Acute Pacing Thresholds Research Articles

Acute pacing threshold elevation during simultaneous Micra leadless pacemaker implantation and AV node ablation: Clinical cases, computer model and practical recommendations.

In patients with refractory atrial fibrillation (AF), atrioventricular nodal (AVN) ablation and permanent pacemaker implantation is recommended. The Micra Transcatheter Pacing System (Micra) is a single chamber leadless pacemaker (LPM) and thus offers the possibility of AV node (AVN) ablation in the same procedure. Pacing threshold (PT) elevation after radiofrequency (RF) ablation is a potential complication. We conducted a single center retrospective cohort study. Patients implanted with a Micra (n = 84) and concomitant or delayed AVN ablation (n = 12) from 2014 to 2022 were included. Two cases of acute Micra PT elevation immediately following RF AVN ablation required device retrieval and implantation of a new Micra. Procedural characteristics and electrophysiological parameters were analyzed, and a computer model was performed to determine factors responsible for acute PT elevations. A total of 84 patients were included. Mean age was 74±10 and 48% were women. Twelve patients (14%) underwent AVN ablation. Two patients had acute PT elevation requiring device retrieval despite no direct contact of the ablation catheter with the Micra. Computer modeling shows that significant dissipated power due to electrical field coupling can occur at the tip or ring electrode if the catheter is not kept at a safe distance (≥35mm) from the Micra when a maximum power of 100W is delivered. Concurrent AVN ablation and Micra implantation is safe in most patients. To prevent acute PT elevation, keeping a safe distance of ≥35mm from the tip and ring electrodes of the Micra and using lower power output may prevent this complication.

Learning Curve for Left Bundle Branch Area Pacing – the Experience of a Romanian Academic Center

Abstract Introduction There is an increasing interest in the past decade for more physiological pacing strategies due to detrimental long-term right ventricular pacing. His bundle pacing is the most physiological one, but it has some drawbacks, mainly an increased pacing threshold. Left bundle branch area pacing (LBBAP) emerged in the recent years as the next step in conduction system pacing. We present our initial experience and learning curve with this latter procedure. Material and methods During January 2019 and February 2021, 20 patients with pacing indications that failed initial permanent His bundle pacing underwent successful LBBAP. Results The mean age was 65.9 ± 12.7 years. The indications for cardiac pacing were AV block in 14 patients (70%) and cardiac resynchronization therapy in 6 patients (30%). At baseline, normal QRS complex was noted in 9 patients, a left bundle branch block pattern in 10 patients and a right bundle branch block in one patient. A total of 18 dual-chamber and one single chamber pacemakers were implanted and a cardiac resynchronization therapy defibrillator (CRT-D) device. The acute pacing threshold was 0.56±0.2 V at 0.4ms, the sensing threshold was 10.3±3.9 mV and the impedance was 684.9±112.2 Ω. The overall QRS duration decreased after LBBAP from 128.5 ± 27ms to 103.6 ± 17.4ms (p= 0.001). In patients with baseline wide QRS complex there was a highly significant decrease from 148.2 ± 11.6 ms to 104.7 ± 19.4 ms (p<0.001). The fluoroscopy time, including the time spent for His bundle location, was 13.8 ± 8.5 minutes. The pacing thresholds remained constant after three-months (0.6 ± 0.2 V vs. 0.56 ± 0.2 V at 0.4 ms). We had two intraprocedural septal perforations without any consequences and three micro dislodgements at follow-up with pure left septal capture. Conclusion Left bundle branch area pacing is a feasible physiological pacing technique with a high success rate and the potential to overcome the limits of permanent His bundle pacing. It can be successfully performed virtually in all types of pacing indications, including cardiac resynchronization therapy as provides a rapid and synchronous activation of the left ventricle.

