EKG Reading                     by Jack CF Chong, MS, MD.

Sequence

• Rate and regularity.
• Axis.
• Atrial activity.
• QRS complex.
• A-V association.
• Rhythm.
• Hypertrophy.
• ST-T change.
• Abnormal Q.
• AMI.

Rate and regularity

• Rule of 300 : 300 - 150 - 100 - 75 - 60 - 50.
• Rate = 300 / ¤¤®æ¼Æ.
• Irregular rate = No of R in 6- strip x 10.
• Normal rate : 60~100 /min.

Axis

• Normal : -30 to 90 degrees.
• +ve lead I ( left axis ) :
  • +ve II : Normal axis.
  • -ve II : LAD.
• -ve lead I ( right axis ) :
  • +ve aVF : RAD.
  • -ve aVF : RSA ( right superior axis ).

Atrial activity

• Sinus P : +ve in I, II, and aVF.
• Components of P wave :
  • Initial 2/3 : RA component.
  • Later 2/3 : LA component ( overlap in middle 1/3 ).
• RAE : Height of P > 2.5mm in II, III, aVF.
  • COPD with cor pulmonale.
  • Pulmonary embolism.
  • ASD ( adult’s most common CHD ).
• LAE : Double peaks in P ( >0.04 sec apart ) in any leads; depth and width of the negative LA component of P in V1 > 1mm.
  • MS or MR.
  • AS or AR.
  • DCM or HCVD.

QRS complex

• Wide QRS : Interval > 0.1 sec ( ¥b­Ó¤¤®æ ).
• Wide QRS :
  • Typical RBBB.
• V1 : rSR with inverted T.
• I and V6 :p slurred S with upward T.
  • Typical LBBB.
• V1 : rS ( deep S ) or QS pattern with upward T.
• I and V6 : RsR?( notched R ) with inverted T.
  • IVCD ( intraventricular conduction delay ).
  • WPW synd if ass?with delta wave and short PR.

A-V association

• AVB :
  • 1^o AVB : PR > 0.22 sec ( 1­Ó¤¤®æ ).
  • 2^o AVB :
• Morbitz I : Grouped beats.
• Morbitz II : Missed beats.
  • 3^o AVB : A-V dissociation.
• Short PR interval : < 0.12 sec ( 3­Ó¤p®æ ).
  • WPW synd if ass¡¦ with delta wave ( slurred upstroke ) and wide QRS.

Rhythm

• NSR.
• Tachycardia :
  • Regular : achycardia, AF, PSVT, VT.
  • Irregular : Af, Vf, MAT, APCs, VPCs.
• Bradycardia :
  • Regular : Sinus bradycardia, junctional bradycardia.
  • Irregular : 2^o AVB, 3^o AVB, SSS.

Hypertrophy

• RVH : R > S in V1.
• LVH :
  • R > 27mm in V5,6.
  • R ( V5,6 ) + S ( V1 ) > 36mm.
• Strain pattern :
  • ST depression
  • T inversion.
• Systolic overloading = Hypertrophy + strain pattern.
  • e.g. COPD + cor pulmonale : RVH + strain pattern.
  • e.g. HCVD : LVH + strain pattern.
• Diastolic overloading :
  • e.g. ASD : RVH + RSR?in V1 ( RBBB pattern ).
  • e.g. MR or AR : LVH + ST?with tall T in V5,6.
    ¡@

ST-T change

• J-point : 0.08 sec from R.
• ST elevation : J-point elevation >1mm or more.
  • Concave ( may be normal variant in youngsters ).
  • Oblique.
  • Convex.
  • Plateau.
• Causes of ST elevation:
  • AMI.
  • Pericarditis ( diffuse ).
  • Prinzmetal or variant angina ( ST normalizes with NTG use ).
• ST depression : J-point elevation >1mm or more.
  • Downsloping.
  • Horizontal.
  • Upsloping ( only when depression >2mm or more ).
  • Scooping ( digitalis effect ).

Abnormal Q

• Width > 0.04 sec.
• Depth > 1/4 of QRS.   

AMI

• Three EKG criteria :
• 1. Localization :
  • Inferior wall : II, III, aVF.
  • Anteroseptal : V1, V2, V3.
  • High lateral : I, aVL, V5, V6.
  • Right : V4R.
  • Posterior : R > S in V1 with poor R progression.
• 2. Reciprocal chage : ST depression in the contralateral side.
• 3. Evolutional change :
  • Hyperacute T.
  • ST elevation ( oblique - convex - plateau ).
  • ST normalization.
  • Q waves.

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