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Objectives. The objectives of this study were 1) to evaluate the effect of different right atrial electrode locations on the efficacy of low energy transvenous defibrillation with an implantable lead system; and 2) to qualitate and quantify the discomfort from atrial defibrillation shocks delivered by a clinically relevant method.Background. Biatrial shocks result in the lowest thresholds for transvenous atrial defibrillation, but the optimal right atrial and coronary sinus electrode locations for defibrillation efficacy in humans have not been defined.Methods. Twenty-eight patients (17 men, 11 women) with chronic atrial fibrillation (AF) (lasting ≥1 month) were studied. Transvenous atrial defibrillation was performed by delivering R wave-synchronized biphasic shocks with incremental shock levels (from 180 to 400 V in steps of 40 V). Different electrode location combinations were used and tested randomly: the anterolateral, inferomedial right atrium or high right atrial appendage to the distal coronary sinus. Defibrillation thresholds were defined in duplicate by using the step-up protocol. Pain perception of shock delivery was assessed by using a purpose-designed questionnaire; sedation was given when the shock level was unacceptable (tolerability threshold).Results. Sinus rhythm was restored in 26 of 28 patients by using at least one of the right atrial electrode locations tested. The conversion rate with the anterolateral right atrial location (21 [81%] of 26) was higher than that with the inferomedial right atrial location (8 [50%] of 16, p < 0.05) but similar to that with the high right atrial appendage location (16 [89%] of 18, p > 0.05). The mean defibrillation thresholds for the high right atrial appendage, anterolateral right atrium and inferomedial right atrium were all significantly different with respect to energy (3.9 ± 1.8 J vs. 4.6 ± 1.8 J vs. 6.0 ± 1.7 J, respectively, p < 0.05) and voltage (317 ± 77 V vs. 348 ± 70 V vs. 396 ± 66 V, respectively, p < 0.05). Patients tolerated a mean of 3.4 ± 2 shocks with a tolerability threshold of 255 ± 60 V, 2.5 ± 1.3 J.Conclusions. Low energy transvenous defibrillation with an implantable defibrillation lead system is an effective treatment for AF. Most patients can tolerate two to three shocks, and, when the starting shock level (180 V) is close to the defibrillation threshold, they can tolerate on average a shock level of 260 V without sedation. Electrodes should be positioned in the distal coronary sinus and in the high right atrial appendage to achieve the lowest defibrillation threshold, although other locations may be suitable for certain patients.

Background Atrial fibrillation (AF) is associated with impaired exercise capacity. Oxygen uptake ( V ˙ o 2 ) kinetics determines cardiopulmonary performance during submaximal exercise, which may be impaired in patients with AF. Aim To study oxygen kinetics and cardiopulmonary performance in patients with AF without structural heart disease and the effects of oral sotalol on these parameters. Patients and methods Twenty consecutive patients (mean age, 56±8 years) with chronic AF were recruited. The protocol design was a randomized, single-blinded, and placebo-controlled trial. Patients received either sotalol or placebo for an 8-week study period, and the alternative treatment in the subsequent period. Cardiopulmonary function tests using constant workload and incremental workload protocols were performed at the end of each phase. Sixteen age-matched normal subjects were included as control subjects. Results During constant submaximal exercise, patients with AF had a larger oxygen deficit (425±140 mL vs 289±80 mL in normal subjects; p

We assessed the relationship between the hemodynamic changes and shock intensity in transvenous atrial defibrillation for chronic AF. The correlation between the clinical profile and atrial DFT and the factors predicting maintenance of SR after successful defibrillation were also investigated. Atrial defibrillation using entirely transvenous leads has been investigated as an alternative means of managing patients with AF. However, the hemodynamic consequence of this technique and the clinical factors predicting defibrillation efficacy have not been evaluated. Thirty-seven patients with chronic AF (4 weeks to 60 months) underwent transvenous atrial defibrillation. Defibrillation was performed by delivering R wave synchronized, biphasic (3/3 ms) shocks with step-up voltages (20-400 V) between defibrillation catheters in the anterolateral right atrium and the distal coronary sinus. Clinical profile of the patients, the DFT, arterial blood pressure, and RR interval during defibrillation and the 6-month recurrence rate were determined. SR was restored in 33 (89%) of 37 patients and the DFT was 3.7 +/- 1.4 J (317 +/- 58 V). Transvenous atrial defibrillation resulted in a mild reduction in blood pressure (6 +/- 10 mmHg), but substantial prolongation of longest postshock RR intervals (507 +/- 546 ms), which were significantly related to the shock intensity (r = 0.5, P < 0.001). There was no ventricular proarrhythmia. The patients' age, body weight, duration of AF, left atrial diameter, and ejection fraction were not related to the success of defibrillation, not the 6-month maintenance rate of SR (39%). However, the patients' age was related to DFT. Apart from transient reduction in blood pressure and shock related pauses that may require backup pacing, transvenous biatrial defibrillation was a highly effective and well-tolerated technique. The absence of clinical determinant for successful defibrillation suggests that restoring SR by transvenous atrial defibrillation could be attempted in most patients with chronic AF.

