Systematic ECG interpretation

SCGH CME

March 17 2016

Components of ECG Rate Rhythm Axis P PR QRS QT ST

Other waves Delta Epsilon Osborne U

Rate Small square 0.04 Big square 0.2

Slow 300/big square Fast 1500/small

square Irregular – count

complexes on rhythm strip x 6 gives average rate

Big squares rate

2 1502.5 1203 1003.5 864 754.5 665 605.5 546 506.5 467 42

Axis https://www.youtu

be.com/watch?v=_CCUWdAaQoA

Axis differentials Left -30 to -90 LBBB LAFB LVH Inferior MI Paced rhythm

Right +90 to +180 RVH LPFB Lateral MI Lung disease –

acute/chronic Hyperkalemia Na channel blockade Dextrocardia NORMAL IN INFANTS and

skinny adults

P WAVE PR interval

120 – 200 msec Long – any heart

block Short – WPW, pre-

excitation Elevation/

depression - pericarditis

Width < 120 msec Amplitude <2.5mm in limb

leads <1.5mm in

precordial leads V1 biphasic Avf inverted

QRS Amplitude Duration Q wave R wave Hypertrophy Bundle branch block J point

Q wave Pathological if >40 ms wide >2mm deep >0.25% QRS Present in leads v1-v3

> 2mm Can be normal in leads III /avR

R wave in V1 RVH - PE Posterior MI RBBB HOCM WPW Dextrocardia Normal in Kids

R WaveR wave in AVR

Na channel blockade

VT Dextrocardia Limb lead reversal

R wave progression

R wave <3mm in V3

Signifies anteroseptal MI

LVH

Left Ventricular hypertrophy

Voltage + non voltage Muscle wall thickens Leading to increased S

wave amplitude in right sided leads

Increased R wave amplitude in left sided leads

Prolonged depolarisation Repolarisation

abnormalities in lateral leads

Causes HTN AR/AS MR HOCM

LVHvoltage

S in V1 + R in V5/V6 > 35mm

AVL R wave 11mm

Non voltage ST depression/T

wave inversion in lateral leads

Increased R wave peak time > 50msec in V5 V6

LVH

RVH Right axis Dominant R in V1 > 7mm or RS ratio >1 Dominant S in V6 > 7mm or RS ratio <1 RV strain – ST depression in V1-4 and

inferiorly

Causes PE Chronic lung disease Pulmonary HTN Mitral stenosis Congenital heart disease Arrythmogenic RV cardiomyopathy

RVH

BBB

ST segment

J pointNotching - BER

Osborne wave - hypothermia

QT Ventricular depolarisation and repolarisation Calculate in lead 2 or V5 V6 Include U waves 440 msec for women 450msec for men Prolongs at slower HR QT> 500 increased risk of toursades Bezetts formula accurate over HR 60-100 HR nomogram for toxicology for risk of

toursades

Long QT

T waves Inverted in V1 and AVR Can be – flat, biphasic, inverted, camel

humped or hyperacute Dynamic change most important Don’t miss Wellens syndrome

Wellens Syndrome

Other Waves

Rhythm Regular, irregular, regularly irregular

Heart block Atrial , AVNRT, Accessory pathways Junctional rhythm Ventricular rhythms Distinguish VT from SVT with BBB

AIVR

VT or SVT with abberancy If >35 or Hx of IHD – likely VT Look for Width > 160msec QRS VT likely Concordance Fusion beats Capture beats Right/left axis AV dissociation – p waves notching the QRS First rabbit ear taller RSR1

Children Right sided dominance as infants Should be normal by age 3-4 Rate age dependent Inverted T waves V1-4 can be normal Infant QT 490 https://www.starship.org.nz/for-health-

professionals/starship-clinical-guidelines/e/electrocardiograph-ecg/

QUIZ TIME