Effect of ischaemia on overdrive suppression in isolated, blood-perfused atrial preparations of dogs.

The magnitude of overdrive suppression of the SA nodal pacemaker activity was markedly influenced by its ischaemia which was produced by occlusion of the perfusion tubing close to the sinus node artery in the in-situ and isolated canine sino-atrial node preparations. In all isolated preparations, postdrive suppression was significantly augmented after occlusion of the perfusion system for at least 120 seconds. It is concluded that total ischaemia depresses sino-atrial node function in the atropinized canine heart and that postdrive suppression is a good index of such impaired function.