Ecg Library

Lists of differential diagnoses of specific ECG findings based on from ECGs for the Emergency Physician 1 and ECGs for the Emergency Physician 2 Atrial fibrillation with slow ventricular response Severe AV nodal disease Hypothermia Medications: Digoxin toxicity, Calcium-channel blocker / beta-blocker toxicity Tachydysrhythmias Narrow-complex regular rhythm: Sinus tachycardia Supraventricular tachycardia Atrial flutter Narrow-complex irregular rhythm: Atrial fibrillation Atrial flutter with variable block Multifocal atrial tachycardia Wide-complex regular rhythm: Ventricular tachycardia Sinus tachycardia with aberrant conduction SVT with aberrant conduction Atrial flutter with aberrant conduction Wide-complex irregular rhythm: Atrial fibrillation with aberrant conduction (for example bundle branch block) Atrial flutter with variable block and aberrant conduction Multifocal atrial tachycardia with aberrant conduction Atrial fibrillation with WPW Polymorphic ventricular tachycardia / Torsades de Pointes Leftward axis Left anterior fascicular block Left bundle branch block Inferior myocardial infarction Left ventricular hypertrophy Ventricular ectopy Paced beats Wolff-Parkinson-White syndrome Low voltage Myxoedema Large pericardial effusion Large pleural effusion End-stage dilated cardiomyopathy Severe chronic obstructive pulmonary disease Severe obesity Infiltrative myocardial diseases (i.e. restrictive cardiomyopathy) Constrictive pericarditis Prior massive MI Low gain settings on ECG machine Increased QRS Duration Hypothermia Hyperkalaemia WPW Aberrant intraventricular conduction (for example bundle branch block) Ventricular ectopy Paced beats Drugs, particularly those with sodium-channel blocking effects Increased QT-interval (and QTc-interval) Hypokalaemia* Hypomagnesaemia Hypocalcaemia Myocardial ischemia Elevated intracranial pressure Sodium-channel blockers Hypothermia Congenital prolonged QT syndrome *Hypokalemia — the actual QT-interval is normal; the QT-interval appears prolonged because of the presence of fusion of the T-wave with a U-wave (a “T-U fusion complex”) ...

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. ...

Characteristic ECG Abnormalities with Raised Intracranial Pressure Widespread giant T-wave inversions (“cerebral T waves”) QT prolongation Bradycardia (the Cushing reflex – indicates imminent brainstem herniation) Other possible ECG changes that may be seen: ST segment elevation / depression — this may mimic myocardial ischaemia or pericarditis Increased U wave amplitude Other rhythm disturbances: sinus tachycardia, junctional rhythms, premature ventricular contractions, atrial fibrillation In some cases, these ECG abnormalities may be associated with echocardiographic evidence of regional ventricular wall motion abnormality (so-called “neurogenic stunned myocardium”). ...

Cardiac axis represents the sum of depolarisation vectors generated by individual cardiac myocytes. Clinically is is reflected by the ventricular axis, and interpretation relies on determining the relationship between the QRS axis and limb leads of the ECG (below diagram) Since the left ventricle makes up most of the heart muscle under normal circumstances, normal cardiac axis is directed downward and slightly to the left: Normal Axis = QRS axis between -30° and +90°. Abnormal axis deviation, indicating underlying pathology, is demonstrated by: ...

Understanding paper speeds Paper output speed is the rate at which the ECG machine produces a trace Standard output is 25mm per second If a different paper speed is used, standard rate calculations will have to be modified appropriately (see other examples below) The standard paper speed is 25mm/sec: 1 SMALL square (1mm) = 0.04 sec (40ms) 5 SMALL squares (5mm) = 1 LARGE square = 0.2 sec (200ms) 5 LARGE squares = 1 second ...

To best understand ECG features of biatrial enlargement, it is recommended that you first review ECG changes seen in left atrial enlargement and right atrial enlargement. Biatrial Enlargement Definition Biatrial enlargement is diagnosed when criteria for both right and left atrial enlargement are present on the same ECG. The diagnosis of biatrial enlargement requires criteria for LAE and RAE to be met in either lead II, lead V1 or a combination of leads ECG Criteria for Biatrial Enlargement The spectrum of P-wave changes in leads II and V1 with right, left, and biatrial enlargement is summarised below: ...

