Initial Experience with 1.5-mm2 High Impedance, Steroid-luting Pacing Electrodes

In this human study, 21 atrial and 62 ventricular 1.5-mm² unipolar steroid-eluting pacing electrodes were implanted in 64 patients. Pacing thresholds, lead impedance, and sensing measurements were measured via pacemaker telemetry within 24 hours postimplont, and at 1, 2, 3, 4, 6, 12. 24. and 52 weeks. Acute pacing impedances measured via a pacing systems analyzer were 1,039 ± 292 (atrial) and 1,268 ± 313 ohms (ventricular). A10%-15% decline in the mean telemetered atrial and ventricular pacing impedances was observed at 1 week, but thereafter remained stable. Acute pacing thresholds at 0.5 ms were 0.5 ± 0.3 V (atrial) and 0.4 ± 0.1 V (ventricular). Filtered P and B wave amplitudes were 3.7 ± 2.3 mV and 14.9 ± 5.9 mV, respectively. In 21 patients, no complications related to the atrial electrode were observed. Of 62 patients with ventricular electrodes, 4 patients (6%) experienced complications and required surgical intervention. On these, causative factors included micro-dislodgment (l patient), and perforation (l patient). Sudden unexplained exit block occurred late (> 6 weeks) in two patients. In the remainder of patients, pacing thresholds and sensed electrogram amplitudes remained stable throughout the 52-week follow-up period. Conclusions: The- present study validates that smaller surface (i.e., 1.5 mm²) steroid- eluting electrode designs offer excellent pacing and sensing performance with significantly higher pacing impedances. Although questions remain as to the cause of late exit block in two patients in this series, this relatively small surface electrode design offers promise toward achieving greater pacing efficiency and a theoretical 13%-16% (minimum) enhancement in permanent pacemaker longevity.     

A gastroesophageal electrode for electrophysiological studies

A novel gastroesophageal electrode has been developed capable of atrial and ventricular pacing. We performed electrophysiological studies using the gastroesophageal electrode (Esothoracic) and compared the results with the standard endocardial approach. The flexible polythene gastroesophageal electrode was passed into the stomach under light sedation. Five ring electrodes, now positioned in the lower esophagus were used for bipolar atrial pacing and recording. Ventricular pacing was performed using a cathodic point source on the gastroesophageal electrode tip; the indifferent electrode (anode) was a high impedance chest pad. Parameters of sinus and AV nodal function were obtained by atrial pacing. Programmed ventricular stimulation was performed using a standard protocol. These electrophysiological parameters were subsequently determined using the endocardial approach. There was close correlation between measurements of sinus and AV node function using the two approaches in 48 subjects: sinus node recovery time (SNRT) r2 = 0.70, corrected sinus node recovery time (CSNRT) r2 = 0.87, AV Wenckebach cycle length (AVWCL) r2 = 0.97. The degree of agreement between the two approaches was estimated by the mean difference delta and standard deviation of the difference sigma (SNRT delta = 40 ms, sigma = 257 ms; CSNRT sigma = 14 ms, delta = 164 ms; AVWCL sigma = 7 ms, delta = 16 ms). Programmed ventricular stimulation was performed in 15 of 48 subjects with known or suspected ventricular tachyarrhythmias. Seven had ventricular tachycardia induced using both esothoracic and endocardial programmed ventricular stimulation. One subject was noninducible using esothoracic programmed ventricular stimulation, but inducible at endocardial electrophysiological studies. Another subject was inducible at esothoracic electrophysiological studies, but noninducible using endocardial programmed ventricular stimulation. Six subjects were noninducible using both endocardial and esothoracic programmed ventricular stimulation. The gastroesophageal electrode permits reliable atrial and ventricular pacing without transvenous catheterization or fluoroscopy. Electrophysiological parameters determined using this electrode are similar to those obtained using endocardial stimulation.     

