkinje network.

Distinctive Left Ventricular Activations Associated With ECG Pattern in Heart Failure Patients

Background—

In contrast to patients with left bundle branch block (LBBB), heart failure patients with narrow QRS and nonspecific intraventricular conduction delay (NICD) display a relatively limited response to cardiac resynchronization therapy. We sought to compare left ventricular (LV) activation patterns in heart failure patients with narrow QRS and NICD to patients with LBBB using high-density electroanatomic activation maps.

Methods and Results—

Fifty-two heart failure patients (narrow QRS [n=18], LBBB [n=11], NICD [n=23]) underwent 3-dimensional electroanatomic mapping with a high density of mapping points (387±349 LV). Adjunctive scar imaging was available in 37 (71%) patients and was analyzed in relation to activation maps. LBBB patients typically demonstrated (1) a single LV breakthrough at the septum (38±15 ms post-QRS onset); (2) prolonged right-to-left transseptal activation with absence of direct LV Purkinje activity; (3) homogeneous propagation within the LV cavity; and (4) latest activation at the basal lateral LV. In comparison, both NICD and narrow QRS patients demonstrated (1) multiple LV breakthroughs along the posterior or anterior fascicles: narrow QRS versus LBBB, 5±2 versus 1±1; P =0.0004; NICD versus LBBB, 4±2 versus 1±1; P =0.001); (2) evidence of early/pre-QRS LV electrograms with Purkinje potentials; (3) rapid propagation in narrow QRS patients and more heterogeneous propagation in NICD patients; and (4) presence of limited areas of late activation associated with LV scar with high interindividual heterogeneity.

Conclusions—

In contrast to LBBB patients, narrow QRS and NICD patients are characterized by distinct mechanisms of LV activation, which may predict poor response to cardiac resynchronization therapy.

Left bundle-branch block contraction patterns identified from radial-strain analysis predicts outcomes following cardiac resynchronization therapy

A left bundle-branch block (LBBB) contraction pattern identified from longitudinal-strain analysis predicts outcomes following cardiac resynchronization therapy (CRT). We investigated the use of an LBBB-contraction pattern identified from radial- or circumferential-strain analysis in the prediction of CRT benefits. Eighty CRT candidates were prospectively enrolled. Before CRT implantation, speckle-tracking analyses in three deformation directions were performed to determine whether an LBBB-contraction pattern was present. The study endpoints were reverse remodeling at 6 months, and adverse outcomes including death or heart failure hospitalization. At 6 months, 49 (61%) patients had reverse remodeling. An LBBB-contraction pattern identified from the radial strain in the mid-ventricular short-axis view or longitudinal strain in the four-chamber view provided excellent true-positive (86%) and false-negative (8%) rates for predicting reverse remodeling. During a median follow-up of 30 months, 31 patients (39%) had adverse outcomes. Absence of an LBBB-contraction pattern in radial (hazard ratio 3.74; 95% confidence interval 1.83-7.62) or longitudinal strain (hazard ratio 3.49; 95% confidence interval 1.71-7.13) was significantly associated with an increased risk of adverse outcomes. Adding the LBBB-pattern assessment by radial-(model χ² from 8.2 to 18.5, p = 0.005), or longitudinal-strain analysis (model χ² from 8.2 to 16.9, p = 0.011) to a risk model significantly improved the model, including QRS duration and ischemic etiology. In conclusion, an LBBB-contraction pattern identified from radial-strain analysis in the mid-ventricular short-axis view predicted reverse remodeling and outcome following CRT, similarly to the longitudinal-strain analysis.

