Bipolar Pacing Research Articles

Left heart atrial and ventricular epicardial pacing through a left lateral thoracotomy in children: a safe approach with excellent functional and cosmetic results☆

Left heart atrial and ventricular epicardial pacing through a left lateral thoracotomy is an alternative approach for lead insertion in children, avoiding venous access complications and right ventricular stimulation, without compromising sporting or musical activities. We analyzed the survival and performance of left atrial and left ventricular epicardial pacing leads, and present mid-term follow-up data. Seventy-five bipolar steroid eluting pacing leads (Medtronic CapSure Epi 4968) were implanted in 41 children, aged 8.6+5.1 years. Pacing systems included 34 DDDR and 7 VVIR. Pacing leads were inserted through a muscle-sparing left lateral thoracotomy, and sutured to the left atrial appendage or atrium, and to the left ventricle. The generators were buried behind the abdominal muscles or between the thoracic muscle layers. Congenital heart disease with previous cardiac surgery was present in 25 children. Indications for pacing were post-operative heart block (n=14), sinus node disease (n=13), congenital heart block (n=9), and various (n=5). Threshold values and measured data were obtained at 6-month intervals. The mean follow-up was 3.8+2.9 years. There was no mortality or major morbidity, with excellent functional and cosmetic results. Lead survival was 94 and 86% for atrial leads, and 97 and 86% for ventricular leads, at 1 and 5 years, respectively. There were five reoperations for lead fracture (n=2), insulation break (n=1), oversensing (n=1), and infection (n=1). Device reprogramming was required in three instances. In the absence of acute lead failure, mid-term follow-up shows very satisfactory and stable lead performance. Left heart atrial and ventricular epicardial pacing leads inserted through a left lateral thoracotomy demonstrate a high probability of survival, with favorable pacing characteristics, and optimal sensing thresholds at mid-term follow-up. Epicardial left heart pacing is reliable, and easy access can be achieved through a cosmetic and functional muscle-sparing left lateral thoracotomy.

Successful Pacemaker Lead Implantation via the Subclavian Vein Despite of High Degree Stenosis of the Vein

This case reports on an 81-year-old man with implanted dual-chamber pacemaker for binodal disease who required ventricular lead revision due to loss of ventricular capture. Successful placement of a new lead via the subclavian vein despite of high degree stenosis of the medial part of the vein is described using a very thin bipolar ventricular pacing lead. Currently available pacing electrodes for this purpose are reviewed.

Ventricular Pacing Thresholds Following High-Energy Ventricular Defibrillation Shocks

Increased ventricular pacing thresholds have been observed following monophasic waveform shocks in implantable cardioverter defibrillators (icds). This study aimed to examine such changes following high-energy biphasic shocks in icds. Ten episodes of VF were induced every 10 minutes in 10 pigs (23.1±3.0 kg). After 10 seconds of VF a 40J biphasic shock (total 10 shocks) was delivered for successful defibrillation in the true-bipolar sensing lead system of the ICD. Ventricular bipolar pacing thresholds before and after these shocks were evaluated at one-minute intervals. The mean pacing threshold before shock delivered was 0.066 ± 0.059 uj. Those of the first, second and third minutes after the first shock were 0.052 ± 0.061 uj, 0.044 ± 0.039 uj, respectively; showing that pacing thresholds gradually decreased. It may not be necessary to pace at a high-voltage output after biphasic shocks in icds.

A New Steroid Eluting, Bipolar Myocardial Pacing Lead with Optimized Electro-Mechanical Characteristics for Cardiac Resynchronization Pacing in CHF Patients

A New Steroid Eluting, Bipolar Myocardial Pacing Lead with Optimized Electro-Mechanical Characteristics for Cardiac Resynchronization Pacing in CHF Patients

804 First experience with a new S-shaped bipolar left ventricular pacing lead

804 First experience with a new S-shaped bipolar left ventricular pacing lead

Relationship between LV pacing thresholds, R-wave amplitudes, and impedances to LV vein size and locations in a bipolar LV lead

Purpose: The Medtronic Model 4194 (Attain® Bipolar OTW) US Clinical Study was a prospective, non-randomized, multicenter clinical trial that evaluated a new 6 Fr. LV bipolar lead in patients receiving a CRT system. A CRT system, including a CRT device and a Model 4194 LV lead was successfully implanted in 165 patients. Data was collected on LV bipolar (LVB) and LVtip-RVring (LVRV) pacing thresholds, bipolar R-wave amplitudes (BRW) and impedances during implant. Additional data was collected on LV lead location and LV vein size. There have been previous reports suggesting that LV pacing thresholds (in linear or non-curved or non-canted leads) may get worse as the vessel size gets larger relative to the electrode diameter (due to lack of electrode contact). We investigated the relationships between LV vein size and location and the LV pacing thresholds, R-wave amplitudes, and impedances.

