Definition:

• T wave is considered inverted when its amplitude ranges from -0.1 to -0.5 mV in leads I, II, aVL, and V2 to V6.
• i.e. negative in any leads that is not right-sided leads (aVR, III, V1)

T wave inversion

T wave inversion may be considered to be evidence of myocardial ischaemia if:

• At least 1 mm deep
• Present in ≥ 2 continuous leads that have dominant R waves (R/S ratio > 1)
• Dynamic — not present on old ECG or changing over time

NB. T wave inversion is only significant if seen in leads with upright QRS complexes (dominant R waves). T wave inversion is a normal variant in leads III, aVR and V1.

DDx

• Ischemia: NSTEMI (+ ST D), Hypertrophic cardiomyopathy, Angina (+ST D), STEMI (+ ST E)
• Brain injury (cerebral hemorrhage → surge of catecholamine) - systemic
• Past MI