OP-448 - The Effect of Serum Thyroid Stimulating Hormone Levels on Acute Pacing Threshold and Lead İmpedance in Patients with Permanent Pacemaker

OP-448 - The Effect of Serum Thyroid Stimulating Hormone Levels on Acute Pacing Threshold and Lead İmpedance in Patients with Permanent Pacemaker

DIRECT HIS-BUNDLE PERMANENT PACING AS AN ALTERNATIVE TO CONVENTIONAL RIGHT VENTRICULAR APICAL PACING: A PILOT STUDY IN ZAGAZIG UNIVERSITY CARDIAC ELECTROPHYSIOLOGY LABORATORY

Aim: was to evaluate the feasibility of direct his bundle pacing (DHBP) as one of the physiological pacing approaches in our EP lab. Methods: All suitable patients admitted for permanent pacemaker implantation, between January and June 2013, were given a trial for DHBP. Using his bundle (HB) recording through a quadripolar catheter as an electrical and radiological guidance, custom shape stylet was used to direct an active fixation lead to the target position; a pacing protocol was applied to insure pure HB capture. A matching group of patients with apical right ventricular pacing (ARVP) were used as control, to assess the feasibility of DHBP technique. Results: Pure DHBP was successful in 12 out of 32 patients 38%.The DHBP procedure was costly when compared to ARVP in total procedure time (94.7±30.4 vs. 43.2±17.4 minutes), fluoroscopy time(35.2±10.9 vs. 10.1±3.6 minutes), patient x-ray exposure (34.1±7.8 vs. 11.9±4.9 Gy Cm2)and acute pacing threshold (2.1±0.6 vs.0.6±0.4 V). But in the other hand it was better in paced QRS width (76.8±14.8 vs. 193.9±35.8 ms.), patients’ exercise capacity as percentage of achieved METS from Max METS for age (75.5±8.7 vs.54.9±8.7%). the DHBP procedure time was progressively shorter indicating a steep learning curve. Conclusion: Although DHBP has many technical difficulties, it can be achieved with a reasonable coast in our EP lab with a demonstrable benefit, and a steep learning curve. Keywords: direct his bundle pacing, apical right ventricular pacing, physiological pacing, pacemaker, paced QRS duration, and active fixation lead.

An observational study of the effect of coronary artery disease severity on acute pacing threshold and lead impedance in patients with permanent pacemaker

This study investigated the effect of coronary artery disease (CAD) severity, distribution and left ventricular ejection fraction (LVEF) on acute ventricular pacing threshold and lead impedance at the time of pacemaker implantation. One hundred and thirty-two patients who received a ventricular pacemaker or internal cardioverter-defibrilator (ICD) lead in our institution between 2007-2010 were included in this observational study. Patients were divided into ICD and anti-bradycardic pacemaker (PM) groups. Groups were compared for ventricular stimulation threshold, lead impedance and LVEF. Later, groups were sub-grouped according to the severity and distribution of CAD and subgroups were compared in both groups for ventricular stimulation threshold, lead impedance. Quantitative data of groups were compared by means of independent samples t-test. Ventricular pacing thresholds were found significantly higher ICD group compared with PM group (p<0.05). Impedance and LVEF values were significantly lower in ICD group (p<0.05). Impedance and ventricular pacing thresholds were comparable in subgroups of ICD and PM groups. Our study does not confirm any relationship between pacing parameters and severity-distribution of CAD and LVEF. Patients with ventricular ICD lead had higher pacing thresholds but lower pacing impedance values comparing with PM group. This study did not find any significant relationship between pacing parameters at implantation and LVEF, severity and distribution of CAD.

Rapid Improvement and Long-term Stability of Pacing Threshold with Active-fixation Screw-in Lead