Clinical Performance of Steroid-Eluting Pacing Leads with 1.2-mm2 Electrodes

To raise pacing impedance and reduce battery current drain, new tined steroid-eluting leads were developed with 1.2-mm² hemispherical electrodes, instead of conventional 5–8 mm². Twenty-two unipolar J-shaped atrial leads and 25 unipolar ventricular leads (models 4533 and 4033, respectively) were implanted in 33 consecutive patients and followed for a mean of 25 months (range 18–29). Handling characteristics of atrial leads were found favorable. The leads slipped easily into the right atrial appendage and were easy to position. Handling characteristics of ventricular leads were satisfying, but more efforts had to be applied to cross the tricuspid valve. Special care was taken to avoid perforation of the myocardium due to the small lead tip. Following implantation, four ventricular and one atrial lead exhibited instability of pacing thresholds that resolved spontaneously within 1–3 days of implantation. Except for this, no lead malfunctioned. The reoperation rate was zero. The mean electrogram amplitudes of 15 mV (ventricle) and 4 mV (atrium), and the mean chronic pacing threshold of 0.085 ms at 1.6 V (app. 0.43 Vat 0.5 ms) were comparable with the best values seen in the literature on passive fixation leads. The rest of the electrophysiological parameters were enhanced: mean pacing impedances were 984 Ω (acute) and 900 Ω (chronic), mean slew rates 3.26 V/s (ventricle) and 1.75 V/s (atrium), mean acute voltage threshold at 0.5 ms was 0.25 V, mean current and energy thresholds calculated at 0.5 ms were 260 μA and 32 nJ (acute) and 478 μA and 103 nJ (chronic). The electrical characteristics of these leads provide for increased pacemaker longevity in combination with substantial safety margins for pacing and sensing.     

Diagnosis and management of inadvertently placed pacing and ICD leads in the left ventricle: a multicenter experience and review of the literature

Three patients from different centers with pacemaker or ICD leads endocardially implanted in the left ventricle are described. All leads, two ventricular pacing leads and one ICD lead, were inserted through a patent foramen ovale or an atrial septum defect. The diagnosis was made 9 months, 14 months, and 16 years, respectively, after implantation. All patients had right bundle branch block configuration during ventricular pacing. Chest X ray was suggestive of a left-sided positioned lead except in the ICD patient. Diagnosis was confirmed with echocardiography in all patients. One patient with a ventricular pacing lead presented with a transient ischemic attack at 1-month postimplantation. During surgical repair of the atrial septum defect 14 months later, the lead was extracted and thrombus was attached to the lead despite therapy with aspirin. The other patients were asymptomatic without anticoagulation (9 months and 16 years after implant). No thrombus was present on the ICD lead at the time of the cardiac transplantation in one patient. We reviewed 27 patients with permanent leads described in the literature. Ten patients experienced thromboembolic complications, including three of ten patients on antiplatelet therapy. The lead was removed in six patients, anticoagulation with warfarin was effective for secondary prevention in the four remaining patients. In the asymptomatic patients, the lead was removed in five patients. In the remaining patients, 1 patient was on warfarin, 2 were on antiplatelet therapy, and in 3 patients the medication was unknown. After malposition was diagnosed, three additional patients were treated with warfarin. In conclusion, if timely removal of a malpositioned lead in the left ventricle is not preformed, lifelong anticoagulation with warfarin can be recommended as the first choice therapy and lead extraction reserved in case of failure or during concomitant surgery.     

全容积三维超声评价人工瓣、补片、封堵器及起搏电极的效果

目的　评价全容积三维超声 (FVTDE)对人工瓣、心内补片、封堵器及起搏电极成像效果。方法　经二维超声检查确定的 71例心内有人工瓣、补片、封堵器及起搏电极的患者接受了 FVTDE成像。结果　二维超声共发现了 88处人工瓣、心内补片、封堵器及起搏电极。 FVTDE可立体显示包括 1例瓣周漏的所有 31处二尖瓣位人工瓣环和瓣叶、 19处主动脉瓣位人工瓣叶和瓣环、 1处主动脉瓣位人工瓣仅人工瓣叶、所有 5处三尖瓣位人工瓣叶和瓣环、16处室间隔补片、 8处房间隔补片、 1处房间隔封堵器和 3处右心内起搏电极。仅 1处主动脉瓣位人工瓣环、 1处主动脉瓣位人工瓣叶和瓣环、 1处室间隔补片和 2处全置换的房间隔边缘显示不清。结论　 FVTDE可立体显示绝大部分人工瓣、心内补片、封堵器及起搏电极 ,但成像角度、观察方向等因素可能影响其显示效果     

Experience and Implantation Techniques with a New Single-Pass Lead VDD Pacing System

