What Causes Rapid Heart Rate Despite Taking Flecainide?

My husband 62 year old male, 6 2 260 lbs, history of High BP and A-Fib - takes meds for both but is exercising, doing well, losing weight. Got new meds yesterday. Today he has rapid heart rate 130 and low BP - 89 - 99 over 65-72. His daily Flecainide usually slows his heart down but today it hasn t. He took an older med that is supposed to help quicker - dil tiazem but it doesn t seem to be helping. He s been drinking water and thought he felt better but then ate and started sweating. He took another of his daily Flecainide. So - Wait and see or go to ER?? He doesn t want to go to ER but admits he is dizzy and