His-Purkinje Conduction Disease Research Articles

Effect of scar and His-Purkinje and myocardium conduction on response to conduction system pacing.

Conduction system pacing (CSP), in the form of His bundle pacing (HBP) or left bundle branch pacing (LBBP), is emerging as a valuable cardiac resynchronization therapy (CRT) delivery method. However, patient selection and therapy personalization for CSP delivery remain poorly characterized. We aim to compare pacing-induced electrical synchrony during CRT, HBP, LBBP, HBP with left ventricular (LV) epicardial lead (His-optimizedCRT [HOT-CRT]), and LBBP with LV epicardial lead (LBBP-optimized CRT [LOT-CRT]) in patients with different conduction disease presentations using computational modeling. We simulated ventricular activation on 24four-chamber heart geometries, including His-Purkinje systems with proximal left bundle branch block (LBBB). We simulated septal scar, LV lateral wall scar, and mild and severe myocardium and LV His-Purkinje system conduction disease by decreasing the conduction velocity (CV) down to 70% and 35% of the healthy CV. Electrical synchrony was measured by the shortest interval to activate 90% of the ventricles (90% of biventricular activation time [BIVAT-90]). Severe LV His-Purkinje conduction disease favored CRT (BIVAT-90: HBP 101.5 ± 7.8 ms vs.CRT 93.0 ± 8.9 ms, p < .05), with additional electrical synchrony induced by HOT-CRT (87.6 ± 6.7 ms, p < .05) and LOT-CRT (73.9 ± 7.6 ms, p < .05). Patients with slow myocardium CV benefit more from CSP compared to CRT (BIVAT-90: CRT 134.5 ± 24.1 ms; HBP 97.1 ± 9.9 ms, p < .01; LBBP: 101.5 ± 10.7 ms, p < .01). Septal but not lateral wall scar made CSP ineffective, while CRT was able to resynchronize the ventricles in the presence of septal scar (BIVAT-90: baseline 119.1 ± 10.8 ms vs.CRT 85.1 ± 14.9 ms, p < .01). Severe LV His-Purkinje conduction disease attenuates the benefits of CSP, with additional improvements achieved with HOT-CRT and LOT-CRT. Septal but not lateral wall scars make CSP ineffective.

His-Purkinje Conduction System Pacing inAtrioventricular Block: New Insights Into Site of Conduction Block.

This study aims to assess the safety and feasibility of achieving His-Purkinje conduction system pacing (HPCSP) in consecutive patients with atrioventricular block (AVB) and to describe the site of conduction block in patients with infranodal AVB. HPCSP has evolved as the preferred form of physiologic pacing. Left bundle branch area pacing (LBBAP) has emerged as an effective alternative to His bundle pacing (HBP). Consecutive patients with AVB referred for pacemaker implantation were included in the study. HBP or LBBAP was attempted in all patients. Site of conduction block was identified as nodal or infranodal (intra-Hisian or infra-Hisian) AVB. HPCSP was attempted in 333 consecutive patients with AVB and was successful in 322 (97%) patients. HBP was achieved in 140 patients, LBBAP in 179 patients, and both in 3 patients. Site of conduction block was nodal in 55% and infranodal in 45% (intra-Hisian 89%; infra-Hisian 4%; indeterminate 7%). QRS duration at baseline was 111 ± 27 versus 129 ± 31 (P< 0.001) compared to 126 ± 24 vs 125 ± 21 milliseconds (P=0.75) during HBP and LBBAP, respectively. HBP thresholds at implant were higher compared to LBBAP (1.2 ± 0.7V at 0.9 milliseconds vs 0.6 ± 0.3V at 0.5 milliseconds; P< 0.001) but remained stable during follow-up. Lead revision was required in 3% and 2% of patients with HBP and LBBAP, respectively. HPCSP pacing was successfully performed in 97% of unselected patients with AVB irrespective of the site of conduction block. True infra-Hisian block (distal His-Purkinje conduction disease) is rare. HBP and LBBAP were complementary in achieving stable and low capture thresholds.

A simple and practical criterion for determining a failed His-bundle pacing.

