Permanent Pacing from the Coronary Sinus in a Patient with an Implantable Defibrillator

A woman with an ICD underwent permanent pacemaker implantation for bradycordia-tachycardia syndrome. Despite multiple right atrial positions, oversensing secondary to "double counting" was always noted. A coronary sinus pacing catheter was inserted and left atrial pacing was accomplished with acceptable pacing and sensing characteristics. The patient has since done well without further shocks.     

Implantable cardioverter defibrillator proarrhythmia due to an interaction with "noncompetitive atrial pacing": an algorithm to prevent atrial arrhythmias

An episode of device related proarrhythmia observed with a dual chamber ICD is reported. Ventricular tachycardia was induced due to an inappropriate interaction of programmed device settings with automatic algorithms, including noncompetitive atrial pacing (NCAP), an algorithm used to prevent atrial tachyarrhythmias.     

Atypical AV nodal reentry with bystander accessory pathway: an unusual mechanism of preexcited tachycardia

We present an unusual mechanism of preexcited tachycardia--atypical AV nodal reentry with bystander AP. It can be differentiated from other preexcited tachycardias by its variable degree of preexcitation (either spontaneous or in response to atrial pacing), higher degree of preexcitation with pacing near the origin of the AP than during tachycardia, inability to preexcite the tachycardia by either late atrial or ventricular premature beats, the presence of nonpreexcited atypical AV nodal reentry tachycardia following successful AP ablation, and by exclusion of atrial tachycardia.     

Termination of Ventricular Tachycardia by an Implantable Atrial Pacemaker and External Pacemaker Activator

An atrial pacemaker was implanted in a patient who had dilated cardiomyopathy, sinus node dysfunction, and drug-resistant ventricular tachycardia (VT). VT episodes were terminated by atrial overdrive pacing using an implanted pacemaker and a newly developed hand-held external programmer/transmitter. Although successful cases of termination of intractable VT by ventricular pacing have recently been reported, the ventricular method might increase the risk of accelerating VT. Atrial overdrive pacing is a safer method since it minimizes the possibility of tachycardia acceleration and, combined with antiarrhythmic drugs, it appeared to be a unique and useful approach for the treatment of drug-resistant VT.     

Optimization of Pacing Algorithms to Prevent and Treat Supraventricular Tachyarrhythmias

Preventive atrial pacing and antitachycardia pacing have been proposed for the treatment of atrial fibrillation and associated arrhythmias in patients with indications for device implantation. Preventive algorithms provide overdrive atrial pacing, reduction of atrial premature beats, and prevent short-long atrial cycles with good patient tolerance. However, clinical trials testing preventive algorithms have shown contradictory results, possibly because of different trial designs, end points and patient populations. Factors probably responsible for neutral results include an already high atrial pacing percentage with the conventional DDDR mode, suboptimal atrial pacing site, and the deleterious effects of high percentages of right ventricular apical pacing. Atrial antitachycardia pacing therapies are effective in treating organized atrial tachyarrhythmias (that precede atrial fibrillation), mainly when delivered early after the onset particularly if the tachycardia is relatively slow. Antitachycardia pacing therapies might influence atrial fibrillation burden, but clinical studies have shown conflicting results about this issue. Consistent monitoring of atrial and ventricular rhythm including progression to persistent forms of atrial arrhythmias, variability of atrial arrhythmia recurrence patterns and onset mechanisms as well as antitachycardia pacing efficacy should be recorded in the stored device memory and used for optimal individual programming of these new functions.     

Esophageal Balloon Electrode Catheter for Transthoracic Recording of His-Bundle Potential with Transesophageal Atrial Pacing

To evaluate the influence of transesophageal atrial pacing of the transthoracic His potential identification, we combined signal-averaged ECG with transesophageal atrial pacing with low threshold for pacing averaging ECG recording. A tripolar 10 French esophageal balloon electrode catheter, with one cylindrical electrode on the tip of the catheter and two balloon electrodes on the cardiac side of the catheter, used in 53 patients, allowed a painless transesophageal atrial pacing and a high signal to noise distance in the signal-averaged ECG. Transesophageal atrial pacing allowed in 37 of 53 patients an identification of His potential by increasing the distance between the end of the atrial potential and the onset of the His potential in the pacing averaging ECG. The esophageal balloon electrode catheter allowed a painless transesophageal atrial pacing with low threshold for atrial capture during a long pacing time and a high signal to noise distance in the pacing averaging ECG. The increasing of the heart rate with transesophageal atrial pacing allowed the transthoracic identification of the His potential in the pacing averaging ECG.     