Association between Latest Activated Sites in the Left Ventricle and Akinetic Segments in Patients with Ischemic Cardiomyopathy

Background: It is not clear whether the latest activation sites in the left ventricle (LV) are matched with infracted regions in patients with ischemic cardiomyopathy (ICM). We aimed to investigate whether the latest activation sites in the LV are in agreement with the region of akinesia in patients with ICM. Methods: Data were analyzed in 106 patients (age = 60.5 ± 12.1 y, male = 88.7%) with ICM (ejection fraction ≤ 35%) who were refractory to pharmacological therapy and were referred to the echocardiography department for an evaluation of the feasibility of cardiac resynchronization therapy. Wall motion abnormalities, time to peak systolic myocardial velocity (Ts) of 6 basal and 6 mid-portion segments of the LV, and 4 frequently used dyssynchrony indices were measured using 2-dimensional echocardiography and tissue Doppler imaging (TDI). To evaluate the influence of the electrocardiographic pattern, we categorized the patients into 2 groups: patients with QRS ≤ 120 ms and those with QRS >120 ms. Results: A total of 1 272 segments were studied. The latest activation sites (with longest Ts) were most frequently located in the mid-anterior (n = 32, 30.2%) and basal-anterior segments (n = 29, 27.4%), while the most common sites of akinesia were the mid-anteroseptal (n = 65, 61.3%) and mid-septal (n = 51, 48.1%) segments. Generally, no significant concordance was found between the latest activated segments and akinesia either in all the patients or in the QRS groups. Detailed analysis within the segments indicated a good agreement between akinesia and delayed activation in the basal-lateral segment solely in the patients with QRS duration ≤ 120 ms (Φ = 0.707; p value ≤ 0.001). Conclusion: The akinetic segment on 2-dimensional echocardiogram was not matched with the latest activation sites in the LV determined by TDI in patients with ICM.

Innovative pacing: Recent advances, emerging technologies, and future directions in cardiac pacing

The field of cardiovascular medicine is rapidly evolving as advancements in technology and engineering provide clinicians new and exciting ways to care for an aging population. Cardiac pacing, in particular, has seen a series of game-changing technologies emerge in the past several years spurred by low-power electronics, high density batteries, improved catheter delivery systems and innovative software design. We look at several of these emerging pacemaker technologies, discussing the rationale, current state and future directions of these pioneering developments in electrophysiology.

Why QRS Duration Should Be Replaced by Better Measures of Electrical Activation to Improve Patient Selection for Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) is a well-known treatment modality for patients with a reduced left ventricular ejection fraction accompanied by a ventricular conduction delay. However, a large proportion of patients does not benefit from this therapy. Better patient selection may importantly reduce the number of non-responders. Here, we review the strengths and weaknesses of the electrocardiogram (ECG) markers currently being used in guidelines for patient selection, e.g., QRS duration and morphology. We shed light on the current knowledge on the underlying electrical substrate and the mechanism of action of CRT. Finally, we discuss potentially better ECG-based biomarkers for CRT candidate selection, of which the vectorcardiogram may have high potential.

Routine Implant of Biventricular Devices Guided by an Electroanatomic Mapping System - Ready for Prime-Time?

Biventricular devices play an important adjunctive role in the treatment of heart failure. However, biventricular device implantation is associated with significant radiation exposure and a high proportion of non-response to cardiac resynchronization therapy (CRT). The use of electroanatomic mapping (EAM) during biventricular device implantation may help overcome these issues. This article will review the literature on the role of EAM in biventricular device implantation.

Cardiac resynchronization therapy update: evolving indications, expanding benefit?

Cardiac resynchronisation therapy (CRT) is an effective intervention for appropriately selected patients with heart failure, but exactly how it works is uncertain. Recent data suggest that much, or perhaps most, of the benefits of CRT are not delivered by re-coordinating left ventricular dyssynchrony. Atrio-ventricular resynchronization, reduction in mitral regurgitation and prevention of bradycardia are other potential mechanisms of benefit that will vary from one patient to the next and over time. Because there is no single therapeutic target, it is unlikely that any single measure will accurately predict benefit. The only clinical characteristic that appears to be a useful predictor of the benefits of CRT is a QRS duration of >140 ms. Many new approaches are being developed to try to improve the effectiveness of and extend the indications for CRT. These include smart pacing algorithms, better pacing-site targeting, new sensors, multipoint pacing, remote device monitoring and leadless endocardial pacing. Whether CRT is effective in patients with atrial fibrillation or whether adding a defibrillator function to CRT improves prognosis awaits further evidence.

