Comparison of the Effects of Epicardial and Endocardial Cardiac Resynchronization Therapy on Transmural Dispersion of Repolarization

QT interval measurement in ventricular pacing: Implications for assessment of drug effects and pro-arrhythmia risk

QT interval prolongation is a known risk factor for development of malignant ventricular arrhythmias. Measurement of the QT interval is difficult in the setting of ventricular pacing (VP), which can prolong depolarization and increase the QT interval, overestimating repolarization time. VP and cardiac resynchronization therapies have become commonplace in modern cardiac care and may contribute to repolarization heterogeneity and subsequent increased risk for ventricular arrhythmias including Torsades de Pointes. It is imperative for the clinician caring for acutely ill cardiac patients to understand the relationship between QT interval prolongation, both drug-induced and pacing-induced, and repolarization changes with subsequent ventricular arrhythmia risk. In this review, we discuss the components of QT interval assessment for arrhythmogenic risk including arrhythmogenic QT prolongation, methods for adjusting the QT interval to identify repolarization changes, methods to adjust for heart rate, and propose a framework for medication management to assess for drug-induced long QT syndrome in patients with VP.

Long-term single-centre large volume experience with transseptal endocardial left ventricular lead implantation

Aims

The aim of our study was to investigate the long-term efficacy and safety of transseptal endocardial left ventricular lead implantation (TELVLI).

Methods and results

Transseptal endocardial left ventricular lead implantation was performed in 54 patients (44 men, median age 69, New York Heart Association III–IV stage) between 2007 and 2017 in a single centre. In 36 cases, the transseptal puncture (TP) was performed via the femoral vein, and in 18 cases, the TP and also the left ventricular (LV) lead placement were performed via the subclavian vein. An electrophysiological deflectable catheter was used to reach the LV wall through the dilated TP hole. The LV lead implantation was successful in all patients. A total of 54 patients were followed up for a median of 29 months [interquartile range (IQR) 8–40 months], the maximum follow-up time was 94 months. Significant improvement in the LV ejection fraction was observed at the 3-month visit, from the median of 27% (IQR 25–34%) to 33% (IQR 32–44%), P < 0.05. Early lead dislocation was observed in three cases (5%), reposition was performed using the original puncture site in all. The patients were maintained on anticoagulation therapy with a target international normalized ratio between 2.5 and 3.5. Four thromboembolic events were noticed during follow-up. A total of 27 patients died, with a median survival of 15 months (IQR 6–40).

Conclusion

The TELVLI is an effective approach for cardiac resynchronization therapy (CRT) however it is associated with a substantial thromboembolic risk (7%).

Patient-tailored SyncAV algorithm: A novel strategy to improve synchrony and acute hemodynamic response in heart failure patients treated by cardiac resynchronization therapy

INTRODUCTION

Several automatic algorithms have developed to optimize the timing cycle setting in cardiac resynchronization therapy (CRT). The present study aims to investigate whether the novel device-based SyncAV algorithm could elicit better synchrony and acute hemodynamic response.

METHODS AND RESULTS

Thirty five patients undergoing CRT implantation were prospectively studied. The device was programmed to three biventricular (BiV) pacing modes sequentially after the procedure: QuickOpt algorithm (mode I), SyncAV algorithm with default 50 ms offset (mode II), and SyncAV algorithm with optimized offset minimizing QRS duration (QRSd) (mode III). After each setting, electrocardiographic and echocardiographic data were collected. As a result, QRSd was reduced from 172.8 ± 17.9 ms during intrinsic conduction to 153.1 ± 15.9 ms in mode I, further narrowed to 140.5 ± 16.7 ms in mode II, and reached shortest (134.8 ± 16.1 ms) in mode III (P < .01 for all). Besides, significantly shorter QT intervals were observed in mode I (453.2 ± 45.5 ms), mode II (443.9 ± 34.2 ms) and mode III (444.1 ± 28.7 ms), compared with native condition (472.5 ± 51.2 ms) (P < .01). All three BiV modes exhibited comparable T_p T_e interval and T_p T_e /QT ratio (P > .05). Mode I presented significantly higher aortic velocity time integral than intrinsic conduction (21.0 ± 6.4 cm vs 18.4 ± 5.5 cm; P < .01), which was even higher in mode II (22.0 ± 6.5 cm) and mode III (23.7 ± 6.5 cm). All three BiV modes significantly reduced standard deviation of time to peak contraction of 12-LV segments (Ts-SD) (Mode I: 55.2 ± 16.5 ms, Mode II: 50.2 ± 14.7 ms, Mode III: 45.4 ± 14.4 ms) compared with intrinsic conduction (66.3 ± 18.4 ms) (P < .01), with Mode III demonstrating the smallest (P < .01).

