Use of Automatic Mode Change Between DDD and AAI to Facilitate Native Atrioventricular Conduction in Patients with Sick Sinus Syndrome or Transient Atrioventricular Block

The benefits of the automatic DDD (DDD/AMC) mode in the Chorus II pacemaker (Chorus 6234; Ela Medical Inc.), which automatically switches the modes between DDD and AAI to respect spontaneous AV conduction as much as possible in AAI while preserving safety pacing in DDD during paroxysmal AV block (AVB) only, remain unproven. This study examined the functions of the DDD/AMC mode in 12 patients with sick sinus syndrome (SSS; n = 10) or paroxysmal complete AVB (n = 2). A short-term (24 hours) comparative study between simple DDD mode and the DDD/AMC mode was performed in 8 of the 12 patients, and a medium-term (55.2 ± 54.6 days) follow-up of the DDD/AMC mode was completed in all 12 patients. A comparative pair of 24-hour surface Holter ECGs was obtained in 6 of the 8 patients in the short-term study. Telemetry and built-in Holter histograms were collected in the outpatient clinic in all 12 patients. Although the percentage atrial pacing of the telemetry increased from 59.2 ± 35.4 in DDD to 70.4 ± 31.8 in DDD/AMC (P < 0.009; n = 8), the percentage ventricular pacing decreased from 64.6 ± 37.7 in DDD to 36.2 ± 43.1 in DDD/AMC (P < 0.027) in the short-term study. In particular, the reduction of percentage ventricular pacing to < 10% was observed in four patients with SSS not associated with ± first-degree (1°) AVB on preoperative ECGs. Between the two modes a significant difference in arrhythmic events was not observed by the 24-hour surface Holter ECGS taken from the six patients in the short-term study. AAI-DDD switching associated with automatic modulation of AV delay and AV hysteresis occurred in all patients in the medium-term study. From the medium-term study, the total AV delay (AV delay plus AV hysteresis) exceeded 300 ms in 6 of the 12 patients in DDD/AMC, and usually became longest during nighttime. From the short- or medium-term study in the 12 patients, two patients preferred the DDD/AMC mode while one preferred the DDD mode. These results suggest that the DDD/AMC mode is useful, at least in SSS patients without ≥ 1° AVB, by reducing the percentage ventricular pacing.     

Noise Reversion of a Dual Chamber Pacemaker without Noise

Three patients are reported whose DDD pacemakers reverted to the asynchronous mode in the absence of skeletal muscle or electromagnetic (EMI) interference. In all three cases, the basic cardiac rhythm was atrial fibrillation with fast ventricular response due to intrinsic AV conduction. Noise reversion was triggered by the patients' own ventricular activity at cycle lengths shorter than the ventricular refractory period of the pulse generator. In one patient, asynchronous AV sequential pacing during atrial fibrillation was noted shortly after resuscitation from ventricular fibrillation; however, the initiation of the malignant ventricular arrhythmia by the pacemaker remains unproven. The mechanism of noise reversion by rapid cardiac activity and possible solutions to the problem by adequate pacemaker design are discussed.     

Treatment of Inappropriate Sinus Tachycardia with Ivabradine in a Patient with Postural Orthostatic Tachycardia Syndrome and a Dual Chamber Pacemaker

We present the case of a 44-year-old woman with postural orthostatic tachycardia syndrome (POTS) and a dual chamber pacemaker. The patient suffered from inappropriate sinus tachycardia that had been resistant to treatment with traditional rate-slowing medications. Ivabradine—the specific sinus node I_f current inhibitor—was used to successfully lower the heart rate. The patient had no evidence of POTS on repeat autonomic function testing, and there was a corresponding symptomatic benefit. We propose that this class of drugs, the use of which is established as antianginals, should be considered in patients with resistant inappropriate sinus tachycardia.     

Pacing of the Atria in Sick Sinus Syndrome Trial: Preventive Strategies for Atrial Fibrillation

SPITZER, S.G., et al .: Pacing of the Atria in Sick Sinus Syndrome Trial: Preventive Strategies for Atrial Fibrillation. This study examines the effects of various atrial lead positions in physiological pacing on the incidence of AF in patients with sick sinus syndrome. The lead is implanted in the RA free wall, in the RA appendage, near the coronary sinus ostium (CSO) or, in dual site RA pacing, in the appendage and the CSO. Since CSO and dual site right atrial pacing aim at modifying the pathological substrate, pacing of two-thirds of all cardiac cycles is attempted by adapting the basic rate and the rate response option. The results of this study are expected to assist in the development of guidelines for the placement of atrial pacing leads in sick sinus syndrome. (PACE 2003; 26[Pt. II]:268–271)     

Is Chronic Atrial Stimulation a Reliable Method for Single Chamber Pacing in Sick Sinus Syndrome?

