Right Ventricular Outflow Tract Septal Pacing: Long-Term Follow-Up of Ventricular Lead Performance

Background: The detrimental effects of right ventricular apical pacing on left ventricular function has driven interest in selective site pacing, predominantly on the right ventricular outflow tract (RVOT) septum. There is currently no information on long-term ventricular lead electrical performance from this site.
Methods: A total of 100 patients with ventricular lead placement on the RVOT septum undergoing pacemaker implantation for bradycardia indications were analyzed retrospectively. Lead positioning was confirmed with the use of fluoroscopy. Long-term (1 year) follow-up was obtained in 92 patients. Information on stimulation threshold, R-wave sensing, lead impedance, and lead complications were collected.
Results: Lead performance at the RVOT septal position was stable in the long term. Ventricular electrical parameters were acceptable with stable long-term stimulation thresholds, sensing, and impedance for all lead types. One-year results demonstrated mean stimulation threshold of 0.71 ± 0.25 V, mean R wave of 12.4 ± 6.05 mV, and mean impedance values of 520 ± 127 Ω. There were no cases of high pacing thresholds or inadequate sensing.
Conclusions: This study confirms satisfactory long-term performance with leads placed on the RVOT septum, comparable to traditional pacing sites. It is now time to undertake studies to examine the long-term hemodynamic effects of RVOT septal pacing.     

Right Ventricular Septal Pacing: The Success of Stylet-Driven Active-Fixation Leads

Background: The detrimental effects of right ventricular (RV) apical pacing on left ventricular function has driven interest in alternative pacing sites and in particular the mid RV septum and RV outflow tract (RVOT). RV septal lead positioning can be successfully achieved with a specifically shaped stylet and confirmed by the left anterior oblique (LAO) fluoroscopic projection. Such a projection is neither always used nor available during pacemaker implantation. The aim of this study was to evaluate how effective is the stylet-driven technique in septal lead placement guided only by posterior-anterior (PA) fluoroscopic view.
Methods: One hundred consecutive patients with an indication for single- or dual-chamber pacing were enrolled. RV septal lead positioning was attempted in the PA projection only and confirmed by the LAO projection at the end of the procedure.
Results: The RV lead position was septal in 90% of the patients. This included mid RV in 56 and RVOT in 34 patients. There were no significant differences in the mean stimulation threshold, R-wave sensing, and lead impedance between the two sites . In the RVOT, 97% (34/35) of leads were placed on the septum, whereas in the mid RV the value was 89% (56/63).
Conclusions: The study confirms that conventional active-fixation pacing leads can be successfully and safely deployed onto the RV septum using a purposely-shaped stylet guided only by the PA fluoroscopic projection. (PACE 2010; 49–53)     

Search for the Optimal Right Ventricular Pacing Site: Design and Implementation of Three Randomized Multicenter Clinical Trials

Background: The optimal site to permanently pace the right ventricle (RV) has yet to be determined. To address this issue, three randomized prospective multicenter clinical trials are in progress comparing the long-term effects of RV apical versus septal pacing on left ventricular (LV) function. The three trials are Optimize RV Selective Site Pacing Clinical Trial (Optimize RV), Right Ventricular Apical and High Septal Pacing to Preserve Left Ventricular Function (Protect Pace), and Right Ventricular Apical versus Septal Pacing (RASP).
Methods: Patients that require frequent or continuous ventricular pacing are randomized to RV apical or septal pacing. Optimize RV excludes patients with LV ejection fraction <40% prior to implantation, whereas the other trials include patients regardless of baseline LV systolic function. The RV septal lead is positioned in the mid-septum in Optimize RV, the high septum in Protect Pace, and the mid-septal inflow tract in RASP. Lead position is confirmed by fluoroscopy in two planes and adjudicated by a blinded panel. The combined trials will follow approximately 800 patients for up to 3 years.
Results: The primary outcome in each trial is LV ejection fraction evaluated by radionuclide ventriculography or echocardiography. Secondary outcomes include echo-based measurements of ventricular/atrial remodeling, 6-minute hall walk distance, brain natriuretic peptide levels, and clinical events (atrial tachyarrhythmias, heart failure, stroke, or death).
Conclusion: These selective site ventricular pacing trials should provide evidence of the importance of RV pacing site in the long-term preservation of LV function in patients that require ventricular pacing and help to clarify the optimal RV pacing site.     

