Ultrastructural study of the pulmonary veins in pigs / 中华心血管病杂志

<p><b>OBJECTIVE</b>To explore the possible relationship between the ultrastructural characteristics of pulmonary veins and the pathogenesis of atrial fibrillation originating from pulmonary veins.</p><p><b>METHODS</b>The pulmonary veins from domestic pigs were serially sectioned (2 mm) transversely along the vessels. The odd number sections were fixed in 10% phosphate buffered formalin solution and the even number sections were fixed in 3% Glutaral for further electron microscopy observations.</p><p><b>RESULTS</b>Two cell types were found in the pulmonary veins of pigs. One cell type was the P-like cells that had an empty-appearing cytoplasm containing only sparse myofibrils and small mitochondria, both of which were randomly distributed. Another cell type was slender transitional cells with plenty of longitudinally displayed myofibrils.</p><p><b>CONCLUSION</b>P-like cells in the pig pulmonary veins were found using electron microscopy in this study and ectopic beats from P-like cells in the myocardial sleeves in the pulmonary veins might be responsible for atrial fibrillation originating from pulmonary veins.</p>

Effects of atrial excitable period on the stability of atrial fibrillation in goats / 中华心血管病杂志

<p><b>OBJECTIVE</b>To investigate the effects of atrial excitable period (EP) on the stability of atrial fibrillation (AF) in goats.</p><p><b>METHODS</b>Ten female goats were instrumented with epicardial electrodes patches on the left atrium (LA) free wall. AF was induced and maintained by a home-made stimulator with frequency of 50 Hz at a 1-second duration and a 2-seconds interval. The stimulator was disconnected regularly. AF-induced duration, average AF cycle length (AFCL), and atrial effective refractory period during AF (ERP(AF)) were measured; EP was calculated by AFCL-ERP(AF).</p><p><b>RESULTS</b>Eight goats were studied. Persistent AF (> 24 h) could be induced in all the 8 goats within 6-16 days. When the induced AF lasted for 3-10 min or 24 h, the AFCL was 98.3 ms +/- 11.0 ms and 84.9 ms +/- 5.2 ms (P < 0.05), respectively, ERP(AF) was 90.5 ms +/- 13.2 ms and 63.0 ms +/- 4.8 ms (P < 0.05), respectively, and EP was 7.8 ms +/- 2.4 ms and 21.9 ms +/- 3.5 ms (P < 0.05), respectively.</p><p><b>CONCLUSION</b>The decrease in ERP(AF) is more significant than the shortening in AFCL, resulting in the gradually widening of EP which may contribute to the perpetuation of AF.</p>