Bradycardia= when heart rate drops below 60BPM. Occurs due to exercise as it increases stroke volume.
Tachycardia= when heart rate exceeds 100BPM. Caused by stress or problems with SAN. Requires surgery or drugs to mend.
Ectopic heart beat= extra heartbeat.
Atrial fibrillation= Irregular waves of electrical excitation pass over atria causing atria to contract rapidly and randomly up too 700 times a minute. Treated with medication or surgery.