Ecg Waves

Osborn Wave (J Wave) Overview The Osborn wave (J wave) is a positive deflection seen at the J point in precordial and true limb leads. It is most commonly associated with hypothermia. These changes will appear as a reciprocal, negative deflection in aVR and V1. The J point in the ECG is the point where the QRS complex joins the ST segment. It represents the approximate end of depolarization and the beginning of repolarization as determined by the surface ECG. There is an overlap of around 10ms. ...

The Q Wave A Q wave is any negative deflection that precedes an R wave The Q wave represents the normal left-to-right depolarisation of the interventricular septum Small ‘septal’ Q waves are typically seen in the left-sided leads (I, aVL, V5 and V6) Q waves in context Q waves in different leads Small Q waves are normal in most leads Deeper Q waves (>2 mm) may be seen in leads III and aVR as a normal variant Under normal circumstances, Q waves are not seen in the right-sided leads (V1-3) Pathological Q Waves Q waves are considered pathological if: ...

T wave Overview The T wave is the positive deflection after each QRS complex. It represents ventricular repolarisation. Normal T wave characteristics Upright in all leads except aVR and V1 Amplitude < 5mm in limb leads, < 10mm in precordial leads (10mm males, 8mm females) Duration relates to QT interval T wave abnormalities Peaked T waves Hyperacute T waves Inverted T waves Biphasic T waves ‘Camel Hump’ T waves Flattened T waves Peaked T waves ...

U wave Overview The U wave is a small (0.5 mm) deflection immediately following the T wave U wave is usually in the same direction as the T wave. U wave is best seen in leads V2 and V3. Source of the U wave The source of the U wave is unknown. 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 Features of Normal U waves The U wave normally goes in the same direction as the T wave U -wave size is inversely proportional to heart rate: the U wave grows bigger as the heart rate slows down U waves generally 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 ...

Delta Wave Overview The Delta wave is a slurred upstroke in the QRS complex. It relates to pre-excitation of the ventricles, and therefore often causes an associated shortening of the PR interval. It is most commonly associated with pre-excitation syndromes such as WPW. The characteristic ECG findings in Wolff-Parkinson-White syndrome are: Short PR interval (< 120ms) Broad QRS (> 100ms) A slurred upstroke to the QRS complex (the delta wave) ...

P Wave Overview The P wave is the first positive deflection on the ECG and represents atrial depolarisation. The P wave is the first positive deflection on the ECG It represents atrial depolarisation Normal duration: < 0.12 s (< 120ms or 3 small squares) Characteristics of the Normal Sinus P Wave Morphology Smooth contour Monophasic in lead II Biphasic in V1 Axis ...

↪ ECG Basics Homepage R wave Overview The R wave is the first upward deflection after the P wave. The R wave represents early ventricular depolarisation Abnormalities of the R wave There are three key R wave abnormalities: Dominant R wave in V1 Dominant R wave in aVR Poor R wave progression 1. Dominant R wave in V1 Causes of Dominant R wave in V1 Normal in children and young adults Right Ventricular Hypertrophy (RVH) Pulmonary Embolus Persistence of infantile pattern Left to right shunt Right Bundle Branch Block (RBBB) Posterior Myocardial Infarction (ST elevation in Leads V7, V8, V9) Wolff-Parkinson-White (WPW) Type A Incorrect lead placement (e.g. V1 and V3 reversed) Dextrocardia Hypertrophic cardiomyopathy Dystrophy Myotonic dystrophy Duchenne Muscular dystrophy Examples of Dominant R wave in V1 Normal paediatric ECG (2 yr old) ...