ECG Library summary of the different types of conduction disturbance, with links to read more about each type of conduction block Conduction Blocks First-degree block First-degree block PR interval >200 msec (1 large square) Second-degree block Mobitz Type I (Wenckebach Block): progressive prolongation of the PR interval before the missed QRS complex Mobitz Type II (Hay Block): absence of progressive prolongation of the PR interval before the missed QRS complex Fixed ratio blocks (e.g. 2:1, 3:1): constant relationship between P waves and QRS complexes (e.g. 2:1 = 2 P waves for each QRS complex). High grade AV block: 2nd degree AV block with a high P:QRS ratio, producing a very slow ventricular rate Third-degree block Third-degree block: absence of any relationship between P waves of sinus origin and QRS complexes (AV dissociation) Fascicular Blocks Left anteriorfascicular block (LAFB) Left axis deviation qR complexes in leads I, aVL rS complexes in leads II, III, aVF Prolonged R wave peak time in aVL > 45ms Left posterior fascicular block (LPFB) Right axis deviation rS complexes in leads I, aVL qR complexes in leads II, III, aVF Prolonged R wave peak time in aVF Right bundle branch block QRS > 120 ms Dominant R wave in V1 RSR’ pattern (“M”) in V1 with wide, slurred S wave (“W”) in V6 (=MaRRoW) Left bundle branch block QRS > 120 ms Dominant S wave in V1 Deep S wave (“W”) in V1 with broad R wave (“M”) in V6 (=WiLLiaM) Bifascicular block RBBB plus either LAFB or LPFB Trifascicular block Bifascicular block plus 3rd degree AV block Interventricular conduction disturbance QRS > 100 ms, not due to LBBB or RBBB. Most important causes are hyperkalaemia or tricyclic antidepressant poisoning Advanced Reading Online ...

Left Atrial Enlargement Left atrial enlargement (LAE) is due to pressure or volume overload of the left atrium. LAE is often a precursor to atrial fibrillation. Also known as: Left Atrial Enlargement (LAE), Left atrial hypertrophy (LAH), left atrial abnormality. P wave changes with Left Atrial Enlargement ECG Criteria for Left Atrial Enlargement LAE produces a broad, bifid P wave in lead II (P mitrale) and enlarges the terminal negative portion of the P wave in V1. ...

Left Axis Deviation LAD Left Axis Deviation = QRS axis less than -30°. Normal Axis = QRS axis between -30° and +90° Right Axis Deviation = QRS axis greater than +90° Extreme Axis Deviation = QRS axis between -90° and 180° (AKA “Northwest Axis”) Hexaxial Reference System Hexaxial Reference System – relationship between QRS axis and frontal leads of the ECG. How to recognise left axis deviation Three Lead analysis QRS is POSITIVE (dominant R wave) in Lead I QRS is NEGATIVE (dominant S wave) in leads II, III and aVF ...

Overview of normal sinus rhythm (NSR) The default heart rhythm Pacemaking impulses arise from the sino-atrial node and are transmitted to the ventricles via the AV-node and His-Purkinje system This results in a regular, narrow-complex heart rhythm at 60-100 bpm ECG features of normal sinus rhythm Regular rhythm at a rate of 60-100 bpm (or age-appropriate rate in children) Each QRS complex is preceded by a normal P wave Normal P wave axis: P waves upright in leads I and II, inverted in aVR The PR interval remains constant QRS complexes < 100 ms wide (unless co-existent interventricular conduction delay present) Normal heart rates in children Newborn: 110 – 150 bpm 2 years: 85 – 125 bpm 4 years: 75 – 115 bpm 6 years+: 60 – 100 bpm Variations on sinus rhythm Sinus tachycardia = sinus rhythm with resting heart rate > 100 bpm in adults, or above the normal range for age in children Sinus bradycardia = sinus rhythm with resting heart rate < 60 bpm in adults, or below the normal range for age in children Sinus arrhythmia = sinus rhythm with a beat-to-beat variation in the P-P interval (the time between successive P waves), producing an irregular ventricular rate Example ECG ...

Pacemaker Components 1. Pulse generator Power source Battery Control circuitry Transmitter / Receiver Reed Switch (Magnet activated switch) 2. Lead(s) Single or multiple Unipolar or bipolar Pacemaker Classification Pacemakers are classified by the nature of their pacing mode. Classification follows pacemaker code developed by the North American Society of Pacing and Electrophysiology (NASPE) and the British Pacing and Electrophysiology Group (BPEG). The NASPE/BPEG Generic (NBG) Pacemaker Code was last revised in 2002, although many textbooks still use the previous version from 1987. The code is expressed as a series of up to five letters. NBG Pacemaker Code (2002) ...

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: ...

