Body surface activation mapping of electrical dyssynchrony in cardiac resynchronization therapy patients: Potential for optimization

Assessment of electrical dyssynchrony in cardiac resynchronization therapy: 12-lead electrocardiogram vs. 96-lead body surface map

AIMS

The standard deviation of activation time (SDAT) derived from body surface maps (BSMs) has been proposed as an optimal measure of electrical dyssynchrony in patients with cardiac resynchronization therapy (CRT). The goal of this study was two-fold: (i) to compare the values of SDAT in individual CRT patients with reconstructed myocardial metrics of depolarization heterogeneity using an inverse solution algorithm and (ii) to compare SDAT calculated from 96-lead BSM with a clinically easily applicable 12-lead electrocardiogram (ECG).

METHODS AND RESULTS

Cardiac resynchronization therapy patients with sinus rhythm and left bundle branch block at baseline (n = 19, 58% males, age 60 ± 11 years, New York Heart Association Classes II and III, QRS 167 ± 16) were studied using a 96-lead BSM. The activation time (AT) was automatically detected for each ECG lead, and SDAT was calculated using either 96 leads or standard 12 leads. Standard deviation of activation time was assessed in sinus rhythm and during six different pacing modes, including atrial pacing, sequential left or right ventricular, and biventricular pacing. Changes in SDAT calculated both from BSM and from 12-lead ECG corresponded to changes in reconstructed myocardial ATs. A high degree of reliability was found between SDAT values obtained from 12-lead ECG and BSM for different pacing modes, and the intraclass correlation coefficient varied between 0.78 and 0.96 (P < 0.001).

CONCLUSION

Standard deviation of activation time measurement from BSM correlated with reconstructed myocardial ATs, supporting its utility in the assessment of electrical dyssynchrony in CRT. Importantly, 12-lead ECG provided similar information as BSM. Further prospective studies are necessary to verify the clinical utility of SDAT from 12-lead ECG in larger patient cohorts, including those with ischaemic cardiomyopathy.

Non-invasive assessment of ventricular electrical heterogeneity to optimize left bundle branch area pacing

BACKGROUND

Left bundle branch area pacing (LBBAP) is a novel therapeutic option for bradycardia and heart failure patients. ECG belt is a novel technology for assessment of ventricular electrical heterogeneity (VEH) using multi-electrode ECG. A metric of overall VEH based on standard deviation of activation times (SDAT) from all electrodes in the ECG belt has been previously shown to predict cardiac resynchronization therapy (CRT) response. The aim of the study is to evaluate non-invasive assessment of VEH using ECG belt to optimize LBBAP.

METHODS

VEH from a 40-electrode ECG belt was characterized in 20 patients (male 15, EF 33 ± 13%, NYHA class 3.05 ± 0.6; CRT indication 18) during LBBAP (20) and LBBAP-Optimized CRT (LOT-CRT-7), anodal capture (16), NS-LBBP (18), S-LBBP (5), LVSP (9). In addition to SDAT, regional (LV/RV) VEH was assessed with average left ventricular activation times (LVAT), SDAT of left-sided (LV dispersion) and right-sided (RV dispersion) electrodes. Optimal LBBAP was determined based on maximal SDAT and QRS duration (d) change.

RESULTS

All metrics were significantly reduced (p < 0.0001 for ECG belt metrics, p = 0.0027 for QRSd) during LBBAP and LOT-CRT compared to intrinsic. QRSd, SDAT, LVAT, and LV and RV dispersion during optimal LBBAP were significantly lower (133 ± 20/157 ± 24; 20.5 ± 7.5/38.6 ± 9; 44.4 ± 14.3/61.4 ± 21; 11.6 ± 11.6/29.5 ± 15; 21.1 ± 7.8/42.5 ± 9.3; p < 0.0001) compared to intrinsic rhythm. However, they were not significantly different among selective, non-selective, anodal, and LV septal captures. EF and NYHA class improved to 46 ± 11% and 1.9 ± 0.6 (p < 0.001).

CONCLUSIONS

LBBAP significantly reduced overall and regional (RV/LV) VEH, irrespective of the mechanism of capture. Detailed assessment of electrical heterogeneity using ECG belt may add valuable insights on effects of LBBAP.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04583709.

