ECG Lecture
Part 1
ECG Interpretation
Selim Krim, MD
Assistant Professor
Texas Tech University Health Sciences Center
Step wise approach to ECG
Measurements
Rhythm Analysis
Conduction Analysis
Waveform Description
ECG Interpretation
Comparison with Previous ECG (if any)
Measurements
Heart rate 60-90 bpm
PR interval (from beginning of P to beginning of
QRS) =0.12-0.20 sec
QRS duration (width of most representative
QRS) <0.12 sec
QT interval (from beginning of QRS to end of T)
= 0.42 sec
QRS axis in frontal plane
Measurements
Heart rate
State atrial and ventricular rate.
P wave rate 60-100 bpm
Rate < 60 = Sinus bradycardia
Rate > 90 = Sinus tachycardia
How to calculate Heart Rate
Standard textbooks of physiology and medicine mention
that heart rate (HR) is readily calculated from the ECG
as follows: HR = 1,500/RR interval in millimeters, HR =
60/RR interval in seconds, or HR = 300/number of large
squares between successive R waves
Measurements
Measurements
The P wave represents atrial activation; the PR
interval is the time from onset of atrial activation
to onset of ventricular activation. The QRS
complex represents ventricular activation; the
QRS duration is the duration of ventricular
activation. The ST-T wave represents ventricular
repolarization. The QT interval is the duration of
ventricular activation and recovery. The U wave
probably represents "after depolarizations" in the
ventricles.
How To Determine Axis
How To Determine Axis
How To Determine Axis
How To Determine Axis
How to Determine Axis
How to Determine Axis
Step wise approach to ECG
Measurements
Rhythm Analysis
Conduction Analysis
Waveform Description
ECG Interpretation
Comparison with Previous ECG (if any)
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
Rhythm Analysis
Sinus rhythm defined as;
Each P wave is followed by QRS
P wave is positive in lead I, II
Constant PR interval
Rhythm Analysis
Rhythm Analysis
Step wise approach to ECG
Measurements
Rhythm Analysis
Conduction Analysis
Waveform Description
ECG Interpretation
Comparison with Previous ECG (if any)
Conduction Analysis
Conduction Analysis
Sino-Atrial Exit Block (SA Block): Type 1,2
Atrio-Ventricular (AV) Block: 1st, 2nd and 3rd degree
AV Dissociation
Intraventricular Blocks; RBBB, LBBB, LAFB, RPFB,
Bifascicular
Nonspecific Intraventricular Conduction Defects (IVCD)
Wolff-Parkinson-White Preexcitation
Step wise approach to ECG
Measurements
Rhythm Analysis
Conduction Analysis
Waveform Description
ECG Interpretation
Comparison with Previous ECG (if any)
Waveform Description
Carefully analyze the 12-lead ECG for abnormalities in each of the
waveforms in the order in which they appear:
P waves: are they too wide, too tall, look funny (i.e., are they
ectopic), etc.?
QRS complexes: look for pathologic Q waves, abnormal voltage,
etc.
ST segments: look for abnormal ST elevation and/or depression.
T waves: look for abnormally inverted T waves.
U waves: look for prominent or inverted U waves.
Waveform Description
Waveform Description
Waveform Description
Waveform Description
The normal U wave has the same polarity
as the T wave and is usually less than
one-third the amplitude of the T wave. U
waves are usually best seen in the right
precordial leads especially V2 and V3. The
normal U wave is asymmetric with the
ascending limb moving more rapidly than
the descending limb (just the opposite of
the normal T wave).
Step wise approach to ECG
Measurements
Rhythm Analysis
Conduction Analysis
Waveform Description
ECG Interpretation
Comparison with Previous ECG (if any)
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
Step wise approach to ECG
Measurements
Rhythm Analysis
Conduction Analysis
Waveform Description
ECG Interpretation
Comparison with Previous ECG (if any)
Let’s practice!
ECG 1
ECG 2
ECG 3
ECG 4
ECG 5
ECG 6
Questions ?
Thank you