This invention provides a group of antiarrhythmic agents of the formula: ##STR1## in which R.sub.1 is --CO.sub.2 H, --CO.sub.2 (CH.sub.2).sub.n --NR.sub.4 R.sub.5, --CONR.sub.6 R.sub.7, --NHCO.sub.2 R.sub.8 or --NHCO.sub.2 (CH.sub.2).sub.o --NR.sub.9 R.sub.10 where R.sub.4 and R.sub.5 are H or alkyl of 1 to 6 carbon atoms and n is 1 to 6; R.sub.6 and R.sub.7 are H or alkyl of 1 to 6 carbon atoms; R.sub.8 is alkyl of 1 to 6 carbon atoms; and R.sub.9 and R.sub.10 are alkyl of 2 to 6 carbon atoms and o is 1 to 6; R.sub.2 and R.sub.3 are, independently, hydrogen or alkyl of 1 to 6 carbon atoms; and m is one of the integers 1, 2, 3 or 4; or a pharmaceutically acceptable salt thereof, and a method for their use.