Nikolay Shlevkov

Induction of atrial fibrillation in mice by rapid transesophageal atrial pacing.

Abstract.Objective: Atrial fibrillation (AF) as an “indicator arrhythmia” for enhanced atrial vulnerability in mouse hearts has not yet been systematically examined. We therefore evaluated a transesophageal rapid atrial stimulation protocol for the induction of AF in C57Bl/6 mice. Methods: 40 C57Bl/6 mice (19 female and 21 male; 5.2 ± 2.1 months; 18 – 27 g) were examined by closed chest transesophageal atrial stimulation. Baseline ECG and electrophysiological parameters, AF-inducing stimulation cycle length (CL) and AF duration were analyzed. Results: The surface ECG demonstrated a significantly faster heart rate in female mice (R-R: 138.7 ± 19.9 ms versus 150.5 ± 15.7 ms, P < 0.05). AF was inducible in 90 % of the population and not inducible in 4 mice, all female (21 % in this subgroup). Mean induction CL was 27.4 ± 7.3 ms. Mean AF duration was 26.9 ± 42.6 s before spontaneous termination. In a subgroup of 4 female and 4 male mice (mean age 7.5 months), successive testing of AF induction showed a range of higher susceptibility to AF at stimulus amplitudes of 3.0 – 4.0 mA and stimulation CLs between 15 – 25 ms. AF induction was observed to be constantly reproducible in the individual animals. No correlation to pacing stimulus length and amplitude was found. Conclusions: This study demonstrates that it is possible to reproducibly induce self-terminating AF and supraventricular arrhythmias in mice by transesophageal atrial burst stimulation. The presented method allowing serial testings of the same animal can be a useful tool in further investigations with transgenic mice and might be helpful in the characterization of underlying genetic or molecular mechanisms of AF.

Impact of age and basic heart rate on heart rate turbulence in healthy persons.

Postextrasystolic acceleration of heart rate (HR), known as HR turbulence (HRT) is attenuated in patients with coronary artery disease at increased risk of adverse events. The influence of age and basic HR on HRT have not been evaluated in a large cohort of persons. In 95 healthy individuals, HRT onset (TO) and slope (TS) were calculated from 24‐hour ambulatory electrocardiograms, as well as the turbulence timing (TT). Gender specific differences in TO and TS were compared in simple, linear, weighted regression model. The influence of age and the basic HR preceding ventricular premature contractions on HRT were examined. We found that, in men and women, TO decreases as basic HR increases (P < 0.01). In contrast, in men, TS decreased as basic HR increases, whereas in women, basic HR influenced TS only slightly (P < 0.01). A multiple, linear regression model revealed a decrease in HRT with increasing age in men. In conclusion, physiological acceleration of the HR within the first 11 beats after premature ventricular complex (VPC) was observed in >75% of healthy individuals. An accelerating HR preceding the VPC influenced HRT in men. An increasing age was associated with a decrease in HRT in men and a decrease in TO in women. These results illustrate the importance of physiological modulations of HRT when used for risk stratification, especially in older populations.

Influence of the point of origin on heart rate turbulence after stimulated ventricular and atrial premature beats

Abstract.Background:Heart rate turbulence (HRT) is a new and auspicious parameter for risk stratification in patients suffering from structural heart disease. The HRT parameters onset (TO) and slope (TS) are derived from Holter ECGs. Only a few studies have evaluated physiologic properties like age or prematurity of the ventricular beat on HRT. Until now, to our knowledge, little is known about the influence of the point of origin of the premature beat on HRT. Therefore, we conducted a study consisting of 25 patients (pts) with premature beats generating from 2 different sites in the atrium and ventricle.Methods:During an electrophysiologic study, premature extra beats were induced. The high right atrium (HRA) and the lateral part of the coronary sinus (CS) represented the atrial pacing sites, while the right ventricular apex (RVAP) and right ventricular outflow tract (RVOT) represented the ventricular pacing sites. Prematurity started at 450 ms and was decreased to the refractoriness of each site. TO and TS were computed and correlated to the site of origin and the coupling interval (CI).Results:Atrial TO was positive in 9 pts (HRA) and 7 (CS) as well as ventricular TO in 2 pts, respectively. TO induced in CS correlated with the CI (r = –0.50, p < 0.05). TS was negative, independent of the site of origin. Atrial TS showed no correlation with the CI. TO generated from both ventricular sites was positive in 2 pts. TO from RVAP correlated with the CI (r = –0.81, p < 0.005), but not with RVOT. TS from both ventricular sites exhibited no correlation with the pacing site, but correlated with themselves (r = –0.69, p < 0.03).Conclusion:The site of origin of the premature beat exhibits no influence on heart rate turbulence slope. The prematurity of the extra beat correlates with turbulence onset, but not with slope. Finally, the site of origin revealed no influence on HRT slope. Therefore, the calculation of heart rate turbulence derived from extra beats extracted from Holter ECG is reliable.

