Taking sotalol post ablation afib surgery told to stop sotalol 3 month after ablation i stop last night now resting pulse is 90 usually 78 normal?

Beta blocker: Sotalol is in the Beta Blocker class and can cause slowing of the heart rate, therefore it would not be unusual for your heart rate to increase on stopping

Probably: After stopping Sotalol, you can experience an increase in the RESTING heart rate (measured after 5 minutes of no exercise, sitting or preferably laying flat, in a darkened room with all lights/sounds off). Most heart rate measurements are not true "resting" heart rates, so an increase to 90 may have confounding factors. A change from 78 to 90 is not significant, then. (Worry if it jumps to 100+).