Long-term Stability of Endocardial Left Ventricular Pacing Leads Placed via the Coronary Sinus

Background: Left ventricular endocardial pacing leads placed via the coronary sinus (CS) are increasingly implanted to achieve cardiac resynchronization therapy (CRT); however, the long-term stability of these leads is unknown. We sought to determine the implant success and long-term stability of CS leads in our single center experience.
Methods: All consecutive patients who underwent CRT via implantation of the CS lead between January 1999 and December 2005 were included. Pacing thresholds at implant and during long-term follow-up were reviewed and the rate of acute (within 24 hours of implant) and chronic (>24 hours) lead failure was determined.
Results: A total of 512 patients (mean age 68 ± 12 years; 409 [80%] male) underwent CRT device implantation and were included. The CS lead implantation was successful on the initial implantation in 487 patients (95%) and subsequently successful in six patients (24%) in whom initial attempts were unsuccessful. Acute lead failure occurred in 25 patients (5.1%) and was most commonly due to persistent extra-cardiac stimulation. The rate of chronic lead failure was 4% in the first year and remained stable during long-term follow-up. The CS lead pacing thresholds remained stable with only minimal increase (1.42 ± 0.85 V/0.42 ± 0.25 ms vs 1.51 ± 1.05 V/0.47 ± 0.29 ms; P = 0.04).
Conclusions: Placement of a left ventricular pacing lead via the CS is feasible and safe in the vast majority of patients. Once placed, the CS leads remain stable with excellent pacing thresholds over the longer term.     

The Road to Right Ventricular Septal Pacing: Techniques and Tools

Prolonged right ventricular (RV) apical pacing is associated with progressive left ventricular dysfunction due to dysynchronous ventricular activation and contraction. RV septal pacing allows a narrower QRS compared to RV apical pacing, which might reflect a more physiological and synchronous ventricular activation. Previous clinical studies, which did not consistently achieve RV septal pacing, were not confirmatory and need to be repeated. This review summarizes the anatomy of the RV septum, the radiographic appearances of pacing leads in the RV, the electrocardiograph correlates of RV septal lead positioning, and the techniques and tools required for implantation of an active‐fixation lead onto the RV septum. Using the described techniques and tools, conventional active‐fixation leads can now be reliably secured to either the RV outflow tract septum or mid‐RV septum with very low complication rates and good long‐term performance. Even though physiologic and hemodynamic studies on true RV septal pacing have not been completed, the detrimental effects of long‐term RV apical pacing are significant enough to suggest that it is now time to leave the RV apex and secure all RV leads onto the septum. (PACE 2010; 888–898)     

Placement of a Pacing Lead at the Inferior Portion of the Interatrial Septum Without Special Tools

Introduction: Previous studies have suggested that, among septal sites, the inferior portion of the interatrial septum (IAS) is the most likely to prevent atrial fibrillation, though inserting an active fixation lead at this site can be tedious and time consuming. We describe a relatively straightforward technique to insert a lead at this site without special tools .
Method: We studied 117 consecutive patients (mean age = 76 ± 8 years, 69% men) with ACC/AHA class I and II pacing indications and histories of paroxysmal or permanent atrial fibrillation, undergoing implantation of a dual chamber pacing system. A technique using the "preshaped" stylet and fluoroscopic guidance is described.
Results: The insertion was successful in 111 patients (95%). Acute dislodgement occurred in six patients (5%). The intrinsic P-wave duration was 117 ± 22 ms, and the paced P-wave duration was 90 ± 20 ms (23% shortening, P < 0.001). The mean time required to insert the atrial lead was 12 ± 8 minutes. No complications occurred.
Conclusions: Insertion of an active fixation lead at the inferior portion of the interatrial septum was safe and highly successful in the majority of patients with this technique.     