Advanced Pacemaker Diagnostic Features in the Characterization of Atrial Fibrillation: Impact on Preventive Pacing Algorithms

YANG, A., et al.: Advanced Pacemaker Diagnostic Features in the Characterization of Atrial Fibrillation: Impact on Preventive Pacing Algorithms. Pacing algorithms to prevent PAF are mainly based on the suppression of premature atrial complexes (PACs), which play an important role in its initiation. In contrast to 24‐hour ambulatory electrocardiograms, advanced pacemaker (PM) diagnostic features are capable of recording AF episodes during long follow‐up periods and of characterizing AF in a detailed fashion. For the specific use of these algorithms, a detailed characterization of AF was performed in 91 dual chamber PM recipients with histories of AF. Fifteen patients with episodes of oversensing due to far‐field signals or frequent episodes of “2:1‐undersensing” of atrial flutter were excluded. The remaining 76 patients had high recurrence rates of AF (median 0.8 episodes/day), however, the majority of episodes lasted <7 minutes. Despite frequent PACs (median 10.8/hour) during sinus rhythm, a median of 66.4% of the AF episodes were preceded by <2 PACs/min before onset. In conclusion, frequent, short‐lived AF episodes seem best suited for AF preventive pacing therapies. However, the small number of PACs preceding many AF episodes may limit the efficacy of PAC suppressing algorithms. (PACE 2003; 26[Pt. II]:310–313)

Amiodarone-associated 'torsade de pointes' Relevance of concomitant cardiovascular medication in a patient with atrial fibrillation and structural heart disease

Eine 69-jährige Patientin mit koronarer Dreigefäßerkrankung, Z. n. Hinterwandinfarkt und paroxysmalen Vorhofflimmern wurde bei computertomographisch gesichertem Occipitalinfarkt in einer neurologischen Klinik stationär aufgenommen. Unter der auswärts eingeleiteten antiarrhythmischen Medikation mit Amiodaron (600 mg p. o. tgl.) in Kombination mit beta-Acetyldigoxin 0,1 mg und Bisoprolol 1,25 mg tgl. wurde eine signifikante QT-Zeit-Verlängerung (maximal 700 ms; QTc: 614 ms) dokumentiert. Im weiteren Verlauf traten rezidivierend selbst-terminierende „Torsade de pointes“-Tachykardien auf, die sich aus normofrequentem und bradykardem Sinusrhythmus heraus entwickelten. Die Kasuistik dokumentiert die Induktion einer Amiodaron-assoziierten ventrikulären Tachykardie unter Kombinationstherapie mit einem β-Blocker sowie einem Digitalispräparat bei einer Patientin mit Vorhofflimmern und struktureller Herzerkrankung. Dies weist auf ein erhöhtes proarrhythmogenes Risiko dieser Kombinationstherapie hin. A 69 year old female with history of coronary heart disease, myocardial infarction and paroxysmal atrial fibrillation suffered from occipital apoplexy. Under treatment with amiodarone 600 mg daily and concomitant medication with beta-acetyldigoxine (0.1 mg daily) and bisoprolole (1.25 mg daily), significant QT-prolongation (max. 700 ms; QTc: 614 ms) could be documented. Out of normofrequent sinus rhythm but as well out of bradycardia, the patient developed repetitive short-lasting “torsade de pointes” tachycardias (320 bpm) which terminated spontaneously. Serum electrolytes, plasma levels of digoxine (1.76 ng/ml) and amiodarone (1.9 mcg/ml) were within therapeutic range. This case report is the first to describe induction of amiodarone-associated “torsade de pointes” tachycardia during concomitant beta-blocker and digitalis medication in a patient with atrial fibrillation and structural heart disease. This points towards an elevated risk for proarrhythmia under this triple therapy.

Pharmacological and ablative hybrid therapy of atrial fibrillation. Long-term effect on quality of life and arrhythmia-related symptoms.