Clinical performance of the EASYTRAK ® 2 bipolar left ventricular pacing lead

Background: The safety and effectiveness of a bipolar left ventricular (LV) pacing lead (EASYTRAK® 2) was prospectively studied as a part of the DECREASE-HF clinical trial. The EASYTRAK 2 lead is intended for LV true bipolar or extended bipolar pacing and sensing when used with a compatible cardiac resynchronization therapy device. The EASYTRAK 2 lead has a distal tip electrode and a proximal ring electrode that confer 4 pacing and 2 sensing configurations.

Pacemaker dependent patients with device infection—a modified approach

A modified surgical concept for temporary cardiac pacing in pacemaker dependent patients requiring total removal of infected devices is presented. Proximal to the infected pocket a permanent bipolar pacing lead is placed transcutaneously into the ipsilateral subclavian or jugular vein. The lead is placed in the right ventricle and fixed into the skin using the suture sleeve. Pacing is established by connecting an external pacing generator. Subsequently the infected device can be removed completely. After wound dressing the externalized lead is connected to a permanent VVI-pacemaker allowing for prolonged temporary pacing.

A New Method of Temporary Epicardial Atrioventricular Pacing Utilizing Bipolar Pacing Leads

We evaluated a convenient method of temporary atrioventricular pacing utilizing bipolar epicardial pacing leads that offer better sensing and pacing performance. Fifty-one patients undergoing coronary artery bypass grafting had atrial and ventricular bipolar leads implanted. The ventricular leads were inserted onto the front of the right ventricle, and the atrial leads were inserted into the lateral muscular part of the right atrium near the interatrial groove. Sensing values, pacing thresholds, and impedance were measured on all leads on postoperative days 0, 2, and 4, and complications of insertion and removal were noted. The method was convenient and there were no complications during insertion or removal. The mean pacing threshold increased from 1.1 V to 1.5 V in both the atrial and ventricular leads from day 0 to day 4 (not significant). The mean sensed p wave amplitude decreased from 2.2 mv to 2.0 mv (not significant), and the mean sensed R wave amplitude decreased from 6.2 mv to 4.1 mv (p = 0.001) from day 0 to day 4. In spite of this significant drop in the sensed R wave amplitude, this value remained in an acceptable range. There was also a significant decrease in impedance, but overall all values were in an acceptable range assuring safe and effective pacemaker function. Only one atrial lead (2%) and three ventricular leads (6.1%) failed to pace on day 4. We conclude that this temporary epicardial pacing method is safe, convenient, and less time consuming. Satisfactory pacing and sensing performance was achieved with low thresholds and minimal complications.

Comparative effects of single- and linear triple-site rapid bipolar pacing on atrial activation in canine models

Nonuniform conduction may cause block and/or delay, thereby providing a substrate for the onset and maintenance of reentrant atrial arrhythmias. We tested the hypothesis that linear triple-site, bipolar, rapid pacing (LTSBRP) of the right atrium generates more uniform wave-front propagation compared with single-site, bipolar, rapid pacing (SSBRP), thereby reducing and/or eliminating conduction block and delay that is otherwise present. Five dogs with pericarditis and three normal dogs were studied. Three plunge-wire electrode pairs were placed 5-7 mm apart in both perpendicular and parallel configurations at the superior aspect of the crista terminalis and were used to pace at 200- and 300-ms cycle lengths for < or =6 s. During pacing, 380 electrograms were recorded simultaneously from electrode arrays placed epicardially on the atria, which produced activation sequence maps for each pacing episode. Local conduction-velocity vectors were computed for each site during each episode. Histograms of absolute velocity vector angles from the x-axis (of the crista terminalis) were plotted to assess uniformity of wave-front propagation, and the magnitude of each vector was computed to assess the local speed. LTSBRP showed 1) more uniform linear activation wave fronts compared with SSBRP, 2) velocity vectors with a more uniform magnitude and direction compared with SSBRP, 3) a predominant absolute velocity vector angle vs. a scattered angle distribution with SSBRP, and 4) shorter right atrial activation time and faster mean epicardial speed than SSBRP for each pacing cycle length. LTSBRP created a more uniform wave-front propagation with less or no conduction block and/or delay compared with SSBRP.

