Hyper-response to cardiac resynchronization with permanent His bundle pacing: Is parahisian pacing sufficient?

His bundle pacing shows similar ventricular electrical activation as sinus: selective and nonselective His pacing indistinguishable

His bundle pacing utilizes the His-Purkinje system to produce more physiological activation compared with traditional pacing therapies, but differences in electrical activation between pacing techniques are not yet quantified in terms of activation pattern. Furthermore, clinicians distinguish between selective and nonselective His pacing, but measurable differences in electrical activation remain to be seen. Hearts isolated from seven dogs were perfused using the Langendorff method. Electrograms were recorded using two 64-electrode basket catheters in the ventricles and a 128-electrode sock situated around the ventricles during sinus rhythm (right atrial pacing), right ventricular (RV) pacing, biventricular cardiac resynchronization therapy (biV-CRT), selective His pacing (selective capture of the His bundle), and nonselective His pacing (capture of nearby myocardium and His bundle). Activation maps were generated from these electrograms. Total activation time (TAT) was measured from the activation maps, and QRS duration was measured from a one-lead pseudo-ECG. Results showed that TAT, QRS duration, and activation sequence were most similar between sinus, selective, and nonselective His pacing. Bland-Altman analyses showed highest levels of similarity between all combinations of sinus, selective, and nonselective His pacing. RV and biV-CRT activation patterns were distinct from sinus and had significantly longer TAT and QRS duration. Cumulative activation graphs were most similar between sinus, selective, and nonselective His pacing. In conclusion, selective pacing and nonselective His bundle pacing are more similar to sinus compared with RV and biV-CRT pacing. Furthermore, selective pacing and nonselective His bundle pacing are not significantly different electrically.NEW & NOTEWORTHY Our high-density epicardial and endocardial electrical mapping study demonstrated that selective pacing and nonselective His bundle pacing are more electrically similar to sinus rhythm compared with right ventricular and biventricular cardiac resynchronization therapy pacing. Furthermore, small differences between selective and nonselective His bundle pacing, specifically a wider QRS in nonselective His pacing, do not translate into significant differences in the global activation pattern.

Permanent His-bundle pacing using stylet-directed, active-fixation leads placed via coronary sinus sheaths compared to conventional lumen-less system

BACKGROUND

The use of coronary sinus (CS) sheaths to deliver stylet-driven leads (SDLs) for His-bundle pacing (HBP) has not been described. Conventionally, HBP is achieved using a stylet-less lead delivered through a customized catheter.

OBJECTIVE

The purpose of this study was to characterize the acute and early-term HBP experience with stylet-driven, active-fixation leads delivered through CS sheaths compared to the conventional approach.

METHODS

Delivery of Medtronic 4471 and 7742 SDLs was attempted in 27 patients. Delivery was facilitated using CS guide catheters and custom-shaped stylets. Procedural characteristics and lead performance were compared to those of a group of 17 patients in whom delivery of 3830 lumen-less leads (LLLs) was attempted. Patients had heterogeneous pacing indications.

RESULTS

HBP with SDL was successful in 24 of 27 patients(89%) compared to 15 of 17 patients (88%) in the LLL group. Mean procedural and fluoroscopy times in the SDL and LLL groups were 129 ± 43 minutes vs 104 ± 43 minutes and 9.6 ± 5.2 minutes vs 8.3 ± 5.0 minutes, respectively (both P = NS). There was a significant difference in procedure and fluoroscopy times within the SDL group between the first and second halves of the series, probably secondary to a learning curve. Acute HBP thresholds were higher with SDL than with LLL (2.6 ± 1.5 V vs 1.5 ± 1.2 V; P = .02) and remained stable at 8.4 ± 5.3 months. Both SDLs exhibited similar pacing thresholds. Two crossovers between groups occurred (1 in each group). Four patients with SDL and 1 patient with LLL exhibited high thresholds during follow-up.

CONCLUSION

Permanent HBP using stylet-driven, active-fixation leads delivered through conventional CS sheaths is feasible. Procedural characteristics and lead performance were clinically acceptable.

His Bundle Pacing for Cardiac Resynchronization

Cardiac resynchronization therapy with left ventricular coronary sinus or epicardial pacing is an established therapy for patients with systolic heart failure and intraventricular conduction system delay, particularly left bundle branch block. Despite large-scale randomized trials demonstrating the efficacy of this therapy, clinical and echocardiographic nonresponse rates remain as high as up to 40%. His bundle pacing (HBP) has reemerged as a means to provide physiologic resynchronization in patients with bundle branch block by correcting QRS by direct capture of the His-Purkinje system. This critical appraisal reviews early clinical data, evaluates possible mechanism, and identifies areas for future investigation for HBP in resynchronization.

His Bundle Pacing: A New Frontier in the Treatment of Heart Failure

Biventricular pacing has revolutionised the treatment of heart failure in patients with sinus rhythm and left bundle branch block; however, left ventricular-lead placement is not always technically possible. Furthermore, biventricular pacing does not fully normalise ventricular activation and, therefore, the ventricular resynchronisation is imperfect. Right ventricular pacing for bradycardia may cause or worsen heart failure in some patients by causing dyssynchronous ventricular activation. His bundle pacing activates the ventricles via the native His-Purkinje system, resulting in true physiological pacing, and, therefore, is a promising alternate site for pacing in bradycardia and traditional CRT indications in cases where it can overcome left bundle branch block. Furthermore, it may open up new indications for pacing therapy in heart failure, such as targeting patients with PR prolongation, but a narrow QRS duration. In this article we explore the physiology, technology and potential roles of His bundle pacing in the prevention and treatment of heart failure.