Die pharmakologische und ablative Hybrid- Therapie von Vorhofflimmern (VF) beinhaltet die Radiofrequenzablation von Antiarrhythmika-induziertem Vorhofflattern (VFl) und mit nachfolgender Fortsetzung der antiarrhythmischen Medikation. Ziel dieser Arbeit war es, die Langzeiteffektivität dieser Therapie auf VF-Symptomen und Lebensqualität zu evaluieren. Bei 46 Patienten mit symptomatischem VF konnte eine Isthmus-Ablation von Antiarrhythmika-induziertem Vorhofflattern durchgeführt werden. Mittels SF-36- und Symptoms Checklist-Frequency and Severity Scale-Fragebogen und der Auswertung von EKGs wurde die VF-Charakteristik, die VF-bezogenen Symptomen und die Lebensqualität vor und nach Ablation retrospektiv evaluiert. 63% der Patienten zeigten während der Nachbeobachtungszeit von 22,4±11,6 Monaten ein VF-Rezidiv. Eine signifikante Reduktion der Anzahl sowie der Dauer der Episoden konnte in 82,6 bzw. 76% der Patienten beobachtet werden. Jede Kategorie des SF-36 zeigte eine signifikante Verbesserung, die VF-bezogenen Symptome verminderten sich signifikant bei 65,8% der Patienten. Mittels einer pharmakologischen und ablativen Hybrid-Therapie konnte eine signifikante Reduktion der Anzahl und Dauer der symptomatischen VF-Episoden, der VF-bezogenen Beschwerden und eine signifikante Verbesserung der Lebensqualität erzielt werden. The pharmacological and ablative hybrid therapy of atrial fibrillation (AF) consists of radiofrequency catheter ablation of antiarrhythmic drug-induced typical atrial flutter (AFl) and continuation of drug therapy. The purpose of this study was to determine the effect of this therapy on AF symptoms and quality of life (QoL). Forty-six patients were monitored after isthmus-ablation of drug-induced typical AFl and continuation of their antiarrhythmic drug treatment over a mean follow-up of 22.4±11.6 months. AF characteristics, symptoms and QoL before and after ablation were evaluated by the SF-36 question- naire, the Symptoms Checklist-Frequency and Severity Scale and the analysis of ECG recordings. 63% of patients demonstrated recurrences of AF. However, the frequency and duration of symptomatic episodes significantly decreased in 82.6 and 76% of patients. All categories of the SF-36 improved significantly and the AF symptomatology showed a relevant attenuation in 65.8% of the study population. The pharmacological and ablative hybrid therapy significantly reduced the mean number and the duration of symptomatic AF episodes as well as AF-correlated symptoms and was associated with significant QoL improvement.

Pharmacological and ablative hybrid therapy of atrial fibrillation

Die pharmakologische und ablative Hybrid- Therapie von Vorhofflimmern (VF) beinhaltet die Radiofrequenzablation von Antiarrhythmika-induziertem Vorhofflattern (VFl) und mit nachfolgender Fortsetzung der antiarrhythmischen Medikation. Ziel dieser Arbeit war es, die Langzeiteffektivität dieser Therapie auf VF-Symptomen und Lebensqualität zu evaluieren. Bei 46 Patienten mit symptomatischem VF konnte eine Isthmus-Ablation von Antiarrhythmika-induziertem Vorhofflattern durchgeführt werden. Mittels SF-36- und Symptoms Checklist-Frequency and Severity Scale-Fragebogen und der Auswertung von EKGs wurde die VF-Charakteristik, die VF-bezogenen Symptomen und die Lebensqualität vor und nach Ablation retrospektiv evaluiert. 63% der Patienten zeigten während der Nachbeobachtungszeit von 22,4±11,6 Monaten ein VF-Rezidiv. Eine signifikante Reduktion der Anzahl sowie der Dauer der Episoden konnte in 82,6 bzw. 76% der Patienten beobachtet werden. Jede Kategorie des SF-36 zeigte eine signifikante Verbesserung, die VF-bezogenen Symptome verminderten sich signifikant bei 65,8% der Patienten. Mittels einer pharmakologischen und ablativen Hybrid-Therapie konnte eine signifikante Reduktion der Anzahl und Dauer der symptomatischen VF-Episoden, der VF-bezogenen Beschwerden und eine signifikante Verbesserung der Lebensqualität erzielt werden. The pharmacological and ablative hybrid therapy of atrial fibrillation (AF) consists of radiofrequency catheter ablation of antiarrhythmic drug-induced typical atrial flutter (AFl) and continuation of drug therapy. The purpose of this study was to determine the effect of this therapy on AF symptoms and quality of life (QoL). Forty-six patients were monitored after isthmus-ablation of drug-induced typical AFl and continuation of their antiarrhythmic drug treatment over a mean follow-up of 22.4±11.6 months. AF characteristics, symptoms and QoL before and after ablation were evaluated by the SF-36 question- naire, the Symptoms Checklist-Frequency and Severity Scale and the analysis of ECG recordings. 63% of patients demonstrated recurrences of AF. However, the frequency and duration of symptomatic episodes significantly decreased in 82.6 and 76% of patients. All categories of the SF-36 improved significantly and the AF symptomatology showed a relevant attenuation in 65.8% of the study population. The pharmacological and ablative hybrid therapy significantly reduced the mean number and the duration of symptomatic AF episodes as well as AF-correlated symptoms and was associated with significant QoL improvement.

Role of high frequency atrial pacing for the termination of acute atrial fibrillation and atypical atrial flutter.

Background: The aim of this study was to assess the efficacy of high‐frequency (HF) pacing from the right atrial appendage (RAA) or coronary sinus ostium (CS‐Os) for the termination of acute atrial fibrillation (AF) and atypical atrial flutter (AAFL) during an electrophysiological (EP) study.