Dual Chamber Pacing with a Single-Lead DDD Pacing System

The successful application of single-lead VDD pacing during the last few years has generated the idea of single-lead DDD pacing. Preliminary data from several single-lead VDD studies attempting to pace the atrium by a floating atrial dipole are unsatisfactory, causing an unacceptably high current drain of the device. We studied the feasibility as well as the short- and long-term stability of atrioventricular sequential pacing, using a new single-pass, tined DDD lead. In eight consecutive patients (age 73+/-16 years) with symptomatic higher degree AV block and intact sinus node function, this new single-pass DDD lead was implanted in combination with a DDDR pacemaker. Correct VDD and DDD function was studied at implantation; at discharge; and at 1, 3, and 6 months of follow-up. At implant, the atrial stimulation threshold was 0.6+/-0.1 V/0.5 ms. During follow-up, the atrial pacing thresholds in different every day positions averaged 2.1+/-0.5 V at discharge, 2.9+/-0.5 V at 1 month, 3.8+/-0.4 V at 3 months, and 3.4+/-0.4 V at 6 months (pulse width always 0.5 ms). The measured P wave amplitude at implantation was 4.5+/-2.2 mV; during follow-up the telemetered atrial sensitivity thresholds averaged 2.1+/-0.3 mV. Phrenic nerve stimulation at high output pacing (5.0 V/0.5 ms) was observed in three (38%) patients at discharge and in one (13%) patient during follow-up; an intermittent unmeasurable atrial lead impedance at 3 and 6 months follow-up was documented in one (13%) patient. This study confirms the possibility of short- and long-term DDD pacing using a single-pass DDD lead. Since atrial stimulation thresholds are still relatively high compared to conventional dual-lead DDD pacing, further improvements of the atrial electrodes are desirable, enabling lower pacing thresholds and optimizing energy requirements as well as minimizing the potential disadvantage of phrenic nerve stimulation.     

Initial Experience of Pacing with a Lumenless Lead System in Patients with Congenital Heart Disease

Background: Long-term pacing is frequently necessary in patients with congenital heart disease (CHD). Preservation of ventricular function and avoidance of venous occlusion is important in these patients. Site-selective pacing with a smaller diameter lead is achievable with the model 3830 lead (SelectSecure®, Medtronic Inc., Minneapolis, MN, USA), which was specifically designed to target these complications. We describe our initial experience with the Model 3830 lead in patients with CHD.
Methods: Retrospective analysis of all patients undergoing site-selective implantation of a Model 3830 lead(s) from two congenital heart centers (Bristol, UK, and Dublin, Ireland) from October 2004 until February 2008.
Results: We implanted 139 SelectSecure® leads (atrial n = 70; ventricular n = 69) in 90 patients (57 male) with CHD. Median age at implantation: 13.4 years (1.1–59.2 years), median weight: 43 kg. Sixty-nine patients (76%) were children (<18 years). Indications for lead implantation included atrioventricular block (n = 55), sinus node disease (n = 18), implantable cardiac defibrillator (n = 12), antitachycardia pacing (n = 4), and cardiac resynchronization (n = 1). Twenty-two patients underwent pre-existing lead extraction during the same procedure. All the attempted procedures resulted in successful pacing. One patient had a significantly raised threshold at implantation. There was no procedural mortality. There were two procedural complications. Three patients required lead repositioning for increasing thresholds early postprocedure (<6 weeks). Four leads (2.9%) had displaced on median follow-up of 21.8 months (0.5–42 months).
Conclusions: The Model 3830 lead is safe and effective in patients with CHD. This is a technically challenging patient group yet procedural complication and lead displacement rates are acceptable.     

Five-Year Follow-Up of a Bipolar Steroid-Eluting Ventricular Pacing Lead

Steroid-eluting pacing leads are known to attenuate the threshold peaking early after implantation. Long-term performance, however, is not yet settled. The lead design tested in this prospective study combines a 5.8-mm2 tip of microporous platinum-iridium with elution of 1.0 mg of dexamethasone sodium phosphate and tines for passive fixation (model 5024, Medtronic Inc.). In 50 patients (mean age 69 +/- 10 years), the electrode was implanted in the right ventricular apex. Follow-up was performed on days 0, 2, 5, 10, 28, 90, 180 and every 6 months thereafter for 5-years postimplant. At each visit, pacing thresholds were determined as pulse duration (ms) at 1.0 V and as the minimum charge (microC) delivered for capture. Lead impedance (omega) was telemetered at 2.5 V-0.50 ms, and sensing thresholds (mV) were measured in triplicate using the automatic sensing threshold algorithm of the pacemaker implanted (model 294-03, Intermedics Inc.). On the day of implantation, mean values were 0.10 +/- 0.03 ms, 0.12 +/- 0.03 microC, 758 +/- 131 omega, and 13.1 +/- 1.8 mV, respectively. Beyond 1-year postimplant, pacing thresholds did not vary significantly. Sensing thresholds and lead impedance values were stable during long-term follow-up. Five years after implantation, mean values were 0.23 +/- 0.11 ms, 0.24 +/- 0.07 microC, 670 +/- 139 omega, and 11.6 +/- 3.1 mV for pulse width and charge threshold, lead impedance, and sensing threshold, respectively, and all leads captured at 1.0 V with the longest pulse duration available (1.50 ms). It is concluded that the bipolar steroid-eluting tined ventricular lead showed stable stimulation thresholds, lead impedance values, and sensing thresholds for 5 years after implantation.     