CONCLUSION

SyncAV CRT ameliorated electrical and mechanical synchrony as well as acute hemodynamic response beyond conventional QuickOpt optimization. An additional individualized adjustment to the SyncAV offset added to its advantage.

Endocardial biventricular pacing for chronic heart failure patients: Effect on transmural dispersion of repolarization

BACKGROUND AND AIM

Conventional epicardial cardiac resynchronization therapy (CRT) can cause fatal arrhythmia associated with increased transmural dispersion of repolarization (TDR). It is unknown whether endocardial biventricular pacing in various locations will decrease TDR and hence the occurrence of fatal arrhythmia. This study aimed to find out the most effective location of endocardial biventricular pacing resulting in the shortest homogenous TDR.

METHODS

A before-and-after study on adult chronic heart failure (CHF) patients undergoing endocardial biventricular pacing in several defined locations. The changes in TDR from baseline were compared among various pacing locations.

RESULTS

Fourteen subjects were included with age ranged 36-74 years old, of which 10 were males. Location revealed the highest post biventricular pacing TDR (113.4 (SD 13.8) ms) was the outlet septum of right ventricle in combination with lateral wall of left ventricle (RVOTseptum-LVlateral) while the lowest one (106.1 (SD 11.6) ms) was of the right ventricular apex and posterolateral left ventricle (RVapex-LVposterolateral). Two CRT locations resulted in the most homogenous TDR, that is the right ventricular apex - left ventricular lateral wall (RVapex-LVlateral, mean difference -9.43; 95% CI (-19.72;0.87) ms, P = 0.07) and right ventricular apex - left ventricle posterolateral wall (RVapex-LVposterolateral, mean difference -6.85; 95% CI (-13.93;0.22) ms, P = 0.056).

CONCLUSION

Endocardial biventricular pacing on right ventricular apex and left ventricular lateral/posterolateral walls results in the most homogenous TDR.

Multicenter prospective observational long-term follow-up study of endocardial cardiac resynchronization therapy using the Jurdham procedure

BACKGROUND

Endocardial cardiac resynchronization therapy (eCRT) avoids the limitations and failures of coronary sinus (CS) resynchronization. However, data regarding long-term outcomes are lacking.

OBJECTIVE

The purpose of this study was to report the long-term outcome of eCRT performed using the Jurdham procedure in a real-world setting.

METHODS

eCRT was performed in patients who failed a CS implant or failed to respond to cardiac resynchronization therapy (CRT), or in selected patients requiring lifelong oral anticoagulation (OAC). Left ventricular ejection fraction (LVEF), New York Heart Association functional class (NYHA FC), and left ventricular stimulation parameters were assessed during long-term follow-up (FU).

RESULTS

From August 2009 to March 2018, the Jurdham procedure was performed in 88 patients at 15 centers in 8 countries, with FU of 32.88 ± 61.52 months (range 0-88 months; 196 patient-years). NYHA FC improved from 2.9 preimplant to 1.3 during FU. LVEF increased <10 percentage points from baseline in 7% of patients, between 10 and 20 percentage points in 11% of patients, and >20 percentage points in 82% of patients. All-cause mortality at 60 months was 30.5%. Three transient ischemic attacks (1.53 per 100 patient-years) and 6 strokes (3.06 per 100 patient-years) occurred. Of the 6 patients with stroke, 4 (66%) had almost complete recovery.

CONCLUSION

eCRT using the Jurdham procedure is an effective and safe technique in anticoagulated patients. This approach may be an attractive option for patients with failed CS implants or nonresponders to CS CRT. In addition, it might be a reasonable approach as a first option for treatment of patients requiring lifelong OAC.

