U wave

A U wave as seen on ECG

An electrocardiogram of an 18-year-old man showing U waves, most evident in lead V3.

The U wave is a wave on an electrocardiogram that is not always seen. It is typically small, and, by definition, follows the T wave. U waves are thought to represent repolarization of the papillary muscles or Purkinje fibers.^[1]

Interpretation

Prominent U waves are most often seen in hypokalemia, but may be present in hypercalcemia, thyrotoxicosis, or exposure to digitalis, epinephrine, and Class 1A and 3 antiarrhythmics, as well as in congenital long QT syndrome, and in the setting of intracranial hemorrhage.

An inverted U wave may represent myocardial ischemia (and especially appears to have a high positive predictive accuracy for left anterior descending coronary artery disease^[2] ) or left ventricular volume overload.^[3]

A U-wave can sometimes be seen in normal younger, athletic individuals.^[4]

References

↑ Pérez Riera AR, Ferreira C, Filho CF, et al. (2008). "The enigmatic sixth wave of the electrocardiogram: the U wave". Cardiol J 15 (5): 408–21. PMID 18810715.
↑ Gerson MC, Phillips JF, Morris SN, McHenry PL (1979). "Exercise-induced U-wave inversion as a marker of stenosis of the left anterior descending coronary artery". Circulation 60: 1014–1020. doi:10.1161/01.CIR.60.5.1014. PMID 487534.
↑ Conrath C, Opthof T (2005). "The patient U wave". Cardiovasc Res 67 (2): 184–6. doi:10.1016/j.cardiores.2005.05.027. PMID 15979057.
↑ EKG-boken Ylva Lind, Lars Lind, Liber, 2011

Physiology of the cardiovascular system

Heart

Cardiac output	Cardiac cycle Cardiac output Heart rate Stroke volume Stroke volume End-diastolic volume End-systolic volume Afterload Preload Frank–Starling law of the heart Cardiac function curve Venous return curve Wiggers diagram Pressure volume diagram

Ultrasound	Fractional shortening = (End-diastolic dimension End-systolic dimension) / End-diastolic dimension Aortic valve area calculation Ejection fraction Cardiac index

Heart rate	Cardiac pacemaker Chronotropic (Heart rate) Dromotropic (Conduction velocity) Inotropic (Contractility) Bathmotropic (Excitability) Lusitropic (Relaxation)

Conduction	Conduction system Cardiac electrophysiology Action potential cardiac atrial ventricular Effective refractory period Pacemaker potential Electrocardiography P wave PR interval QRS complex QT interval ST segment T wave U wave Hexaxial reference system

Chamber pressure	Central venous Right atrial ventricular pulmonary artery wedge Left atrial ventricular Aortic

Other	Ventricular remodeling

Vascular system/
Hemodynamics

Blood flow	Compliance Vascular resistance Pulse Perfusion

Blood pressure	Pulse pressure Systolic Diastolic Mean arterial pressure Jugular venous pressure Portal venous pressure

Regulation of BP	Baroreflex Kinin–kallikrein system Renin–angiotensin system Vasoconstrictors Vasodilators Autoregulation Myogenic mechanism Tubuloglomerular feedback Cerebral autoregulation Paraganglia Aortic body Carotid body Glomus cell

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