The t wave is the positive deflection after each qrs

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The T wave is the positive deflection after each QRS complex. It represents ventricular repolarisation. Upright in all leads except aVR and V1 Amplitude < 5mm in limb leads, < 10 mm in precordial leads T - wave 43
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Hyperacute T waves Inverted T waves Biphasic T waves T wave abnormalities 44
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Tall, narrow, symmetrically peaked T-waves are characteristically seen in hyperkalaemia. Broad, asymmetrically peaked or ‘hyperacute’ T- waves are seen in the early stages of ST-elevation MI (STEMI). Peaked T waves 45
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New T-wave inversion (compared with prior ECGs) is always abnormal . Pathological T wave inversion is usually symmetrical and deep (>3mm). Inverted T waves 46
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Inverted T waves are seen in the following conditions: Normal finding in children Myocardial ischaemia and infarction Bundle branch block Ventricular hypertrophy (‘strain’ patterns) Pulmonary embolism Hypertrophic cardiomyopathy Raised intracranial pressure 47
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Myocardial ischaemia and infarction:- T-wave inversions due to myocardial ischaemia or infarction occur in contiguous leads based on the anatomical location of the area of ischaemia/infarction . Inferior = II, III, aVF Lateral = I, aVL, V5-6 Anterior = V2-6 Ventricular hypertrophy (‘strain’ patterns) :- 48
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The U wave is a small (0.5 mm) deflection immediately following the T wave , usually in the same direction as the T wave. It is best seen in leads V2 and V3. The source of the U wave is delayed repolarisation of Purkinje fibres. 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 U Wave 49
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U waves are prominent if > 1-2mm or 25% of the height of the T wave. The most common cause of prominent U waves is bradycardia. Abnormally prominent U waves are characteristically seen in severe hypokalaemia. Prominent U waves 50
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U-wave inversion is abnormal (in leads with upright T waves) A negative U wave is highly specific for the presence of heart disease. The main causes of inverted U waves are: Coronary artery disease Hypertension Cardiomyopathy Hyperthyroidism Inverted U waves 51
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The PR interva l is the time from the onset of the P wave to the start of the QRS complex. It reflects conduction through the AV node. The normal PR interval is between 120 – 200 ms duration. PR Interval 52
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If the PR interval is > 200 ms, first degree heart block is said to be present. PR interval < 120 ms suggests pre- excitation (the presence of an accessory pathway between the atria and ventricles) or AV nodal (junctional) rhythm . rst degree AV block- marked 1st degree heart block (PR interval 340ms) Second degree AV block (Mobitz I) with prolonged PR interval Short PR (<120ms), broad QRS and delta waves in WPW syndrome 53
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PR interval > 200ms (five small squares) ‘Marked’ first degree block if PR interval > 300ms First Degree Heart Block 54
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Wenckebach Phenomenon Progressive prolongation of the PR interval culminating in a non-conducted P wave.
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  • Winter '16
  • jean grey
  • Cardiac electrophysiology, QRS, Rate

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