Key words: Atrial fibrillation; animal model; goat; pulmonary vein
Abstract: Objective: Chronic intermittent stimulation of the left atrium rapid method, the goat with persistent atrial fibrillation (AF) model. METHODS: In 10 goats left atrium Article electrode free wall suture, suture in the left superior pulmonary vein 1 on the root of the electrode. the left atrium of the connector 1 on the electrode self-stimulation in vitro, periodically stop the stimulation, the physiological indicators of power until the spontaneous atrial fibrillation maintained over 24 h. Echocardiography continuous measurement of baseline and post-AF atrial area were measured. Results: 10 goats, 8 completed the study, in the 9 + / -5 6 ~ 16 d in the last more than 24 h induced atrial fibrillation. With prolonged stimulation, gradually reduce the circumference of atrial fibrillation waves, the atrial fibrillation pulmonary vein wave length of the left atrium week; atrial fibrillation after the area was continuing to expand. Conclusion: Atrial fibrillation developed by intermittent stimulation of stimulation of left atrial membrane goat can be from 1 3 weeks induced hair maintained over 24 h from the sustained atrial fibrillation.
atrial fibrillation (AF) is the most common chronic arrhythmia in the clinical study and treatment of atrial fibrillation mechanisms establish a simple, fast and consistent with clinical features animal model is the basis and key. At present there are several reported animal models of atrial fibrillation, atrial fibrillation, but there is no current domestic model of lasting more than 24 h reported. In this study, goats in the left atrial suture electrode membrane, made use of in vitro 50 Hz stimulation released intermittent stimulation, development of persistent AF> 24 h animal models, and using the model of the dynamic-related changes in electrophysiological indices.
1 Materials and methods
1. 1 experimental animal < br> surgery and epicardial electrode production method and similar to previous studies in our laboratory. from April 2004 to April 2005, with 10 healthy female goats (PLA General Hospital Experimental Animal Center), body mass 28 ~ 45 (37 + / -6) kg, 30g / L of sodium pentobarbital 30 mg / kg intravenous anesthesia, the establishment of intravenous access, each additional 1h pentobarbital sodium 10 mg / kg. endotracheal intubation, respiratory mechanical ventilation. left intercostal thoracotomy 4 to open the pericardium, exposing the heart, pericardial sewing hammocks. from the left superior pulmonary vein epicardial suture 1 on the root of the electrode, after the suture in the left atrial free wall with 5 pairs of silver electrode (electrode spacing 5 mm) of silicone. step by step off the chest, through subcutaneous tunnel will lead to the neck skin electrode wire, the suture fixation. ampicillin before surgery with intravenous infusion of 1000 mg, 1000 mg after intramuscular injection of ampicillin Penicillin 3 d, 2 times / d, to prevent infection. After 2 weeks, the goat animal cage placed at the beginning awake electrophysiological study.
1. 2 atrial stimulation and the production
Centre Court Development of Medical Electronic Engineering. stimulate the frequency of 50 Hz, continuous discharge time 1 s, the output intensity - 6 ~ 6 V adjustable, the discharge interval of 2 s. Using commercially available 1. 5V battery to provide power two series, each 1 24 h measured remaining capacity, if necessary (usually 3 d) replacement.
1. 3
data collection and analysis will be 1 on the left atrium and the atrial stimulation electrodes connected, respectively, to stimulate the beginning, stimulus for 6,12,24 h, and then every 24 h stimulation with electrodes disconnected the connection, observe the duration of atrial fibrillation, left atrium and left superior pulmonary vein atrial fibrillation wave circumference (atrial fibrillation cycle length, AFCL). in atrial fibrillation when measured over 200 consecutive atrial activation wave interval, the average value as the AFCL. night only connect to 1 on the left atrial electrode and the stimulator to maintain the stimulation. spontaneous AF were observed during the day to maintain 12 h, night maintain the stimulation; the first 2 days to stop stimulus, such as sustained AF during the day and night to stop stimulation, whether the observed atrial fibrillation lasting more than 24 h. Using echocardiography device, the sword four chamber section measured left and right atrium area, in the sternum next to the long axis view to measure left ventricular end diastolic diameter and ejection fraction., respectively, before the start of the stimulus and the atrial fibrillation ���� 24 h after the completion of awake goats
measurement.
1. 3 statistically
all the data x + /-s that the application of SPSS 10. 0 statistical software, are few compared with single factor analysis of variance (ANOVA) analysis, Pl0. 05 for the difference was significant.
2 results
10 goats, there are 8 completed the study after only pull .1 intubation aspiration after death; an endotracheal tube too deeply, there on the right lung injury, died after extubation, were confirmed by Autopsy confirmed.
2. 1
AF duration changes induced by stimulation of atrial fibrillation atrial fibrillation connector (see Figure 1) after the break, AF sustained 5 + / -5 s; maintenance of spontaneous atrial fibrillation 3 ~ 10 min, 30 ~ 60 min, 6 ~ 8 h, 10 ~ 12 h and 24h of stimulation time was 21 + / -6 h, 2. 5 + / -1. 0 d, 5. 0 + / - 2. 2d, 6. 8 + / -3. 6 d and 9. 3 + / -4. 6 d. all of the goats on the 6 ~ 16 d in the last more than 24 h induced atrial fibrillation, 3 of which only 24 h After four more than 48 h, to transfer complex, a 72 h intravenous infusion in the propafenone cardioversion. after conversion of atrial fibrillation were not spontaneous.
