Left Ventricular Lead Placement Targeted at the Latest Activated Site Guided by Electrophysiological Mapping in Coronary Sinus Branches Improves Response to Cardiac Resynchronization Therapy

Computational electrophysiology of the coronary sinus branches based on electro-anatomical mapping for the prediction of the latest activated region

This work dealt with the assessment of a computational tool to estimate the electrical activation in the left ventricle focusing on the latest electrically activated segment (LEAS) in patients with left bundle branch block and possible myocardial fibrosis. We considered the Eikonal-diffusion equation and to recover the electrical activation maps in the myocardium. The model was calibrated by using activation times acquired in the coronary sinus (CS) branches or in the CS solely with an electroanatomic mapping system (EAMS) during cardiac resynchronization therapy (CRT). We applied our computational tool to ten patients founding an excellent accordance with EAMS measures; in particular, the error for LEAS location was less than 4 mm. We also calibrated our model using only information in the CS, still obtaining an excellent agreement with the measured LEAS. The proposed tool was able to accurately reproduce the electrical activation maps and in particular LEAS location in the CS branches, with an almost real-time computational effort, regardless of the presence of myocardial fibrosis, even when information only at CS was used to calibrate the model. This could be useful in the clinical practice since LEAS is often used as a target site for the left lead placement during CRT.

Clinical impact of MultiPoint pacing in responders to cardiac resynchronization therapy

BACKGROUND

Cardiac resynchronization therapy demonstrated benefits in heart failure. However, only 60-70% are responders and only 22% are super-responders. MultiPoint pacing (MPP) improves structural remodeling, but data in responder patients is scarce.

METHODS

A prospective, randomized study of the efficacy of MPP was conducted in patients who were CRT responders after 6 months of bi-ventricular (BiV) therapy. At 6 months, responder patients (LV end-systolic volume [LVESV] reduction ≥15%) were randomized to either continued BiV therapy or to MPP programmed with wide anatomical separation ≥30 mm, and followed until 12 months. Efficacy was determined by 6-12 month changes in LVESV and LV ejection fraction (LVEF). Evaluations of super-responder rate (LVESV reduction ≥30%) and quality of life (NYHA, EQ-5D, MLHFQ) were also performed.

RESULTS

From February 2017 to February 2019, 73 CRTs with Quartet LV leads were implanted (42.9% female, 65.7 ± 10.8 years old, 79.5% dilated cardiomyopathy). At 6 months, 74.2% responded to BiV and were randomized to BiV (n = 25) or MPP (n = 24). MPP versus BiV delivered greater LVESV improvement (8.3% decrease in MPP vs. 10.3% increase in BiV patients, p = .047), greater increase in LVEF (7.7% vs. 1.8%, p = .008), and higher 0-12 month super-responder rate (86.4% vs. 56.0%, p = .027). More MPP vs. BiV patients experienced an improvement in NYHA (84.6% vs. 50.0%, p = .047) and EQ-5D (94.4% vs. 54.0%, p = .006).

CONCLUSIONS

MPP with wide anatomical spacing in CRT responder patients resulted in improved LV reverse remodeling with higher rates of super-responders, and better quality of life metrics.

Integration of activation maps of epicardial veins in computational cardiac electrophysiology

In this work we address the issue of validating the monodomain equation used in combination with the Bueno-Orovio ionic model for the prediction of the activation times in cardiac electro-physiology of the left ventricle. To this aim, we consider four patients who suffered from Left Bundle Branch Block (LBBB). We use activation maps performed at the septum as input data for the model and maps at the epicardial veins for the validation. In particular, a first set (half) of the latter are used to estimate the conductivities of the patient and a second set (the remaining half) to compute the errors of the numerical simulations. We find an excellent agreement between measures and numerical results. Our validated computational tool could be used to accurately predict activation times at the epicardial veins with a short mapping, i.e. by using only a part (the most proximal) of the standard acquisition points, thus reducing the invasive procedure and exposure to radiation.

