Comparison of effects of propranolol on action potentials of normal and hypoxic myocardial cells

Propranolol (Pro) 2 microg/ml prolonged APD and ERP both in normal and hypoxic myocardial cells, and increased the ERP/APD ratio of the hypoxic cell (1.84 to 2.18, P<0.05, Pro 30 min), but had no effect on the ERP/APD ratio of normal cell (P>0.05). Pro also prolonged the latency of hypoxic cell from 13+/-5 ms (control) to 23+/-13 ms (P<0.01, Pro 15 min) and to 17+/-6 ms (P<0.01, Pro 30 min), but had no effect on the latency of normal cell.
The results suggest that the effects of Pro in slowing conduction and increasing the ERP/APD ratio of hypoxic myocardial cells may be accounted for its anti-arrhythmic effects in acute myocardial ischemia.