Prediction of response to cardiac resynchronization therapy using left ventricular pacing lead position and cardiovascular magnetic resonance derived wall motion patterns: a prospective cohort study

BACKGROUND

Despite marked benefits in many heart failure patients, a considerable proportion of patients treated with cardiac resynchronization therapy (CRT) fail to respond appropriately. Recently, a "U-shaped" (type II) wall motion pattern identified by cardiovascular magnetic resonance (CMR) has been associated with improved CRT response compared to a homogenous (type I) wall motion pattern. There is also evidence that a left ventricular (LV) lead localized to the latest contracting LV site predicts superior response, compared to an LV lead localized remotely from the latest contracting LV site.

METHODS

We prospectively evaluated patients undergoing CRT with pre-procedural CMR to determine the presence of type I and type II wall motion patterns and pre-procedural echocardiography to determine end systolic volume (ESV). We assessed the final LV lead position on post-procedural fluoroscopic images to determine whether the lead was positioned concordant to or remote from the latest contracting LV site. CRT response was defined as a ≥ 15% reduction in ESV on a 6 month follow-up echocardiogram.

RESULTS

The study included 33 patients meeting conventional indications for CRT with a mean New York Heart Association class of 2.8 ± 0.4 and mean LV ejection fraction of 28 ± 9%. Overall, 55% of patients were echocardiographic responders by ESV criteria. Patients with both a type II pattern and an LV lead concordant to the latest contracting site (T2CL) had a response rate of 92%, compared to a response rate of 33% for those without T2CL (p = 0.003). T2CL was the only independent predictor of response on multivariate analysis (odds ratio 18, 95% confidence interval 1.6-206; p = 0.018). T2CL resulted in significant incremental improvement in prediction of echocardiographic response (increase in the area under the receiver operator curve from 0.69 to 0.84; p = 0.038).

CONCLUSIONS

The presence of a type II wall motion pattern on CMR and a concordant LV lead predicts superior CRT response. Improving patient selection by evaluating wall motion pattern and targeting LV lead placement may ultimately improve the response rate to CRT.

Optimizing CRT - Do We Need More Leads and Delivery Methods

Cardiac resynchronization therapy (CRT) is an established therapeutic option in symptomatic heart failure with reduced ejection fraction and evidence of left ventricular (LV) conduction delay (QRS width ≥120 ms), especially when typical left bundle branch block is present. The rationale behind CRT is restoration of aberrant LV electrical activation. As there is considerable heterogeneity of the LV electrical activation pattern among CRT candidates, an individualized approach with targeting of the LV lead in the region of latest electrical activation while avoiding scar tissue may enhance CRT response. Echocardiography, electro anatomic mapping, and cardiac magnetic resonance imaging with late gadolinium enhancement are helpful to guide such targeted LV lead placement. However, an important limitation remains the anatomy of the coronary sinus, which often does not allow concordant LV lead placement in the optimal region. Epicardial LV lead placement through minimal invasive surgery or endocardial LV lead placement through transseptal punction may overcome this limitation, obviously with an increased complication risk. Furthermore, recent pacing algorithms suggest superiority of LV-only versus biventricular pacing in patients with preserved atrio ventricular (AV) conduction and a typical LBBB pattern. Finally, pacing from only one LV site might not overcome the wide electrical dispersion often seen in patients with LV conduction delays. Therefore, multisite pacing has gained significant interest to improve CRT response. The use of multiple LV leads may potentially lead to more favorable reverse remodeling, improved functional capacity and quality of life in CRT candidates, but adverse events and a shorter battery span are more frequent because of the extra lead. The use of one multipolar LV lead increases the number of pacing configurations within the same coronary sinus side branch (within small distances from each other) without the use of an additional lead. Small observational studies suggest that more effective resynchronization can be achieved with this approach. Finally, there are many reasons for non effective CRT delivery in carefully selected patients with an adequately implanted device. Multidisciplinary, post implantation care inside a dedicated CRT clinic ensures optimal CRT delivery, improves response rate and should be considered standard of care.

