I have tachyarhythmia and reflex anoxic seizures. at times i get sudden heart pain or heart ache. what would be the safest way to strengthen my heart?

Sounds like POTS: Your problem is your autonomic nervous system not your heart. Read the will power instinct by kelly mcgonigal. You will learn to breathe and relax. You should get 8 hours of sleep, eat 6 equal healthy meals with 6 fresh cooked or raw vegetables and 1 apple every day with slow carb whole grains, high quality protein and fats, and do exercises lying down or short exercises like jump roping, no rope.