Dislodgment of an atrial screw-in pacing lead 10 years after implantation

Dislodgment of an atrial screw-in pacing lead is quite rare. This report describes a rare case of an atrial screw-in lead dislodgment 10 years after implantation. Although it is an uncommon complication, very late dislodgment can occur postoperatively, and careful follow-up is necessary.     

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.     

Shift of Atrial Reentrant Tachycardia with Transient Entrainment to an Uncommon and a Common Type of Atrial Flutter

Atrial reentrant tachycardia (ART) which demonstrated transient entrainment shifted to an uncommon type of atrial flutter (AF) with premature atrial stimulation, and then returned to ART spontaneously, Subsequently, this ART shifted to a common type of AF by rapid atrial pacing, which was further transformed into an uncommon type of AF and finally terminated by rapid atrial pacing. The mechanism of AF in clinical cases is still controversial, but in this case, AF, both uncommon and common types, is considered due to macro-reentry within the atria. To explain (he shift of ART to AF and mutual transformation between common and uncommon type of AF, we made a schematic figure of reentry loop within (he atria of ART and AF.     

Percutaneous Extraction of an Abandoned Coiled Pacing Lead

Abandoning redundant pacing leads has been an accepted practice in most cases. Late migration of a lead is a rare, unpredictable, and potentially lethal complication of this approach and requires immediate removal. We report the case of an atrial pacing lead that had migrated and was found coiled in the right atrium. It was removed by a snare catheter via a femoral approach.     

Long-Term Performance of Bipolar Epicardial Atrial Pacing Using an Active Fixation Bipolar Endocardial Lead

Bipolar epicardial leads are not yet widely available for atrial use. Since September 1986, we have used a bipolar active fixation endocardial lead (Cardiac Pacemakers model number's 4266, 4268, and 4269) as a bipolar epicardial atrial lead by attaching the corkscrew tip to the atrial surface and imbricating atrial tissue around the more proximal electrode. A total of 77 bipolar epicardial atrial leads have been implanted using this approach in 72 patients with congenital heart disease (ages 3 months to 38.7 years; mean 8.9 ± 8.8 years). Indications for atrial pacing included AV block (n = 46), sinus node dysfunction (n = 17), and antitachycardial pacing (n = 9). Indications for epicardial pacing included the presence of an intracardiac right to left shunt (n = 33), concomitant cardiac surgery (n = 26), surgeon preference (n = 7), and lack of transvenous access to the atrial endocardium (n = 6). Follow-up (median 23 months; mean 28.0 ± 23.1 months; range 1–78 months) data beyond 1 month postimplantation were available for 44 leads. Atrial sensing was ≥ 2.0 mV for 26 leads (59%) with sensing possible at ≥ 0.75 mV for 42 leads (95%). Threshold data were available at 5 V for 37 leads and at 2.5 V for 36 leads with mean pulse width thresholds measuring 0.21 ± 0.33 ms and 0.34 ± 0.34 ms, respectively. Two leads failed (high capture thresholds at 5 days [n = 1], lead fracture at 42 months [n = 1]); one of which was replaced. Four additional leads were replaced electively (marginal thresholds [n = 1], intermittent phrenic nerve stimulation [n = 1], damaged during subsequent surgery [n = 1], clinically irrelevant insulation break [n = 1]) concomitant with additional cardiac surgery. Until a commercially available lead is developed and released, improvisation with a bipolar active fixation endocardial lead as a bipolar epicardial atrial lead is a reasonable approach to providing bipolar atrial sensing and pacing in patients for whom endocardial pacing is contraindicated.     

