Ii. Method Of Ecg Interpretation

II. "Method" of ECG Interpretation Frank G. Yanowitz, MD Professor of Medicine University of Utah School of Medicine

This "method" is recommended when reading all 12-lead ECG's. Like the physical examination, it is desirable to follow a standardized sequence of steps in order to avoid missing subtle abnormalities in the ECG tracing, some of which may have clinical importance. The 6 major sections in the "method" should be considered in the following order:

1. 2. 3. 4. 5. 6.

Measurements Rhythm Analysis Conduction Analysis Waveform Description Ecg Interpretation Comparison with Previous ECG (if any)

1. Measurements (usually made in frontal plane leads):

Heart rate (state atrial and ventricular, if different) PR interval (from beginning of P to beginning of QRS) QRS duration (width of most representative QRS) QT interval (from beginning of QRS to end of T) QRS axis in frontal plane (go to: "How To Determine Axis") Go to: ECG Measurement Abnormalities (Lesson IV) for description of normal and abnormal measurements

2. Rhythm Analysis State basic rhythm (e.g., "normal sinus rhythm", "atrial fibrillation", etc.) Identify additional rhythm events if present (e.g., "PVC's", "PAC's", etc) Consider all rhythm events from atria, AV junction, and ventricles Go to: ECG Rhythm Abnormalities (Lesson V) for description of arrhythmias

3. Conduction Analysis "Normal" conduction implies normal sino-atrial (SA), atrio-ventricular (AV), and intraventricular (IV) conduction.

The following conduction abnormalities are to be identified if present: SA block (lesson VI): 2nd degree (type I vs. type II) AV block (lesson VI): 1st, 2nd (type I vs. type II), and 3rd degree IV blocks (lesson VI): bundle branch, fascicular, and nonspecific blocks Exit blocks: blocks just distal to ectopic pacemaker site (Go to ECG Conduction Abnormalities (Lesson VI) for a description of conduction abnormalities)

4. Waveform Description Carefully analyze the 12-lead ECG for abnormalities in each of the waveforms in the order in which they appear: Pwaves, QRS complexes, ST segments, T waves, and... Don't forget the U waves. P waves (lesson VII): are they too wide, too tall, look funny (i.e., are they ectopic), etc.? QRS complexes: look for pathologic Q waves (lesson IX), abnormal voltage (lesson VIII), etc. ST segments (lesson X): look for abnormal ST elevation and/or depression. T waves (lesson XI): look for abnormally inverted T waves. U waves (lesson XII): look for prominent or inverted U waves.

5. ECG Interpretation This is the conclusion of the above analyses. Interpret the ECG as "Normal", or "Abnormal". Occasionally the term "borderline" is used if unsure about the significance of certain findings. List all abnormalities. Examples of "abnormal" statements are: Inferior MI, probably acute Old anteroseptal MI Left anterior fascicular block (LAFB) Left ventricular hypertrophy (LVH) Nonspecific ST-T wave abnormalities Any rhythm abnormalities

Example:

Left Anterior Fascicular Block (LAFB)-KH Frank G.Yanowitz, M.D. HR=72bpm; PR=0.16s; QRS=0.09s; QT=0.36s; QRS axis = -70o (left axis deviation) Normal sinus rhythm; normal SA and AV conduction; rS in leads II, III, aVF Interpretation: Abnormal ECG: 1)Left anterior fascicular block

6. Comparison with previous ecg If there is a previous ECG in the patient's file, the current ECG should be compared with it to see if any significant changes have occurred. These changes may have important implications for clinical management decisions.