Effects of m-nisoldipine on ischemic arrhythmia in conscious rats

m-Nisoldipine iv 3, 5 and 10 micrograms/kg before coronary artery ligation markedly reduced the early ischemic arrhythmia in conscious rats. Nifedipine iv 5 and 10 micrograms/kg had the same effect on preventing ischemic arrhythmia. Nisoldipine was less effective than m-nisoldipine at equal doses. Myocardial infarct size was reduced and electrical stability of the myocardium was markedly improved as a result of the increment in VDT, VFT and VERP. These effects may be related to the mechanisms of their respective antiarrhythmic actions. It is unlikely that these calcium antagonists prevent ischemic arrhythmia by improving the blood supply to the ischemic myocardium.