appropriate DISCORDANCE

Appropriate discordance describes a pattern of repolarization abnormality (seen with left bundle branch block, paced rhythms, VT, PVCs, etc.) in which the ST segment and T wave are directed opposite to the main vector of the QRS complex:

• ST depression and T wave inversion in leads with a dominant R wave.

• ST elevation with upright T waves in leads with a dominant S wave.

• Expected repolarization abnormalities, like in LBBB’s cause ST-segment & T wave changes that can make the identification of acute MI difficult

• Patients with LBBB are expected to have ST segment & T wave changes that are discordant to the direction of the QRS complex. This is normal & referred to as the “Rule of Appropriate Discordance”

• ST-segment deviations that are concordant (in same direction) to the QRS complex are abnormal​

• To learn more about how to diagnose LBBB in MI check out MI in LBBB & Paced Rhythm Criteria