Tachycardia
Definition:Persistent,resting adult herat rate >100bpm
Positive Chronotropic Agents:Stress,anxiety,drugs,heart disease,fever

Bradycardia
Definition:Persistent,resting adult herat rate <60bpm
Negative Chronotropic Agents:Hypothermia

Arrhythmias
Definition:Dysfunctions cause abnormalities in impulse formation and condition in the myocardium
Causes:(1)Abnormal automaticity...The SA node shows the fastest rate of Phase4 depolarization
       (2)Effect of drugs on automaticity...drugs blocking sodium ions or calcium ions
       (3)Abnormalities in impulse condition
       (4)Effects of drugs on condition abnormalities

Classification of drugs treating arrhythmias (Antiarrhythmic Drugs)
Class IA,IB,IC:sodium ions channel blocker
Class II:beta-Adrenoreceptor blocker
Class III:potassium ions channel blocker
Class IV:calcium ions channel blocker