Background: Active‐fixation screw‐in leads are associated with initially high thresholds. However, pacing thresholds have been shown to improve within several minutes after screwin. The aim of this study is to investigate the long‐term stability of rapidly improved pacing thresholds following the implantation of active‐fixation screw‐in leads.Methods: We performed a prospective observational study on 68 consecutive patients, who were referred for an initial pacemaker or implantable cardioverter defibrillator implantation. Pacing thresholds, sensing amplitudes, and lead impedances were measured immediately after screw‐in. If the initial pacing threshold was higher than 2.0 volts, lead reposition was performed. If the initial pacing threshold was lower than 1.0 volts, the lead position was considered adequate. If the initial pacing threshold was slightly high, i.e., between 1.0 and 2.0 volts, all parameters were measured again 5 minutes after screw‐in without lead repositioning, and 1 week, 1 month, 6 months, and 1 year after the procedure.Results: Fifty‐three atrial leads and 59 ventricular leads were implanted using activefixation screw‐in leads. The initial pacing threshold was slightly high, i.e., between 1.0 and 2.0 volts in 16 (30%) atrial leads and 28 (47%) ventricular leads. Pacing thresholds significantly improved after 5 minutes in both atrial and ventricular leads as follows: 1:5 ± 0:2 to 0:9 ± 0:3 volts (p &lt; 0:05) in atrial leads and 1:5 ± 0:3 to 0:9 ± 0:3 volts (p &lt; 0:05) in ventricular leads. These improved pacing thresholds remained stable during the first year and were 0:8 ± 0:3 volts in atrial leads and 0:8 ± 0:2 volts in ventricular leads after the initial year. P‐ and R‐wave amplitudes did not change significantly during the follow‐up. Lead impedances decreased 1 week after the procedure and remained stable in both atrial and ventricular leads.Conclusions: Slightly high pacing thresholds using active‐fixation screw‐in leads improved rapidly and remained stable in the long term. An acute pacing threshold of &lt;2:0 volts immediately after screw‐in may change to an acceptable value without lead repositioning.

A Feasible Approach for Direct His‐Bundle Pacing Using a New Steerable Catheter to Facilitate Precise Lead Placement

Much clinical evidence has shown that right ventricular (RV) apical pacing is detrimental to left ventricular function. Preservation of the use of the His-Purkinje (H-P) system may be ideal in heart block that is restricted to the AV node, but may be of no benefit when H-P disease exists. To investigate the feasibility of direct His-bundle pacing (DHBP) using a new system consisting of a steerable catheter and a new 4.1 F screw-in lead. Between May and December 2004, 26 patients (19 male, mean age: 77 +/- 5 years) with a standard pacemaker (PM) indication and preserved His-bundle conduction were enrolled and DHBP was attempted. DHBP was achieved in 24 patients (92%); two patients were paced in the His area, but the paced QRS morphology and duration were different from the native QRS. The mean time for lead positioning was 19 +/- 17 minutes, the mean fluoroscopy time was 11 +/- 8 minutes, and the total procedure time (skin-to-skin including positioning of a quadripolar diagnostic catheter for His recording) was 75 +/- 18 minutes. In DHBP pacing, the acute pacing threshold was 2.3 +/- 1.0 V at a pulse duration of 0.5 msec, and the sensed potentials were 2.9 +/- 2.0 mV. At a 3-month follow-up examination, the same QRS duration and morphology recorded on implantation were observed in all patients. The pacing threshold was 2.8 +/- 1.4 V, and sensed potentials were 2.5 +/- 1.8 mV; the sensing configuration was changed from bipolar to unipolar in 6 patients to resolve undersensing issues. No major complications were observed. This feasibility study shows that DHBP can be accomplished with a new system consisting of a steerable catheter and an active fixation lead in 92% of the patients in whom it was attempted.