Reproducibility and repeatability of identifying the latest electrical activation during mapping of coronary sinus branches in CRT recipients

INTRODUCTION

Studies have shown an association between the outcome in cardiac resynchronization therapy (CRT) and longer interventricular delay at the site of the left ventricular (LV) lead. Targeted LV lead placement at the latest electrically activated segment increases LV function further as compared with standard treatment. We aimed to determine reproducibility and repeatability of identifying the latest electrically activated segment during mapping of all available coronary sinus (CS) branches in patients receiving CRT.

METHODS

We included 35 patients who underwent CRT implantation with protocolled mapping guided LV lead implantation aiming for the site of the latest electrical activation. Three different doctors experienced in electrophysiology and implantation of CRT devices independently measured time interval from the local bipolar right ventricular (RV) electrogram (EGM) to the local unipolar LV EGM at all mapped sites (RV-LV). The segment with the latest electrical activation was defined as the target segment (TS) and the CS tributary containing TS was defined as the target vein (TV). Weighted κ statistics with 95% confidence intervals were computed to assess intra- and interobserver agreement for TS and TV.

RESULTS

We mapped 258 segments within 131 veins. Weighted κ values for repeatability were 0.85 (0.81-0.89) for TS and 0.92 (0.89-0.93) for TV, and weighted κ values of interobserver agreement ranged from 0.70 (0.61-0.73) to 0.80 (0.76-0.83) for TS and 0.73 (0.64-0.78) to 0.86 (0.83-0.89) for TV among all three observers.

CONCLUSION

The reproducibility and repeatability of identifying the latest electrically activated segment during mapping of all available CS branches in patients receiving CRT range from good to very good.

Mechanical contraction to guide CRT left-ventricular lead placement instead of electrical activation in myocardial infarction with left ventricular dysfunction: An experimental study based on non-invasive gated myocardial perfusion imaging and invasive electroanatomic mapping

BACKGROUND

Whether the region of the latest electrical activation (LEA) corresponds with the segment of the latest mechanical contraction (LMC) in ischemic cardiomyopathy (ICM) is uncertain. We aimed to investigate the relationship between the left-ventricular (LV) viable segments with LEA and with LMC after myocardial infarction (MI) and analyze the acute hemodynamic responses (dP/dtmax) after cardiac resynchronization therapy (CRT) pacing at different LV sites.

METHODS AND RESULTS

Bama suckling pigs (n = 6) were subjected to create MI models. Both gated myocardial perfusion imaging (GMPI) and electroanatomic mapping (EAM) were performed successfully before MI and 4 weeks after MI. LMC was assessed by phase analysis of GMPI, while LEA was evaluated by EAM. The dP/dtmax was measured before CRT and when the CRT LV electrode was implanted in viable segments of LMC, viable segments of lateral wall and scar, respectively. The viable segments of LEA were consistent with the sites of LMC for five in six cases. The dP/dtmax increased significantly compared with that before CRT when the CRT LV electrode was implanted in viable segments of LMC (1103.33 ± 195.76 vs 717.83 ± 80.74 mmHg·s-1, P = .001), which was also significantly higher than in viable segments of lateral wall (751.17 ± 105.62 mmHg·s-1, P = .000) and scar (679.50 ± 60.87 mmHg·s-1, P = .001).

CONCLUSIONS

Non-invasive GMPI may be a better option than invasive EAM for guiding LV electrode implantation for CRT in ICM.

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.

Electrically guided versus imaging-guided implant of the left ventricular lead in cardiac resynchronization therapy: a study protocol for a double-blinded randomized controlled clinical trial (ElectroCRT)

BACKGROUND

Cardiac resynchronization therapy (CRT) is an established treatment in patients with heart failure and prolonged QRS duration where a biventricular pacemaker is implanted to achieve faster activation and more synchronous contraction of the left ventricle (LV). Despite the convincing effect of CRT, 30-40% of patients do not respond. Among the most important correctable causes of non-response to CRT is non-optimal LV lead position.