New Developments for Upper Rate Response in DDD Pacing

Although widely accepted as an effective method of dealing with rapid atrial rates in a DDD pacemaker, Wenckebach-type and multiblock-type upper rate behaviors may exacerbate pacemaker-mediated tachycardia through AV dissociation. In addition, pathologic atrial rates (e.g., atrial fibrillation, atrial flutter, automatic atrial tachycardia, etc.) frequently result in ventricular pacing at inappropriately high rates. New, more sophisticated algorithms available in today's microprocessor-based DDD pacing systems provide the capability to discriminate successfully a normal atrial rate response to exercise from a pathologic atrial rate. These and other improved capabilities allow the clinician to provide safe rate-responsive pacing to patients in whom rate-responsive pacing was previously contraindicated.     

Acute Pericarditis Resulting From an Endocardial Active Fixation Screw-In Atrial Lead

We examined the occurrence of acute pericarditis after pacemaker implantation in 123 consecutive patients (61 males, 62 females, ages 17–87 years) in whom a newer atrial active fixation bipolar lead was inserted endocardially in the right atrium for dual chamber pacing. The atrial leads were positioned to obtain the best possible pacing and sensing thresholds, after an initial attempt was made for insertion into the right atrial appendage or medially into the right atrial septum. Six patients (4.9%) developed acute symptomatic pericarditis with effusion within 24 hours of implantation. Of these six patients, four had leads screwed into the lateral waH. and the other two had leads placed in the anterolateral wall. The lead implantation parameters between patients with pericarditis and those without did not show any significant difference in the atrial P wave amplitude (2.3 ± 0.4 vs 2.9 ± 0.9 mV), pacing threshold (1.1 ± 0.2 vs 1.1 ± 0.4 V), or resistance (524 ± 112 vs 480 ± 94 ohms). All symptomatic patients were treated with nonsteroidal anti-inflammatory drugs with symptoms resolving in 1–2 weeks. We condude that: (1) a significant number of patients (4.9%) developed acute symptomatic pericarditis after insertion of this type of atrial fixation lead: (2) because of the lead design, the implantation parameters coud not be taken to predict the occurrence of pericarditis: and (3) caution should be taken for the insertion of this lead into the thin atrial wall.     

First Experience with an Automatic Sensing Algorithm in Single-Lead VDD Stimulation

An "Autosensing" algorithm available in SSI(B) and DDD(R) pacemakers automatically adapts the device's sensitivity to changing intracardiac signals. The atrial sensing function of this algorithm was tested for the first time with a VDD pacing system in which large variations of the atrial signal may occur because the atrial electrodes float in the atrial blood pool. Methods: 15 patients with a VDD pacing system were studied (Unity 292–07, lead 425; Sulzer Intermedics). The atrial sensing threshold was measured, and the atrial sensitivity was programmed with a 2:1 safety margin. The autosensing algorithm and sensitivity profile were temporarily activated, and an ambulatory ECG with continuous marker annotation was recorded. All patients underwent a 30-minute daily life activities protocol. A beat-to-beat analysis of the ambulatory ECG was correlated with the changes in atrial sensitivity. Results: The algorithm changed the baseline sensitivity from 0.57 ± 0.23 mV during the test to 0.39 ± 0.20 mV after the final rest period (P < 0.05). During the test 12.6 ± 10.2 adaptations of the sensitivity occurred (range 0–33). In eight patients atrial undersensing occurred in 4.4%± 7.5% of the cycles (4–458 unsensed P waves]. In these patients, the algorithm continuously adjusted the sensitivity towards more sensitive values, operating 19.1 ± 18.3 changes compared with 5.4 ± 7.3 changes in patients without undersensing (P = 0.009). Oversensing did not occur. Conclusion: The autosensing algorithm effectively optimized atrial sensitivity in VDD pacing. In patients with atrial undersensing the algorithm continuously remained near the most sensitive settings, thus reacting as intended. A faster sensitivity adjustment of the system would be desirable.     