2. 2 left atrium and the left superior pulmonary vein AFCL changes
begun to stimulate the left atrium when the AFCL and the left superior pulmonary vein was 152 + / -29 and 147 + / -25 ms, after 24 h in the continuous AF, the two were 85 + / -5 and 75 + / -6 ms (P <0. 05, see Table 1).
2. 3 atrial fibrillation and left ventricular function before and after the atrial area change based on state
left and right atrial end-diastolic area were was 9.5 + / -0. 4 and 6. 7 + / -0. 1 cm; AF area continued after 24 h were 12.1 + / -1. 2 and 9.9 + / -2. 3 cm (versus baseline, P <0. 05), were expanded (28 + / -10)% and (49 + / -36)%. fibrillation before and after left ventricular end diastolic diameter was 35 + / -14 and 39 + /-11cm (P> 0. 05); ejection fraction was (68 + / -5)% and (64 + / -2)% (P> 0. 05).
3 discussions
present, reported a variety of animal models of atrial fibrillation, such as increased vagal tone model, sterile pericarditis model of chronic mitral regurgitation model, low ventilation model of canine atrial fibrillation, rapid ventricular pacing model. The model number of patients with clinically associated with structural heart disease associated with atrial fibrillation, but also a large number of clinical atrial fibrillation in patients without structural heart disease, that lone atrial fibrillation. on the isolated treatment of atrial fibrillation mechanisms and electrophysiological study abroad a hot research community, there is now some animal models.
Morillo and other reports, the right atrial appendage in the dog pacing electrodes placed to 400 times / min frequency rapid atrial pacing after 6 weeks, 82% of the dog may induce persistent AF (> 15 min), the average duration of 45 + / -7 min, 18% of the dogs do not need to program stimulation can occur atrial fibrillation. The study also found that atrial area increased by at least 40%, atrial effective refractory period was shortened, the left atrial posterior wall of the shortest AFCL. domestic scholars use this model also done some work, such as use of buried high Diao Hongying frequency pacemaker, the right atrial appendage in the dog to 370 ~ 400 / min rapid pacing of atrial frequencies 8 to 10 weeks. that stimulate the 8 to 10 weeks, eight (80%) can be evoked by a continuous process atrial fibrillation, the average duration of 53 + / -11 min, 3 only (30%) dogs without induced atrial fibrillation appears. Liuxing Peng, etc. to 400 times / min, frequency, continuous pacing the right atrium from 9 to 10 weeks . that after termination of pacing, 7 / 8 dogs to induce sustained atrial fibrillation> 15 min. However, the model experiments time-consuming, short duration of atrial fibrillation and atrial fibrillation can not be the dynamic of the evolution of .
Wijffels, etc. embedded in the outer membrane of goat atrial electrodes to the frequency of 50 Hz stimulation of the left atrium 1 s, induce spontaneous paroxysmal atrial fibrillation to be terminated, once perceived to sinus rhythm, repeat once stimulation of 1 s, once again induced AF, sustained until AF (> 24 h) study found that maintenance of stimulus 7. 1 + / -4. 8 d after the 10/11 goats had persistent atrial fibrillation. Zhou and other thoracic left atrial appendage in dogs after implantation of spiral electrode, the use of nerve stimulator embedded in the skin to give intermittent stimulation. cycle length 50 ms 20 Hz, duration 5 s, output 3.V, at intervals of 2 s. 23 + / -7 d later, all 6 dogs induced out of the last more than 48 h of sustained atrial fibrillation. The two models took a short, high rate of induced atrial fibrillation, atrial fibrillation of long duration, and clinical persistent isolated good correlation between atrial fibrillation, but also the evolution of the dynamics of atrial fibrillation, but due to the need of the apparatus, equipment is more complex, research is not yet see. In this study, developed the stimulator, the goats were intermittent left atrium The 50 Hz stimulation, succeeded in 9 + / -5 6 ~ 16 d within all 8 / 8 goats induce atrial fibrillation lasting more than 24 h, and the progression of atrial fibrillation center conducted electrophysiological changes of room.
authors found that prolonged AFCL progressively shorter with stimulation, and Wijffels, etc. results. fibrillation at first, the left atrium and left pulmonary veins was no significant difference in AFCL, with the stimulation time, both significantly shorter but the shortening of left superior pulmonary vein AFCL more obvious. to be self-sustained AF 30 ~ 60 min to stimulate the 2. 5 + / -1. 0 d, significant difference between the two. fibrillation sustained 24 h, both of 84 . 9 + / -5. 2 and 74. 7 + / -6. 2 ms, consistent with the results of Zhou and other, suggesting that the pulmonary veins in atrial fibrillation an important role in the maintenance process.
In summary, the model short experimental time-consuming, long duration of atrial fibrillation, atrial fibrillation induced by high, does not require complex equipment, and animal awake in the dynamic study. The results suggest that the maintenance of the pulmonary veins in atrial fibrillation play an important role.
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