Thirty-six patients were implanted with a single-lead atrial-synchronous ventricular pacing (VDD) system at our center in the first and second phases of a clinical trial between October 1987 and December 1989. The clinical system comprised a pulse generator in conjunction with a pacing lead incorporating two diagonal atrial bipolar (DAB) electrodes designed to lie in the mid-to upper-right atrium and a distal tip electrode for ventricular pacing and sensing. Twenty five of the patients had complete heart block, ten had second-degree block, and one had AV nodal block. A modified Bruce protocol limiting treadmill speed to 1.7 miles per hour was used to establish sinus node competency as evidenced by sustained sinus rate increase in a more-or-less linear fashion. The mean acute P wave amplitude measured at implant was 1.66 mV +/- 1.04 SD; the mean P wave amplitude (minimum and maximum, both sitting and supine) for all patients at all follow-up (N = 420) was 1.54 mV +/- 0.9 SD. The follow-up interval for all patients ranged from a minimum of 13 days and a maximum of 762 days, with a mean of 261 +/- 206 days as of December 1, 1989. Four dislodgments of the ventricular electrode occurred with the more pliable of two passive fixation mechanisms used on the lead; atrial sensing remained intact at all times with both fixation systems. Changes in atrial sensing threshold were quite frequent during the early follow-up visits due to electrode movement in the right atrium; however, adequate ventricular tracking of the atrial rate was achieved in all cases once the threshold values were established initially, even though several patients required atrial sensing of 0.2 mV at some of the follow-up visits. Two patients presented with pacemaker-mediated tachycardia associated with retrograde conduction, which was resolved with reprogramming; they are presently maintaining atrial synchrony in the VDD mode. Successful single-lead VDD pacing with consistent P wave sensing has been achieved with this atrial rate responsive system.     

A Method of Esophageal Electrogram Recording for Diagnostic Atrial and Ventricular Pacing

This study evaluates improvement of the electrogram sensed via an esophageal catheter with the sensing electrode adjacent to the stimulating electrode with and without a specialized artifact suppression system. In 100 patients (65 men and 35 women) aged 16-60 years (mean 48 years), esophageal recordings of left atrial activity were obtained during simultaneous transesophageal atrial pacing. Transesophageal ventricular pacing was performed in an additional 34 patients. Without the suppression system, ventricular paced activity, recorded from the esophagus, was not suitable for interpretation. About 10% of the atrial electrogram response could be recorded and evaluated during atrial pacing. With the stimulus artifact suppression system, interpretable recordings were obtained 100% of the time during atrial and ventricular recordings. The method described allows use of transesophageal diagnostic testing where previously only the intracardiac route was possible.     

Preliminary Experience with the Helifix Electrode for Transvenous Atrial Implantation

A Helifix electrode was inserted transvenously in the right atrial appendage for temporary atrial stimulation in three patients. The low stimulation threshold as well as the excellent stability of the electrode encouraged us to proceed to permanent implantation of this lead in thirteen patients. The lead was introduced through the saphenous vein in twelve patients and through the cephalic vein in one patient. Five patients had sinoatrial dysfunction and five had bradycardia-tachycardia syndrome; they received atrial demand pacemakers. Two patients had atrioventricular block and received atrial synchronous ventricular pacemarkers. Our last patient had restrictive cardiomyopathy, heart failure and a drug-refractory atrial arrhythmia. She received a dual-chamber sequential pacing device. Atrial electrode displacement occurred in one patient soon after implantation. The lead was promptly repositioned without difficulty. Partial sensing of spontaneous P waves was observed in two patients. One recovered spontaneously, the second after substituting a pulse generator with a higher input sensitivity. Our clinical experience during the period from November 1977 to January 1979 has shown that the Helifix electrode is suitable for transvenous atrial implantation.     

Stable electrical performance of high efficiency pacing leads having small surface, steroid-eluting pacing electrodes

Previous experience with steroid-eluting small electrode designs have described their increased pacing efficiency, yet some reports have questioned their electrical stability. We report our experience with a new pacing lead design incorporating small surface (i.e. 1.2 mm2), high impedance pacing electrodes. Medtronic Model 5034 ventricular pacing leads were implanted by a single physician in 167 patients. Of those, 96 patients had an additional Model 5534 atrial lead implanted. All patients were followed for at least 9 months. Microdislodgment, as defined by a sudden increase in pacing threshold accompanied by radiographic stability, was observed in 6 of 263 (2.3%) leads implanted. Of the 4/167 (2.4%) ventricular leads that exhibited electrical instability, only 2 were sustained. Importantly, neither was significant enough to result in loss of capture. The other two cases of ventricular electrode instability manifested as a transient threshold rise with eventual return to near the original values. By comparison, the atrial lead model exhibited a sudden and sustained pacing threshold rise 5 which was evident in two patients (2.1%) with neither requiring invasive intervention. For all remaining chronic leads, clinically acceptable electrical performance profiles were demonstrated. We conclude that low microdislodgment rates and stable electrical performance profiles can be achieved with the small electrode steroid-eluting pacing electrodes as long as careful lead positioning and securing techniques are followed during implantation. We further suggest that successful high impedance lead design is critically dependent on its stiffness and mass characteristics.     

