ELECTRICAL AXIS OF HEARTELECTRICAL AXIS OF HEART

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Rear_avisRear_avis

ELECTRICAL AXIS OF HEARTELECTRICAL AXIS OF HEART

Action potential is the movement of ions so it is also called Action potential is the movement of ions so it is also called as electrical current. This current after origin in SA Node as electrical current. This current after origin in SA Node travels in all directions in atria and ventricles.travels in all directions in atria and ventricles.

If we represent movement of current in each direction by If we represent movement of current in each direction by an arrow it will be called as vector. Head of the arrow will an arrow it will be called as vector. Head of the arrow will point towards direction of current and its length will point point towards direction of current and its length will point the magnitude of current.the magnitude of current.

Mean vector of all these vectors is called AXIS of heart.Mean vector of all these vectors is called AXIS of heart.

As left ventricle has largest mass and performs maximum As left ventricle has largest mass and performs maximum function of heart the net current moves in the direction of function of heart the net current moves in the direction of left ventricle i.e downwards and to the left.left ventricle i.e downwards and to the left.

So normal axis of heart is downwards and to the left.So normal axis of heart is downwards and to the left.

CURRENT MOVES IN ALL DIRECTIONS BUT CURRENT MOVES IN ALL DIRECTIONS BUT NET CURRENT MOVES DOWNWARD AND TO NET CURRENT MOVES DOWNWARD AND TO

LEFT TOWARDS APEX OF LEFT VENTRICLE LEFT TOWARDS APEX OF LEFT VENTRICLE

BIPOLAR LIMB LEADS UNIPOLAR LEADSBIPOLAR LIMB LEADS UNIPOLAR LEADS

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NORMAL AXIS AXIS DEVIATIONNORMAL AXIS AXIS DEVIATION

CAUSES OF AXIS DEVIATIONCAUSES OF AXIS DEVIATION

LEFT AXISLEFT AXIS

DEVIATIONDEVIATION

RIGHT AXIS RIGHT AXIS DEVIATIONDEVIATION

EXTREME AXIS OR EXTREME AXIS OR NORTH WEST AXIS NORTH WEST AXIS DEVIATIONDEVIATION

1.HTN1.HTN

2. LVH2. LVH

3. LBBB3. LBBB

4. LAH4. LAH

5. INFERIOR M.I5. INFERIOR M.I

1. RVH1. RVH

2. RBBB2. RBBB

3. LPH3. LPH

4. ANTERIOR M.I4. ANTERIOR M.I

5. PULMONARY5. PULMONARY

EMBOLISMEMBOLISM

6. CHRONIC LUNG6. CHRONIC LUNG

DISEASESDISEASES

7.DEXTROCARDIA7.DEXTROCARDIA

1.VENTRICULAR 1.VENTRICULAR

TACHYCARDIATACHYCARDIA

2. HYPERKALEMIA2. HYPERKALEMIA

3. LEAD3. LEAD

TRANSPOSITIONTRANSPOSITION

4. ARTIFICIAL PACE4. ARTIFICIAL PACE

MAKERMAKER

Determining the AxisDetermining the Axis

Predominantly Positive

Predominantly Negative

Equiphasic

EQUIPHASIC APPROACHEQUIPHASIC APPROACHSTEP 1.STEP 1. Determine which lead among 6 limb leads is equi phasic Determine which lead among 6 limb leads is equi phasic ( equal QRS portion above and below baseline)( equal QRS portion above and below baseline)STEP 2STEP 2 Move to the lead which is perpendicular to this leadMove to the lead which is perpendicular to this lead LEADS I & AVF are perpendicular to each otherLEADS I & AVF are perpendicular to each other LEADS II & AVL are perpendicular to each otherLEADS II & AVL are perpendicular to each other LEADS III & AVR are perpendicular to each otherLEADS III & AVR are perpendicular to each otherSTEP 3.STEP 3. Note the QRS complex is predominantly upwards or Note the QRS complex is predominantly upwards or downwards in this lead downwards in this lead STEP 4STEP 4 If QRS complex is predominantly upward, Axis is on theIf QRS complex is predominantly upward, Axis is on the positive terminal of this lead.positive terminal of this lead. If QRS complex is predominantly downwards Axis is onIf QRS complex is predominantly downwards Axis is on the negative terminal of this lead.the negative terminal of this lead.NOTE:NOTE: If no lead is equi phasic then find the lead with lowestIf no lead is equi phasic then find the lead with lowest voltage of QRS complex and consider it as equiphasicvoltage of QRS complex and consider it as equiphasic