Comparison of Arrhythmogenicity of Atrial Pacing at Several Right Atrial Pacing Sites: Evaluation of Canine Atrial Electrograms During Atrial Pacing and Arrhythmogenicity for Atrial Fibrillation

The changes in the duration of atrial electrograms and the appearance of AF during atrial pacing were compared among five atrial pacing sites in dogs to clarify the arrhythmogenicity of atrial pacing at different atrial pacing sites. In seven mongrel dogs (15–20 kg), the right atrial surface was exposed by right thoracotomy. Atrial electrograms were recorded via bipolar electrodes with an interelectrode distance of 1.2 mm at four right atrial sites: (1) the high right atrium (HRA), (2) the mid-right atrium (MRA), (3) the low right atrium (LRA), and (4) the center of the pectinate muscle (PM). The duration of the atrial electrograms at these four recording sites were measured during atrial pacing with fixed cycle lengths of 200, 150, and 120 ms delivered at five atrial sites: (1) the HRA, (2) the inferior vena cava (IVC), (3) the right atrial appendage (RAA), (4) Bachman's bundle (BB), and (5) the atrial septum (AS). In each dog, the atrial pacing with the 120-ms cycle length was performed five times at each pacing site to evaluate the in-ducibility of AF. When AF was induced, the atrial recording site which first showed a fragmented atrial electrogram was considered the initiation site of the AF. AF was induced during 9 of 35 episodes of atrial pacing at the HRA site, 11 of 35 at the IVC site, 5 of 35 at the RAA site. 3 of 35 at the BB site, and none at the AS site. The initiation site of AF was in the HRA site in 11 of 28 episodes of induced AF, in the MRA site in 9 of 28, and in the LRA site in 8 of 28. At each recording site, the shorter the paced cycle length, the longer the duration of the atrial electrogram regardless of the pacing site. During the atrial pacing with the 200-ms cycle length, the HRA pacing resulted in the shortest duration of the atrial electrogram at each recording site in comparison with the other pacing sites. However, during atrial pacing at the two shorter paced cycle lengths, the duration of the atrial electrogram was shorter during the pacing at the BB or AS sites in comparison with the other three pacing sites, i.e., the HRA, IVC, and RAA sites. These results were the same for all atrial recording sites, but the prolongation of the atrial electrogram was most prominent at the HRA and MRA recording sites, which are most likely initiation sites of the induced AF. In the canine atria, (1) the initiation sites of AF were likely to be the HRA, MRA, or LRA sites in comparison with the PM site; and (2) the atrial pacing at the BB or AS sites was considered less arrhythmogenic for AF than the pacing at the HRA, LRA, or RAA sites.     

Effects of continuous and triggered atrial overdrive pacing on paroxysmal atrial fibrillation in pacemaker patients

Background: The aim of the study was to compare the effects of different pacing strategies to prevent paroxysmal atrial fibrillation (AF): triggered atrial overdrive pacing versus the combination of triggered and continuous overdrive pacing.
Methods : Patients with an indication for dual-chamber pacing (Selection 9000, Prevent AF; Vitatron B.V., Arnhem, the Netherlands) and a history of paroxysmal AF were randomized to triggered atrial pacing (three pacing functions, "triggered group": PAC Suppression™, Post-PAC Response™, and Post-Exercise Response™) or to the combination of continuous (Pace Conditioning™) and triggered atrial pacing (four pacing functions, "combined group"). After 3 months, there was a crossover to the other pacemaker setting.
Results : In 171 enrolled patients, the median AF burden of the combined group was with 2.1% versus 0.1% in the triggered group (P = 0.014). Fewer AF episodes were observed in the triggered (median: 7) than in the combined group (median: 116; P = 0.016). The combined group had more frequent atrial pacing (median 97%) than the triggered group with 85% (P < 0.001), but ventricular pacing was not significantly different with 95% and 96% in the combined and triggered group, respectively. After the crossover, the AF burden increased in the triggered group to 0.3% and decreased in the combined group to 0.4%.
Conclusions : Triggered atrial pacing functions alone resulted in a low AF burden. The additional activation of continuous atrial overdrive pacing increased the percentage of atrial pacing, but had no beneficial effects on the prevention of paroxysmal AF.     