Ventricular Dyssynchrony and Pacing-induced Cardiomyopathy in Patients with Pacemakers, the Utility of Ultra-high-frequency ECG and Other Dyssynchrony Assessment Tools

The majority of patients tolerate right ventricular pacing well; however, some patients manifest signs of heart failure after pacemaker implantation and develop pacing-induced cardiomyopathy. This is a consequence of non-physiological ventricular activation bypassing the conduction system. Ventricular dyssynchrony was identified as one of the main factors responsible for pacing-induced cardiomyopathy development. Currently, methods that would allow rapid and reliable ventricular dyssynchrony assessment, ideally during the implant procedure, are lacking. Paced QRS duration is an imperfect marker of dyssynchrony, and methods based on body surface mapping, electrocardiographic imaging or echocardiography are laborious and time-consuming, and can be difficult to use during the implantation procedure. However, the ventricular activation sequence can be readily displayed from the chest leads using an ultra-high-frequency ECG. It can be performed during the implantation procedure to visualise ventricular depolarisation and resultant ventricular dyssynchrony during pacing. This information can assist the electrophysiologist in selecting a pacing location that avoids dyssynchronous ventricular activation.

Body Surface Potential Mapping: Contemporary Applications and Future Perspectives

Body surface potential mapping (BSPM) is a noninvasive modality to assess cardiac bioelectric activity with a rich history of practical applications for both research and clinical investigation. BSPM provides comprehensive acquisition of bioelectric signals across the entire thorax, allowing for more complex and extensive analysis than the standard electrocardiogram (ECG). Despite its advantages, BSPM is not a common clinical tool. BSPM does, however, serve as a valuable research tool and as an input for other modes of analysis such as electrocardiographic imaging and, more recently, machine learning and artificial intelligence. In this report, we examine contemporary uses of BSPM, and provide an assessment of its future prospects in both clinical and research environments. We assess the state of the art of BSPM implementations and explore modern applications of advanced modeling and statistical analysis of BSPM data. We predict that BSPM will continue to be a valuable research tool, and will find clinical utility at the intersection of computational modeling approaches and artificial intelligence.

Optimal CRT Implantation-Where and How To Place the Left-Ventricular Lead?

Purpose of Review

Cardiac resynchronization therapy (CRT) represents a well-established and effective non-pharmaceutical heart failure (HF) treatment in selected patients. Still, a significant number of patients remain CRT non-responders. An optimal placement of the left ventricular (LV) lead appears crucial for the intended hemodynamic and hence clinical improvement. A well-localized target area and tools that help to achieve successful lead implantation seem to be of utmost importance to reach an optimal CRT effect.

Recent Findings

Recent studies suggest previous multimodal imaging (CT/cMRI/ECG torso) to guide intraprocedural LV lead placement. Relevant benefit compared to empirical lead optimization is still a matter of debate. Technical improvements in leads and algorithms (e.g., multipoint pacing (MPP), adaptive algorithms) promise higher procedural success. Recently emerging alternatives for ventricular synchronization such as conduction system pacing (CSP), LV endocardial pacing, or leadless pacing challenge classical biventricular pacing.

Summary

This article reviews current strategies for a successful planning, implementation, and validation of the optimal CRT implantation. Pre-implant imaging modalities offer promising assistance for complex cases; empirical lead positioning and intraoperative testing remain the cornerstone in most cases and ensure a successful CRT effect.

Clinical Utility of Body Surface Potential Mapping in CRT Patients

This paper reviews the current status of the knowledge on body surface potential mapping (BSPM) and ECG imaging (ECGI) methods for patient selection, left ventricular (LV) lead positioning, and optimisation of CRT programming, to indicate the major trends and future perspectives for the application of these methods in CRT patients. A systematic literature review using PubMed, Scopus, and Web of Science was conducted to evaluate the available clinical evidence regarding the usage of BSPM and ECGI methods in CRT patients. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement was used as a basis for this review. BSPM and ECGI methods applied in CRT patients were assessed, and quantitative parameters of ventricular depolarisation delivered from BSPM and ECGI were extracted and summarised. BSPM and ECGI methods can be used in CRT in several ways, namely in predicting CRT outcome, in individualised optimisation of CRT device programming, and the guiding of LV electrode placement, however, further prospective or randomised trials are necessary to verify the utility of BSPM for routine clinical practice.

Electrical wavefront fusion in heart failure patients with left bundle branch block and cardiac resynchronization therapy: Implications for optimization

BACKGROUND

Novel metrics of electrical dyssynchrony based on multi-electrode mapping and ECG-based markers of fusion are better predictors of cardiac resynchronization therapy (CRT) response than QRS duration.

OBJECTIVE

To describe a new methodology for measuring electrical synchrony based on wavefront fusion and electrocardiographic cancellation in patients with CRT and its potential for CRT optimization.

