Methods: Six anesthetized open-chested swine, 31 ± 2 kg, were studied that were part of an ongoing study with up to 6 h of previous closed-chest percutaneous pacing with repeated VF cycles. Similar to the human study of Horowitz et al., 24 pulses of 4 ms each were applied at a rate of 100 Hz during the ST segment to the epicardium via a pair of 7-mm diameter platinum electrodes whose centers were 15 mm apart. Current was increased until VF was induced.