Definition Time from the start of the Q wave to the end of the T wave Represents time taken for ventricular depolarisation and repolarisation, effectively the period of ventricular systole from ventricular isovolumetric contraction to isovolumetric relaxation The QT interval is inversely proportional to heart rate: The QT interval shortens at faster heart rates The QT interval lengthens at slower heart rates An abnormally prolonged QT is associated with an increased risk of ventricular arrhythmias, especially Torsades de Pointes Congenital short QT syndrome has been found to be associated with an increased risk of paroxysmal atrial and ventricular fibrillation and sudden cardiac death How to measure the QT interval The QT interval is usually measured in either lead II or V5-6, however the lead with the longest measurement should be used Several successive beats should be measured, with the maximum interval taken Large U waves (> 1mm) that are fused to the T wave should be included in the measurement Smaller U waves and those that are separate from the T wave should be excluded The maximum slope intercept method is used to define the end of the T wave (see below) ...

ECG Criteria of Right Atrial Enlargement Right atrial enlargement produces a peaked P wave (P pulmonale) with amplitude: 2.5 mm in the inferior leads (II, III and AVF) 1.5 mm in V1 and V2 Also known as: Right Atrial Enlargement (RAE), Right atrial hypertrophy (RAH), right atrial abnormality P wave changes with Right Atrial Enlargement Causes of Right Atrial Enlargement The principal cause is pulmonary hypertension due to: ...

Sinus Arrhythmia Overview Sinus rhythm with a beat-to-beat variation in the P-P interval (the time between successive P waves), producing an irregular ventricular rate. Characteristics Variation in the P-P interval of more than 120 ms (3 small boxes). The P-P interval gradually lengthens and shortens in a cyclical fashion, usually corresponding to the phases of the respiratory cycle. Normal sinus P waves with a constant morphology (i.e. no evidence of premature atrial contractions). Constant P-R interval (i.e. no evidence of Mobitz I AV block). Mechanism Sinus arrhythmia is a normal physiological phenomenon, most commnonly seen in young, healthy people. ...

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 ...

S-T Segment The ST segment is the flat, isoelectric section of the ECG between the end of the S wave (the J point) and the beginning of the T wave. The ST Segment represents the interval between ventricular depolarization and repolarization. The most important cause of ST segment abnormality (elevation or depression) is myocardial ischaemia or infarction. Causes of ST Segment Elevation ...

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 ...

Regular broad complex tachycardias can be ventricular (VT) or supraventricular (SVT with aberrancy) in origin, and differentiation between the two will significantly influence management of your patients. Unfortunately, the electrocardiographic differentiation of VT from SVT with aberrancy is not always possible. Differential diagnosis of regular broad complex tachycardia Ventricular tachycardia (VT) Supraventricular tachycardia (SVT) with aberrant conduction due to bundle branch block SVT with any metabolic disturbance that slows supraventricular action potential propagation — hyperkalaemia, sodium channel blockade, severe acidosis Antidromic AVRT — re-entrant tachyarrhythmia seen in Wolff-Parkinson-White syndrome Accelerated idioventricular rhythm (AIVR) ECG features increasing the likelihood of VT Electrocardiographic features that increase the likelihood of VT include: ...

The rhythm is best analyzed by looking at a rhythm strip. On a 12 lead ECG this is usually a 10 second recording from Lead II. Confirm or corroborate any findings in this lead by checking the other leads. A longer rhythm strip, recorded perhaps recorded at a slower speed, may be helpful. 7 step approach to ECG rhythm analysis 1. Rate Tachycardia or bradycardia? Normal rate is 60-100/min. 2. Pattern of QRS complexes Regular or irregular? If irregular is it regularly irregular or irregularly irregular? 3. QRS morphology Narrow complex: sinus, atrial or junctional origin. Wide complex: ventricular origin, or supraventricular with aberrant conduction. 4. P waves Absent: sinus arrest, atrial fibrillation Present: morphology and PR interval may suggest sinus, atrial, junctional or even retrograde from the ventricles. 5. Relationship between P waves and QRS complexes AV association (may be difficult to distinguish from isorhythmic dissociation) AV dissociation *complete:*atrial and ventricular activity is always independent. incomplete: intermittent capture. 6. Onset and termination Abrupt: suggests re-entrant process. Gradual: suggests increased automaticity. 7. Response to vagal manoeuvres Sinus tachycardia, ectopic atrial tachydysrhythmia: gradual slowing during the vagal manoeuvre, but resumes on cessation. AVNRT or AVRT: abrupt termination or no response. Atrial fibrillation and atrial flutter: gradual slowing during the manoeuvre. VT: no response. Differential Diagnosis Follow links below for examples of individual rhythms. ...