Use of Single Lead VDD Pacing in Children

The development of transvenous ventricular pacing leads with proximal electrodes capable of atrial sensing and the recent availability of smaller generators has created the opportunity to treat children with complete AV block and normal sinus node function with a transvenous single lead VDD pacing system. Studies in adults have demonstrated this system to be efficacious with low complication rates. Transvenous single lead VDD pacemakers were implanted in ten children, aged 5–15 years, between December 1993 and April 1996, in our institution. The indications were complete AV block with severe bradycardia in 5 patients, second-degree or complete A V block following congenital heart surgery in 3, complete A V block with long QT syndrome in 1, and second-degree AV block and syncope in 1. There were no complications related to the procedure in any case. P and R wave amplitudes were measured and thresholds were determined intraoperatively on all patients. Amplitudes and thresholds were remeasured on seven patients with a mean follow-up of 17 months; Holter monitors were performed on seven patients with a mean follow-up of 16 months. P and H wave amplitudes were generally diminished at follow-up compared to initial values but remained within an acceptable range for all patients. Four patients required reprogramming after pacemaker insertion, 1 received an atrial lead for dual chamber pacing, 1 required repositioning for lead dislodgment. and 1 patient required a new lead for an inadequate ventricular pacing threshold. No patient had evidence of failure to sense or capture as evaluated by Halter monitoring at last follow-up. Single lead VDD pacing systems can be successfully used in properly selected children with high degree or complete AV block with normal sinus node function.     

Active Fixation of Endocardial Pacing Leads: The Preferred Method of Pediatric Pacing

Pacing system failure due to lead related problems may necessitate repositioning or explantation of the problem lead. Pediatric patients with permanent pacemakers have additional considerations that necessitate revision or explantation of pacing leads. Active fixation type leads appear to offer the physician advantages over passive fixation leads that may make them the lead of choice for use in children. We reviewed our experience with active fixation type leads to determine whether the ease with which these leads could be revised or explanted justified recommending their use in our patients. Eleven patients underwent 13 lead revisions. The time from implant to revision was a mean of 12.3 months. Six patients had previously undergone repair of a congenital heart defect. Modes of pacing were: DDD (seven); AAI (three); and VVI (one). Exposed, isodiametric leads accounted for 11/13 leads. Leads were successfully explanted in nine cases and repositioned in four cases. The only lead that could not be revised and resulted in retention was a nonisodiametric, retractable helix lead at the junction of the subclavian vein and clavicle. We conclude isodiametric active fixation leads can be safely repositioned or explanted in children and should be considered the preferred method for endocardial pacing in children.     

Backup Right Ventricular Pacing with a 0.035" Guidewire during Implantation of Left Ventricular Leads

Introduction: During implantation of biventricular devices, manipulation of the guiding sheath during localization of the coronary sinus (CS) ostium may result in injury to the right bundle and complete heart block. A preventive measure is to implant the right ventricular (RV) lead first, though this may interfere with manipulation of the guiding sheath and dislodge the permanent lead . We tested the feasibility of backup pacing with a 0.035" guidewire, advanced through the guiding sheath during CS localization.
Methods: One hundred six consecutive patients (mean age = 70 ± 11 years, 81 men) undergoing biventricular device implantation were studied. A 0.035" guidewire with an uncoated tip was advanced into the right ventricle through the guiding sheath, and unipolar capture threshold, R-wave sensing amplitude, and pacing impedance were measured.
Results: RV pacing was successful in all patients. The mean capture threshold was 3.8 ± 2.1 V/0.5 ms, R-wave amplitude 5.4 ± 4.3 mV, and pacing impedance 226 ± 78 Ω. No arrhythmia was observed during the tests. Two patients developed complete heart block during the implant procedure and were successfully paced temporarily using the 0.035" guidewire.
Conclusion: Temporary RV pacing, using a 0.035" guidewire within the guiding sheath, is a simple, reliable, and safe method that allows backup pacing in case of traumatic complete heart block, developing during the implantation of biventricular devices.     