Steroid-Eluting Epicardial Pacing Electrodes: Six Year Experience of Pacing Thresholds in a Growing Pediatric Population

Indications for pacemaker implantation in the pediatric population often include sinus or atrioventricular node dysfunction following surgery for congenital heart defects. However, patient size, cardiac defects, and vascular and valvular concerns may limit transvenous lead utilization. Since the epicardial surface of these patients often exhibits variable degrees of fibrosis from scar tissue formation or pericardial adhesions, chronic low output (2.5/1.6 V, 0.3 ms) epicardial pacing from implant is not currently recommended in children due to frequent threshold changes and electrode exit block. As a result, pacing in children is often viewed as a less efficient system than in adults. The addition of steroid combined with newer low threshold electrode designs however stabilizes the electrode-tissue interface and eliminates postimplant changes seen with standard smooth surface electrodes potentially permitting efficient chronic pacemaker application to all patient ages. The stability of chronic low output epicardial pacing with steroid-eluting electrodes was prospectively studied in 22 patients (ages 2 days-18.5 years, median 3.5 years) for up to 6 years. Chronic pulse width thresholds were compared according to implant site and association of prior cardiac surgery. A total of 26 pacing leads were implanted. The acute implant mean pulse width threshold (2.5 V) for all the electrodes studied was 0.10 ms ± 0.05 ms. Stable low thresholds were maintained for up to 6 years without significant variation from implant. Mean ventricular pulse width thresholds (0.12 ms ± 0.05 ms) were significantly higher (P < 0.001) than atrial thresholds (0.06 ms ± 0.03 ms) at implant and throughout the study period. The thresholds in the patients following cardiac surgery were comparable to those without previous cardiac surgery (P = NS). Stable low thresholds may be chronically maintatined for up to 6 years for epicardial steroid-eluting electrodes irrespective of pacing site or associated cardiac surgery.     

Low Energies and Helifix Electrodes in the Successful Ablation of Atrioventricular Conduction

High energies delivered via standard pacing catheter electrodes produce permanent atrioventricular conduction block and generate high pressures. We investigate the use of lower energies and an active fixation electrode. Ten patients with refractory supraventricular tachycardias (six with paroxysmal atrial fibrillation, three with dual AV nodal pathways, and one with a concealed accessory atrioventricular pathway) were treated. A 6F Vitatron Helifix electrode was positioned to give the maximum His bundle deflection. Four shocks of only 50 joules each were delivered at 1-minute intervals. Long-term follow-up showed that seven patients (70%) had persistent complete heart block and two had atrial fibrillation with slower ventricular rates. Nine patients (90%) were symptom-free without antiarrhythmic therapy. Permanent pacemakers were implanted in eight patients. There were no complications resulting from the procedure. Transvenous ablation of atrioventricular conduction can be safely achieved using a Vitatron Helifix electrode and much lower energy values than have been previously employed.     

Single Lead DDD System: A Comparative Evaluation of Unipolar, Bipolar, and Overlapping Biphasic Stimulation and the Effects of Right Atrial Floating Electrode Location on Atrial Pacing and Sensing Thresholds