Serial Changes in Right Ventricular Apical Pacing Lead Impedance Predict Changes in Left Ventricular Ejection Fraction and Functional Class in Heart Failure Patients

Pacing impedance has been proposed to monitor the clinical status of patients with congestive heart failure (CHF). This study examined whether changes in right ventricular (RV) pacing impedance correlate with changes in left ventricular ejection fraction (LVEF) and New York Heart Association (NYHA) functional class during long-term follow-up in pacemaker recipients with CHF. The study included 67 patients, 70 +/- 12 years of age, in NYHA class II or III, and with a mean LVEF = 29 +/- 8% at implant. LVEF, NYHA class, and bipolar pacing impedance at the RV outflow tract (RVOT) and apex (RVA) were measured at implant and at 3, 6, 9, and 12 months of follow-up. At implant, impedance was similar in RVOT (548 +/- 115 Omega) and RVA (571 +/- 174 Omega). Between implant and 3 months, mean impedance decreased (P < 0.0001) at both the RVOT (472 +/- 62 Omega) and RVA (488 +/- 86 Omega), LVEF increased (43 +/- 14%, P < 0.0001), and the NYHA class decreased from 2.4 +/- 0.5 to 2.1 +/- 0.6 (P = 0.0001). Changes in RVA impedance correlated with changes in LVEF (r = 0.45, P = 0.002). A 50 Omega decrease in RVA impedance corresponded to a 3% decrease in LVEF. RVA impedance decreased significantly as NYHA class increased from I to IV (P = 0.04). There was no correlation between impedance measured at the RVOT and LVEF or NYHA class. A decrease in bipolar pacing impedance at the RVA was associated with worsening LVEF and the NYHA class. The use of pacing impedance to monitor the clinical status in CHF is dependent on the RV pacing site.

Messen tragbare Herzfrequenz-Messgeräte (Sportuhren) bei Schrittmacherpatienten zuverlässig?

Regular physical exercise is advantageous for physical fitness and endurance. The intensity of exercising can be controlled by portable heart rate monitors. The aim of the study was to investigate if wearable monitors work properly in pacemaker patients. In 30 patients with an implanted single or dual chamber pacemaker made by five different manufacturers their heart rate was determined simultaneously by surface ECG and Holter ECG, and was compared with the heart rates derived from portable heart rate monitors (Polar A1) at rest, during 6 minutes in-house walk, and while exercising at 25, 50, and 75 watts in a bicycle exercise test. The tests were done with pacing set at uni- as well as bipolar stimulation mode. At rest in two of 30 patients (6,6 %) paced in unipolar mode the portable heart rate monitors counted double. Under exercise conditions the portable monitors counted double in six of 26 patients (23 %) while being stimulated in unipolar mode. In bipolar stimulation mode, the portable heart rate monitors were working properly in all patients under all conditions. Patients with an implanted bipolar pacing system can control their physical exercising safely and accurately by means of portable heart rate monitors. Pacemaker patients who are planning regular physical exercising should be provided with an implanted bipolar pacemaker system.

Endocardial Implantation of a Cardioverter-Defibrillator in a 13-Month-Old Child Affected by Long-QT Syndrome and Syndactyly

A 13-month-old child with the uncommon variant of long-QT syndrome associated with syndactyly of feet and hands experienced an apparently life-threatening event during full-dose β-blocker therapy. The indication for an implantable cardioverter-defibrillator (ICD) was established, and the patient was admitted to the hospital. The QTc interval was 580 ms, and no mutations were present in any of the known LQTS genes. The child weighed 11.9 kg with a length of 76 cm. To minimize the surgical injury and reduce the potential risk …

Basic assessment of paced activation sequence mapping: implications for practical use.

