<unk> , also known as QRS<unk>  is when all<unk>  leads on an electrocardiogram are either positive (positive<unk>  or negative (negative<unk> . When there is a negative<unk> , it almost always represents a life-threatening condition called ventricular tachycardia because there is no other condition that suggests any abnormal conduction from the apex of the heart to the upper parts. However, in positive<unk>  another rare conditions such as left side accessory pathways or blocks are also possible.
Precordial concordance
Infradian rhythm
Spike-triggered covariance
Ultradian rhythm
Collapsing pulse
Electrical alternans
Pulsus alternans
Isochronic tones