cardiac arrests with low false positive rate. In the future work, more ECG metrics and combination rules will be analyzed. http://dx.doi.org/10.1016/j.jelectrocard.2014.08.019 Monitoring respiration rate in sleep-disordered breathing patients using chest belts or ECG Reza Firoozabadi, Eric D. Helfenbein, Saeed Babaeizadeh Advanced Algorithm Research Center, Philips Healthcare, Andover, MA, USA Background: For patients with suspected sleep-disordered breathing respiration rate (RR) is typically measured using a nasal airflow sensor. Additionally, two belts measure the movement of the chest ribcage and upper abdominal walls. At least one channel of ECG is also monitored. Instead of airflow, which could be considered the gold standard, RR may be computed using belts or ECG-derived respiration (EDR) techniques. In this study we compare the performance of such techniques to using airflow. Methods: Evaluation was done on 24 adult polysomnograms from the publicly available PhysioNet/ucddb database. Subjects were randomly selected from patients referred to a sleep lab for possible diagnosis of sleep apnea. Subjects had no known cardiac disease, autonomic dysfunction, and were not on medication known to interfere with heart rate. ECG was automatically analyzed using the Philips ST/AR algorithm to detect normal and exclude abnormal QRS complexes. The EDR waveform was then constructed by measuring the peak to trough amplitude in each normal QRS complex, and interpolating the measurements using cubic splines. A frequency-domain method was developed to calculate RR in a 30-second sliding window with a 5-second step by finding the fundamental frequency of oscillations. This method was applied to all four waveforms: airflow, EDR, ribcage, and abdominal belts. The RR values computed from airflow, used as reference, were compared with RRs from the other waveforms. Results: A total of 119,698 respiration cycles were analyzed. The average difference in RR from airflow was 0.7 ± 1.8 breaths-per-minute (bpm) for abdominal belt, 1.0 ± 2.4 for ribcage belt, and 1.8 ± 2.7 for EDR. Percentage distributions of RR differences are listed below. Rate from flow minus rate from… (bpm) ≤- 5 [- 5 - 3] [- 3 - 1] [- 1 1] [1 3] [3 5] ≥5 Abdominal belt 1.1 1.4 3.5 86.2 4.5 1.8 1.6 Ribcage belt 2.0 2.1 4.8 82.8 4.4 1.9 2.1 EDR waveform 3.2 3.7 8.1 63.0 9.8 5.8 6.5 As seen, the difference in RR from airflow and every other technique was between [- 1 1] bpm for the majority of cases. Conclusion: RR can accurately be measured using either chest belts or ECG. Although EDR does not perform quite as well as belts, it has the huge advantage of no need for additional hardware for patients whose ECG is being monitored. It may be possible to achieve even higher performance by developing waveform-specific methods. http://dx.doi.org/10.1016/j.jelectrocard.2014.08.020 Reduction of corrected QT interval during the first week after cardioversion of atrial fibrillation to sinus rhythm during sotalol treatment Hanna Lenhoff, Börje Darpö, Mårten Rosenqvist, Mats Frick Department of Cardiology, Karolinska Institutet at Södersjukhuset, Stockholm, Sweden Background: Patients with symptomatic atrial fibrillation are often cardioverted to restore sinus rhythm. To prevent recurrence of atrial fibrillation sotalol is one of the recommended drugs to maintain sinus rhythm. Sotalol prolongs the action potential by blocking Ikr, a potassium ion channel, which can be observed as QTc prolongation on the ECG. Pronounced QTc prolongation is also a biomarker for proarrhythmias and sudden death. Previous studies have indicated that recent cardioversion to sinus rhythm is a risk factor for the development of proarrhythmias with class III anti-arrhythmic drug therapy. The objective of the current study is to assess the dynamicity of QT prolongation after cardioversion to stable sinus rhythm. Aim: Examine if the QTc interval decreases during the week following cardioversion of atrial fibrillation in sotalol-treated patients, compared with metoprolol-treated patients. Methods: This is a clinical study performed at Department of Cardiology at Södersjukhuset in Stockholm. It is prospective and non-randomized with 104 patients on sotalol treatment and an equally sized control group on metoprolol treatment. ECGs were recorded one hour and one week after cardioversion in a standardized manner and triplicate ECGs were recorded in majority of cases. The ECGs were analyzed for QT interval and heart rate using a semiautomated digitizing program by a single observer. The QT interval is corrected for heart rate. Results: Treatment groups were generally similar in baseline characteris- tics, but low ejection fraction and digoxin treatment were more frequent in metoprolol patients. One hour after cardioversion to sinus rhythm, QTc was longer in sotalol patients than in metoprolol patients (466 ms vs. 423 ms; p ≤ 0.05). One week later, QTc interval had decreased 22.8 ms in the sotalol group compared with 1.9 ms in the metoprolol group (p b 0.001). The difference remained significant when controlled for disparities in baseline characteristics and outliers. Mean heart rate was 55 bpm 1 hour and 56 bpm one week after restoration of sinus rhythm in sotalol patients (p = NS) and 58 and 59 bpm respectively in metoprolol patients (p = NS). The difference in heart rate between treatment groups was significant. Conclusion: The QTc interval was significantly reduced during the week following cardioversion in patients treated with sotalol, an effect that was not seen in patients on metoprolol treatment. The underlying mechanism for this reduction is not known. The finding may have implications for the treatment and dosing of antiarrhythmic therapy after cardioversion, a time period known to be arrhythmic vulnerable. http://dx.doi.org/10.1016/j.jelectrocard.2014.08.021 Analysis of arrhythmia episodes stored in ICDs with implantable cardioverter-defibrillator lead with a floating atrial sensing dipole A. Schirdewan a , D. Schmitz b , T. Konorza c , C. Wende d , J. Olague de Ros e , D. Brala a , O. Göing a a Arrhythmia & Ablation Center, Sana Klinikum Lichtenberg, Berlin b Elisabeth Hospital, Essen c West German Heart Center, Essen d Marien Hospital, Papenburg, Germany e Hospital University La FE Valencia, Arrhythmias Service, Spain Background: The multicenter, international, nonrandomized study evalu- ated the clinical efficacy and safety of a single-ICD lead system with atrial sensing capabilities (BIOTRONIK). We investigated the arrhythmia episodes stored during the study and transmitted by telemonitoring and the therapeutic interventions by the device as well as physicians possibilities to reduce inappropriate therapies. Methods: The study enrolled 116 patients. All were treated with a single- lead implantable cardioverter-defibrillator (ICD), with a floating dipole and a home monitoring function. We evaluated arrhythmia events during a 6- month follow-up. Results: Two hundred fifty analyzable tachyarrhythmia detections were documented for 101 patients, 162 detections induced at implantation in 98 patients and 88 spontaneous detections during the follow-up period in 23 patients. Fifteen were VF or VT episodes; they were adequately detected and treated by the ICD. The remaining 73 spontaneous detections were triggered by SVT, sinus tachycardia, T-wave oversensing, and electrocau- tery surgery. In 54 of these detections, ICD therapy was withheld appropriately. In the remaining 19 detections in 9 patients, inappropriate antitachycardia pacing therapy was delivered. Two patients presented ISCE Poster Session I / Journal of Electrocardiology 47 (2014) 907–909 908