To establish a simple criterion for determining a failed His-bundle pacing (HBP). This criterion states that if stimulus to QRS end interval is longer than His-bundle potential to QRS end interval ('S-QRSend > H-QRSend') then a failed HBP can be determined. We performed retrospective analysis on 737 pacing tests around His-bundle in 241 patients and prospective analysis on 400 tests in 123 patients. A successful HBP is defined as that whole His-bundle is captured with or without capture of adjacent ventricular myocardium, otherwise, a failed HBP was considered. The output criteria and effective refractory period criteria were used as the gold standards for determining a successful HBP. The gold standards are that if decreasing the pacing output or pacing cycle length to a certain level results in duration or morphology changes of QRS, then a successful HBP is ascertained. In retrospective analysis of patients with normal His-Purkinje conduction, a failed HBP was determined in 31% (154/492) of pacing tests according to 'S-QRSend > H-QRSend'; all of them were validated by the gold standards (specificity = 100%). In prospective study, a failed HBP was confirmed according to the simple criterion with 100% accuracy in 33% (79/241) pacing tests. This simple criterion was also suitable for patients with His-Purkinje conduction disease although cases with 'S-QRSend > H-QRSend' rarely occurred. A failed HBP can be easily and reliably determined solely by 'S-QRSend > H-QRSend' in more than 30% pacing tests.

Impact of electroanatomical mapping-guided lead implantation on procedural outcome of His bundle pacing.

Conventional His bundle pacing (HBP) can be technically challenging and fluoroscopy-intense, particularly in patients with His-Purkinje conduction disease (HPCD). Three-dimensional electroanatomical mapping (EAM) facilitates non-fluoroscopic lead navigation and HB electrogram mapping. We sought to assess the procedural outcome of routine EAM-guided HBP compared with conventional HBP in a real-world population and evaluate the feasibility and safety of EAM-guided HBP in patients with HPCD. We included 58 consecutive patients (72 ± 13 years; 71% male) who underwent an attempt to conventional (EAM- group; n = 29) or EAM-guided (EAM+ group; n = 29) HBP between June 2019 and April 2020. The centre's learning curve was initially determined (n = 40 cases) to define the conventional control group and minimize outcome bias favouring EAM-guided HBP. His bundle pacing was successful in 26 patients (90%) in the EAM+ and 27 patients (93%) in the EAM- group (P = 0.64). The procedure time was 90 (73-135) and 110 (70-130) min, respectively (P = 0.89). The total fluoroscopy time [0.7 (0.5-1.4) vs. 3.3 (1.4-6.5) min; P < 0.001] and fluoroscopy dose [21.9 (9.1-47.7) vs. 78.6 (27.2-144.9) cGycm2; P = 0.001] were significantly lower in the EAM+ than EAM- group. There were no significant differences between groups in His capture threshold (1.2 ± 0.6 vs. 1.4 ± 1.0 V/1.0 ms; P = 0.33) and paced QRS duration (113 ± 15 vs. 113 ± 17 ms; P = 0.89). In patients with HPCD, paced QRS duration was similar in both groups (121 ± 15 vs. 123 ± 12 ms; P = 0.77). The bundle branch-block recruitment threshold tended to be lower in the EAM+ than EAM- group (1.3 ± 0.7 vs. 1.8 ± 1.2 V/1.0 ms; P = 0.31). No immediate procedure-related complications occurred. One patient (2%) experienced lead dislodgement during 4-week follow-up. Implementation of routine EAM-guided HBP lead implantation is feasible and safe in a real-world cohort of patients with and without HPCD and results in a tremendous reduction in radiation exposure without prolonging procedure time or increasing procedure-related complications.