METHODS

We will enroll 122 patients in this patient-blinded and assessor-blinded, randomized, clinical trial aiming to investigate if implanting the LV lead guided by electrical mapping towards the latest LV activation as compared with imaging-guided implantation, causes an excess increase in left ventricular (LV) ejection fraction (LVEF). The patients are randomly assigned to either the intervention group: preceded by cardiac computed tomography of the cardiac venous anatomy, the LV lead is placed according to the latest LV activation in the coronary sinus (CS) branches identified by systematic electrical mapping of the CS at implantation and post-implant optimization of the interventricular pacing delay; or patients are assigned to the control group: placement of the LV lead guided by cardiac imaging. The LV lead is targeted towards the latest mechanical LV activation as identified by echocardiography and outside myocardial scar as identified by myocardial perfusion (MP) imaging. The primary endpoint is change in LVEF at 6-month follow up (6MFU) as compared with baseline measured by two-dimensional echocardiography. Secondary endpoints include relative percentage reduction in LV end-systolic volume, all-cause mortality, hospitalization for heart failure, and a clinical combined endpoint of response to CRT at 6MFU defined as the patient being alive, not hospitalized for heart failure, and experiencing improvement in NYHA functional class or/and > 10% increase in 6-minute walk test.

DISCUSSION

We assume an absolute increase in LVEF of 12% in the intervention group versus 8% in the control group. If an excess increase in LVEF can be achieved by LV lead implantation guided by electrical mapping, this study supports the conduct of larger trials investigating the impact of this strategy for LV-lead implantation on clinical outcomes in patients treated with CRT.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02346097 . Registered on 12 January 2015. Patients were enrolled between 16 February 2015 and 13 December 2017.

Optimal site selection and image fusion guidance technology to facilitate cardiac resynchronization therapy

INTRODUCTION

Cardiac resynchronization therapy (CRT) has emerged as one of the few effective treatments for heart failure. However, up to 50% of patients derive no benefit. Suboptimal left ventricle (LV) lead position is a potential cause of poor outcomes while targeted lead deployment has been associated with enhanced response rates. Image-fusion guidance systems represent a novel approach to CRT delivery, allowing physicians to both accurately track and target a specific location during LV lead deployment.

AREAS COVERED

This review will provide a comprehensive evaluation of how to define the optimal pacing site. We will evaluate the evidence for delivering targeted LV stimulation at sites displaying favorable viability or advantageous mechanical or electrical properties. Finally, we will evaluate several emerging image-fusion guidance systems which aim to facilitate optimal site selection during CRT.

EXPERT COMMENTARY

Targeted LV lead deployment is associated with reductions in morbidity and mortality. Assessment of tissue characterization and electrical latency are critical and can be achieved in a number of ways. Ultimately, the constraints of coronary sinus anatomy have forced the exploration of novel means of delivering CRT including endocardial pacing which hold promise for the future of CRT delivery.

Shortening of paced QRS duration after electrocardiographic optimization of left ventricular pacing vector in patients treated with Cardiac Resynchronization Therapy

Background

Choice of left ventricular pacing vector (LVPV) affects the QRS-duration (QRSd) in patients with Cardiac Resynchronization Therapy (CRT). It is not known whether testing all LVPVs reduces QRSd compared to device-based “standard-programming”.

Methods

In patients implanted with CRT several ECGs were recorded for each usable LVPV (no phrenic nerve stimulation and threshold <3.5 V) and during “standard-programming” after device-based optimization of AV/VV delays.

Results

22 consecutive patients were included. Average QRSd reduction after CRT + “standard-programming” was 27.3 ± 22 ms. Additional QRSd-reduction was possible in 4 patients by changing the LVPV, and in 5 other patients after optimization of AV- and VV delays without changing LVPV.

Conclusions

Shortening of QRSd compared to “standard-programming” was possible approximately 40% of these patients treated with CRT by testing all LVPVs and re-optimizing AV/VV delays during follow-up. Studies of clinical effects are needed.

