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This article reviews current pharmacological and electrical approaches to the restoration of sinus rhythm in patients who suffer from atrial fibrillation and atrial flutter. Spontaneous conversion to sinus rhythm occurs in a high proportion of atrial fibrillation of < 24 h duration. Among patients presenting with atrial fibrillation, which was clinically estimated to have lasted < 48 h, the likelihood of cardioversion-related clinical thromboembolism is low, which supports the current practice of early cardioversion without anticoagulation. Antiarrhythmic drugs effective in terminating atrial fibrillation of short duration are those which possess class IA, IC and III properties. Electrical transthoracic cardioversion by using different electrode positions and additional pressure over the electrodes during shock delivery is a highly effective and well-tolerated method in restoration of sinus rhythm even in patients under conscious sedation. Immediate spontaneous reinitiation of atrial fibrillation can occur in a significant proportion of patients undergoing electrical cardioversion and can be reduced after a pretreatment with antiarrhythmic drugs. In patients with failed external cardioversion, internal low energy cardioversion offers an effective option for restoring sinus rhythm. After cardioversion in a high proportion of patients antiarrhythmic drugs are necessary to prevent atrial fibrillation from recurring. A serial cardioversion approach can prevent the evolution of permanent atrial fibrillation in a subgroup of patients. Overdrive atrial pacing is an effective and minimally invasive procedure for termination of atrial flutter. The acute administration of class IA, IC and III antiarrhythmic drugs increases the success rate of this method in restoring sinus rhythm.

Recent studies have shown that transvenous atrial cardioversion is feasible with lead configurations primarily designed for implantable cardioverter defibrillators (ICD). The purpose of this study was to examine the influence of an active pectoral ICD can on the atrial cardioversion threshold (ADFT). Forty consecutive patients received a transvenous single lead system (Endotak DSP 0125, CPI, St. Paul, MN, USA) in combination with a left subpectoral ICD (Ventak Mini, CPI) for treatment of malignant ventricular tachyarrhythmias. Patients were randomized into two groups: 21 received a Hot Can 1743 and 19 patients a Cold Can 1741. Step-down testing of the ventricular defibrillation threshold (VDFT) was performed intraoperatively and evaluation of the ADFT for induced atrial fibrillation (AF) at predischarge. After testing, each patient received a 2-J shock and was asked to quantify discomfort on a numerical scale ranging from 0 to 10. Both groups were comparable with regard to all clinical parameters studied. The mean VDFT in patients with a Hot Can device was significantly lower than in patients with a Cold Can (7.5 +/- 2.3 J vs 9.8 +/- 3.8 J; P < 0.03). The mean ADFT in the Hot Can group tended to be lower than in the group with Cold Cans (3.4 +/- 1.4 J vs 4.5 +/- 2.4 J; P = 0.07), and the proportion of patients in whom atrial cardioversion was accomplished at low energies (< or = 3 J) was higher in patients with active compared with patients with inactive pulse generators (57% vs 26%; P < 0.04). The mean discomfort reported after delivery of a 2-J shock was comparable in both groups (Hot Can 5.2 +/- 1.9; Cold Can: 5.3 +/- 2.1; P = NS). We conclude that the inclusion of an active left subpectoral can in the defibrillation vector of a ventricular ICD seems to reduce the energy requirements for atrial cardioversion without increasing the discomfort caused by low energy shocks.

The analysis of endocardial signals obtained from an electrode located in the right atrium enabled by new dual chamber implantable cardioverter defibrillators may be helpful to provide additional therapies such as overdrive pacing or low energy atrial cardioversion for the treatment of concomitant atrial flutter (AFL) or atrial fibrillation (AF). Algorithms for discrimination of atrial tachyarrhythmias based on rate counting are of limited efficacy. The aim of this study was to assess the intersignal variability by using fast discrete wavelet transforms (FDWT) as a new method of discrimination of AF from AFL. Patients with spontaneous episodes of AF/AFL or patients who developed AF/AFL during an electrophysiological study were studied. The endocardial signals were recorded from the high right atrium using a transvenous 5 Fr bipolar electrode catheter (interelectrode spacing: 1 cm). The signals were digitized (2 kHz, 12-bit resolution) after amplification and filtering (40-500 Hz). Within data segments of 10-second duration, 25 consecutive signals were selected and normalized and FDWT was applied. Standard deviations of the wavelet coefficients (SD) from coarse scales (scale 4-8) were calculated. A total of 94 data segments (AF: 52, AFL: 42) from 28 patients were analyzed. SD at each considered scale was higher for AF than for AFL (P < 0.001). SD at scale 8 discriminated between AF from AFL with 100% sensitivity and specificity. We conclude that assessment of intersignal variability of bipolar endocardial recordings using FDWT is an effective method for the discrimination of AF from AFL. The implementation of this tool in a discrimination algorithm of an implantable device may help provide the appropriate differential therapy for atrial tachyarrhythmias.

