: J Cardiovasc Electrophysiol. 2001 May;12(5):592-9. Related Articles, Links
Comment in:
· J Cardiovasc Electrophysiol. 2001 May;12(5):600-1.
Focal atrial fibrillation: experimental evidence for a pathophysiologic role of the autonomic nervous system.
Schauerte P, Scherlag BJ, Patterson E, Scherlag MA, Matsudaria K, Nakagawa H, Lazzara R, Jackman WM.
Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, USA.
psch@pcserver.mk1.rwth-aachen.de
INTRODUCTION: Focal paroxysmal atrial fibrillation (AF) was shown recently to originate in the pulmonary veins (PVs) and superior vena cava (SVC). In the present study, we describe an animal model in which local high-frequency electrical stimulation produces focal atrial activation and AF/AT (atrial tachycardia) with electrogram characteristics consistent with clinical reports. METHODS AND RESULTS: In 21 mongrel dogs, local high-frequency electrical stimulation was performed by delivering trains of electrical stimuli (200 Hz, impulse duration 0.1 msec) to the PVs/SVC during atrial refractoriness. Atrial premature depolarizations (APDs), AT, and AF occurred with increasing high-frequency electrical stimulation voltage. APD/AT/AF originated adjacent to the site of high-frequency electrical stimulation and were inducible in 12 of 12 dogs in the SVC and in 8 of 9 dogs in the left superior PV (left inferior PV: 7/8, right superior PV: 6/8; right inferior PV: 4/8). In the PVs, APDs occurred at 13+/-8 V and AT/AF at 15+/-9 V (P < 0.01; n = 25). In the SVC, APDs were elicited at 19+/-6 V and AT/AF at 26+/-6 V (P < 0.01; n = 12). High-frequency electrical stimulation led to local refractory period shortening in the PVs. The response to high-frequency electrical stimulation was blunted or prevented after beta-receptor blockade and abolished by atropine. In vitro, high-frequency electrical stimulation induced a heterogeneous response, with shortening of the action potential in some cells (from 89+/-35 msec to 60+/-22 msec; P < 0.001; n = 7) but lengthening of the action potential and development of early afterdepolar-izations that triggered APD/AT in other cells. Action potential shortening was abolished by atropine. CONCLUSION: High-frequency electrical stimulation evokes rapid ectopic beats from the PV/SVC, which show variable degrees of conduction block to the atria and induce AF, resembling findings in patients with focal idiopathic paroxysmal AF. The occurrence of the arrhythmia in this animal model was likely due to alterations in local autonomic tone by high-frequency electrical stimulation. Further research is needed to prove absolutely that the observed effects of high-frequency electrical stimulation were caused by autonomic nerve stimulation.
Ter Arkh. 2001;73(9):55-61. Related Articles, Links
[Psychoautonomic correlations in patients with paroxysmal atrial fibrillation]
[Article in Russian]
Nedostup AV, Solov'eva AD, San'kova TA.
AIM: To study psychovegetative correlations in patients with paroxysmal atrial fibrillation (PAF). MATERIAL AND METHODS: The trial included 50 patients with non-rheumatic PAF and 20 healthy subjects. Clinical cardiological and cliniconeurological examinations, assessment of autonomic nervous system, emotional sphere, sleep disorders were performed. RESULTS: The diagnosis of marked psychovegetative syndrome was made in all PAF patients. It manifested stronger in older women, young men, survivors of myocardial infarction or acute disorders of cerebral circulation, in frequent paroxysms of cardiac fibrillation, its long-term history, in night PAF attacks, in sleep apnea. CONCLUSION: The policy of antiarrhythmic antirecurrence therapy should consider modalities correcting psychovegetative disorders.
J Cardiovasc Electrophysiol. 2001 Mar;12(3):285-91. Related Articles, Links
Comment in:
· J Cardiovasc Electrophysiol. 2001 Mar;12(3):292-3.
Fluctuation in autonomic tone is a major determinant of sustained atrial arrhythmias in patients with focal ectopy originating from the pulmonary veins.
Zimmermann M, Kalusche D.
