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)
* Significantly higher rate of CAD (88% vs. 58%) (P-value <. 0001) in the negative T-U concordance group
References
Sovari AA, Farokhi F, et al. Inverted U-wave, a specific electrocardiographic sign of cardiac ischemia. Am J Emerg Med. 2007 Feb;25(2):235-7.
Reinig MG, Harizi R, et al. Spodick Electrocardiographic T- and U-wave discordance. Ann Noninvasive Electrocardiol. 10 (1) (2005), pp. 41–46.