In patients with sinoatrial disease, unexpected atrial flutter (Af) or fibrillation (AF) is a common problem during implantation of atrial-based pacing systems. As an alternative approach to blind atrial lead placement, lead positioning could be optimized by atrial electrogram mapping. It was the object of this study to evaluate if atrial lead implantation according to this approach and during ongoing arrhythmia is reasonable or if it should be postponed until restoration of sinus rhythm (SR). Twenty-nine consecutive patients (group I) with sick sinus syndrome received a dual-chamber pacemaker during an episode of Af (n = 11) or AF (n = 18). All but two atrial leads were of the screw-in type and had bipolar sensing. Atrial lead position was optimized by mapping the electrogram under fluoroscopy to find locations with high potential amplitudes. The patients were followed for 15.1 +/- 9.8 months, and atrial sensing threshold (AST), atrial pulse width threshold (PWT) at 2.0 V, the pacing mode programmed, and the clinical outcome (OUT) were recorded. The control group consisted of 30 patients (group II) who equally had a history of AF or Af, but were in SR during implantation. The atrial peak-to-peak potential (APEAK) after final lead placement was lower for AF (median value 2.5 mV, lower-upper quartile: 1.7-3.1 mV) as compared to Af (3.8 mV, 2.7-4.9 mV, P < 0.05) and SR (4.1 mV, 3.3-6.2 mV, P < 0.001). There was a correlation (P < 0.01) between APEAK during Af/AF and the postoperative AST immediately after restoration of SR. No lead in any group had to be corrected due to improper sensing in the postoperative course. Median chronic AST was 2.8 mV (2.0-4.0 mV) in group I and 4.0 mV (2.8-4.0 mV) in group II. Median chronic PWT at 2.0 V was 0.15 ms (0.12-0.26 ms) in group I and 0.15 ms (0.09-0.20 ms) in group II. There was no significant difference in chronic AST and PWT between both groups. All but two patients in group I preserved SR as the basic rhythm. A stable SR was observed in 10 of 29 patients, intermittent Af/AF was documented in 17 of 29 patients, seven of whom were asymptomatic. There was no significant difference in OUT between group I and II. Hence, sinus rhythm is not a prerequisite of atrial lead implantation. Mapping the Af or AF waves appears to be useful to guide lead placement and to achieve sufficient sensing and pacing conditions after conversion to sinus rhythm.

Introduction: Analysis of endocardial signals obtained from an electrode located in the right atrium as realized in newly designed dual chamber, implantable cardioverter defibrillators might be used to provide additional therapeutic options, such as overdrive pacing or low-energy atrial cardioversion for the treatment of concomitant atrial flutter (AFL) or atrial fibrillation (AF). Therefore, we developed a computer algorithm for discrimination of normal sinus rhythm (NSR), AFL, and AF that may lead to adequate differential therapy of atrial tachyarrhythmias in an automated mode., Methods and Results: During an electrophysiologic study, bipolar endocardial signals from the high right atrium were obtained in 28 patients during sustained AFL or AF and after restoration of NSR. A total of 286 data segments of 5-second duration were recorded (NSR: 96, AFL: 86, AF: 104). Mean atrial cycle length (MCL), standard deviation of mean atrial cycle length (SDCL), and index of irregularity (IR), defined as the ratio between MCL and SDCL, were calculated for each data segment. A cutoff of 315 msec for MCL allowed discrimination of NSR from atrial tachyarrhythmias with 100% sensitivity and specificity. For discrimination of AF from AFL by using SDCL, a cutoff value of 11.5 msec led to a sensitivity of 99% and a specificity of 90%. Best discrimination of AF from AFL was found for the criterion IR > or = 7.5%, resulting in a sensitivity of 100% with a specificity of 95% for AF detection., Conclusion: The investigated algorithm provides discrimination of NSR, AFL, and AF with high sensitivity and specificity. Incorporation of this algorithm in an implantable automated antitachycardia device may lead to adequate differential therapy in patients suffering from spontaneous episodes of AF and AFL.

A biatrial pacemaker was inserted in a 68-year-old female with paroxysmal atrial fibrillation and atrial flutter refractory to antiarrhythmic drugs based on a sick-sinus-syndrome and concomitant interatrial conduction delay. One electrode positioned in the right atrium and another electrode located in the coronary sinus were connected to a dual-chamber pacemaker. The electrode in the right atrium was connected to the atrial channel, the electrode in the coronary sinus to the ventricular channel. The pacemaker was programmed in DDD-mode with an AV-delay of 30 ms. Under a chronic antiarrhythmic medication with 160 mg sotalol per day there was no evidence for recurrent episodes of atrial tachyarrhythmias in the patient's history, 24-h-Holter-ECG, nor in the memory of the pacemaker during a follow-up of 8 months.

