The Heart Rhythm Society did a few randomized trials to assess the efficacy of calcium channel blockers, beta-blockers
and digoxin in SVT. A comparison of verapamil, propranolol
and digoxin showed equivalent efficacy in a small group of patients. However, in general calcium channel blockers and beta-blockers are preferred to digoxin. Digoxin has been around for a long time! I used Digoxin over 50 years ago for my PSVT, and my recollection was that it did little to prevent episodes.