METHODS

Patients with left bundle branch block (LBBB) type conduction and CRT (n = 84) were studied at multiple device settings using an ECG belt (53 anterior and posterior electrodes). The area between combinations of anterior and posterior curves (AUC) was calculated and cardiac resynchronization index (CRI) defined as percent change in AUC compared to LBBB.

RESULTS

In 14 patients with complete heart block or atrial fibrillation, CRI at optimal ventriculo-ventricular delay (VVD) (40 ± 19 ms) was significantly higher than with simultaneous biventricular pacing (BiVp) (90 ± 8.6% vs. 54.2 ± 24.2%, p < 0.001). In all 70 patients paced LV-only, LV-paced wavefront was ahead of native wavefront at short atrio-ventricular delay (AVD) and CRI increased with increase in AVD, peaked, and then decreased. Optimal CRI during LV-only pacing was significantly better than optimal CRI with simultaneous BiVp (89.6 ± 8% vs. 64.4 ± 22%, p < 0.001), and occurred at AVD 68 ± 22 ms less than the atrial-RV sensed interval. With sequential BiVp, best CRI was 83.9 ± 13% (with LV preactivation of 40 ± 20 ms). Best CRI at any setting was markedly better than CRI at standard setting (91.6 ± 7.7% vs. 52.7 ± 23.3, p < 0.001).

CONCLUSION

We describe a novel non-invasive investigational tool that quantifies wavefront fusion and electrical dyssynchrony, and may allow for individualized CRT optimization.

Electrocardiographic optimization techniques in resynchronization therapy

Cardiac resynchronization therapy (CRT) is a cornerstone of therapy for patients with heart failure, reduced left ventricular (LV) ejection fraction, and a wide QRS complex. However, not all patients respond to CRT: 30% of CRT implanted patients are currently considered clinical non-responders and up to 40% do not achieve LV reverse remodelling. In order to achieve the best CRT response, appropriate patient selection, device implantation, and programming are important factors. Optimization of CRT pacing intervals may improve results, increasing the number of responders, and the magnitude of the response. Echocardiography is considered the reference method for atrioventricular and interventricular (VV) intervals optimization but it is time-consuming, complex and it has a large interobserver and intraobserver variability. Previous studies have linked QRS shortening to clinical response, echocardiographic improvement and favourable prognosis. In this review, we describe the electrocardiographic optimization methods available: 12-lead electrocardiogram; fusion-optimized intervals (FOI); intracardiac electrogram-based algorithms; and electrocardiographic imaging. Fusion-optimized intervals is an electrocardiographic method of optimizing CRT based on QRS duration that combines fusion with intrinsic conduction. The FOI method is feasible and fast, further reduces QRS duration, can be performed during implant, improves acute haemodynamic response, and achieves greater LV remodelling compared with nominal programming of CRT.

Non-invasive cardiac mapping for non-response in cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is an effective intervention in selected patients with moderate-to-severe heart failure with reduced ejection fraction and abnormal left ventricular activation time. The non-response rate of approximately 30% has remained nearly unchanged since this therapy was introduced 25 years ago. While intracardiac mapping is widely used for diagnosis and guidance of therapy in patients with tachyarrhythmia, its application in characterization of the electrical substrate to elucidate the mechanisms involved in CRT response remain anecdotal. In the present review, we describe the traditional determinants of CRT response before presenting novel non-invasive techniques used for CRT optimization. We discuss efforts to identify the target electrical substrate to guide the deployment of pacing electrodes during the operative procedure. Non-invasive body surface mapping technologies such as ECG imaging or ECG belt enables prediction of acute and chronic CRT response. While electrical dyssynchrony parameters provide high predictive accuracy for CRT response when obtained during intrinsic conduction, their predictive value is less when acquired during CRT or LV-pacing. Key messages Classic predictors of CRT response are female gender, NYHA class ≤ III, left ventricular ejection fraction ≥25%, QRS duration ≥150 ms and estimated glomerular filtration rate ≥60 mL/min. ECG-imaging is a comprehensive non-invasive mapping system which allows to express the amount of electrical asynchrony of a CRT candidate. Non-invasive body surface mapping technologies enables excellent prediction of acute and chronic CRT response before implantation. When performed during CRT or LV-pacing, the added value of these mapping systems remains unclear.

