What are the different types of cardiac arrhythmias?

• AV nodal reentrant tachycardia (AVNRT): An extra pathway in or close to the AV node in the heart causes electrical impulses to travel in a circular motion, passing through areas already crossed.

• Accessory pathway: When an extra pathway (present from birth) connects the atria and ventricles, the heart rate can be too fast because electrical impulses travel back to the heart's upper chambers abnormally.

• Atrial fibrillation and atrial flutter: Extra electrical impulses originating in different parts of the atrium, or upper chambers of the heart, cause them to contract quickly (an atrial flutter) or quiver (atrial fibrillation).

• Ventricular tachycardia: This fast, possibly life-threatening heart rhythm stems from abnormal electrical impulses in the ventricles, or lower chambers of the heart. As a result, they do not fill with adequate amounts of blood and are unable to pump enough blood through the body.

There are many different types of cardiac arrhythmias ranging from the completely benign to the immediately life threatening. Arrhythmia simply means "abnormal heart rhythm."

Sinus arrhythmia is a common, completely benign rhythm disturbance where breathing in and out alters the heart rate—typically the heart rate briefly accelerates during inspiration and briefly decelerates during expiration.

Premature atrial contractions (PACs) are generally benign electrical signals originating in the upper chambers of the heart (the atria) that may cause the sensation of a "skipped" heart beat. PACs may initiate other arrhythmias such as atrial fibrillation, atrial flutter, or SVT though this is the exception rather than the rule. PACs are common and generally do not necessitate treatment unless they are highly symptomatic or are recurrently triggering other arrhythmias.

Premature ventricular contractions (PVCs) are premature heart beats originating in the lower chambers of the heart (the ventricles). PVCs may cause the sensation of a "skipped" heart beat. PVCs are generally benign though in the setting of a heart attack, a severely weakened heart, or severe structural heart disease they may be a prognosticator of potentially life-threatening rhythm problems. 

SVT stands for supraventricular tachycardia which is a "catch-all" term for inappropriate fast heart rhythms that originate from the upper chambers (or atria) of the heart. SVTs may produce symptoms ranging from palpitations to dizziness to shortness of breath. 

Atrial fibrillation is a totally disorganized, chaotic rhythm in the atria that frequently causes the heart to beat fast and irregularly. 

Atrial flutter is an organized, regular short circuit in the atria that tends to cause the heart to beat fast and regularly. Both atrial fibrillation and flutter may increase the risk of stroke.

Ventricular tachycardia (VT) is a fast heart rhythm originating from the lower chambers of the heart. VT may be life threatening in the setting of a heart attack, a weakened heart, or severe structural heart disease. There are also benign forms of VT.

Ventricular fibrillation is an immediately life-threatening rhythm where the heart stops effectively pumping blood.

Heart block: Heart block means there is ineffective transmission of electrical signals within different area of the heart ranging from benign to immediately life-threatening. This should not be confused with blockage in a heart artery.