Between January and September 1995, 54 consecutive patients (male: 34, age: 66 +/- 10 years) with symptomatic chronic atrial fibrillation (median duration: 4.5 months) were referred for external electrical cardioversion to our hospital. Mean left atrial diameter was 49 +/- 9 mm, heart disease was apparent in 81%. All patients were under antiarrhythmic drugs (class III: 85%). In 49 patients (91%) sinus rhythm was achieved. In five patients atrial fibrillation persisted after delivery of 360 Joules. These five patients were characterized by a significantly higher body weight in comparison to patients with successful external cardioversion. All five patients underwent low energy internal cardioversion the following day: biphasic R-wave synchronous shocks were delivered through catheters positioned in the right atrium and the coronary sinus using stepwise increased energy levels. Internal cardioversion was successful in all patients resistant to external cardioversion: stable sinus rhythm was established at a mean energy level of 13 +/- 6.7 Joules. No complications were observed. During the follow-up, each patient revealed a relapse of symptomatic atrial fibrillation within 2 weeks after internal cardioversion despite antiarrhythmic therapy, whereas only 16 patients (33%) lost sinus rhythm during the same period of time after external cardioversion (p < 0.01). During a mean follow-up of 283 +/- 72 days 21 patients (43%) preserved stable sinus rhythm after external cardioversion. Internal low energy cardioversion seems to be effective and safe in conversion of chronic atrial fibrillation resistant to external cardioversion. The clinical value of this invasive, time- and material-consuming therapy seems to be limited in this setting because of the high early relapse-rate in the investigated patient population. Further clinical studies in a larger cohort of patients are necessary.

Atrial fibrillation (AF), the most common arrhythmia resulting in hospital admission, is a major health problem. The limited efficacy of antiarrhythmic drugs to control this rhythm disorder and their potential proarrhythmic risk led to the development of new techniques to ameliorate the treatment of AF. Transvenous atrial defibrillation using endocardial electrodes has been shown to be effective at low energy levels. An implantable atrial defibrillator could be a potentially valuable treatment option for patients with paroxysmal AF that is medically refractory. Research is currently under way to investigate several critical issues concerning this new therapeutic concept: long-term efficacy, safety, patient's tolerance, and an acceptable cost/benefit ratio. It is well known that AF often complicates the use of the implantable cardioverter-defibrillator (ICD) for ventricular tachyarrhythmias. Therefore, it would seem desirable to implement the capability for atrial defibrillation into current ICD systems. It has been shown that atrial defibrillation, using endocardial lead configurations specifically designed for ventricular defibrillation, is feasible at energies well within the capabilities of current ICD technology. Further research is needed to evaluate if some enhancement of the lead configuration in combination with possible advanced technology could reduce the atrial defibrillation threshold to a well tolerated level as a prerequisite for automated atrial defibrillation, in ICD recipients with concomitant paroxysmal AF.

136 patients were followed after implantation a DDD pacemaker (PM) for a total of 1,919 patient-months (m = 14.1 months/patient). 22/136 patients had one or more episodes of atrial flutter or fibrillation (AF) postoperatively. In 121/136 patients (group A) AF had not been documented before, in 4 it was unknown at the time of implantation, but was verified retrospectively (group B). 11 patients (group C) had a positive history of previous AF. Post implantation 7.4% in group A and 81.8% in group C developed AF. In patients with sick sinus syndrome (SSS) the incidence was 10/37 (27%), in those with AV block (AV) 6/77 (7.8%) and in cases with both SSS and AV 6/22 (27.3%). The first AF episode occurred during the implantation itself (n = 2) or during the hospital course in 9/22 patients (A: 11%, B/C: 64% early attacks), and later on in 13 with a time delay of 1-24 months (m = 8.5, 8 patients) in group A and 2-15 months (m = 6.6, 4 patients) in groups B/C. 2 patients of group C had no AF episodes post implantation. In the individual patient the number of attacks ranged from 1 to 3 (10.4/100 patient-months) in group A and from 1 to 6 (20.1/100 patient-months) in groups B/C. During AF 16/22 patients had a ventricular rate of 110-185, m = 132 bpm. In 6 patients the tachycardia was mediated by the PM and in 10 by fast intrinsic AV conduction. 1 patient with SSS, 2 with SSS + AV (spontaneous ventricular rate less than 45 bpm) and 3 with AV needed ventricular backup-pacing during AF. In 7 patients a total of 15 attacks of atrial flutter could be terminated by atrial overdrive pacing, in 5 of these episodes by temporary high rate A00 stimulation via the implanted pacemaker lead system. Otherwise AF was converted to sinus rhythm by antiarrhythmic drugs. After termination AF often recurred, but only 3 patients developed chronic atrial fibrillation. In 2 patients a ventricular rate greater than 180 bpm during AF reverted the PM to asynchronous mode, a possible cause of ventricular fibrillation in one. No other complications due to the PM itself have been encountered. AF, therefore, common during DDD pacing, even in patients without any AF history before implant. Both the incidence and the recurrence of AF depend on the presence or absence of previous atrial arrhythmias.(ABSTRACT TRUNCATED AT 400 WORDS)