Permanent, Direct His-Bundle Pacing

Direct His-bundle pacing (DHBP) produces synchronous ventricular depolarization and improved cardiac function relative to apical pacing. Although it has been performed transiently in the electrophysiology laboratory and persistently in open-chested canines, permanent DHBP in humans has not been achieved. A total of 18 patients aged 69+/-10 years who had a history of chronic atrial fibrillation, dilated cardiomyopathy, and normal activation (ie, QRS< or =120 ms) were screened for permanent DHBP using an electrophysiology catheter. In 14 patients, the His bundle could be reliably stimulated. Of these 14, permanent DHBP using a fixed screw-in lead was successful in 12 patients. Radiofrequency atrioventricular node ablation was performed in patients exhibiting a fast ventricular response. All patients received single-chamber rate-responsive pacemakers. Acute pacing thresholds were 2.4+/-1.0 V at a pulse duration of 0.5 ms. Lead complications included exit block requiring reoperative adjustment and gross lead dislodgment. Echocardiographic improvement in heart function was shown by reductions in the left ventricular end-diastolic dimension from 59+/-8 to 52+/-6 mm (P</=0.01) and in the end-systolic dimension from 51+/-10 to 43+/-8 mm (P<0.01), with an accompanying increase in fractional shortening from 14+/-7% to 20+/-10% (P=0.05). The left ventricular ejection fraction improved from 20+/-9% to 31+/-11% (P<0. 01), and the cardiothoracic ratio decreased from 0.61+/-0.06 to 0. 57+/-0.07 (P<0.01). Despite DHBP, 2 patients died at 8 and 36 months. Conclusions-Permanent DHBP is feasible in select patients who have chronic atrial fibrillation and dilated cardiomyopathy. Long-term, DHBP results in a reduction of left ventricular dimensions and improved cardiac function.

Left ventricular lead insertion using a modified transseptal catheterization technique: A totally endocardial approach for permanent biventricular pacing in end-stage heart failure.

This article describes a new technique of LV lead insertion, using transseptal catheterization performed through the right internal jugular vein, to obtain a totally endocardial biventricular chronic pacing in end-stage heart failure. Three patients with QRS widening (> 180 ms) linked to complete left bundle branch block (n = 2) or right ventricular pacing (n = 1) were included in this preliminary study. Catheterization was performed under fluoroscopy and transesophageal echocardiography guidance. Transseptal catheterization was achieved by puncture of the right internal jugular vein at the base of the neck and by using a Brockenbrough needle, the tip curve of which was more curved than the standard model. A flexible long sheath was advanced in the left atrium through the interatrial septum and then a unipolar electrode was placed easily in the LV. The proximal tip of the LV lead was tunneled from the neck to the subclavian area and connected to the ventricular channel of a dual (n = 1) or simple (n = 2) chamber pacemaker. Efficient acute sensing (V wave amplitude = 13 +/- 3 m V) and pacing (acute pacing threshold = 0. 7 +/- 0.4 V) were obtained in the three patients. Early loss of capture occurred in two patients requiring lead replacement. Functional status dramatically improved in all three patients. At 6-month follow-up, biventricular pacing was maintained in all patients (mean threshold 1.4 V) who were free of clinical embolic event with oral anticoagulation therapy. This modified technique of jugular transseptal catheterization appears promising for the development of left heart pacing.

Unconventional approaches to cardiac pacing in patients with inaccessible cardiac chambers

Background. Transvenous endocardial implantation can be impossible or contraindicated in patients with inaccessible right cardiac chambers. These patients usually undergo epicardial implantation, which has been associated with frequent rising thresholds and limited lead survival. We have used the following two alternative approaches in these patients: (1) transatrial puncture and passage of pacing leads for patients with no access to the right atrium and (2) ventricular pacing from the coronary sinus or its tributaries for patients with inaccessible ventricles.Methods. We retrospectively reviewed our experience in 9 patients who had those procedures. Five patients had pacing from the coronary sinus, and 4 by transatrial puncture.Results. Seven of the 9 patients had DDD pacing. Low acute pacing thresholds and satisfactory sensing levels were obtained with both approaches. One instance of high stimulation threshold (20%) occurred in the coronary sinus group and none in the transatrial puncture group. One patient in the transatrial puncture group died from unrelated causes. No malignant arrhythmias, pneumothorax, diaphragmatic pacing, or infectious complications have been observed.Conclusion. These unconventional approaches are safe, relatively simple, and reliable. Although the short-term follow-up is favorable, long-term follow-up is necessary to ascertain the relative merit of these approaches.

Permanent left atrial pacing with a specifically designed coronary sinus lead.