Electrocardiographic imaging of heart rhythm disorders: from bench to bedside

Noninvasive electrocardiographic imaging (ECGI; also called ECG mapping) can reconstruct potentials, electrograms, activation sequences, and repolarization patterns on the epicardial surface of the heart with high resolution. ECGI can possibly be used to quantify synchrony, identify potential responders/nonresponders to cardiac resynchronization therapy, and guide electrode placement for effective resynchronization therapy. This article provides a brief description of the ECGI procedure and selected previously published examples of its application in important clinical conditions, including heart failure, cardiac resynchronization therapy, atrial arrhythmias, and ventricular tachycardia.

Integration of mechanical, structural and electrical imaging to understand response to cardiac resynchronization therapy

INTRODUCTION AND OBJECTIVES

There is extensive controversy exists on whether cardiac resynchronization therapy corrects electrical or mechanical asynchrony. The aim of this study was to determine if there is a correlation between electrical and mechanical sequences and if myocardial scar has any relevant impact.

METHODS

Six patients with normal left ventricular function and 12 patients with left ventricular dysfunction and left bundle branch block, treated with cardiac resynchronization therapy, were studied. Real-time three-dimensional echocardiography and electroanatomical mapping were performed in all patients and, where applicable, before and after therapy. Magnetic resonance was performed for evaluation of myocardial scar. Images were postprocessed and mechanical and electrical activation sequences were defined and time differences between the first and last ventricular segment to be activated were determined. Response to therapy was defined as a reduction in left ventricular end-systolic volume ≥ 15% after 12 months of follow-up.

RESULTS

Good correlation between electrical and mechanical timings was found in patients with normal left ventricular function (r(2) = 0.88; P = .005) but not in those with left ventricular dysfunction (r(2) = 0.02; P = not significant). After therapy, both timings and sequences were modified and improved, except in those with myocardial scar.

CONCLUSIONS

Despite a close electromechanical relationship in normal left ventricular function, there is no significant correlation in patients with dysfunction. Although resynchronization therapy improves this correlation, the changes in electrical activation may not yield similar changes in left ventricular mechanics particularly depending on the underlying myocardial substrate.

A U-shaped type II contraction pattern in patients with strict left bundle branch block predicts super-response to cardiac resynchronization therapy

BACKGROUND

New criteria to define strict left bundle branch block (LBBB) on the basis of pathophysiological principles predict response to cardiac resynchronization therapy (CRT). Heterogeneous activation and contraction patterns have been identified in patients with classical LBBB. Cardiac magnetic resonance (CMR) imaging has demonstrated that a U-shaped (type II) contraction predicts reverse remodeling post-CRT. A homogeneous spread of (type I) contraction is less predictive.

OBJECTIVES

The purpose of this study was to investigate contraction patterns among patients with strict LBBB and to test whether a type II contraction pattern better predicts CRT response and super-response.

METHODS

Thirty-seven patients with strict LBBB (QRS duration ≥140 ms for men and ≥130 ms for women with mid-QRS notching or slurring in ≥2 contiguous leads) underwent cine CMR imaging pre-CRT with an analysis of their contraction patterns by using endocardial contour tracking software. Patients were evaluated for reverse remodeling 6 months postimplantation.

RESULTS

Nineteen patients (51%) had a type II contraction pattern. A total of 25 patients (68%) of the cohort reverse remodeled. In the type II contraction group, all 19 patients (100%) reverse remodeled as compared with 6 patients (33%) in the type I contraction group (P < .01). Super-response was achieved in 21 patients (57%) of the total cohort: 5 patients with a type I contraction pattern (28%) and 16 patients with a type II contraction pattern (84%) (P < .01).

CONCLUSION

Patients with strict LBBB who are guideline indicated for CRT have heterogeneous contraction patterns derived from cine CMR. A type II contraction pattern is strongly predictive for reverse remodeling and super-response. This questions whether strict LBBB criteria alone are sufficient to reliably predict a positive response to CRT.

