Effects of Atenolol on Regional Myocardial Blood Flow and St Segment Elevation in the Canine Myocardium

1 The effects of atenolol on regional myocardial blood flow (RMBF) and on ST segment elevation were studied both in normal and ischaemic regions of the myocardium in dogs. Some of the experiments were performed with cardiac pacing or after bilateral stellectomy. 2 In the absence of cardiac pacing, atenolol (1 mg/kg, i.v.) induced a marked reduction in heart rate and contractile force and a decrease in RMBF, which was of the same magnitude in normal and ischaemic areas. There was no modification in the endo/epi flow ratio. ST segment elevation in ischaemic areas was significantly reduced. 3 Bilateral stellectomy induced similar effects to those of atenolol. Atenolol after bilateral stellectomy exhibited no additional effects. 4 In dogs submitted to cardiac pacing, atenolol no longer decreased RMBF and ST segment elevation. 5 These results demonstrate that with atenolol, there is no correlation between bradycardia and the endo/epi flow ratio while there is one between bradycardia and reduction in ST segment elevation.