5 step + mimicers + ECG signs

Question 1

5 Step

Answer 1

Rate 
Rhythm 
P waves 
PR interval
QRS

Question 2

300 method

Answer 2

300 150 100 75 60 50 43 38

Question 3

P waves normals

Answer 3

Duration: < 0.06-0.10 s
Amplitude

< 2.5 to 0.5mm (0.25mV) in the limb leads
< 1.5 mm (0.15mV) in the precordial leads

Peak mean R atrial enlargement
Longer mean L atria enlargement

Question 4

P-R interval

Answer 4

(0.12-0.20s) in duration
Short PR interval (<120ms)
A short PR interval is seen with:

Preexcitation syndromes
AV nodal (junctional) rhythm.

Question 5

Pathological Q waves

Answer 5

Pathological Q Waves
Q waves are considered pathological if:

> 40 ms (1 mm) wide
> 2 mm deep
> 25% of depth of QRS complex
Seen in leads V1-3
Pathological Q waves usually indicate current or prior myocardial infarction.

Question 6

QRS

Answer 6

Duration 0.12
Tall -  hypertrophy of one or both ventricles
–  an abnormal pacemaker
–  aberrantly conducted beat
small-   obese patients
–  hyperthyroid patients
–  pleural effusion

Question 7

T waves

Answer 7

< 5mm in limb leads, < 10mm in precordial leads
Tall, narrow, symmetrically peaked T-waves are characteristically seen in hyperkalaemia.
Broad, asymmetrically peaked or ‘hyperacute’ T-waves are seen in the early stages of ST-elevation MI (STEMI) and often precede the appearance of ST elevation and Q waves.

They are also seen with Prinzmetal angina.
Inverted T waves are seen in the following conditions:

Normal finding in children
Persistent juvenile T wave pattern
Myocardial ischaemia and infarction
Bundle branch block
Ventricular hypertrophy (‘strain’ patterns)
Pulmonary embolism
Hypertrophic cardiomyopathy
Raised intracranial pressure

Question 8

Biphasic T waves

Answer 8

Biphasic T waves
There are two main causes of biphasic T waves:

Myocardial ischaemia
Hypokalaemia
The two waves go in opposite directions:

Biphasic T waves due to ischaemia – T waves go UP then DOWN

Question 9

Left axis deviation

Answer 9

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”)

QRS is POSITIVE (dominant R wave) in Lead I
QRS is NEGATIVE (dominant S wave) in leads II, III and aVF

If the QRS is upright in lead I (positive) and downward in lead aVF (negative), then the axis is between 0 and -90 degrees. QRS axis could fall between 0 and -30, which is within normal limits. To further distinguish normal from left axis deviation in this setting, look at lead II. If lead II is downward (negative), then the axis is more towards -120, and left axis deviation is present.

Causes Left anterior fascicular block
Left bundle branch block
Left ventricular hypertrophy
Inferior MI
Ventricular ectopy
Paced rhythm
Wolff-Parkinson White syndrome

Question 10

QT

Answer 10

0.36-0.44

Question 11

Tall QRS/ small QRS

Answer 11

Usually caused by:
–  hypertrophy of one or both ventricles
–  an abnormal pacemaker
–  aberrantly conducted beat

Seen in:
–  obese patients
–  hyperthyroid patients
–  pleural effusion

Question 12

RAD

Answer 12

lead one neg

AVf postitive

Question 13

LAD

Answer 13

lead one posigtive

AVF neg

Question 14

Wave check

Answer 14

Q waves
ST elevation/depression
Tall T waves 
Inverted T waves 
axis R or L