Low energy biatrial shock is an effective means of restoring sinus rhythm in patients with atrial fibrillation (AF). Ventricular proarrhythmia is avoided provided that shocks are well synchronized to R waves that are not at closely coupled intervals or preceded by long-short cycles. Based on these principles, an implantable atrial defibrillator has been developed and was implanted in three patients with drug refractory paroxysmal AF. The device detects AF via an actively fixed right atrial and a self-retaining coronary sinus defibrillating leads, and delivers 3/3 ms biphasic shocks up to 300 V synchronized to the R wave. The mean implant threshold (ED50) was 195 V (1.8 J). and minimum voltage at conversion during follow-up assessments at 1, 3, and 6 months were 260 V, 2.5 J. 250 V, 2.3 J, and 300 V, 3.0 J respectively. Detection of AF was 100% specific and shocks were 100% synchronized, although only a proportion of synchronized R waves were considered suitable for shock delivery primarily because of closely coupled cycles. Three patients had 9 spontaneous AF episodes, 8/9 (89%) successfully defibrillated by shocks of 260-300 V. Sedation was not used in 4 out of 9 (45%) episodes. Backup ventricular pacing was initiated by the device in 6 out of (67%) episodes. One patient had more frequent AF after lead placement, which subsided after a change of medication. There was no ventricular proarrhythmia. It is concluded that an implantable atrial defibrillator is a viable therapy for selected patients with paroxysmal AF. The device is capable of accurate AF detection, R wave synchronization and ventricular support pacing after successful defibrillation of AF.

To determine the prevalence of palpitations, cardiac arrhythmias and associated cardiovascular risk factors in an ambulatory elderly population, 1454 ambulatory elderly people (219 men and 1235 women, age range 60-94 years) were assessed in a territory-wide health survey including anthropometric measurements, biochemical blood tests, questionnaire interview and resting surface ECG examination. Prevalence of palpitations and ECG abnormalities were determined and correlated with coronary risk factors and biochemical blood tests. Palpitations were present in 121 subjects (8.3%) and cardiac arrhythmias were found in 183 subjects (12.6%). Conduction abnormalities and sinus bradycardia were the commonest findings (9.8%). Premature beats (atrial 2.3%; ventricular 1%) were the next most frequent arrhythmia. Atrial fibrillation was the commonest sustained arrhythmia that was present in 19 subjects (1.3%). Compared with those without arrhythmia on ECG, people with arrhythmias were predominantly males and were older (72 +/- 8 years vs. 70 +/- 6 years, P0.05), had a higher prevalence of smoking (12.9% vs. 5%, P0.05) and coronary heart disease (30.7% vs. 11.4%, P0.05). The prevalence of palpitations between subjects with documented arrhythmias (excluding conduction disturbance) and those without arrhythmias on surface ECG was similar (9% vs. 7.7%, P = N.S.). We conclude that cardiac arrhythmias are common in the elderly and are often asymptomatic. Subjects with ECG documented arrhythmias are more common in males, and are associated with smoking and ischaemic heart disease. Palpitation was a frequent complaint in the ambulatory elderly with no bearing on arrhythmias recorded on resting ECG.

The aim of this study was to evaluate the cardiovascular autonomic function and vasovagal reaction in patients with paroxysmal atrial fibrillation without significant structural heart disease. Twenty-eight patients with paroxysmal atrial fibrillation (9 patients were categorized to have autonomic-mediated atrial fibrillation while atrial fibrillation in other patients was nonautonomic mediated) and 19 normal control subjects were recruited. Cardiovascular autonomic function tests included measuring heart rate response to standing, deep breathing, Valsalva maneuver, baroreflex sensitivity, 24-hour heart rate variability, and also head-up tilt test. Compared with normal subjects, no significant autonomic dysfunction was found in patients with autonomic-mediated and nonautonomic-mediated atrial fibrillation. All subjects had negative baseline tilt test. With isoproterenol provocation, six patients developed atrial fibrillation. Four of 9 patients and 3 of 19 patients with autonomic mediated and nonautonomic mediated atrial fibrillation had a positive tilt test respectively, while none occurred in the controls. A significant percentage (32%) of patients with paroxysmal atrial fibrillation had episodes of atrial fibrillation provoked by changes in autonomic tone, although there was no underlying abnormal cardiac autonomic function nor sympathetic-parasympathetic imbalance. A heightened susceptibility to vasovagal cardiovascular response may have important implications on the occurrence and symptomatology of patients with paroxysmal atrial fibrillation.