Some experiences support the use of atrial paced activation sequence mapping, but there is no systematic study assessing its spatial resolution, reproducibility, and influence of pacing parameters. The aim of this study was to evaluate these issues by using a 24-pole catheter positioned at the atrial aspect of the tricuspid and mitral annuli in 15 patients. Bipolar pacing was performed at two sites (right and left atria), 2 cycle lengths (300 and 500 ms) and two outputs (twice and tenfold the late diastolic threshold voltage for 2-ms pulses). The elapsed time between the atrial activation at the two dipoles adjacent to the pacing dipole (activation time [AT]) was measured during each pacing sequence. Changes in cycle length did not modify the AT. The increase in voltage slightly modified the AT (maximum -2 ms at the RA; 95% CI -3 to -1 ms) due to a greater shortening of the conduction time to the dipole located next to the anode. The 95% limits of the intraobserver and interobserver agreements in the AT measurement were -2 to 3 ms and -3 to 3 ms, respectively. The spatial resolution was studied in ten patients by measuring the AT during pacing from each dipole of a 20-pole catheter with a 1-3-1 mm interelectrode distance. The mean AT change was 10 +/- 4 ms per 6 mm of pacing site displacement (95% CI 8-11 ms, range 2.5-20 ms). In conclusion, paced atrial activation sequence analysis is reproducible, accurate, and relatively independent of pacing parameters.

1035-222 Local velocity estimation analysis during bipolar single site and linear triple site rapid pacing in canine models: Implications for antitachycardia pacing

1035-222 Local velocity estimation analysis during bipolar single site and linear triple site rapid pacing in canine models: Implications for antitachycardia pacing

Atrioventricular Nodal Ablation and His‐Bundle Pacing:

QT interval prolongation following drug exposure is considered a marker for increased risk of drug-induced arrhythmias. QT interval measurements are common components of the safety pharmacology assessment of new therapeutic compounds but are potentially confounded by concurrent changes in heart rate that also alter QT intervals. We describe an anesthetized canine model of AV dissociation with His-bundle pacing that overcomes the confounding effects of a change in heart rate. Transvenous radiofrequency ablation of the AV node was performed in isoflurane-anesthetized dogs and followed by open chest implantation of bipolar pacing electrodes in the vicinity of the His bundle. Pace rates were adjusted from 50 to 190 in steps of 20 beats/min, holding each step for 30 seconds. At each paced rate, QT intervals were measured manually to the nearest 1 ms to construct paced QT interval-heart rate (QT-HR) relationships. Paired QT-HR relationships using identical ascending ramps of pace rates were compared to paired QT-HR relationships with an ascending and descending pace ramp to evaluate short-term reproducibility and hysteresis effects. For proof of concept, an additional QT-HR relationship was constructed in three dogs after intravenous administration of a compound known to alter QT intervals: one dog received terfenadine (0.48 mg/kg bolus followed by 0.017 mg/kg/min infusion), one dog received quinidine (20 mg/kg), and the third dog received sotalol (1 and 3 mg/kg). Substantial inter-dog variation was found for QT-HR, although short-term reproducibility was high within one dog (average absolute difference for paired ascending ramps < 5 ms). QT intervals measured during descending paced ramps were generally lower than the value for the corresponding paced rate on an ascending ramp. This hysteretic effect was small, averaging < 7 ms over the entire ramp. All test compounds prolonged QT intervals and shifted the QT-HR relationship upward. Maximal QT prolongation was 30 ms for terfenadine, 50 ms for quinidine, and 59 ms for sotalol. AV nodal ablation and His-bundle pacing provide a sensitive animal model to identify acute effects of test compounds on indices of myocardial repolarization such as the QT interval. The model is devoid of confounding effects of changing heart rates while enabling identification of effects of drugs over a wide range of controlled rates.

