- The subject is taking digoxin, alpha-adrenergic or beta-adrenergic agonist or antagonist (e.g., clonidine, propranolol, albuterol), anti-arrhythmic medications, or vasodilators (e.g. ACE inhibitors) on the day of the study procedures. It is routine for children taking these medications to hold them on the day of their procedure, as requested by the clinical team.