Ischemic ECG Findings: Significance of the U-wave

The U-wave is a small deflection immediately following the T-wave, commonly with the same polarity as the T-wave and most prominently seen in precordial leads V2–V3.

Prominent U-waves are most often seen with bradycardia and hypokalemia, but can also be secondary to other electrolyte imbalances and medications.

Typically, T- and U-wave polarities are concordant; discordant U-waves have been identified several hours prior to other ECG changes in acute myocardial infarction.

Some studies note that exercise induced U-wave inversion is highly predictive of CAD; negative U -waves in the precordial leads during exercise had a higher specificity (88% vs. 70%) & positive predictive value (77% vs. 61%) for ischemia than ST-depression.

Reinig et al. 2005 showed that negative concordance of T- and U-waves have poor prognosis & is quite specific for ischemia.

· ECG’s were divided into 3 groups:

o Type 1 T-U discordance (negative T waves + positive U waves)

o Type 2 T-U discordance (positive T waves + negative U waves)

o Negative T-U concordance (both T & U waves negative)