ECG Lecture ECG Lecture Part 1 Part 1

ECG InterpretationECG Interpretation

Selim Krim, MDSelim Krim, MDAssistant ProfessorAssistant Professor

Texas Tech University Health Sciences CenterTexas Tech University Health Sciences Center

Step wise approach to ECGStep wise approach to ECG

Measurements

Rhythm Analysis

Conduction Analysis

Waveform Description

ECG Interpretation

Comparison with Previous ECG (if any)

MeasurementsHeart rate 60-90 bpmHeart rate 60-90 bpm

PR interval (from beginning of P to beginning of PR interval (from beginning of P to beginning of QRS) =QRS) =0.12-0.20 sec0.12-0.20 sec

QRS duration (width of most representative QRS) QRS duration (width of most representative QRS) <0.12 sec<0.12 sec

QT interval (from beginning of QRS to end of T) QT interval (from beginning of QRS to end of T) = = 0.42 sec0.42 sec

QRS axis in frontal plane QRS axis in frontal plane

Measurements

Heart rateHeart rate

State atrial and ventricular rate.State atrial and ventricular rate.

P wave rate 60-100 bpmP wave rate 60-100 bpm

Rate < 60 = Rate < 60 = Sinus bradycardiaSinus bradycardia

Rate > 90 = Rate > 90 = Sinus tachycardiaSinus tachycardia

How to calculate Heart RateHow to calculate Heart Rate

Standard textbooks of physiology and medicine mention Standard textbooks of physiology and medicine mention that heart rate (HR) is readily calculated from the ECG that heart rate (HR) is readily calculated from the ECG as follows: HR = 1,500/RR interval in millimeters, HR = as follows: HR = 1,500/RR interval in millimeters, HR = 60/RR interval in seconds, or HR = 300/number of large 60/RR interval in seconds, or HR = 300/number of large squares between successive R waves squares between successive R waves

Measurements

Measurements

The P wave represents atrial activation; the PR The P wave represents atrial activation; the PR interval is the time from onset of atrial activation interval is the time from onset of atrial activation to onset of ventricular activation. The QRS to onset of ventricular activation. The QRS complex represents ventricular activation; the complex represents ventricular activation; the QRS duration is the duration of ventricular QRS duration is the duration of ventricular activation. The ST-T wave represents ventricular activation. The ST-T wave represents ventricular repolarization. The QT interval is the duration of repolarization. The QT interval is the duration of ventricular activation and recovery. The U wave ventricular activation and recovery. The U wave probably represents "after depolarizations" in the probably represents "after depolarizations" in the ventricles. 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 ECGStep wise approach to ECG

Measurements

Rhythm Analysis

Conduction Analysis

Waveform Description

ECG Interpretation

Comparison with Previous ECG (if any)

Rhythm AnalysisRhythm Analysis

State basic rhythm (e.g., "normal sinus rhythm", "atrial State basic rhythm (e.g., "normal sinus rhythm", "atrial fibrillation", etc.) fibrillation", etc.)

  Identify additional rhythm events if present (e.g., Identify additional rhythm events if present (e.g., "PVC's", "PAC's", etc) "PVC's", "PAC's", etc)

  Consider all rhythm events from atria, AV junction, and Consider all rhythm events from atria, AV junction, and ventricles ventricles

Rhythm AnalysisRhythm Analysis

Sinus rhythm defined as;Sinus rhythm defined as;

Each P wave is followed by QRSEach P wave is followed by QRS

P wave is positive in lead I, IIP wave is positive in lead I, II

Constant PR intervalConstant PR interval

Rhythm Analysis

Rhythm Analysis

Step wise approach to ECGStep wise approach to ECG

Measurements

Rhythm Analysis

Conduction Analysis

Waveform Description

ECG Interpretation

Comparison with Previous ECG (if any)

Conduction AnalysisConduction 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

Conduction Analysis

Step wise approach to ECGStep wise approach to ECG

Measurements

Rhythm Analysis

Conduction Analysis

Waveform Description

ECG Interpretation

Comparison with Previous ECG (if any)

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

Waveform Description

The normal U wave has the same polarity The normal U wave has the same polarity as the T wave and is usually less than as the T wave and is usually less than one-third the amplitude of the T wave. U one-third the amplitude of the T wave. U waves are usually best seen in the right waves are usually best seen in the right precordial leads especially V2 and V3. The precordial leads especially V2 and V3. The normal U wave is asymmetric with the normal U wave is asymmetric with the ascending limb moving more rapidly than ascending limb moving more rapidly than the descending limb (just the opposite of the descending limb (just the opposite of the normal T wave). the normal T wave).

Step wise approach to ECGStep 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 This is the conclusion of the above analyses. Interpret the ECG as "Normal", or "Abnormal". Occasionally the term "borderline" is used "Normal", or "Abnormal". Occasionally the term "borderline" is used if unsure about the significance of certain findings. List all if unsure about the significance of certain findings. List all abnormalities. Examples of "abnormal" statements are:  Inferior MI, abnormalities. Examples of "abnormal" statements are:  Inferior MI, probably acute probably acute    Old anteroseptal MI Old anteroseptal MI

Left anterior fascicular block (LAFB) Left anterior fascicular block (LAFB)

Left ventricular hypertrophy (LVH) Left ventricular hypertrophy (LVH)

Nonspecific ST-T wave abnormalities Nonspecific ST-T wave abnormalities

Any rhythm abnormalities Any rhythm abnormalities

Step wise approach to ECGStep wise approach to ECG

Measurements

Rhythm Analysis

Conduction Analysis

Waveform Description

ECG Interpretation

Comparison with Previous ECG (if any)

Let’s practice!Let’s practice!

ECG 1

ECG 2

ECG 3

ECG 4

ECG 5

ECG 6

Questions ?Questions ?

Thank youThank you