Comparative effects of verapamil, diltiazem and felodipine during experimental digitalis-induced arrhythmias.
We compared the abilities of three different calcium (Ca2+) entry blockers, verapamil, diltiazem and felodipine to abolish ouabain-induced ventricular ectopy (100 X ectopic/total beats, VE) in anesthetized, closed-chest dogs. Ventricular tachycardia (VT) was produced in anesthetized, bilaterally vagotomized, closed-chest dogs by an average dose of 65 +/- 19 micrograms/kg ouabain. 30 min after establishing VT, either verapamil (25-50 micrograms/kg + 5-10 micrograms/kg/min), diltiazem (50-100 micrograms/kg + 20-50 micrograms/kg/min), felodipine (3 micrograms/kg + 0.3 micrograms/kg/min) or saline was administered for another 30 min. Verapamil, at the higher dose utilized, practically abolished ouabain-induced VT (97 +/- 3 to 8 +/- 19% VE); diltiazem was moderately effective (96 +/- 4 to 50 +/- 8% ectopy) at 100 micrograms/kg, and felodipine exerted no antiarrhythmic effects in this model. All three Ca2+ entry blockers lowered mean aortic pressure, felodipine lowering this parameter most prominently. Thus, these structurally and electrophysiologically dissimilar Ca2+ entry blockers differed in their abilities to abolish the digitalis glycoside-induced arrhythmias in vivo. The superiority of verapamil may be related to its multiple, additional electrophysiologic effects.
D000818:Animals; D000889:Anti-Arrhythmia Agents; D001145:Arrhythmias, Cardiac / Q000139:chemically induced / Q000517:prevention & control*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004110:Diltiazem / Q000494:pharmacology*; D004285:Dogs; D015736:Felodipine; D005260:Female; D008297:Male; D009568:Nitrendipine / Q000031:analogs & derivatives* / Q000494:pharmacology; D010042:Ouabain; D014700:Verapamil / Q000494:pharmacology*
D000889:Anti-Arrhythmia Agents; D002121:Calcium Channel Blockers; D010042:Ouabain; D009568:Nitrendipine; D014700:Verapamil; D004110:Diltiazem; D015736:Felodipine