Strategies to improve cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) emerged 2 decades ago as a useful form of device therapy for heart failure associated with abnormal ventricular conduction, indicated by a wide QRS complex. In this Review, we present insights into how to achieve the greatest benefits with this pacemaker therapy. Outcomes from CRT can be improved by appropriate patient selection, careful positioning of right and left ventricular pacing electrodes, and optimal timing of electrode stimulation. Left bundle branch block (LBBB), which can be detected on an electrocardiogram, is the predominant substrate for CRT, and patients with this conduction abnormality yield the most benefit. However, other features, such as QRS morphology, mechanical dyssynchrony, myocardial scarring, and the aetiology of heart failure, might also determine the benefit of CRT. No single left ventricular pacing site suits all patients, but a late-activated site, during either the intrinsic LBBB rhythm or right ventricular pacing, should be selected. Positioning the lead inside a scarred region substantially impairs outcomes. Optimization of stimulation intervals improves cardiac pump function in the short term, but CRT procedures must become easier and more reliable, perhaps with the use of electrocardiographic measures, to improve long-term outcomes.

Noninvasive electrocardiographic imaging of arrhythmogenic substrates in humans

Cardiac excitation is determined by interactions between the source of electric activation (membrane depolarization) and the load that cardiac tissue presents. This relationship is altered in pathology by remodeling processes that often create a substrate favoring the development of cardiac arrhythmias. Most studies of arrhythmia mechanisms and arrhythmogenic substrates have been conducted in animal models, which may differ in important ways from the human pathologies they are designed to represent. Electrocardiographic imaging is a noninvasive method for mapping the electric activity of the heart in humans in real-world conditions. This review summarizes results from electrocardiographic imaging studies of arrhythmogenic substrates associated with human clinical arrhythmias. Examples include heart failure, myocardial infarction scar, atrial fibrillation, and abnormal ventricular repolarization.

Coronary sinus anatomy by computerized tomography, overlaid on live fluoroscopy can be successfully used to guide left ventricular lead implantation: a feasibility study

OBJECTIVE

This study aims to optimize coronary sinus (CS) computerized tomography (CT) imaging and evaluate its utility for preprocedural planning and intraoperative guidance by overlay of 3D reconstructed CS images on live fluoroscopy.

BACKGROUND

Optimal CS lead placement for cardiac resynchronization therapy (CRT) remains challenging. Preprocedural knowledge of CS anatomy can significantly affect procedural outcome. Optimal CS imaging protocols by CT have not been well defined.

METHODS

Seventeen consecutive CRT recipients underwent contrast-enhanced functional cardiac CT on a 64-slice scanner. The CS target branch closest to the most dyssynchronous LV segment was identified. 3D volume rendered CS images were superimposed onto live fluoroscopy via EP Navigator (Philips Healthcare, Best, The Netherlands) to guide CS cannulation and lead placement. The imaging protocol was optimized.

RESULTS

CT images were successfully reconstructed and overlaid on live fluoroscopy in 16/17 patients. The overlay facilitated CS cannulation and lead placement into a predefined target branch. Excellent correlation between CT and angiographic CS anatomy was noted. By using the overlaid 3D CS as a road map, average total fluoroscopy time (14.56 ± 4.22 min) was significantly shorter when compared to historical controls. Total radiation exposure was significantly higher in the CT-guided group. Images obtained using double bolus injection and gated acquisition at 40 % of the cardiac cycle contained the most anatomical detail of the CS.

CONCLUSION

Overlay of 3D CS anatomy defined by preprocedural cardiac CT is feasible. It allows planning of CRT implantation and live guidance of CS lead placement into a predefined target branch. Limiting the CT imaging to 40 % of the cardiac cycle phase provides optimal CS images and reduces radiation exposure. This approach may result in shorter procedural time and more optimal CS lead positioning. However, the concept remains to be confirmed by future studies.