Atria or ventricles
Supra ventricular tachycardia
: from upper chambers of the heart
, is due to irritability (increased automaticity) or a short circuit (reentry), heart is usually structurally normal.
Ventricular tachycardia: from lower chambers of the heart, due to irritability, can occur in normal hearts but is more often seen in hearts with scar tissue or weak hearts and can be life threatening.