Guidewire Method for Measuring Local Left Ventricular Electrical Activation Time During Cardiac Resynchronization Implantation

The timing of local activation at left ventricular (LV) pacing leads is measured from the onset of the QRS complex to the peak of the LV electrogram (QLV). Pacing from the sites of late activation is associated with higher response rates to cardiac resynchronization therapy (CRT). Prior studies have measured QLV from permanent pacing leads, or have used electroanatomic mapping systems. The current study compares QLV measurements made with a guidewire to those collected from permanent LV pacing leads positioned at the same venous site without the use of electroanatomic mapping systems. In this study, 20 patients undergoing CRT implantation (14 males, mean QRS: 164.0 ms) had QLV measurements taken using a guidewire. QLV and LV electrogram duration measurements were made at LV pacing sites, and were repeated after positioning the permanent LV pacing lead at the same site. There was no difference in QLV measurements obtained using a guidewire and those obtained using the permanent pacing lead placed at the same site (p = 0.569). QLV measurements obtained with a guidewire and the permanent LV pacing lead at the same site, respectively, were strongly correlated (r = 0.965; p < 0.001). The median absolute difference in electrogram duration was 7.0 ms (p = 0.55). The average time required to make QLV measurements using the guidewire was 11.7 minutes [standard deviation (SD): 6.8]. The average total fluoroscopy time for the entire CRT implant procedure was 10.9 minutes (SD: 5.1). In light of these results, it can be suggested that a guidewire can be used to prospectively measure LV prior to selection or placement of a permanent pacing lead without the use of an electroanatomic mapping system.

Coronary sinus lead delay index for optimization of coronary sinus lead placement

AIM

Optimization of coronary sinus (CS) lead position to the latest activated left ventricular (LV) area is important to increase cardiac resynchronization therapy (CRT) response. We aimed to detect the relationship between coronary sinus lead delay index (CSDI) and echocardiographic, electrocardiographic response to CRT treatment.

METHODS

We prospectively included 137 consecutive patients with heart failure (HF) diagnosis, QRS ≥ 120 ms, left bundle branch block (LBBB), New York Heart Association score (NYHA) II-IV, LV ejection fraction (LVEF) <35% and scheduled for CRT (84 male, 53 female; mean age 65.1 ± 10.1 years). Echocardiographic CRT response was defined as ≥15% reduction in LV end-systolic volume (LVESV). CS lead sensing delay was calculated as the time interval from the onset of surface QRS wave to the onset of depolarization wave recorded from the CS lead by using the CS pacing lead as a bipolar electrode. CSDI was calculated by dividing the CS lead sensing delay by the QRS duration.

RESULTS

LVESV reduction was associated with baseline QRS width (r = .257, p = .002), QRS narrowing (r = .396, p < .001), CSDI (r = .357, p < .001), and NT-proBNP (r = -0.213, p = .022) in bivariate analysis. In logistic regression analysis, CSDI was found to be only independent parameter for predicting significant LVESV reduction (Beta = 0.318, p < .001). CSDI was also found to be significantly associated with LVEF increase (r = .244, p = .004) and QRS narrowing (r = .178, p = .046).

CONCLUSION

CSDI may be used as a marker to predict the favorable response to CRT. It may be useful to integrate CSDI to CRT implantation procedure in order to minimize nonresponders.

Coronary sinus activation patterns in patients with and without left bundle branch block undergoing electroanatomic mapping system-guided cardiac resynchronization therapy device implantation

BACKGROUND

Implantation of the left ventricular (LV) lead in segments with delayed electrical activation may improve response to cardiac resynchronization therapy (CRT).

OBJECTIVE

The purpose of this study was to evaluate the amount and regional distribution of LV electrical delay (LVED) in patients with or without left bundle branch block (LBBB).

METHODS

We enrolled 60 patients who underwent electroanatomic mapping system-guided CRT device implantation. Activation mapping of the coronary sinus (CS) branches was performed using an insulated guidewire. LVED was defined as the interval between the beginning of the QRS complex on the surface electrocardiogram (ECG) and the local electrogram and expressed in milliseconds or as percentage of the total QRS duration (LVED%).

RESULTS

Forty-three patients showed a LBBB and 17 a non-LBBB electrocardiographic pattern. A total of 148 CS branches (mean 2.5 per patient; range 2-4 per patient) were mapped. Patients with LBBB showed higher maximum LVED (135 ms [108-150 ms] vs 100 ms [103-110 ms]; P < .001) and LVED% (86% [79%-89%] vs 72% [54%-80%]; P < .001) than did patients without LBBB. The maximum LVED was recorded in mid-basal anterolateral or inferolateral LV segments (traditional CRT targets), significantly more often in patients with LBBB than in patients without LBBB (85% vs 59%; P = .02). The number of CS branches showing LVED >50% of the total QRS duration, >75% of the total QRS duration, and >85 ms was significantly higher in patients with LBBB than in patients without LBBB.