Performance of an automatic external cardioverter-defibrillator algorithm in the discrimination of supraventricular from ventricular tachycardia

An automatic external cardioverter-defibrillator (AECD) with a programmable supraventricular–ventricular tachycardia (VT) zone underwent evaluation of arrhythmia discrimination performance in the electrophysiologic laboratory during induced supraventricular tachycardia (SVT) and unipolar and bipolar atrial pacing. The AECD SVT zone was programmed so that the induced SVT rate would fall within this zone. Atrial pacing was also performed at a rate within this zone. The ability of the AECD to accurately discriminate between VT and SVT and to recommend shock delivery was assessed. A total of 98 patients underwent conventional diagnostic electrophysiologic studies (49 men, age 59 ± 19 years) with a total of 55 inducible sustained SVTs. High right atrial pacing was performed in 56 patients in unipolar and in 82 patients in bipolar fashion. In response to induced sustained SVT, the AECD correctly classified 47 episodes as nonshockable, 4 incorrectly as shockable, and 4 episodes correctly as shockable with a resultant sensitivity of 100% and specificity of 92%. Bipolar high right atrial pacing was correctly identified as nonshockable in 75 episodes, incorrectly identified as shockable in 5 episodes, and correctly identified as shockable in 2 episodes with a resultant sensitivity of 100% and specificity of 94%. The Powerheart AECD accurately discriminates SVT from VT and is expected to correctly deliver automatic external shocks rapidly in the presence of spontaneous life-threatening tachycardia and appropriately withhold therapy during SVT.

Autocapture Enhancements: Unipolar and Bipolar Lead Compatibility and Bipolar Pacing Capability on Bipolar Leads

Beat-by-beat Autocapture maximizes device longevity by minimizing stimulus amplitude while assuring patient safety. Currently, Autocapture permits use of only bipolar leads. The authors have devised a detection method that operates with unipolar and bipolar leads and covers all pacing and sensing combinations (but bipolar pace and sense simultaneously). This new detection method for unipolar sensing uses the integral of the negative portion of the unipolar evoked response as a robust capture detection feature. When using bipolar leads, the method provides the flexibility of bipolar or unipolar pacing. In this study, unipolar ventricular intracardiac electrograms (EGMs) were recorded in 71 patients, 73.7 +/- 9.9 years of age; 9 with high polarization, 62 with low polarization. High polarization had polished platinum or activated carbon electrodes. Low polarization had TiN, platinized platinum, or IrOx electrodes. The intracardiac EGMs were recorded 544 +/- 796 days after implant. The pacemakers performed an automatic capture threshold test while the intracardiac EGM signals were recorded in a programmer. These digitized signals were saved for off-line analysis. The unipolar evoked response was calculated at up to six (depending on capture threshold) pacing voltages and the polarization integral at 4.5 V and at loss of capture. An automatic calibration algorithm determined if the signal-to-noise ratio was adequate for Autocapture operation. Autocapture was possible with 60 of 62 of the low polarizations, and with 6 of 9 of the high polarizations. The average values form the data collected were: average unipolar evoked response--4.1 +/- 2.1 mV, average peak negative voltage--10.0 +/- 3.7 mV, average polarization 0.3 +/- 0.34 mV, and average signal-to-noise ratio (unipolar evoked response/ polarization) 38 +/- 71. In all cases the algorithm correctly determined the appropriateness of using Autocapture with the electrodes tested and the unipolar evoked response threshold to be used.

Atrial evoked response integral for automatic capture verification in atrial pacing.

Beat-by-beat Autocapture is currently limited to operation in the ventricle with bipolar leads. The authors investigated the integral of the negative-going portion of the atrial evoked response integral (AERI) as a potential resource for verification of atrial capture. Intracardiac electrogram signals were collected from 59 patients (ages 67.8 +/- 15.1 years) with bipolar, low polarization atrial leads. The signals were collected over a mean period of 6.1 months (minimum 4 days) after lead implantation. St. Jude Medical Affinity pulse generators were used to perform automatic capture threshold tests while the electrogram signals were recorded by a Model 3510 programming device. These signals were transferred to a personal computer in digital form for later analysis. The AERI was calculated at each programmable pacing voltage until capture was lost. The difference between the polarization integral at loss of capture and evoked response integral with successful capture was sufficient to justify enabling the atrial Autocapture feature in 53 of 59 patients in whom bipolar pacing and unipolar sensing was performed. The authors developed a calibration routine to identify automatically those patients in whom atrial Autocapture could be programmed On, based on the polarization integral at loss of capture, the estimated maximum polarization integral, and the AERI. Preliminary analysis indicated that the AERI is a practical resource for beat-by-beat atrial capture detection when used with low polarization leads.

Unexpected late clinical problems associated with a ventricular bipolar pacing lead

Unexpected late clinical problems associated with a ventricular bipolar pacing lead