Sinus node responses to perfusion pressure changes, ischaemia and XXXX in the isolated blood-perfused @entity235 atrium.

@entity308 @entity235 @entity10804 @entity2778 @entity3897 @entity432 @entity7129 @entity2332
Sinus node responses to perfusion pressure changes, ischaemia and @entity2332 were evaluated in 22 isolated blood-perfused @entity235 atria. Sinus cycle length (SCL) was measured and sinoatrial conduction time (SACT) was estimated using the premature atrial stimulation technique (PAS) and the constant atrial pacing method (CAP). There was a good correlation between the results obtained with both techniques (r = 0.8297) but CAP had less @entity308 action on sinus node @entity10804 . Increasing the perfusion pressure from 100 to 200 mmHg did not influence estimated SACT nor SCL. However, a reduction in perfusion pressure (from 100 to 50 mmHg) markedly shortened SCL without significantly decreasing estimated SACT. Lowering temperature from 37 to 25 degrees C caused a linear increase in estimated SACT and SCL. @entity432 induced a @entity7129 which was not blocked by @entity2778 . Estimated SACT was significantly shorter 1 min after occlusion and longer 3 min after occlusion; this increase was significantly inhibited by @entity3897 infusion. Thus, the increase in estimated SACT seen after occlusion might be related to cholinergic activity. However, the @entity7129 following a decrease in perfusion pressure might be due to activation of the stretch-receptors while the one seen after reduction in blood flow and @entity432 seems more likely to be a consequence of ischaemia.