Differentiation of Arrhythmias by Measurement of Intracardiac Pressures in Man

Antitachycardia devices currency use sustained high rate, abrupt changes in cycle length, and probability density function to determine the onset of ventricular tachycardia. Hemodynamic changes occur with the onset of tachycardia and may provide a method of discriminating supraventricular from ventricular tachycardia. In this study, patients had atrial and ventricular pressures measured during rapid atrial and ventricular pacing. Right atrial pressure increased significantly with ventricular pacing but not with atrial pacing. Right ventricular pressures did not significantly differ with atrial or ventricular pacing. The change in atrial pressure compared to baseline was greater, with ventricular pacing compared to atria] pacing. Right ventricular pressure increased compared to baseline with atrial or ventricular pacing, but there was no significant difference between pacing modalities. Measurement of right atrial pressure might prove useful in discriminating supraventricular from ventricular tachycardia.     

The Reliability of Rate-Pressure Product as an Index of Myocardial Oxygen Consumption in Atrial Synchronized Versus Fixed Rate Ventricular Pacing

The product of heart rate and blood pressure was tested as an index of myocardial oxygen consumption (MVO2) and compared with directly determined MVO2 during ventricular demand (VVI) fixed rate pacing and atrial synchronized (VAT) pacing at rest and during exercise. Systolic brachial artery pressure, pulmonary wedge pressure and MVO2 were similar in the two pacing modes and showed similar response to exercise. The correlation between rate-pressure product and MVO2 was closer with VAT than with VVI pacing (r = 0.74 and r = 0.64, respectively), and the latter value was not improved by using the product of atrial rate and systolic pressure (r = 0.61). The rate-pressure product was significantly higher during VAT pacing compared to VVI during exercise, although MVO2 was similar. The similarity of MVO2 during exercise indicated some other contributory factor than heart rate in VVI pacing, probably increase of contractility and/or volume. Because such factors are not included in currently used indices of MVO2 assessments must be interpreted cautiously, particularly in cases of complete heart block with VVI pacing.     

Holter Documented Sudden Death in a Patient with an Implanted Defibrillator

A 68-year-old man with recurrent attacks of monomorphic ventricular tachycardia (VT) received a pacer cardioverter defibrillator featuring antitachycardia pacing and cardioversion/defibrillation. Over 300 episodes of VT were successfully terminated by antitachycardia pacing. During Holter monitoring the patient experienced supraventricular tachycardia with delivery of multiple antitachycardia pacing, cardioversion, and defibrillation therapies ending with the death of the patient. The following factors played a role in the unfortunate outcome of this patient: 1. triggering of VT therapy by an unexpected high sinus rate; 2. atrial fibrillation induced by cardioversion therapy; 3. a gradual and continuous increase in rate during atrial fibrillation possibly caused by repeated VT and ventricular fibrillation therapies and/or by a thrombus, found at autopsy, in a bypass graft; and 4. the limited ability of presently available defibrillators to distinguish between ventricular and supraventricular arrhythmias.     

Electrocardiographic Characteristics of Pacing From the Right Atrial Appendage During Atrioventricular Sequential Pacing

In the interpretation of electrocardiograms recorded during atrioventricular sequential pacing, uncertainty frequently arises in the assessment for evidence of atrial capture. In the present study, electrocardiographic characterization of pacing from the right atrial appendage as a component of atrioventricular pacing was performed on tracings obtained from 16 patients with bipolar dual chamber pacing units, and from 18 patients with unipolar dual chamber pacing units in which large overshoot potentials occurred following the atrial pacing spike. Atrial complexes resulting from bipolar pacing of the right atrial appendage were found to be uniformly prolonged and of diminished amplitude compared to those in sinus rhythm; they were also noted to contain sequential inferoposterior and leftward-posterior component vectors. The exponential overshoot-decay complex associated with unipolar atrial pacing appeared as a vector directed along the axis from the pulse generator to the pacing lead; the degree to which this deflection interfered with identification of atrial capture in various leads was thus largely dependent on pulse generator location. It was concluded that careful systematic inspection of multiple electrocardiographic leads will generally permit the characteristic features of pacing the right atrial appendage to be recognized, thus facilitating correct interpretation of atrial capture during atrioventricular sequential pacing.