4th part ECG Basics: cardiac axis Dr Salah Mabrouk Khallaf

4th part ECG Basics: cardiac axis Dr Salah Mabrouk Khallaf

• 1.
  ECG BASICSECG BASICS 44thth LectureLecture CardiacAxisCardiac Axis By Salah Mabruok Khalaf South Egypt Cancer Institute 2017 Course of Medical Oncology Medical Oncology department
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  QRS axis (cardiac axis)
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  III=120 AvF=90 AvR=-120 AvL= -30 I=0 II= 60
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  Cardiac AxisCardiac Axis
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  QRS Axis Determination •First method: inspect QRS in Lead I and aVF • both I and aVF +ve = normal axis • both I and aVF -ve = axis in the Northwest Territory • lead I -ve and aVF +ve = right axis deviation • lead I +ve and aVF -ve – lead II +ve = normal axis – lead II -ve = left axis deviation F F F
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  2nd method 1- find theisoelectric limb leadisoelectric limb lead if there is one; i.e., the lead with equal forces in the positive and negative direction. 2-The QRS axis is perpendicular to that lead's orientation 3- Since there are two perpendiculars to each isoelectric lead, chose the perpendicular that best fits the direction of the other ECG leads. 4-If there is no isoelectric lead, there are usually two leads that are nearly isoelectric, and these are always 30o apart. Find the perpendiculars for each lead and chose an approximate QRS axis within the 30o range.
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  Examples of QRSAxis 1. Lead aVF is the isoelectric lead. 2. The two perpendiculars to aVF are 0 and 180 . 3. Lead I is positive (i.e., oriented to the left). 4. Therefore, the axis has to be 0 .
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  Left axis deviation •Lead aVR is the smallest and isoelectric lead. • The two perpendiculars are -60 and +120 . • Leads II and III are mostly negative (i.e., moving away from it) • The axis, therefore, is -60 .
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  • Left AxisDeviation (LAD): > -30o (i.e., lead II is mostly 'negative') 1. Left Anterior Fascicular Block (LAFB 2. Some cases of inferior MI with Qr complex in lead II (making lead II 'negative') 3. Inferior MI + LAFB in same patient 4. Some cases of LVH 5. Some cases of LBBB 6. Some cases of WPW syndrome (right sided accessory pathway) 7. Emphysema 8. Hyperkalaemia
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  Right axis deviation •Lead aVR is closest to being isoelectric (slightly more positive than negative) • The two perpendiculars are -60 o and +120 • Lead I is mostly negative; lead III is mostly positive. • Therefore the axis is close to +120 o. Because aVR is slightly more positive, the axis is slightly beyond +120 o (i.e., closer to the positive right arm for aVR).
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  • Right AxisDeviation (RAD): > +90o (i.e., lead I is mostly 'negative') 1. Left Posterior Fascicular Block (LPFB) 2. RVH 3. High lateral wall MI with Qr or QS complex in leads I and aVL 4. Some cases of RBBB 5. Some cases of WPW syndrome (left sided accessory pathway) 6. Children, teenagers, and some young adults
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  Bizarre QRS axis =Northwestaxis (no man's land) +150o to -90o (lead I and lead II are both negative) 1. Consider limb lead error 2. Some cases of ventricular tachycardia 3. Artificial cardiac pacing 4. Hyperkalaemia 5. Some cases of complex congenital heart disease (e.g., transposition) 6. Dextrocardia 7. Emphysema