To evaluate the feasibility of chronic atrial pacing (AAI) in sick sinus syndrome (SSS), 22 patients (pts) with bradytachycardia syndrome (BTS) and 17 patients with only bradyarrhythmias (BA) were studied on the incidence of supraventricular tachycardias (SVT) and occurring AV block. A scoring system based on symptoms of SVT was developed (grade 0–5). All patients had proven normal AV conduction before PM implantation. In the BTS-group, nine patients (41%) had symptomatic SVT at the end of follow-up (mean 53 months), despite drug therapy. These patients had a high SVT score on entry (mean 3.2). High degree AV block occurred in three patients. Although in the BA-group SVT arose in six patients (35%), there was only one symptomatic patient at the end of follow-up (mean 36 months). In this group, only one patient developed high degree AV block. Atrial stimulation should be considered as a reliable therapy in patients with SSS and low SVT score before PM implantation when normal AV conduction is present.     

Dynamic Left Ventricular Arterial Pressure Gradient and Sick Sinus Syndrome with Heterozygous Fabry''s Disease Improved Following Implantation of a Dual Chamber Pacemaker

A 63-year-old woman with heterozygous Fabry's disease, sick sinus syndrome, sinus pauses, congestive heart failure, syncope, and a dynamic pressure gradient between the left ventricle and systemic arteries underwent implantation of a dual chamber (DDD) pacemaker. Following pacemaker implantation, the pressure gradient has been reduced and congestive heart failure controlled for the past 3 years.     

Ventricular and Dual Chamber Pacing for Treatment of Carotid Sinus Syndrome

Thirty-nine consecutive patients with recurrent syncope and either cardioinhibitory or mixed type carotid sinus syndrome were studied to determine the efficacy of ventricular (VVI) pacing in 16, and dual chamber (DDD/DVI) in 23 patients. Only those patients affected by the isolated vasodepressor form were excluded. Follow-up lasted 12 ± 5 months. Symptoms were totally eliminated in 67% of patients and ameliorated with persistence of minor symptoms in 33%. All patients underwent an initial 2-month follow-up in the VVI mode. Evaluation of the 19 patients who remained symptomatic and the 20 who became asymptomatic with VVI pacing demonstrated that factors observed prior to pacemaker implant were related to failure of the VVI mode. These included symptomatic pacemaker effect (42% vs 0%), mixed carotid sinus syndrome (95% vs 65%), orthostatic hypotension (47% vs 15%), or ventriculoatrial conduction (68% vs 38%). In the 23 patients with dual chamber pacing, random 2 month comparisons were performed between VVI and DVI/DDD pacing. The dual chamber mode was preferred by 14 patients, none preferred the VVI mode and nine noted no difference. Comparison of the two groups found that the factors linked to DVI/DDD preference were symptomatic pacemaker effect (50% vs 0%), ventriculoatrial conduction (78% vs 44%), or orthostatic hypotension (50% vs 11 %). VVI pacing is efficacious in a high proportion of patients affected by cardioinhibitory or mixed carotid sinus syndrome. The identification of causes of VVI pacing failure allows determination of those who will benefit from VVI pacing and those who should have DVI/DDD. VVI pacing is suggested for the cardioinhihitory type with no symptomatic pacemaker effect and for the mixed type with no symptomatic pacemaker effect or orthostatic hypotension or ventriculoatrial conduction. Dual chamber pacing should be used in all other instances.     

Reliability of a New Algorithm for Automatic Mode Switching from DDDR to DDIR Pacing Mode in Sinus Node Disease Patients with Chronotropic Incompetence and Recurrent Paroxysmal Atrial Fibrillation

To evaluate the safety and efficacy of a new algorithm for automatic mode switching (AMS) from DDD-DDDR to DDIR, 26 patients, 16 females and 10 males, mean age 73 ± 6 years of age, affected by sinus node disease, chronotropic incompetence, and recurrent paroxysmal atrial fibrillation (PAF) received the Medtronic Them DR pacemaker. The device continuously calculates, in ms, the running average of the intrinsic atrial rate (MAR) and compares the current atrial interval (CAI) with the stored MAR. When the CAI is greater than the MAR it increases by 8 ms, and when the CAI is less than the MAR, it decreases by 23 ms. When MAR ± 330 ms (182 beats/mm), tachycardia is detected and AMS is activated. All patients had clinical evaluation, 12-lead ECG, Holter monitoring, and exercise testing after implantation and every 3 months for 1 year. The results were compared with the data stored in the pacemaker memory: AMS episodes number; the histogram of the last 14 episodes; and atrial electrogram recording. Twenty-two Holier recordings in 13 patients showed PAF and in all of them AMS occurred simultaneously. AMS lasted between 10 seconds and 20 hours, and MAR ranged from 195–400 beats/mm. No episode of PAF and no AMS were recorded in 39 Holter recordings in 22 patients. Appropriate AMS was confirmed in five patients by stored atrial electrogram and in nine by 12-lead ECG and pacemaker event markers. Mean atrial sensing was 2.13 ± 1.04 mV during PAF and 3,18 ± 1.46 mV during sinus rhythm. No PAF episode and no AMS were recorded during exercise testing. In conclusion, this new algorithm was very reliable, sensitive, and specific.     

