Atrial fibrillation storms.

Evolving pacemaker and device technology now allows the onset pattern of arrhythmias to be identified. It is recognised that some cardiac arrhythmias have a circadian pattern of onset and that ventricular arrhythmias can occur in clusters of electrical storms. The long-term follow-up of patients with an atrial defibrillator suggests that in some patients persistent atrial fibrillation recurrences are not random, but can occur in clusters of 'atrial fibrillation storms'. A case report is used to demonstrate this newly recognised phenomenon.

Quality of life after use of the patient activated atrial defibrillator.

The aim of the study was to evaluate the effects of long-term use of the patient-activated atrial defibrillator for recurrent persistent atrial fibrillation (AF) on quality of life (QOL). Fifteen patients were implanted with the Medtronic Jewel AF 7250 device (dual chamber atrial and ventricular defibrillator) for AF only. AF recurrences were treated by out-of-hospital patient-activated atrial defibrillation shocks following the self-administration of oral sedation. QOL was assessed at pre-implant and up to one year with SF36, symptom checklist and HADS questionnaires. A total of 238 (median 10) out-of-hospital patient-activated atrial defibrillation shocks were performed. The SF36 demonstrated a trend toward improvement over the 12-month period compared with baseline values. There was no significant change in the symptom frequency or severity scores. Pre-implant levels of both anxiety and depression were within the predefined range of normality (6 +/- 3 and 3 +/- 2, respectively) and no significant change was seen at 6 months (5 +/- 4 and 3 +/- 3) or 12 months post implant (5 +/- 4 and 2 +/- 2, respectively). After one year of follow-up, 13 (87%) patients said they would have the device implanted again (two were undecided). The study demonstrates that patient-activated atrial defibrillation is a well tolerated therapeutic strategy for maintaining sinus rhythm.

The effect of endocardial defibrillator shocks on basic atrial electrophysiology in man. Is post cardioversion atrial electrical 'remodelling' artefact?

AIMS: To determine the effect of an endocardial DC shock on the basic electrophysiology of the human atrium if delivered in sinus rhythm. METHODS AND RESULTS: A 5J endocardial R wave synchronized DC shock was delivered in 10 patients in stable sinus rhythm during ICD implantation for ventricular arrhythmias. There was no prior history of atrial fibrillation. Monophasic action potential duration (APD) and atrial effective refractory periods (AERP) were evaluated before, 1 min post DC shock, and 15 min post shock. These parameters were assessed at basic cycle lengths and at atrial paced cycle lengths of 600 ms and 400 ms at two right atrial sites; mid lateral right atrial wall (MRLA) and the right atrial appendage (RAA). There were no significant differences in APD 90, AERP or atrial refractory dispersion at any site or drive cycle length before, immediately after or 15 min after shock delivery. CONCLUSIONS: There are no significant changes in basic electrophysiological parameters following a DC shock delivered in sinus rhythm in patients with no prior history of atrial fibrillation. This suggests that atrial electrical remodelling occurs as a result of atrial fibrillation and is unrelated to shock artefact.

Effect of atrial antitachycardia pacing treatments in patients with an atrial defibrillator: randomised study comparing subthreshold and nominal pacing outputs.

