Vector Basics of 12 Lead ECG's1.1

Basics of 12 Lead ECG's Vector

Which way did they go??????

Making sense of Axis in the critical care setting

Basics of 12 Lead ECG's Vector

There are three basic "laws" of There are three basic "laws" of Electrocardiography.Electrocardiography.

These "laws" have to do with the direction of flow of electrical conduction in the heart or what we term as vector.

Basics of 12 Lead ECG's: Vector

a biphasic deflection

Basics of 12 Lead ECG's:Vector

Basics of 12 Lead ECG'sVector By understanding this concept of vector and

knowing the "normal" vector of each of the 12 leads of the 12 lead ECG it becomes quite easy to identify problems in the direction of depolarization. It is also from this knowledge that one identifies the Mean QRS Axis. Using the six limb leads we identify the axis in relation to what is known as the frontal plane. Two major factors help to determine this mean QRS Axis, they are:

1. The anatomical position of the heart2. The direction of ventricular depolarization.

Basics of 12 Lead ECG's:Determining AXIS

Technique #1: Two Lead Method or Quadrant Method

This method uses just two leads of the six limb leads and works well in critical situations to get a general idea of the Mean Axis of the QRS. We will look at Lead 1 and at Lead AVF for this technique.

Basics of 12 Lead ECG's Determining AXIS

1. Leads 1 and AVF dividethe thorax into quadrants, (Left, Normal, Right, No Man's) 2. If leads 1 and AVF are both

upright then the Axis is normal. 3. If lead 1 is upright and lead

AVF is downward the Axis is Left.


4. If lead AVF is upright and lead 1 is downward then the Axis is Right

5. If both leads are downward then the Axis is extreme Right Shoulder and most often is Vent. Tachy


Method 2 : Three Lead technique This method uses the three limb leads I,

II, III to determine the axis of the QRS.

LEAD 1 LEAD 2 LEAD 3

Normal UPRIGHT UPRIGHT UPRIGHT

Physiological Left Axis

UPRIGHTUPRIGHT / BIPHASIC

NEGATIVE

Pathological Left Axis

UPRIGHT NEGATIVE NEGATIVE

Right Axis NEGATIVEUPRIGHTBIPHASICNEGATIVE

UPRIGHT

Extreme Right Axis

NEGATIVE NEGATIVE NEGATIVE

Axis

Normal Axis0° to + 90°

Lead I uprightLead II uprightLead III upright

Axis



PhysiologicalLAD0° to -30°LI UprightLII BiphasicLIII Negative

Lead I UprightLead II NegativeLead III Negative

Pathologic LAD-30° to -90°

Basics of 12 Lead ECG'sCauses of Abnormal Axis Left Axis Deviation = An axis between -30 Left Axis Deviation = An axis between -30

and -90and -90

May be normal in the elderly and very obeseDue to high diaphragm during pregnancy, ascites, or ABD tumorsLeft Anterior HemiblockLeft Bundle Branch BlockWPW SyndromeCongenital LesionsRight Vent. Pacer or ectopic rhythmsEmphysema

Axis




Axis






Lead I NegativeLead II NegativeLead III Negative

Extreme RAD-90 ° to 180 °

Lead I NegativeLead II BiphasicLead III Positive

RAD+90 ° to +180 °

Basics of 12 Lead ECG's Causes of Abnormal Axis Right Axis Deviation = An axis between +120 Right Axis Deviation = An axis between +120

and +180and +180

Can be normal variantRight Vent. HypertrophyRight Bundle Branch BlockLeft Posterior HemiblockLeft Ventricular ectopic rhythmsSome right Vent. Ectopic rhythmsWPW Syndrome

Axis






Lead I NegativeLead II NegativeLead III Negative

Extreme RAD-90 ° to 180 °

Basics of 12 Lead ECG's Causes of Abnormal Axis

Extreme Right Axis Deviation = An Extreme Right Axis Deviation = An axis between -90 and +180axis between -90 and +180

Ventricular ectopic rhythmsRight Vent. Paced rhythmsLess commonly seen in patients with cardiomyopathies and in those with multiple MI's

Practice Strips

Documents

Vector Basics of 12 Lead ECG's1.1