Precordial concordance
Precordial concordance, also known as QRS concordance, is a pattern in which all precordial leads on an electrocardiogram are either positive or negative. When there is a negative concordance, it almost always represents a life-threatening condition called ventricular tachycardia because there is no other condition that suggests any abnormal Electrical [conduction system of the heart|conduction] from the apex of the heart to the upper parts. However, in positive concordance another rare conditions such as left side accessory pathways or blocks are also possible.