Addition of a left ventricular lead to conventional pacing systems in patients with congestive heart failure: feasibility,safety, and early results in 60 consecutive patients

Left bundle branch block worsens congestive heart failure (CHF) in patients with LV dysfunction. Asynchronous LV activation produced by RV apical pacing leads to paradoxical septal motion and inefficient ventricular contraction. Recent studies show improvement in LV function and patient symptoms with biventricular pacing in patients with CHF. The aim of this study was to determine the feasibility, safety, acute efficacy, and early effect on symptoms of the upgrade of a chronically implanted RV pacing system to a biventricular system. Sixty patients with NYHA Class III and IV underwent the upgrade procedure using commercially available leads and adapters. The procedure succeeded in 54 (90%) of 60 patients. Acute LV stimulation thresholds obtained from leads placed along the lateral LV wall via the coronary sinus compare favorably to those reported in current biventricular pacing trials. The complication rate was low (5/60, 8.3%): lead dislodgement (n = 1), pocket hematoma (n = 1), and wound infections (n = 3). During 18 months of follow-up (16.7%) of 60 patients died. Two patients that died failed the initial upgrade attempt. At 3-month follow-up, quality of life scores improved 31 +/- 28 points (n = 29), P < 0.0001). NYHA Class improved from 3.4 +/- 0.5 to 2.4 +/- 0.7 (P = < 0.0001) and ejection fraction increased from 0.23 +/- 0.8 to 0.29 +/- 0.11 (P = 0.0003). Modification of RV pacing to a biventricular system using commercially available leads and adapters can be performed effectively and safely. The early results of this study suggest patients may benefit from this procedure with improved functional status and quality of life.     

Acute and Chronic Cycle Length Dependent Increase in Ventricular Pacing Threshold

Several factors have been shown to influence ventricuJar pacing threshold in humans, including pacing lead location (endocardial vs epicardial), lead maturation, and antiarrhythmic agents. To determine whether ventricuJar pacing rate has a significant influence on acute and chronic pacing thresholds, we measured pacing thresholds in 16 patients receiving an implantafaleantitachycardia pacemaker cardioverter defibrillator (Cadence?). Ventricular pacing thresholds were determined using the device programmer at cycle lengths of GOO, 400, and 300 msec at the time of implantation; prior to hospital discharge at 3-14 days; and during follow-up outpatient visits at 6-8 weeks, 3 months, and 6 months to 1 year. Eleven patients had an epicardial lead system and five an endocardial lead system. Eleven patients were being treated with antiarrhythmic drug therapy. Device output ranged from 1-10 V and was adjustable in 1-V increments (pulse width was held constant at 1 msec). A cycle length dependent increase in pacing threshold (defined as a ≤ 1-V increase in threshold at 400 or 300 msec relative to 600 msecj was observed in 10/16 patients during 12/72 pacing trials at 400 msec, and in 15/16 patients during 31/67 trials at 300 msec. In trials in which an increase in pacing threshold occurred, the magnitude of the increase at 400 msec relative to 600 msec was only 1 V in all 12 trials, but at 300 msec the increase ranged from 4–9 V in 7/31 (23%) trials. There was an equal percentage (67%) of patients demonstrating a cycle length dependent increase in threshold with measurements made at the time of device implantation and at the 6 month to 1 year follow-up period. Two-way analysis of variance showed a significant effect of cycle length and time from implantation on mean pacing thresholds at the three cycle lengths. In conclusion, a cycle length dependent increase in pacing threshold occurred in virtually all patients during follow-up of up to 12 months and, thus, its presence was independent of lead location, presence of antiarrhythmic agents, and the state of lead maturation. These findings suggest that pacing thresholds measured at rates just above the sinus rate may not always apply to the faster rates utilized for antitachycardia pacing and indicates the need for threshold measurement at the designed pacing rate.     