The comparative efficacy and safety of transvenous defibrillation for acute and chronic AF and the effect of antiarrhythmic agents on this therapy have not been evaluated. Transvenous atrial defibrillation was performed in 25 patients with chronic AF and 13 patients with acute AF by delivering R wave synchronized, biphasic shocks between the right atrium and coronary sinus. The lowest energy and voltage resulting in successful defibrillation were considered to be atrial defibrillation threshold (ADFT). Intravenous sotalol (1.5 mg/kg) was then given over 15 minutes and ADFT was determined again. The mean ADFT was 1.5 J and 3.6 J for acute and chronic AF, respectively, and the threshold was highly reproducible. Sotalol reduced ADFT in patients with acute AF while the reduction in chronic AF group was not significant. There was no significant increase in creatinine kinase nor reduction in blood pressure, but prolonged pause after successful defibrillation required ventricular supporting pacing. We conclude that transvenous atrial defibrillation is a safe and effective means for defibrillating both acute and chronic AF. ADFT was lower in acute AF than in chronic AF. ADFT was highly reproducible during repeated defibrillation. Sotalol reduced ADFT in acute AF and to a lesser extent in chronic AF, and increased the defibrillation success rate. Ventricular pacing will often be required because of prolonged pause after successful defibrillation.

Two hundred and ninety one patients admitted with atrial fibrillation through the emergency room of a regional hospital in the year 1993 were reviewed to evaluate the presenting features and in-hospital treatment of patients with symptomatic atrial fibrillation. The incidence of atrial fibrillation increased with age (mean age was 73 ± 12 years) and the ratio of female to male was 1.8:1. The commonest presenting features were palpitation (42.3%), dyspnoea (38.1%) and heart failure (16.4%). The most frequently associated cardiac conditions were hypertension (28.9%), atherosclerotic cardiovascular disease (24.7%) and rheumatic heart disease (17.5%). Pulmonary diseases (18.6%), diabetes mellitus (12.7%) and thyrotoxicosis (6.2%) were the principal associated non-cardiac conditions. Thromboembolic complications were found in 15 patients at presentation (5.2%). Cardiac enzyme assessment was investigated in two thirds of the patients (68.1%), while thyroid function test (59.5%) and echocardiography (29.6%) were less commonly investigated. Digoxin was still the most popular drug used for ventricular rate control, and cardioversion was performed in only 6.9% of patients. Antithrombotic therapy was used in 5.8% of patients only although it was clinically indicated in more than half of the patients (52%). Contraindications of anticoagulation were found in 23 patients (7.9%), including a history of gastrointestinal or cerebrovascular bleeding, active bleeding, chronic renal failure and poor drug compliance. The mean hospital stay was 5 ± 4 days, compared to a mean stay of 2.7 days for other medical patients. Fourteen patients (4.8%) died during hospitalisation. The causes of death were septicaemia in 6 patients (42.9%) and cerebrovascular events in 4 patients (28.6%). We conclude that atrial fibrillation is predominately a disease of the elderly female, with significant associated medical problems and a longer hospital stay. There is a general reluctance for using cardioversion and antithrombotic treatment.

Objectives. This prospective, multicenter trial was aimed at defining efficacy and safety of low energy shocks during atrial fibrillation in a diverse cohort of patients.Background. Experimental studies in sheep and preliminary data in humans have suggested that low energy internal shocks delivered between right atrial and coronary sinus electrode catheters may terminate atrial fibrillation.Methods. Biphasic 3/3-ms R wave synchronous shocks were delivered between two electrode catheters in the right atrium and coronary sinus. The defibrillation protocol started with a test shock of 20 V, and shocks increased in 40-V steps until restoration of sinus rhythm or a maximum of 400 V. Shock delivery was withheld after short RR intervals. In 141 patients with atrial fibrillation, the protocol was carried out under sedation in case the shock was associated with discomfort. The atrial arrhythmia was paroxysmal (≤7 days) in 50 patients, chronic (>30 days) in 53, intermediate (>7 days, ≤30 days) in 18 and induced in 20. Underlying heart disease was present in 88 patients (62%).Results. Paroxysmal atrial fibrillation was successfully terminated in 46 (92%) of 50 patients, chronic atrial fibrillation in 37 (70%) of 53, intermediate in 16 (89%) of 18 and induced in 16 (80%) of 20. Mean conversion threshold was 1.8 J (213 V) in the induced group, 2.0 J (229 V) in the paroxysmal group, 2.8 J (272 V) in the intermediate group and 3.6 J (311 V) in the chronic group. The conversion voltage was significantly (p < 0.001) higher in the chronic group than in the other groups of atrial fibrillation and increased significantly with the duration of atrial fibrillation and with left atrial size (p < 0.05). Of 1,779 R wave synchronized shocks delivered with a mean (±SD) preceding RR interval of 676 ± 149 ms, no ventricular arrhythmia was induced. The latter may occur after unsynchronized shocks.Conclusions. Low energy transvenous shocks in patients with atrial fibrillation are effective and safe, provided that shocks are properly synchronized to R waves with preceding RR intervals that meet appropriate cycle length criteria. This study provides data that may be useful in the development of an implanted atrial defibrillator.(J Am Coll Cardiol 1997;29:750–5)