Hello! Welcome on HCM! It seems that a premature heart beat (most probable atrial extra-systole) be the cause of your unpleasant feeling. As far as it is quite isolated and your sustained cardiac rhythm is normal sinus you shouldn t worry about. It is a normal finding not rarely seen in normal individual during certain periods of physical or psychological stress. You may start weaning off form Propafenone and remaining that way only on Diltiazem. In addition, I recommend performing some lab tests, like liver function tests, thyroid hormones level and blood electrolytes level, just to be sure that everything is OK and no triggering factors for extra-systoles or adverse interaction with the therapy will occur. Hope to have been helpful to you! Kind regards, Dr. Iliri