Right Ventricular Septal Pacing: A Comparative Study of Outflow Tract and Mid Ventricular Sites

Background: Prolonged right ventricle (RV) apical pacing is associated with left ventricle (LV) dysfunction due to dysynchronous ventricular activation and contraction. Alternative RV pacing sites with a narrower QRS compared to RV pacing might reflect a more physiological and synchronous LV activation. The purpose of this study was to compare the QRS morphology, duration, and suitability of RV outflow tract (RVOT) septal and mid‐RV septal pacing. Methods: Seventeen consecutive patients with indication for dual‐chamber pacing were enrolled in the study. Two standard 58‐cm active fixation leads were passed to the RV and positioned in the RVOT septum and mid‐RV septum using a commercially available septal stylet (model 4140, St. Jude Medical, St. Paul, MN, USA). QRS duration, morphology, and pacing parameters were compared at the two sites. The RV lead with less‐satisfactory electrical parameters was withdrawn and deployed in the right atrium. Results: Successful positioning of the pacing leads at the RVOT septum and mid‐RV septum was achieved in 15 patients (88.2%). There were no significant differences in the mean stimulation threshold, R‐wave sensing, and lead impedance between the two sites. The QRS duration in the RVOT septum was 151 ± 14 ms and in the mid‐RV septum 145 ± 13 ms (P = 0.150). Conclusions: This prospective observational study shows that septal pacing can be reliably achieved both in the RVOT and mid‐RV with active fixation leads using a specifically shaped stylet. There are no preferences in regard to acute lead performance or paced QRS duration with either position. (PACE 2010; 33:1169–1173)     

Septal Short Atrioventricular Delay Pacing: Additional Hemodynamic Improvements in Heart Failure

Controversy exists as to whether short AV delay pacing is beneficial in left ventricular dysfunction with the studies performed coming to disparate conclusions. The right ventricular apical pacing previously studied results in asynchronous contraction and relaxation sequences and may limit the potential benefits of short AV delay pacing. In this study the hemodynamic effects of septal (resulting in a more physiological activation sequence) and apical right ventricular activation were compared in 15 patients with heart failure. VDD pacing with AV delays of 50,100, and 150 msec was evaluated. Apical VDD pacing did not increase the cardiac output significantly, 4.1 ± 0.75 to 4.45 ± 0.74 L/min, whereas septal VDD pacing increased the cardiac output to 4.86 ± 0.79 L/min (P = 0.037). Apical pacing increased the cardiac output in 10 patients and septal pacing in 11 patients. We conclude that selected patients with ventricular dysfunction benefit from short AV delay pacing. Septal ventricular activation confers significant hemodynamic improvements over apical activation.     

Long-Term Experience with a Preshaped Left Ventricular Pacing Lead

OLLITRAULT, J., et al. : Long-Term Experience with a Preshaped Left Ventricular Pacing Lead. This study describes a long-term experience with a new LV pacing lead. The study population consisted of 62 patients (85% men,   71 ± 10   years old) with advanced dilated cardiomyopathy, in NYHA Class III or IV despite optimal drug therapy, and a QRS duration >150 ms. Patients in sinus rhythm were implanted with a triple chamber pacemaker to maintain atrioventricular synchrony. A dual chamber pacemaker was implanted in patients in atrial fibrillation for biventricular pacing only. A clinical evaluation and interrogation of the resynchronization pacemaker were performed at implant, at 1 week (W1), one (M1), four (M4), and seven (M7) months after implantation. A longer follow-up (2 years) is available for patients implanted at the authors institution. LV measurements were pacing threshold at 0.5-ms pulse duration and pacing impedance. R wave amplitude (mV) was measured at the time of implantation only. The system was successfully implanted in 86% of patients with the latest design of the lead. Mean R wave amplitude at implant was   15 ± 7 mV   and mean pacing impedance was   1054 ± 254 Ω   . Between implant   (n = 38)   and M7   (n = 15)   , pacing threshold rose from   0.73 ± 0.54   to   1.57 ± 0.60 V (P < 0.001)   . In conclusion, the situs lead was successfully implanted in a high percentage of patients. In addition, low pacing threshold and high impedance measured during follow-up are consistent with a low pacing current drain, ensuring a durable pulse generator longevity. (PACE 2003; 26[Pt. II]:185–188)     

Septal lead implantation for the reduction of paced QRS duration using passive-fixation leads