Single lead DDD pacing using unipolar or bipolar stimulation is limited by high atrial threshold. Overlapping biphasic (OLBI) waveform stimulation via atrial floating ring electrodes may preferentially enhance atrial pacing and avoid diaphragmatic pacing. Single lead DDD pacing with OLBI atrial pacing was studied in 12 patients (6 men and 6 women; mean age 74 ± 7 years) with complete heart block. At implantation, atrial bipolar rings (area 27 mm², separation 10 mm) were positioned at radiological defined high, mid, and low right atrial (RA) levels, and P wave amplitude and atrial and diaphragmatic pacing thresholds were determined in each position using unipolar, bipolar, and OLBI stimulation in random order. Although statistically insignificant, both the maximum and minimum sensed P wave amplitudes tended to be lower in the low RA position. Independent of the stimulation modes, minimum atrial pacing threshold occurred in the mid-RA. At mid-RA. the atrial pacing threshold was significantly lower with OLBI pacing compared with either unipolar or bipolar mode (3.9 ± 2.2 V vs 6.7 ± 3.5 V and 6.9 ± 3.5 V, P < 0.05). Although the diaphragmatic thresholds were similar, OLBI pacing modes in the mid-RA and final location significantly improved the Safety margin for avoidance of diaphragmatic pacing compared with unipolar mode. There was no correlation between atrial pacing and sensing threshold. At predischarge testing, all but one patient who developed atrial fibrillation had satisfactory atrial capture and a stable atrial pacing threshold (day 0: 2.6 ± 1.1 V vs day 2: 3.2 ± 1.3V, P = NS). However, diaphragmatic pacing occurred in four of 11 (36%) patients, especially in the upright position (sitting and standing). Our preliminary clinical results suggest that OLBI pacing via atrial floating ring electrodes can reduce the atrial pacing threshold. To optimize atrial pacing and sensing, the bipolar electrodes should be located at the mid-RA level first, although the high RA is an alternative. Despite significant improvements in the safety margin for diaphragmatic pacing with OLBI pacing, diaphragmatic stimulation remains a clinical problem.     

Intracardiac Echocardiography-Guided Cardiac Resynchronization Therapy: Technique and Clinical Application

Background: We undertook a pilot investigation to evaluate the feasibility of a novel technique using intracardiac echocardiography (ICE) for intraoperative assessment of cardiac resynchronization therapy (CRT).
Methods: We evaluated ICE intraoperative imaging of left ventricular (LV) function and aortic valvular flow as well as safety of implementation. ICE was used to guide CRT system lead placement, assess impact of pacing modes, and optimization of device programming.
Results: Twenty-three patients underwent ICE imaging. ICE showed global hypokinesis in six patients, regional wall motion abnormality only in 10 patients, and both in seven patients. Optimized CRT modes included mean atrioventricular (AV) interval of 170 ms and interventricular timing using simultaneous right ventricular (RV)-LV pacing (five patients), LV pacing only (one patient), and sequential LV to RV stimulation (15 patients) or RV to LV stimulation (two patients). ICE-guided CRT acutely improved mean left ventricular ejection fraction (LVEF) from 24 ± 9% to 41 ± 1% (P < 0.00001). During follow-up of 3–24 (mean 11) months, New York Heart Association class improved in all patients from a mean of 3.2 ± 0.4 at implant to 1.6 ± 0.7 (P < 0.0001), with improvement of LVEF from 19 ± 7% to 34 ± 12% (P = 0.0001). Actuarial survival was 83% at 12 months.
Conclusions: (1) ICE imaging is reliable and safe for continuous intraoperative imaging of LV wall motion, and assesses baseline status and impact of CRT interventions. (2) Intraoperative ICE-guided CRT optimization resulted in an increase in LVEF acutely and consistent improvement in heart failure. (3) Sequential biventricular pacing and longer AV interval programming were more often used in ICE-guided CRT.     

Removal of Infected Dual Chambered Transvenous Pacemaker and Implantation of a New Epicardial Dual Chambered Device with Cardiopulmonary Bypass: Experience with Seven Cases

ABAD, C., et.al .: Removal of Infected Dual Chambered Transvenous Pacemaker and Implantation of a New Epicardial Dual Chambered Device with Cardiopulmonary Bypass: Experience with Seven Cases . Seven patients with infected transvenous dual chambered pacemakers have undergone removal of the device using cardiopulmonary bypass. There were four women and three men with a mean age of 58 years. Six patients had localized infection in the generator pocket (mean of 4.6 previous unsuccessful operations for surgical sterilization). Four infections were due to Staphylococcus epidermidis, two to Staphylococcus aureus, and one patient presented septicemia caused by Staphylococcus epidermidis and Pseudomonas aeruginosa. The atrial and ventricular transvenous electrodes were removed under direct vision using cardiopulmonary bypass. A new dual chambered epicardial pacemaker was implanted. The procedure was well-tolerated, and all patients are infection free with working pacemakers after a mean follow-up of 25.4 months.     

