In the present study, we used a goat model of chronic complete AV block to produce progressive dilatation of the atria. Finally, stretch-induced focal activity could induce or perpetuate AF in dilated atria.
Third, inhomogeneities in atrial refractoriness or conduction could stabilize the arrhythmia. Second, a shortening of the wavelength because of a shortening of the atrial effective refractory period (AERP) and/or a reduced conduction velocity (CV) would augment the number of waves that can be present simultaneously. First, an increase in atrial surface per se may allow more reentrant circuits to coexist. 2 However, the mechanisms by which atrial dilatation creates a substrate for AF are largely unknown. 1 Furthermore, spontaneous conversion of AF to sinus rhythm is less likely to occur in enlarged atria. Large prospective clinical trials have shown that chronic atrial dilatation is an important and independent risk factor for the development of atrial fibrillation. The increase in AF stability was not a result of a shortening of atrial refractoriness or atrial fibrosis. Connexin40 and connexin43 expression was unchanged.Ĭonclusions- Chronic AV block in the goat leads to progressive atrial dilatation, prolongation of induced AF paroxysms, and local conduction delays. Histological analysis showed hypertrophy without atrial fibrosis. Atrial mapping during rapid pacing revealed that slow conduction (<30 cm/s) was present in 3.7☑.0% of the mapped area (control, 0.9☐.5%, P<0.05). Spontaneous paroxysms of AF were not observed. Atrial effective refractory period and AF cycle length remained constant. The duration of induced AF paroxysms increased from 4.6 seconds to 6.4 minutes ( P<0.05). Right atrial diameter increased gradually by 13.5☓.9% during 4 weeks of AV block ( P<0.01). After His-bundle ablation, the ventricular rate decreased from 113.8±4.8 to 44.6☒.5 bpm.
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After 4 weeks of complete AV block, the free wall of the right atrium was mapped and the atrium was fixed in formalin for histological analysis. After His-bundle ablation, the above measurements were repeated once a week.
AF paroxysms were induced by burst pacing to determine the baseline AF cycle length and stability of AF. After 2 weeks, atrial diameter and effective refractory period were measured. Methods and Results- In 8 goats, 2 screw-in leads with piezoelectric crystals were implanted transvenously in the right atrium. In the present study, we monitored the electrophysiological changes during progressive atrial dilatation in chronically instrumented goats.
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