In 120 consecutive patients with standard pacing indications, we tested the feasibility of RV septal lead implantation technique guided by surface ECG and the degree to which this technique reduces paced QRS duration compared to RV apical stimulation when passive-fixation leads are used. During implantation, an ECG was recorded with a paper speed of 100 mm/s using the orthogonal Frank leads, and QRS was measured from the earliest to the latest deflection in any of the Frank leads. Pace-mapping of the septum was performed until QRS was minimal. The lead was attached, where QRS, pacing threshold, lead impedance, and EGM amplitude provided the best compromise. An average of 3.7 +/- 2.5 attempts (range 1-18, median 7) was needed until a final implantation site was found. There were no technical problems during implantation. QRS could be reduced by 5-55 ms (mean delta QRS 19 +/- 11 ms) in 83 (69%) of 120 patients. In 22 (18%) patients, QRS was identical with apical and septal pacing, and in 15 (13%) patients, QRS was 5-20 ms (10 +/- 4) longer despite septal stimulation. Average QRS was significantly shorter during septal pacing compared with apical pacing (151 +/- 20 vs 162 +/- 23 ms, P < 0.001). There was a tendency towards greatest QRS reduction when the high septum was stimulated (22 +/- 11 ms reduction) as compared with mid- (18 +/- 11 ms) or apical parts of the RV septum (16 +/- 10 ms). QRS reduction was most likely if apical QRS width was > 170 ms (P = 0.0002), and there was an inverse correlation between apical QRS and delta QRS (r = 0.53, P < 10(-7)). During a mean follow-up of 14 months, there was no pacing or sensing problem and no lead dislodgment occurred.     

Programmable Polarity: Effects on Pacing and Sensing of Bipolar Steroid-Eluting Leads

Presently available bipolar pacemakers connected to bipolar leads allow the programming of polarity to either bipolar or unipolar configuration. The bipolar configuration improves sensing because of its lack of oversensing. In respect to the pacing impulse, it may be beneficial to program the bipolar to unipolar configuration, because the unipolar pacing configuration seems to lead to lower pacing thresholds. The aim of the study was to investigate the effects of the two configurations on pacing and sensing in 11 patients with a new ventricular steroid-eluting lead (Encor Dec 033–301. Telectronics Inc.) connected to the same types of VVI(R) pacemakers. Follow-up was 12 months after implantation. Pacing was assessed by pulse duration thresholds at 0.8-, 1.6-, and 2.5-V pulse amplitude and by pacing impedance. Parameters for sensing included sensing thresholds, R wave amplitudes, and amplitude of intrinsic deflection. Pulse duration thresholds were similar for the two configurations. At implantation, pacing impedance was significantly higher with bipolar (672 ± 60 Ω) than with unipolar pacing configuration (626 ± 82 Ω, P < 0.005). The difference lasted until 1 month after implantation (bipolar: 670 ± 49 Ω: unipolar: 630 53 Ω, P < 0.01). No significant differences were detected after 3 (bipolar: 683 ± 63 Ω; unipolar: 662 ± 70 Ω) and 12 months (bipolar: 658 ± 64 Ω: unipolar: 660 ± 63 Ω) between the 2 configurations. Although intrinsic deflections of ventricular electrograms were different, mean R wave amplitudes were similar in unipolar and bipolar configuration. Pacing and sensing characteristics of unipolar and bipolar configuration were similar for the studied bipolar pacing lead. Pacing impedance was initially higher for bipolar than for unipolar configuration and equilibrated within 3 months after implantation.     

Chronic Right Ventricular Pacing and Cardiac Performance:

Cardiac stimulation from right ventricular apical or free-wall lead positions alters inter- and intraventricular impulse conduction and distorts biventricular contractility. This may contribute to eventual cellular remodeling and the development of histopathological changes which, over time, adversely affect left ventricular systolic and diastolic functions. This concept has especially important implications when pacemaker therapy is initiation in young patients. Recent studies demonstrating physiological benefits of right ventricular septal, outflow, or bundle of His pacing, in deference to the apical implant site, have gained interest to potentially prevent dysfunction and improve paced myocardial contractility. Pacing initiated in children can be expected to have more far-reaching consequences than pacing initiated in the elderly. Unfortunately, there have been limited clinical pediatric studies that evaluate precise site-specific lead locations. This current report presents a review of pacemaker applications in children, both with and without structural congenital heart defects, including the earliest applications in which patient survival was the prime concern, to more recent studies attempting to optimize physiological and histological parameters associated with pacemaker induced contractility. The past decade has seen direct evidence that right ventricular apical pacing in children contributes to adverse histological remodeling and eventual contractile dysfunction. More recent studies demonstrate that selective site pacing can be effectively applied to all children with and without structural congenital defects and shows promise in the prevention of previously documented adverse remodeling and deterioration of systemic ventricular contractility. (PACE 2004; 27[Pt. II]:844–849)