ECG/EKG Analysis

Calibration

• paper speed is normally 25mm/second
  • therefore each 1mm box in the x axis = 0.04sec
• a 1mV test pulse is normally over 10 mm
  • therefore each 1mm box in the y axis = 0.1 mV

Rhythm

• P wave upright in I, II, AVF
• PR interval > 0.12
• P wave for every QRS
• QRS for every P wave

Rate

• 300,150,100,75, 60, 50 rule
• If rhythm is not normal count the number of QRS complexes in 25 big boxes (5 seconds) and multiply by 12
• tachycardia >100bpm
• bradycardia <60bpm

Axis

• QRS upright in I and aVF
• If not upright in aVF look @ II
  • If upright then axis is normal
  • If not then there is left axis deviation

Intervals

• PR 0.12-0.20 (3-5 squares)
• QRS < 0.10 (2.5 square)
• QT <0.44 (11 squares)

Atrial enlargement

• Right atrium - lead II - p wave wave's initial component is enlarged, taller 2.5mm
• Left atrium - Lead V1 - p wave downward deflection of terminal component

Ventricular hypertrophy

• Right ventrical - tall R waves in V1 and V2, deep S in V6
• Left ventrical - tall R wave in V6, deep S in V1, plus one of
  • R in V5/6 > 26mm
  • S in V1 or 2 + R in V5 or V6 > 35 mm
  • R+S in any chest lead > 45mm

• • R in aVL > 11mm
  • R in I > 15mm

Bundle Branch Blocks

note: normally depolarization of the ventricular septum is stimulated by a branch of the left bundle

incomplete block: QRS 0.10-0.12 (2.5-3 squares) complete block: QRS > 0.12 (3)

RBBB

• R' in V1
• S in V6

LBBB

• absent normal R in V1 and Q in V6 (initial depolarization directed to LV)
• terminal R' in V6 and downward deflection in V1

LAFB

• Q wave in I, aVL
• initial R wave in II, III, aVF

LPFB

• Q in II, III, aVF
• initial R wave in I, aVL

Q waves

• may be normal in V6 and aVL
• pathologic > 0.04, depth >25% QRS height

Inferior: II, III, aVF RCA Anteroseptal: V1-V2 LAD Anteroapical: V3-V4 LAD (distal) Aterolateral: V5-V6, I, aVL CFx Posterior: V1-V2 (tall R, no Q) RCA

MI

• ST elevation - returns to baseline in days
• T wave inversion - weeks to months
• Q wave - persists
• if ST remains elevated - fibrotic scar (ventricular anurysm) developed

Pericarditis

• diffuse ST elevation
• PR depression

Hyperkalemia

• tall "peaked" T waves
• flat p
• wide QRS

Hypokalemia

• U wave
• ST depression
• flat T

Hypercalcemia

• decreased QT interval

Hypocalcemia

• increased QT interval

External link

• EKG Reference Guide - Arrhythmia lessons, drills and tracings

Other OSCE modules