Outcome of resynchronization therapy on superficial and endocardial electrophysiological findings

Cardiac resynchronization therapy (CRT) has proven efficacious in the treatment of patients with heart failure and dyssynchronous activation. Currently, we select suitable CRT candidates based on the QRS complex duration (QRSd) and morphology with left bundle branch block being the optimal substrate for resynchronization. To improve CRT response rates, recommendations emphasize attention to electrical parameters both before implant and after it. Therefore, we decided to study activation times before and after CRT on the body surface potential maps (BSPM) and to compare thus obtained results with data from electroanatomical mapping using the CARTO system. Total of 21 CRT recipients with symptomatic heart failure (NYHA II-IV), sinus rhythm, and QRSd >/=150 ms and 7 healthy controls were studied. The maximum QRSd and the longest and shortest activation times (ATmax and ATmin) were set in the BSPM maps and their locations on the chest were compared with CARTO derived time interval and site of the latest (LATmax) and earliest (LATmin) ventricular activation. In CRT patients, all these parameters were measured during both spontaneous rhythm and biventricular pacing (BVP) and compared with the findings during the spontaneous sinus rhythm in the healthy controls. QRSd was 169.7+/-12.1 ms during spontaneous rhythm in the CRT group and 104.3+/-10.2 ms after CRT (p<0.01). In the control group the QRSd was significantly shorter: 95.1+/-5.6 ms (p<0.01). There was a good correlation between LATmin(CARTO) and ATmin(BSPM). Both LATmin and ATmin were shorter in the control group (LATmin(CARTO) 24.8+/-7.1 ms and ATmin(BSPM) 29.6+/-11.3 ms, NS) than in CRT group (LATmin(CARTO) was 48.1+/-6.8 ms and ATmin(BSPM) 51.6+/-10.1 ms, NS). BVP produced shortening compared to the spontaneous rhythm of CRT recipients (LATmin(CARTO) 31.6+/-5.3 ms and ATmin(BSPM) 35.2+/-12.6 ms; p<0.01 spontaneous rhythm versus BVP). ATmax exhibited greater differences between both methods with higher values in BSPM: in the control group LATmax(CARTO) was 72.0+/-4.1 ms and ATmax (BSPM) 92.5+/-9.4 ms (p<0.01), in the CRT candidates LATmax(CARTO) reached only 106.1+/-6.8 ms whereas ATmax(BSPM) 146.0+/-12.1 ms (p<0.05), and BVP paced rhythm in CRT group produced improvement with LATmax(CARTO) 92.2+/-7.1 ms and ATmax(BSPM) 130.9+/-11.0 ms (p<0.01 before and during BVP). With regard to the propagation of ATmin and ATmax on the body surface, earliest activation projected most often frontally in all 3 groups, whereas projection of ATmax on the body surface was more variable. Our results suggest that compared to invasive electroanatomical mapping BSPM reflects well time of the earliest activation, however provides longer time-intervals for sites of late activation. Projection of both early and late activated regions of the heart on the body surface is more variable than expected, very likely due to changed LV geometry and interposed tissues between the heart and superficial ECG electrode.

Twelve-Lead ECG Optimization of Cardiac Resynchronization Therapy in Patients With and Without Delayed Enhancement on Cardiac Magnetic Resonance Imaging

Background

Delayed enhancement (DE) on magnetic resonance imaging is associated with ventricular arrhythmias, adverse events, and worse left ventricular mechanics. We investigated the impact of DE on cardiac resynchronization therapy (CRT) outcomes and the effect of CRT optimization.

Methods and Results

We studied 130 patients with ejection fraction (EF) ≤40% and QRS ≥120 ms, contrast cardiac magnetic resonance imaging, and both pre‐ and 1‐year post‐CRT echocardiograms. Sixty‐three (48%) patients did not have routine optimization of CRT. The remaining patients were optimized for wavefront fusion by 12‐lead ECG. The primary end point in this study was change in EF following CRT. To investigate the association between electrical dyssynchrony and EF outcomes, the standard deviation of activation times from body‐surface mapping was calculated during native conduction and selected device settings in 52 of the optimized patients. Patients had no DE (n=45), midwall septal stripe (n=30), or scar (n=55). Patients without DE had better ∆EF (13±10 versus 4±10 units; P<0.01). Optimized patients had greater ∆EF in midwall stripe (2±9 versus 12±12 units; P=0.01) and scar (0±7 versus 5±10; P=0.04) groups, but not in the no‐DE group. Patients without DE had greater native standard deviation of activation times (P=0.03) and greater ∆standard deviation of activation times with standard programming (P=0.01). Device optimization reduced standard deviation of activation times only in patients with DE (P<0.01).

Conclusions

DE on magnetic resonance imaging is associated with worse EF outcomes following CRT. Device optimization is associated with improved EF and reduced electrical dyssynchrony in patients with DE.