Ventricular Activation Onset-Triggered Left Ventricular Pacing:

Ventricular activation onset-triggered (VAOT) left ventricular pacing modalities synchronize left ventricular paced activation with existing intrinsic ventricular activation, in patients with complete LBBB and adequate rate. The purpose of this study was to evaluate the safety and feasibility of VAOT pacing with one left ventricular pacing lead, during temporary pacing in the postoperative period following open heart surgery. VAOT pacing was studied in five patients with LBBB and two patients with previously implanted right ventricular pacemakers. The VAOT pacing system used was assembled by modifying the function of existing equipment and its programming is described in detail. Comparative ECGs are reported, documenting the changes in ventricular activation produced by VAOT pacing. Stability of surface ECG acquisition was found to be essential to the success of temporary VAOT pacing and inappropriate pacing due to ECG instability is described. Patients were studied at rest and none experienced congestive heart failure. In the comparison of cardiac output, with and without VAOT pacing, no significant differences were found in LBBB patients or those with right ventricular pacemakers. In the comparison of arterial pressure, with and without VAOT pacing, no significant differences were found in six patients, however, in one LBBB patient with intrinsic predominant ventricular trigeminy, VAOT pacing was observed to have an antiarrhythmic effect resulting in suppression of ventricular ectopy and stabilization of arterial pressure. All patients survived VAOT pacing and the postoperative period without complications requiring additional intervention or treatment. (PACE 2004; 27[Pt. I]:730–739)     

Autodecremental Pacing—A Microprocessor Based Modality for the Termination of Paroxysmal Tachycardias

Autodecremental pacing—A microprocessor based modality for the termination of paroxysmal tachycardias. Five patients aged between 27 and 48 years were referred for investigation of recurrent paroxysmal tachycardias. EJectrophysiological studies revealed concealed ventriculoatrial accessory pathways in two patients, possible atrionodal pathways in two patients and dual intranodal pathways in one patient. During electrophysiologicol study, particular attention was paid to methods of terminating tachycardia by pacing techniques including single or double atrial and ventricular extrastimuli, atriaJ or ventricular underdrive, atriaJ overdrive pacing, and in two patients, rapid ventricular pacing. Autodecremental' atrial pacing was employed in all five patients and autodecremental ventricular pacing in two patients. This system is controlled by a microprocessor interfaced with a stimulator. When tachycardia of a cycle length less than 375 ms is sensed the system initiates pacing sequences. The initial stimulus is introduced at an interval less than the tachycardia cycle determined by a preset decremental value D. Each subsequent pacing interval is reduced by the value of D resulting in a gradual acceleration of pacing. The total duration of pacing is limited by the value of the pacing period (P). The final pacing rate is determined by P but cannot exceed 275 bpm (cycle length of 218 ms). Both P and D are operator programmable variables. Tachycardias of a cycle length less than 218 ms do not activate the pacemaker. The postpacing sensing deadtime of the system is set at 50 ms. In three patients, double atrial extrastimuli or atrial overdrive initiated atrial flutter or fibrillation. Autodecremental atrial pacing was successful in converting tachycardia to sinus rhythm in all five patients without initiation of other tachyarrhythmias. Autodecremental ventricular pacing was successful in one of the two patients in which it was used. This new modality of pacing has several theoretical advantages over conventional methods: the decremental mode may avoid stimulation in the vulnerable period and minimizes the rislt of initiating other tachyarrhythmias; gradual acceleration of pacing over a short period results in stimulation at different phases of the tachycardia cycle length; and the operator variables D and P provide a flexible system which may be adjusted to suit a particular patient and tachycardia. The development of a fully implantable programmable system is made attractive by the simplicity and adaptability of this technique.     

Pullout His Bundle/Electrophysiologic Studies Using Leads Previously Inserted Via the Subclavian Vein

Conventional electrophysiologic studies involve the insertion of several catheter electrodes, positioned to pace and record from the high right atrium, His bundle region, and the right ventricular apex. The present study was undertaken to determine whether similar information could be obtained during removal of temporary pacing leads previously inserted via the subclavian vein, without the need for further invasive studies. Attempts to record a His bundle potential were successful in 157 of 200 patients (79%). A His bundle potential could be recorded during low right atrial pacing on 24 of 58 attempts. The Wenckebach cycle length was compared during high and low right atrial pacing in 34 patients, and did not differ significantly. Ventricular stimulation from the right ventricular apex and right ventricular inflow tract could be performed for assessment of ventricular vulnerability. Similarly, high right atrial pacing for sinus node testing was readily accomplished. In conclusion, detailed electrophysiologic studies can be performed during termination of temporary pacing, in sufficient detail to provide results equivalent to those of a more formal study.     

