ECG, Medical, Normal ECG

[Safa mughal]

Normal adult 12-lead ECG

Normal sinus rhythm

each P wave is followed by a QRS

P waves normal for the subject

P wave rate 60 – 100 bpm with <10% variation

rate <60 = sinus bradycardia

rate >100 = sinus tachycardia

variation >10% = sinus arrhythmia

normal QRS axis

normal P waves

height < 2.5 mm in lead II

width < 0.11 s in lead II

for abnormal P waves see right atrial hypertrophy, left atrial hypertrophy, atrial premature beat, hyperkalaemia

normal PR interval

0.12 to 0.20 s (3 – 5 small squares)

for short PR segment consider Wolff-Parkinson-White syndrome or Lown-Ganong-Levine syndrome (other causes – Duchenne muscular dystrophy, type II glycogen storage disease (Pompe’s), HOCM)

for long PR interval see first degree heart block and ‘trifasicular’ block

normal QRS complex < 0.12 s duration (3 small squares)

for abnormally wide QRS consider right or left bundle branch block, ventricular rhythm, hyperkalaemia, etc.

no pathological Q waves

no evidence of left or right ventricular hypertrophy

normal QT interval

Calculate the corrected QT interval (QTc) by dividing the QT interval by the square root of the preceeding R – R interval. Normal = 0.42 s.

Causes of long QT interval

myocardial infarction, myocarditis, diffuse myocardial disease

hypocalcaemia, hypothyroidism, subarachnoid haemorrhage, intracerebral haemorrhage, drugs (e.g. sotalol, amiodarone), hereditary, Romano Ward syndrome (autosomal dominant)

Jervill + Lange Nielson syndrome (autosomal recessive) associated with sensorineural deafness, normal ST segment,no elevation or depression, causes of elevation include acute MI (e.g. anterior, inferior), left bundle branch block, normal variants (e.g. athletic heart, Edeiken pattern, high-take off), acute pericarditis

causes of depression include myocardial ischaemia, digoxin effect, ventricular hypertrophy, acute posterior MI, pulmonary embolus, left bundle branch block

normal T wave

causes of tall T waves include hyperkalaemia, hyperacute myocardial infarction and left bundle branch block

causes of small, flattened or inverted T waves are numerous and include ischaemia, age, race, hyperventilation, anxiety, drinking iced water, LVH, drugs (e.g. digoxin), pericarditis, PE, intraventricular conduction delay (e.g. RBBB)and electrolyte disturbance.

normal U wave

source:ecglibrary.com