Cardiology Department, Hopital de La tour, Meyrin, Switzerland.
zimmermann.family@bluewin.ch
INTRODUCTION: This study was designed to analyze dynamic changes in autonomic tone preceding the onset of sustained atrial arrhythmias in patients with focal atrial fibrillation (AF) to determine why patients with frequent discharge from the arrhythmogenic foci develop sustained AF. METHODS AND RESULTS: Holter tapes from 13 patients (10 men and 3 women; mean age 53 +/- 5 years) with paroxysmal "lone" AF (mean 18 +/- 13 episodes per week) and a proven focal origin (pulmonary veins in all cases) were analyzed. A total of 38 episodes of sustained (>30 min) were recorded and submitted to frequency-domain heart rate variability analysis. Six periods were studied using repeated measures analysis of variance: the 24-hour period, the hour preceding AF, and the 20 minutes before AF divided into four 5-minute periods. A significant increase in high-frequency (HF, HF-NU) components was observed during the 20 minutes preceding AF (P = 0.003 and 0.002, respectively), together with a progressive decrease in normalized low-frequency (LF-NU) components (P = 0.035). An increase in LF/HF ratio followed by a linear decrease starting 15 minutes before sustained AF also was observed, indicating fluctuations in autonomic tone, with a primary increase in adrenergic drive followed by a marked modulation toward vagal predominance immediately before AF onset. CONCLUSION: In patients with focal ectopy originating from the pulmonary veins, sustained episodes of atrial arrhythmias are mainly dependent on variations of autonomic tone, with a significant shift toward vagal predominance before AF onset.
J Investig Med. 1999 Jul;47(6):293-303. Related Articles, Links
Verapamil prolongs atrial fibrillation by evoking an intense sympathetic neurohumoral effect.
[
www.ncbi.nlm.nih.gov]
Eur J Pharmacol. 1998 Aug 28;356(1):31-40. Related Articles, Links
Effects of pilsicainide and propafenone on vagally induced atrial fibrillation: role of suppressant effect in conductivity.
Iwasa A, Okumura K, Tabuchi T, Tsuchiya T, Tsunoda R, Matsunaga T, Tayama S, Yasue H.
Division of Cardiology, Kumamoto University School of Medicine, Japan.
The effects of pilsicainide on vagally induced atrial fibrillation and on electrophysiological parameters were compared with those of propafenone in alpha-chloralose-anesthetized dogs. Conduction velocity, effective refractory period, wavelength, averaged atrial fibrillation cycle length and activation sequence in the right atrial free wall were determined before and after drug administration. Pilsicainide (2 mg/kg/5 min and 3 mg/kg/h)(n=10) or propafenone (2 mg/kg/15 min and 4 mg/kg/h)(n=10) was intravenously infused during stable atrial fibrillation sustaining > 30 min. Pilsicainide terminated atrial fibrillation in nine dogs, while propafenone did so in three (p < 0.01). After the drug, conduction velocity was suppressed more in the pilsicainide than in the propafenone group(p < 0.01). There was no difference in effective refractory period after drug between the two groups. Mean wavelength was prolonged from 46.0 to 70.4 mm in the pilsicainide group and from 45.0 to 110.8 mm in the propafenone (p < 0.01 vs. pilsicainide). Activation mapping during atrial fibrillation showed Type II or III atrial fibrillation as previously defined [Konings, K.T.S., Kirchhof, C.J.H.J., Smeets, J.R.L.M., Wellens, H.J.J., Penn, O.C., Allessie, M.A., 1994. High-density mapping of electrically induced atrial fibrillation in humans. Circulation. Vol. 89, pp. 511-521.] before the drug, and changed to Type I before atrial fibrillation termination. Thus, pilsicainide was more effective to terminate vagally induced atrial fibrillation than was propafenone despite a greater effect of propafenone than of pilsicainide on wavelength. In this canine atrial fibrillation model, the suppression of conduction velocity may play an important role in changing the activation pattern of atrial fibrillation and thus, terminating atrial fibrillation.
[
www.ncbi.nlm.nih.gov]
Pacing Clin Electrophysiol. 1998 Feb;21(2):386-95. Related Articles, Links
Abnormal vasovagal reaction, autonomic function, and heart rate variability in patients with paroxysmal atrial fibrillation.
Lok NS, Lau CP.
Department of Medicine, Queen Mary Hospital, Hong Kong.
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.
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www.ncbi.nlm.nih.gov]