OBJECTIVE: To assess the true efficacy of antitachycardia pacing on spontaneous persistent atrial fibrillation in patients with an implanted atrial defibrillator, by comparing the effects of nominal pacing treatment with subthreshold pacing treatment. DESIGN: The effects of antitachycardia pacing and burst 50 Hz atrial pacing on spontaneous atrial arrhythmias were evaluated six months after implantation of a Medtronic Jewel AF((R)) atrial defibrillator. SETTING: Cardiology department in a district general hospital. PATIENTS: 15 patients with persistent atrial fibrillation. INTERVENTIONS: Patients were randomised to either "nominal" output pacing treatment or surface ECG and endocardial electrogram proven subthreshold "sham" pacing treatment for three months, and then crossed over to the alternative treatment for a further three months. RESULTS: During the nominal output phase, 31 episodes of atrial fibrillation were treated with 53 bursts of 50 Hz pacing, 98 sequences of ramp atrial pacing, and 61 sequences of burst atrial pacing. Atrial fibrillation was not pace terminated during any episode. Thirty one episodes of atrial tachycardia were treated with 19 bursts of 50 Hz atrial pacing, 103 sequences of ramp atrial pacing, and 38 sequences of burst atrial pacing. Termination of atrial tachycardia was observed in 17 episodes. During the "sham" pacing period, no episodes were terminated by any pacing treatment. CONCLUSION: Atrial antitachycardia pacing treatments are ineffective at terminating persistent atrial fibrillation but may be useful in terminating episodes of atrial tachycardia or flutter, thus reducing the burden of arrhythmia.

What is the optimal electrode configuration for atrial defibrillators in man?

AIMS: To compare the atrial defibrillation threshold (DFT) for two electrode configurations in patients with drug refractory persistent atrial fibrillation (AF). METHODS AND RESULTS: 11 patients, 73% male, mean age 60.9 (range 38 to 83), underwent implantation of a Medtronic Jewel AF dual chamber defibrillator (model 7250). A step-up atrial DFT was performed in a randomized sequence for two electrode configurations: (1) Right atrial to distal coronary sinus electrode (RA > CS) and (2) defibrillator can to right ventricular and right atrial electrodes (CAN > RV + RA). The RA > CS configuration restored SR in 10 patients (91%). The CAN > RA + RV configuration restored SR in four patients (36%). The mean atrial DFT was significantly lower for the RA > CS than CAN > RA + RV configuration (10 +/- 7 Joules vs 25 +/- 6 Joules), P < 0.01. At 3 months post implantation, AF was reinduced and the protocol was repeated for the optimal electrode configuration. There was no significant difference in the atrial DFT compared with that at implant. CONCLUSION: The right atrium to coronary sinus electrode configuration significantly reduces the atrial DFT. The atrial DFT also remains stable at 3 months post-implantation. Patients with persistent AF undergoing insertion of an atrial defibrillator should have a coronary sinus electrode implanted.

Importance of rate control or rate regulation for improving exercise capacity and quality of life in patients with permanent atrial fibrillation and normal left ventricular function: a randomised controlled study.

OBJECTIVE: To determine the importance of rhythm regulation or rate control in patients with permanent atrial fibrillation (AF) and normal left ventricular function. PATIENTS AND INTERVENTIONS: Thirty six patients with a mixed fast and slow ventricular response rate to their AF were randomised to either His bundle ablation (HBA) and VVIR pacemaker (HBA group) or VVI pacemaker and atrioventricular modifying drugs (Med group). Outcomes assessed at one, three, six, and 12 months included exercise duration and quality of life. RESULTS: Exercise duration significantly improved from baseline in both groups. There was no difference in outcome between the groups (Med +40% v HBA +20%, p = NS). The heart rate profile on exercise was similarly slowed in both groups compared to baseline. Quality of life significantly improved in both treatment arms for the modified Karolinska questionnaire (KQ) (Med +50% v HBA +50%, p = NS) and the Nottingham health profile (NHP) (Med +40% v HBA +20%, p = NS). However, for the individual symptom scores of each questionnaire more were improved in the Med group (KQ-Med 6 improved v HBA 4, NHP-Med 3 v HBA 1). Left ventricular function was equally preserved by both treatments during follow up. CONCLUSION: In these patients control of ventricular response rate with either HBA + VVIR pacemaker or atrioventricular modifying drugs + VVI pacemaker will lead to a significant improvement in exercise duration and quality of life. Rhythm regulation by HBA did not confer additional benefit, suggesting rate control alone is necessary for the successful symptomatic treatment of these patients in permanent AF.