U WAVE IN ECG AND ITS ABNORMALITIES IN ECG

U WAVE IN ECG AND ITS ABNORMALITIES

1. U WAVE Dr.G.VENKATA RAMANA MBBS DNB FAMILY MEDICINE

2. U wave Overview S mall (0.5 mm) deflection immediately following the T wave U sually in the same direction as the T wave B est seen in leads V2 and V3 More commonly seen when patients are bradycardic Source of the U wave U nknown Three common theories regarding its origin are: Delayed repolarisation of Purkinje fibres Prolonged repolarisation of mid-myocardial “M-cells” After-potentials resulting from mechanical forces in the ventricular wall

3. Features of Normal U waves N ormally goes in the same direction as the T wave S ize is inversely proportional to heart rate: the U wave grows bigger as the heart rate slows down G enerally become visible when the heart rate falls below 65 bpm The voltage of the U wave is normally < 25% of the T-wave voltage: disproportionally large U waves are abnormal Maximum normal amplitude of the U wave is 1-2 mm

4. Abnormalities of the U wave Prominent U waves Inverted U waves Prominent U waves U waves are described as prominent if they are >1-2mm or 25% of the height of the T wave

5. Causes of prominent U waves Prominent U waves most commonly found with: Bradycardia Severe hypokalemia Prominent U waves may be present with: Hypocalcemia Hypomagnesemia Hypothermia Raised intracranial pressure Left ventricular hypertrophy Hypertrophic cardiomyopathy Drugs  associated with prominent U waves: Digoxin Phenothiazines ( thioridazine ) Class Ia antiarrhythmics (quinidine, procainamide) Class III antiarrhythmics ( sotalol , amiodarone ) Note  Many of the conditions causing prominent U waves will also cause a long QT

6. Prominent U waves due to sinus bradycardia

7. U waves associated with hypokalemia Prominent U waves in a patient with a K+ of 1.9

8. U waves associated with left ventricular hypertrophy

9. U waves associated with digoxin use

10. U waves associated with quinidine use

11. Inverted U waves U-wave inversion is abnormal (in leads with upright T waves) A negative U wave is highly specific for the presence of heart disease Common causes of inverted U waves Coronary artery disease Hypertension Valvular heart disease Congenital heart disease Cardiomyopathy Hyperthyroidism In patients presenting with chest pain, inverted U waves: Are a very specific sign of  myocardial ischaemia May be the earliest marker of unstable angina and evolving myocardial infarction Have been shown to predict a ≥ 75% stenosis of the LAD / LMCA and the presence of left ventricular dysfunction

12. Unstable angina I nverted U waves in a patient with unstable angina

13. Inverted U waves in Prinzmetal angina

14. NSTEMI Note the subtle U-wave inversion in the lateral leads (I, V5 and V6) in this patient with a NSTEMI; these were the only abnormal findings on his ECG