EXAMPLEEXAMPLE

1. LEAD AVF IS EQUI PHASIC1. LEAD AVF IS EQUI PHASIC

2. AVF IS PERPENDICULAR TO LEAD I SO AXIS IS SITUATED ON LEAD I2. AVF IS PERPENDICULAR TO LEAD I SO AXIS IS SITUATED ON LEAD I

3. NOW NOTE THAT LEAD I IS PREDOMONANTLY UPWARDS3. NOW NOTE THAT LEAD I IS PREDOMONANTLY UPWARDS

SO AXIS IS ON POSITIVE TERMINAL OF LEAD ISO AXIS IS ON POSITIVE TERMINAL OF LEAD I

4. POSITIVE TERMINAL OF LEAD I IS AT 0 DEGREE SO AXIS4. POSITIVE TERMINAL OF LEAD I IS AT 0 DEGREE SO AXIS

OF THIS ECG IS ZERO DEGREE WHICH IS NORMALOF THIS ECG IS ZERO DEGREE WHICH IS NORMAL

Q. DETERMINE AXIS BY EQUI PHASIC APPROACHQ. DETERMINE AXIS BY EQUI PHASIC APPROACH

THUMB METHOD TO DETECT ELECTRICAL AXISTHUMB METHOD TO DETECT ELECTRICAL AXIS Place your left thumb over lead I &Right thumb overPlace your left thumb over lead I &Right thumb over lead AVF.lead AVF.

Point the thumb upwards if QRS complex in the respective Point the thumb upwards if QRS complex in the respective lead is predominantly upward and Point the thumb lead is predominantly upward and Point the thumb downwards if QRS complex in the respective lead is downwards if QRS complex in the respective lead is predominantly downwardspredominantly downwards

BOTH THUMBS UPBOTH THUMBS UP = NORMAL AXIS = NORMAL AXIS

LEFT UPLEFT UP RIGHT DOWN RIGHT DOWN = LAD= LAD

LEFT DOWNLEFT DOWN RIGHT UPRIGHT UP = RAD = RAD

BOTH THUMS DOWNBOTH THUMS DOWN = INDETERMINATE AXIS/ = INDETERMINATE AXIS/ NORTH WEST AXIS/ NORTH WEST AXIS/ NO MANS LAND AREANO MANS LAND AREA

NORMAL AXIS NORMAL AXIS (LEAD I & AVF BOTH UPWARDS --- BOTH THUMBS UP)(LEAD I & AVF BOTH UPWARDS --- BOTH THUMBS UP)

LAD LAD (LEAD I UP & AVF DOWN --- LEFT THUMB UP, RIGHT DOWN)(LEAD I UP & AVF DOWN --- LEFT THUMB UP, RIGHT DOWN)

RADRAD ( LEAD I IS DOWN & AVF IS UP– LEFT THUMB UP, RIGHT DOWN ( LEAD I IS DOWN & AVF IS UP– LEFT THUMB UP, RIGHT DOWN

INDETERMINATE AXISINDETERMINATE AXIS ( BOTH LEADS --- DOWN BOTH THUMBS DOWN) ( BOTH LEADS --- DOWN BOTH THUMBS DOWN)

Q. DETERMINE THE AXIS BY THUMB METHODQ. DETERMINE THE AXIS BY THUMB METHOD

THANK YOUTHANK YOU