I think you hear the majority of people are on Metoprolol, followed by Atenolol, Propanolol, then Sotalol all beta
blockers. Then comes Verapamil, which is a calcium channel blocker
like Diltiazem. Perhaps is has something to do with the nature of how a Class IV anti-arrhythmic affects the cardiovascular system. It decreases or slows conduction through the AV node, and reduces the contractility of the heart, so it could be inappropriate in cases of heart failure.