Balloon Electrode Catheter for Transesophageal Atrial Pacing and Transesophageal EGG Recording

A new balloon electrode catheter (10 French) with five or six balloon electrodes placed on the cardiac side was developed for transesophageal atrial pacing and bipolar ECG recording. The diameter of the hemispheric electrodes is 6 mm and the length of the esophageal balloon is 10 cm. The transesophageal atrial pacing threshold was measured with the balloon electrode catheter by transesophageal programmed atrial stimulation (TPS) (n = 54). At the onset of TPS, the feeling, capture fn = 54), and pain voltage threshold (n = 6) were measured by increasing the amplitude of the pacing voltage during high rate bipolar atrial pacing and bipolar atrial ECG recording. In 38 TPS, the capture threshold was lower than the feeling threshold (n = 28). In 16 TPS, the capture threshold was higher than the feeling threshold. In conclusion, painless atrial pacing and excellent ECG recording can be achieved with a multipolar esophageal balloon electrode catheter with a low pacing voltage amplitude and a high P wave amplitude.     

Clinical Experience with a New Software-Based Antitachycardia Pacemaker for Recurrent Supraventricular and Ventricular Tachycardias

The Intermedics Intertach 262-12 tachycardia reversion pulse generator was implanted in 14 patients (six male, eight female, mean age at implantation 45 +/- 16 years) with recurrent symptomatic tachycardias. Six patients had atrioventricular (AV) nodal reentrant tachycardia, three patients had orthodromic tachycardia with Wolff-Parkinson-White syndrome, two had circus movement tachycardia via a concealed bypass tract, two had ventricular tachycardia, one patient had atrial flutter. Mean duration of symptoms before implantation was 8 +/- 4 years and mean number of antiarrhythmic drug trials was 3.5 +/- 1. The primary tachycardia response made consisted of autodecremental pacing in one patient, burst pacing in two patients, and adaptive scanning of the initial delay or burst cycle length in eleven patients. The secondary tachycardia response mode consisted of autodecremental pacing in four patients, burst pacing in three patients and burst scanning in four patients. Tachycardia response was automatic in all but one patient with ventricular tachycardia. During a follow-up period of 30.5 +/- 10.6 months, one patient with ventricular tachycardia died from a nonarrhythmic cause. Reinterventions were necessary due to electrode fracture in one patient and due to pacemaker software defect in another one. Two patients underwent surgical cure of their arrhythmia: one patient with atrial flutter and one patient with AV nodal reentry tachycardia, 24 months and 11 months postpacemaker implantation, respectively. Four patients required digitalis to prevent pacing induced atrial fibrillation. Other proarrhythmic effects were not encountered. The pacemaker proved to be a versatile system with reliable tachycardia detection and termination functions. It provided a valuable adjunctive therapy in these selected patients.     

Clinical Evaluation of a Single-Pass Implantable Electrode for All Modes of Pacing. The "Crown of Thorns" Lead

Physiological pacing was instituted in 37 patients (33 men and 6 women), mean age 67 years (range 33–77 years), using a variety of multiprogram-mable generators attached to a permanent single-pass dual chamber electrode. Eleven patients were paced in VAT mode (Cordis 208A or Siemens-Elema 625 generator), two patients in DVI mode (Inter-medics Cyberlith IV generator) and four patients in DDD mode (Siemens-Elema 664/P33 or Telec-tronics Autima unit). Mean intracardiac P wave amplitude was 2.0 mV ± 0.78/SD, range 0.7–3.6 mV, and mean atrial and ventricular pacing thresholds were 1.0 V and 0.5 V, respectively. Fourteen patients had completely successful A-V pacing during a follow-up period of 4-33 months (mean 7 ± 2.7 months). Two failures were associated with malposition of the atrial crown and occurred exclusively with the Cordis 208A generator. In both patients generator replacement using a more sensitive unit (Siemens-Elema 625) resulted in successful VAT pacing for most of the time, Complete failure of A-V pacing occurred in only one patient who died from coronary artery disease after four months of follow-up. Thus, all of the remaining 36 patients achieved long-term (6 months) satisfactory physiological pacing using this new lead. We conclude that the "Crown of Thorns" electrode is a successful single-pass unipolar lead and can be used with all types of dual chamber generator for all modes of pacing.