ECG

P wave

• Rounded
•  Height 2.5 sm .sq
• Width 2.5 sm.sq

 PR interval

• 0.12-0.20 s(maximum 5 sm. sq)

Q wave

• Absent in most leads
• Height(Depth) 2 sm. sq
• Width 1 sm. sq

R wave

• Height : AVL <13mm , AVF<20mm , V5-6<25mm
• R wave progression-Amplitude of R wave  gradually increases  from V1-V6(S wave decreases with R wave)
• Poor progression R wave-Amplitude of R wave gradually decreases from V1-V6

QRS complex

• 0.08-0.11 s
• Height <25mm
• Width <3 mm(2.5 sm sq.)

ST segment

• In isoelectric line
• Considered normal upto-

·         1mm in limb lead and 2mm in chest lead above isoelectric line

·         0.5mm below isoelectric line

T wave

• Rounded
• Upright in all leads except AVR
• Height>2mm
• May be inverted in V1&2

QT interval

• 0.34-0.43s
• Best seen in AVL as there is no U wave

Side and surface

Anterior surface

• V1,V2-RV
• V3,V4-IV septum

Lateral surface

• V5,V6-Low lateral
• Lead 1 ,avL-High lateral

Inferior surface

• Lead 2 , lead 3 ,avF

Extensive anterior surface

• Anterior+lateral

Rhythm strip

• Lead 2 is rhythm strip
• If irregular R-R interval>Find rhythm strip>(No. of R wave within 30 large sq.)10 =HR

Abnormality of waves/complex with interpretation

P wave(Absent ,tall ,small ,wide ,inverted ,variable ,multiple)

• Absent-AF(f wave replacement) ,AF(Saw tooth appearance) ,VT, VE , SVT
• Tall/P pulmonale-RAE
• Small-AT
• Wide and notched/P mitrale-LAE
• Inverted-Dextrocardia ,incorrect lead placement
• Variable-Wandaring pacemaker

PR interval-(Prolonged ,short ,variable)

• Prolonged-1st degree HB ,IHD
• Short-WPWS(Wolff parkison white syndrome-Re entry circuit via accessory pathway from ventricle to atria with normal impulse from atria to ventricle.Delta wave is found) ,LGLS(lown ganong levine syndrome-No delta wave)
• Variable-

·         Wenckebach phenomenon/MT1-Progressive lengthening  followed by drop beat

·         MT2-Fixed and prolonged

                                     2:1-2 wave complex and 1 drop beat

                                     3:1-3 wave complex and 1 drop beat

·         Complete HB-No relation between P wave and QRS complex

• Q wave

Pathological Q wave-MI ,LBBB

R wave(Tall ,small)

• Tall-LVH ,RVH
• Small-Pericardial effusion

RVH------------------------------------------------	V1: R>/=S wave Right axis deviation(Opposite)
LVH------------------------------------------------ Dilated cardiomyopathy>No LVH feat. Hypertrophied cardiomyopathy>LVH feat.	avL: R>13mm avF: R>20mm SV1+RV6>35 mm Left axis deviation(tR1 ,dS3)

tR1-tall R in lead 1

dS3-deep S in lead 3

QRS complex(Wide ,narrow ,variable)

• Wide-Ventricular ectopics , ventricular ectopic ,VT
• Narrow-SVT
• Variable-VF

Ventricular ectopic	Wide QRS <3
VT	3/more consequetive wide QRS
Ventricular ectopics	Many wide QRS but not consequetive
Multifocal  ventricular ectopics	Many wide QRS complex Different shaped
Multiple ventricular ectopics	Many wide QRS complex All same shaped
VT/VE/SVT	Very high pulse rate ,so do ECG
Cardioversion	To return abnormal heart  rhythm back to sinus rhythm e.g. Chemical cardioversion(Lignocaine) Electrical cardioversion(DC shock) When cardioversion fails>Radio frequency catheter ablation>Chance of HB>Pacemaker

Arrhythmia

• Abnormality in rate/rhythm/both.
• Abnormality in initiation and propagation of cardiac impulse
• Slow AF=Rate<60
• Fast AF=Rate>100

Atrial fibrillation

• Absent P wave ,may be replaced by f wave
• RR interval irregular

Causes

• Chronic rheumatic heart disease specially MS
• Coronary artery disease specially MI
• HTN
• Thyrotoxicosis

Complication

• Systemic embolism(LH)
• Pulmonary embolism(RH)
• HF

Types

• Paroxysmal
• Persistent-Long duration ,Rx response
• Permanent-Long duration ,difficult to control even  with cardioversion

ST segment(Elevation ,depression)

• Elevation-Recent MI(Convexity upward) ,acute pericarditis(Concavity upward)
• Depression-Subacute MI ,angina ,digoxin toxicity(Thumb impression/reverse tick)

T wave(Inversion ,tall ,small)

• Inversion-Subendocardial MI(Non Q wave MI) ,acute pericarditis
• Tall-Hyperkalemia ,hyperacute MI
• Small-Hypokalemia ,pericardial effusion

U wave(Inversion ,prominent)

• Inversion-IHD ,hypertensive heart disease
• Prominent-Hypokalemia

QT interval(Short ,prolonged)

• Short-Hypercalcemia
• Prolonged-Hypocalcemia , acute myocarditis