12 Lead ECG Interpretation

Course overview

Objectives Explain 12 lead electrophysiology Describe the interpretation steps of 12 lead ECGs Content Lead systems and heart surfaces ECG rhythm analysis Value Limitations Heart surfaces Inferior Left lateral Precordial Acute signs of ischemia injury and necrosis Possible early identification of patients with acute myocardial infarction for intervention thrombolysis PTCA The role of out of hospital 12 lead ECG is not universally available but is appropriate in most EMS settings with proper medical oversight Advantages and disadvantages ST segment elevation Height depth and contour ST acute changes Anterior wall significant ST elevation in V1 V4 may indicate anterior involvement Inferior wall significant ST elevation in II III and aVF may indicate inferior involvement Q waves ST segment depression in eight or more leads ST segment elevation in aVR and V1 Depth duration and significance Greater than 5 mm greater than 04 seconds May indicate necrosis May indicate extensive transient ischemia Cardiac arrhythmias Approach to analysis P wave Configuration Duration Atrial rate and rhythm PR interval QRS complex Configuration Duration Ventricular rate and rhythm ST segment Contour Elevation Depression QT interval Duration Implication of prolongation Relationship of P waves to QRS complexes Consistent Progressive prolongation No relationship T waves U waves Interpretation of the ECG Origin of complex Rate Rhythm Clinical significance Arrhythmias originating in the sinus node Sinus bradycardia Sinus tachycardia Sinus arrhythmia Sinus arrest Arrhythmias originating in the atria Premature atrial complex Atrial ectopic tachycardia Reentrant tachycardia Multifocal atrial tachycardia Atrial flutter Atrial fibrillation Atrial flutter or atrial fibrillation with junctional rhythm Atrial flutter or atrial fibrillation with preexcitation syndromes Arrhythmias originating within the AV junction First degree AV block Second degree AV block Type I Wenckebach Type II infranodal classical Complete AV block third degree block Arrhythmias sustained or originating in the AV junction AV nodal reentrant tachycardia AV reciprocating tachycardia Narrow Wide Junctional escape rhythm Premature junctional complex Accelerated junctional rhythm Junctional tachycardia Arrhythmias originating in the ventricles Idioventricular rhythm Accelerated idioventricular rhythm Premature ventricular complex ventricular ectopic R on T phenomenon Paired couplets Multiformed Frequent uniform Rule of bigeminy pertaining to precipitating ventricular arrhythmias Ventricular tachycardia Monomorphic and polymorphic Ventricular fibrillation Ventricular standstill Asystole Abnormalities originating within the bundle branch system Incomplete or complete Right bundle branch block Left bundle branch block Differentiation of wide QRS complex tachycardia Potential causes Supraventricular tachycardia with bundle branch block Accessory pathways Differentiation Physical evaluation Cannon A waves Varying intensity of first heart tone Beat to beat changes in blood pressure ECG differences Aberration as a result of premature atrial complex Identify PAC in previous ST segment or T wave Sudden change in rate with bundle branch aberration Concealed retrograde conduction Right bundle branch refractoriness may be time dependent Compare with previous ECG when available Right bundle branch block aberration V1 positive Biphasic lead I with broad terminal S wave Triphasic QRS in V4 Left bundle branch block aberration V1 negative Monophasic notched lead I Slurred notched or RSr pattern in leads V4 V5 or V6 Concordant precordial pattern Totally negative precordial pattern is diagnostic of ventricular tachycardia Totally positive precordial pattern is suggestive of ventricular tachycardia Preexisting bundle branch block prior to onset of tachycardia Other considerations When in doubt Cardioversion when hemodynamic state is compromised or changing