Symptomatic Improvement in a Patient with Sick Sinus Syndrome After the Onset of Stable Atrial Flutter

A patient with sick sinus syndrome (SSS) presented with episodic lightheadedness and weakness. The electrocardiographic features were marked supraventricular bradyarrhythmias and paroxysmal atrial flutter. The symptoms lasted for four years and disappeared with the onset of stable atrial flutter which has persisted for the past seven years. Over the 11-year period of observation, there has been progressive involvement of the His-Purkinje system manifested by the development of left anterior fascicular block, right bundle-branch block, and prolongation of the HV conduction time. The patient has refused pacemaker implantation. In the absence of angina and in the presence of a normal heart size, the etiology of his SSS is postulated to be idiopathic fibrosis of his conduction system.     

Initial Experience with a New Balloon-Guided Single Lead Catheter for Internal Cardioversion of Atrial Fibrillation and Dual Chamber Pacing

Background: Based on the observation that internal cardioversion (IntCV) of atrial fibrillation is effective with electrodes in the right atrium and pulmonary artery, a new balloon-guided catheter and external defibrillation device with optional dual chamber pacing was evaluated. Methods: IntCV was attempted in 27 patients (age: 57 ± 10 years, duration: 14 ± 18 months, left atrial diameter 56 ± 8 mm) using a new defibrillation device (Alert, EP MedSystems, Inc., NJ, USA) that allows the delivery of biphasic shocks (0.5–15 J, variable tilt), atrial and ventricular pacing, and online signal recording. Pacing and defibrillation shocks were applied via a 7.5 Fr balloon-guided catheter (EP MedSystems, Inc.). Pacing, sensing, and triggering were established through the proximal atrial array and an electrode ring between both defibrillation arrays and a single ventricular electrode ring. Catheters were inserted from the antecubital vein. Results: In 25 of 27 patients sinus rhythm was restored with a mean energy of 6.7 ± 4.5 J. In five patients, atrial postshock pacing was required for bradycardia and atrial premature beats. The mean fluoroscopy time was 2.0 ± 1.3 minutes. Conclusion: The high success rate, ease of application, and backup dual chamber pacing suggest that this system is an alternative to established methods of cardioversion. In certain indications, such as failure of prior external cardioversion and situations in which a standard pulmonary balloon catheter is needed, this system would be advantageous.     

Transesophageal Programmed Atrial Pacing as a Method of Selecting Patients with Sick Sinus Syndrome for Permanent Atrial Pacing

Many recent studies have shown transesophageal programmed atrial pacing (TP) as a very practical, safe and convenient way for assessment of sinus node function and AV conduction. On the other hand, permanent atrial pacing is known to be superior to ventricular pacing due to arrhythmogenic and hemodynamic reasons. This is the reason why we decided to use TP as a method of choosing patients with sick sinus syndrome (SSS) for permanent atrial pacing. Sixty-three patients with symptomatic (58) and asymptomatic (5) SSS in a variety of clinical situations were examined in this way. The following electrophysiological features were examined: sinus cycle length, sinus node recovery time as well as corrected time, secondary pause after overdrive stimulation, sinoatrial conduction time, Wenckebach point, induction of supraventricular arrhythmias by S1, S2, S3 programmed stimulation and burst pacing. Patients with abnormal parameters were examined once more after intravenous atropine 0.2 mg/kg to evaluate parasympathetic component. Standard 12-lead ECG was performed in ail, and Holter monitoring in most of patients.
Twenty-six patients were candidates for permanent AAI pacing. Failures occurred in eight patients usually due to low P wave amplitude and electrode instability. Eighteen patients received AAI pacing systems: eight with brady-tachycardia syndrome, nine with brady-arrhythmia and one with sinoatrial block. In the follow-up of 5–28 months in one patient occurred high degree AV block (11°) during digitalis therapy. Reduction of doses made this block disappear. Examination of Wenckebach point and possibility of inducation of supraventricular lachyarrhythmias in cases of atrial overexcitability are particularly useful in selecting patients for AAI pacing. (PACE, Vol 11 November Part II 1988)