Prospective evaluation of feasibility and electrophysiologic and echocardiographic characteristics of left bundle branch area pacing

His bundle pacing (HBP) is the most physiologic form of pacing but associated with higher thresholds and lower success in patients with His-Purkinje conduction disease. Recent reports have described transvenous left bundle branch area pacing (LBBAP). We aimed to prospectively evaluate the feasibility and the electrophysiologic and echocardiographic characteristics of LBBAP. Patients requiring pacing for bradycardia or heart failure indications (failed left ventricular [LV] lead) were prospectively enrolled. LBBAP was performed with a Medtronic 3830 lead. Presence of left bundle branch (LBB) potential, paced QRS morphology/duration, and peak LV activation time (pLVAT) were recorded at implant. Pacing threshold and sensing was assessed at implant and follow-up. Echocardiography was performed to assess the approximate lead location and impact on tricuspid valve function. LBBAP was successful in 93 of 100 (93%) patients. Mean age was 75 ± 13 years; men 69%, left bundle branch block 24%, right bundle branch block 25%, intraventricular conduction defect 8%. Indications for pacing were atrioventricular (AV) block 54%, sinus node dysfunction 23%, AV node ablation 7%, cardiac resynchronization therapy 11%, HBP lead failure 7%. Baseline QRS duration was 133 ± 35 ms. Paced QRS duration was 136 ± 17 ms. LBB potentials were observed in 63 patients with left bundle branch - ventricle (LBB-V) interval of 27 ± 6 ms. pLVAT was 75 ± 16 ms. Pacing threshold at implant was 0.6 ± 0.4 V @ 0.5 ms and R waves were 10 ± 6 mV and remained stable at median follow-up of 3 months. The lead depth in the septum was approximately 1.4 ± 0.23 cm. LBBAP was feasible in a high percentage of patients with low thresholds during acute follow-up. HBP and LBBAP may significantly increase the overall success of physiologic pacing.

Cycle length criteria for His-bundle capture are capable of determining pacing types misclassified by output criteria

His-bundle pacing is currently defined according to the output criteria. However, potential nonselective His-bundle pacing (NSHBP) might be misclassified as right ventricular pacing by the output criteria. The purpose of this study was to use the novel cycle length (CL) criteria by decremental CL pacing to determine the type of pacing and to differentiate NSHBP from right ventricular pacing in particular. His-bundle pacing was performed in 212 patients with normal His-Purkinje conduction (group 1) and 39 patients with His-Purkinje conduction disease for correction of the condition (group 2). The CL criteria state that if decreasing the CL to a certain level results in QRS morphology changes, then NSHBP is ascertained. NSHBP was obtained in 170 patients in group 1 and 22 patients in group 2. In group 1, NSHBP was validated in 160 patients by both output criteria and CL criteria. NSHBP was misclassified as right ventricular pacing by the output criteria but was correctly classified by CL criteria in the remaining 10 patients (6%). In group 2, NSHBP was all validated by both criteria. Among the 192 patients with NSHBP, the shortest CL (318 ± 29 ms; range 270-470 ms) with which a stimulus can be conducted along the His bundle was at least 20 ms longer than that of surrounding myocardium (264 ± 16 ms; range 250-330 ms) for each patient, suggesting potentially high sensitivity of the CL criteria. CL criteria can determine the types of cardiac pacing independently and can avoid misclassification by output criteria.

PERMANENT HIS BUNDLE PACING IS FEASIBLE IN PATIENTS WITH LONGSTANDING COMPLETE HEART BLOCK AND CHRONIC RIGHT VENTRICULAR PACING

His bundle pacing (HBP) is a physiological alternative to RV pacing (P). The long-term progression of distal His-Purkinje conduction disease in pts with complete heart block (CHB) is unknown. The aim of the study is to assess the feasibility of permanent HBP in patients with longstanding (L) CHB and

Electrophysiological studies in two patients with dystrophia myotonica and atrioventricular conduction block.

Two patients with dystrophia myotonica showed high-grade atrio-ventricular block. Both underwent electrophysiological studies which revealed sinus and A-V nodal disease with normal intraventricular conduction in 1 case and His-Purkinje conduction disease in the other. Dystrophia myotonica may, therfore, involve all parts of the cardiac conduction system and may affect the generation of cardiac impulses. Pacemaker implantation may be necessary especially if drugs such as procainamide, which in addition to controlling myotonic symptoms may aggravate conduction disorders, are to be used.