Classification
Arrhythmia may be classified by rate (tachycardia, bradycardia), mechanism (automaticity, re-entry, triggered) or duration (isolated premature beats; couplets; runs, that is 3 or more beats;  non-sustained = less than 30 seconds or sustained= over 30 seconds).Arrhythmias are also classified by site of origin:

Atrial arrhythmia
Sinus bradycardia
Sinus arrhythmia
Sinus tachycardia
Premature atrial contractions (PACs)
Wandering atrial pacemaker
Atrial tachycardia
Multifocal atrial tachycardia
Supraventricular tachycardia (SVT)
Atrial flutter
Atrial fibrillation (Afib)
AV nodal reentrant tachycardia

Junctional arrhythmia
AV nodal reentrant tachycardia
Junctional rhythm
Junctional tachycardia
Premature junctional contraction

Ventricular arrhythmia
Premature ventricular contractions (PVCs), sometimes called ventricular extra beats (VEBs)
Premature ventricular beats occurring after every normal beat are termed ventricular bigeminy
PVCs that occur at intervals of 2 normal beats to 1 PVC, or 1 normal beat to 2 PVCs, are termed "PVCs in trigeminy"
Groups of three premature ventricular beats are called triplets and are considered a brief run of non-sustained ventricular tachycardia (NSVT); if the grouping lasts for more than 30 seconds, it is considered sustained ventricular tachycardia (VT). Accelerated idioventricular rhythm
Monomorphic ventricular tachycardia
Polymorphic ventricular tachycardia
Ventricular fibrillation
Torsades de pointes
Arrhythmogenic right ventricular dysplasia
Re-entry ventricular arrhythmia

Heart blocks
These are also known as AV blocks, because the vast majority of them arise from pathology at the atrioventricular node. They are the most common causes of bradycardia:
First-degree heart block, which manifests as PR prolongation
Second-degree heart block
Type 1 Second degree heart block, also known as Mobitz I or Wenckebach
Type 2 Second degree heart block, also known as Mobitz II
Third-degree heart block, also known as complete heart blockFirst, second, and third-degree blocks also can occur at the level of the sinoatrial junction.
Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), myocardial ischemia, or simply heart disease, involves the reduction of blood flow to the heart muscle due to build-up of atherosclerotic plaque in the arteries of the heart. It is the most common of the cardiovascular diseases. Types include stable angina, unstable angina, myocardial infarction, and sudden cardiac death. A common symptom is chest pain or discomfort which may travel into the shoulder, arm, back, neck, or jaw. Occasionally it may feel like heartburn. Usually symptoms occur with exercise or emotional stress, last less than a few minutes, and improve with rest. Shortness of breath may also occur and sometimes no symptoms are present. In many cases, the first sign is a heart attack. Other complications include heart failure or an abnormal heartbeat.Risk factors include high blood pressure, smoking, diabetes, lack of exercise, obesity, high blood cholesterol, poor diet, depression, and excessive alcohol consumption. A number of tests may help with diagnoses including: electrocardiogram, cardiac stress testing, coronary computed tomographic angiography, and coronary angiogram, among others.Ways to reduce CAD risk include eating a healthy diet, regularly exercising, maintaining a healthy weight, and not smoking. Medications for diabetes, high cholesterol, or high blood pressure are sometimes used. There is limited evidence for screening people who are at low risk and do not have symptoms. Treatment involves the same measures as prevention. Additional medications such as antiplatelets (including aspirin), beta blockers, or nitroglycerin may be recommended.