CONCLUSION

Patients without LBBB showed lower LVED and more heterogeneous electrical activation of the CS than did patients with LBBB. This finding may contribute to a lower rate of response to CRT of patients without LBBB and suggests the use of activation mapping to guide LV lead placement.

High Left Ventricular Lead Sensing Delay Predicts QRS Narrowing and Good Response to Cardiac Resynchronization Therapy

BACKGROUND

Cardiac resynchronization therapy (CRT) was shown to improve heart failure (HF) prognosis. But many patients do not benefit from CRT. Optimization of left ventricular (LV) lead position to the latest activated LV area is important to increase CRT response. We aimed to detect the relationship between LV lead sensing delay and echocardiographic and electrocardiographic response to CRT treatment.

METHODS

We prospectively included 156 consecutive patients with HF diagnosis, QRS ≥ 120 ms, left bundle branch block, New York Heart Association II-IV, LV ejection fraction (LVEF) < 35%, and scheduled for CRT (100 male, 56 female; mean age 65.8 ± 10.06 years). Echocardiographic CRT response was defined as ≥15% reduction in LV end-systolic volume (LVESV). LV lead sensing delay was calculated as the time interval from the onset of surface QRS wave to the onset of depolarization wave recorded from the LV lead by using the LV pacing lead as a bipolar electrode.

RESULTS

LVESV reduction was associated with baseline QRS width (r = 0.292, P = 001), QRS narrowing (r = 0.332, P < 001), and LV lead sensing delay (r = 0.454, P < 001) in bivariate analysis. In logistic regression analysis, LV lead sensing delay was found to be the only independent parameter for predicting significant LVESV reduction (β = 0.423, P < 0.001). LV lead sensing delay was also found to be significantly associated with LVEF increase (r = 0.320, P < 0.001) and QRS narrowing (r = 0.345, P < 0.001).

CONCLUSION

LV lead sensing delay is the only independent predictor for significant reduction in LVESV and was found to be significantly associated with LVEF increase and QRS narrowing after CRT treatment. We suggest that LV lead sensing delay may be used as a marker to predict the favorable response to CRT.

Insights from Novel Noninvasive CT and ECG Imaging Modalities on Electromechanical Myocardial Activation in a Canine Model of Ischemic Dyssynchronous Heart Failure

INTRODUCTION

The interplay between electrical activation and mechanical contraction patterns is hypothesized to be central to reduced effectiveness of cardiac resynchronization therapy (CRT). Furthermore, complex scar substrates render CRT less effective. We used novel cardiac computed tomography (CT) and noninvasive electrocardiographic imaging (ECGI) techniques in an ischemic dyssynchronous heart failure (DHF) animal model to evaluate electrical and mechanical coupling of cardiac function, tissue viability, and venous accessibility of target pacing regions.

METHODS AND RESULTS

Ischemic DHF was induced in 6 dogs using coronary occlusion, left bundle ablation and tachy RV pacing. Full body ECG was recorded during native rhythm followed by volumetric first-pass and delayed enhancement CT. Regional electrical activation were computed and overlaid with segmented venous anatomy and scar regions. Reconstructed electrical activation maps show consistency with LBBB starting on the RV and spreading in a "U-shaped" pattern to the LV. Previously reported lines of slow conduction are seen parallel to anterior or inferior interventricular grooves. Mechanical contraction showed large septal to lateral wall delay (80 ± 38 milliseconds vs. 123 ± 31 milliseconds, P = 0.0001). All animals showed electromechanical correlation except dog 5 with largest scar burden. Electromechanical decoupling was largest in basal lateral LV segments.

CONCLUSION

We demonstrated a promising application of CT in combination with ECGI to gain insight into electromechanical function in ischemic dyssynchronous heart failure that can provide useful information to study regional substrate of CRT candidates.