[Leadless endocardial ultrasound based left ventricular stimulation : WISE CRT System: alternative to conventional methods]

There are still several limitations in delivering cardiac resynchronisation therapy (CRT). After 6 months, 20-40% of patients fail to have clinical benefit due to various reasons. Endocardial stimulation rather than conventional epicardial pacing has been shown to be more physiological, improves electrical stimulation of the left ventricle (LV), has less dispersion of electrical activity and results in better resynchronisation. The WiSE™ CRT System ("Wireless stimulation endocardial system"; EBR Systems, Sunnyvale, CA, USA) provides an option for wireless, LV endocardial pacing triggered by a conventional right ventricular pacing spike from a co-implant. The feasibility of the WiSE™ CRT System has been successfully demonstrated in a population of failed cardiac resynchronisation patients with either failed implantation of a conventional system, nonresponse to conventional therapy or upgrade from pacemaker or defibrillator, where a conventional system was not an option. The WiSE™ CRT System is an innovative technology with promising safety, performance and preliminary efficacy.

Electro-echocardiographic Indices to Predict Cardiac Resynchronization Therapy Non-response on Non-ischemic Cardiomyopathy

Cardiac resynchronization therapy (CRT) threw lights on heart failure treatment, however, parts of patients showed nonresponse to CRT. Unfortunately, it lacks effective parameters to predict CRT non-response. In present study, we try to seek effective electro-echocardiographic predictors on CRT non-response. This is a retrospective study to review a total of 227 patients of dyssynchronous heart failure underwent CRT implantation. Logistic analysis was performed between CRT responders and CRT non-responders. The primary outcome was the occurrence of improved left ventricular ejection fraction 1 year after CRT implantation. We concluded that LVEDV > 255 mL (OR = 2.236; 95% CI, 1.016-4.923) rather than LVESV > 160 mL (OR = 1.18; 95% CI, 0.544-2.56) and TpTe/QTc > 0.203 (OR = 5.206; 95% CI, 1.89-14.34) significantly predicted CRT non-response. Oppositely, S wave > 5.7 cm/s (OR = 0.242; 95% CI, 0.089-0.657), E/A > 1 (OR = 0.211; 95% CI, 0.079-0.566), E'/A' > 1 (OR = 0.054; 95% CI, 0.017-0.172), CLBBB (OR = 0.141; 95% CI, 0.048-0.409), and QRS duration >160 ms (OR = 0.52; 95% CI, 0.305-0.922) surprisingly predicted low-probability of CRT non-response.

Effects of allocryptopine on outward potassium current and slow delayed rectifier potassium current in rabbit myocardium

Objective

Allocryptopine (ALL) is an effective alkaloid of Corydalis decumbens (Thunb.) Pers. Papaveraceae and has proved to be anti-arrhythmic. The purpose of our study is to investigate the effects of ALL on transmural repolarizing ionic ingredients of outward potassium current (I_to) and slow delayed rectifier potassium current (I_Ks).

Methods

The monophasic action potential (MAP) technique was used to record the MAP duration of the epicardium (Epi), myocardium (M) and endocardium (Endo) of the rabbit heart and the whole cell patch clamp was used to record I_to and I_Ks in cardiomyocytes of Epi, M and Endo layers that were isolated from rabbit ventricles.

Results

The effects of ALL on MAP of Epi, M and Endo layers were disequilibrium. ALL could effectively reduce the transmural dispersion of repolarization (TDR) in rabbit transmural ventricular wall. ALL decreased the current densities of I_to and I_Ks in a voltage and concentration dependent way and narrowed the repolarizing differences among three layers. The analysis of gating kinetics showed ALL accelerated the channel activation of I_to in M layers and partly inhibit the channel openings of I_to in Epi, M and Endo cells. On the other hand, ALL mainly slowed channel deactivation of I_Ks channel in Epi and Endo layers without affecting its activation.

Conclusions

Our study gives partially explanation about the mechanisms of transmural inhibition of I_to and I_Ks channels by ALL in rabbit myocardium. These findings provide novel perspective regarding the anti-arrhythmogenesis application of ALL in clinical settings.