This article reports the original use of a specifically designed coronary sinus (CS) lead for permanent left atrial (LA) pacing. The device is characterized by its distal end shape featuring a double 45 degree angulation, which ensures very close contact with the CS upper wall. The device was successfully implanted in 39 out of 40 patients (97.5%). The tip electrode was eventually positioned in the distal CS in 9 patients, in the middle CS in 21 patients, and close to the ostium in the proximal CS in 9 patients. The mean acute pacing threshold voltage was 0.9 +/- 0.5 V with a mean impedance of 578 +/- 144 omega as measured in unipolar distal configuration at 0.5 ms pulse width (PW). The mean A wave amplitude was 3.5 +/- 2.1 mV. Early lead dislodgment occurred only once (3%) when the tip electrode was placed in the distal or middle CS, but more often (4/9 cases) when it was placed in the proximal CS. After a mean follow-up duration of 14 +/- 8.5 months, 35 of the 39 successfully implanted leads (89.7%) were still functional in terms of LA pacing and sensing. The mean chronic pacing threshold voltage was 1.5 +/- 0.8 V and the mean A wave amplitude was 2.7 +/- 1.6 mV. There were no lead related complications. In conclusion, the device proved to be safe and highly effective for permanent LA pacing, provided the distal tip could be positioned in the distal or middle part of the CS.

Serum creatine kinase activity and sensing characteristics after intraoperative arrhythmia induction using implantable defibrillator rate sensing leads.

In 29 patients (24 men, 5 woman, mean age 57 +/- 14 years) we evaluated the effect of intraoperative arrhythmia induction during implantable defibrillator (ICD) placement using alternating current (AC) applied through the epicardial rate sensing leads on acute and chronic pacing thresholds, electrogram amplitudes, slew rates and serum creatine kinase levels. In 15 patients undergoing new ICD implantation, pacing thresholds, electrogram amplitudes, slew rates, and resistances were measured before and following at least three inductions of ventricular fibrillation (VF) using AC applied through the epicardial rate sensing leads. Fourteen patients who underwent VF induction using AC through the epicardial leads during initial implant (mean time of 31 months previously) underwent ICD pulse generator replacement only with parameters measured as above before and after at least two inductions, and these compared to the values at initial implant. In all 29 patients serum creatine kinase levels were obtained before, immediately following, and at 8, 16, and 24 hours after surgery. No significant change in acute pacing threshold, electrogram amplitude, slew rate or resistance occurred. Chronically there was an expected 154% increase in pacing threshold but no significant change in electrogram amplitude or resistance. Serial serum creatine kinase and MB isoenzyme determinations demonstrated no evidence of myocardial necrosis. We conclude that intraoperative arrhythmia induction during ICD implantation using AC applied through the rate sensing leads is a safe and effective technique.

Atrial pacemaker leads compared

In order to analyze the impact of different polarity and electrode designs on the acute pacing and sensing characteristics of pacemaker leads, 80 patients with complete heart block or sinus node dysfunction undergoing pacemaker implantation received eight different leads from five manufacturers. Once the leads were positioned, volt and current thresholds, P wave, peak-to-peak, and slew rate were assessed prospectively. There was no statistically significant difference between acute pacing thresholds, sensing characteristics, or unipolar and bipolar pacing thresholds. Active fixation leads allow atrial mapping and lead placement in areas generally inaccessible to tined tip leads. This is an advantage, especially for patients with a history of open heart surgery.

Improved silastic sleeve temporary cardiac pacing electrodes

New atrial clip-on and ventricular suture-on temporary pacemaker electrode systems were evaluated in dogs. The ability of these electrodes to sense cardiac electrical activity was evaluated during a 14-day period. At no time did the P-wave potential fall below 3.3 mV and the R-wave potential fall below 6.0 mV. The acute pacing thresholds never exceeded 1.025 V and 1.95 mA. All values are well within acceptable standards for temporary pacing. The lead wires were easily, quickly, and painlessly removed without injury to the myocardium, yet the electrical contact remained tight between the lead wire and electrode preventing premature displacement.