Lecture 4 - The Heart Axis Flashcards
What is flat line also known as?
Asystole
What is asystole?
A condition in which the heart ceases to beat (no systolic beat) No proper ventricle activity
What is the preferred method of restart?
CPR and/or injection with vasopressin
The equipment: lead
Place on body and it would record a voltage shift as the waves of electrical activity sweep over the heart
If the wave is traveling in the direction of (parallel to) the lead…
It will give a strong signal
If the wave is travelling perpendicular to lead…
It will give no signal as the voltage is not being changed in favour of the positive or negative electrode
Where does a wave of depolarisation travel toward?
Positive lead - positive deflection of the ECG trace
A wave of repolarization travel toward
Positive lead results in the opposite
What results in opposite deflections?
Waves travelling away from positive electrode
What is fibrillation?
When the heart is totally out of sync
What is tachycardia?
Ventricles are beating too fast
What is the Einthoven’s triangle?
Imaginary formation of 3 limb lead in a triangle used in electrocardiography formed by 2 shoulders and pubis
What is lead I?
Right arm to left arm
What is lead II?
Right arm to left leg
What is lead III?
Left arm to left leg
What does the electrode placed on the right leg serve?
As a ground and does not record Reduces noise interference
What are the unipolar leads?
avR, avL and avF
What is he direction of ECG dependent on?
The direction of the depolarisation and depolarisation wave moving across the heart
What is used to view the heart?
2 leads One lead: positive electrode Other:negative electrode
What does unipolar lead measure?
Electric impulses at only one only one point
avR (augmented vector right)
Positive electrode right shoulder
avL (augmented vector left)
Positive electrode left shoulder
AvF (augmented vector foot)
Positive electrode on foot
What can one wave of AP give?
Higher or lower recordings depending on which lead you are considering
How can you find a cardiac vector?
Looking at all 3 leads of the triangle
What is heart axis defined by?
Magnitude an angle
What can the axial reference system be used to determine?
Electrical axis of heart
What does each lead pick up?
Electrical activity from a different position on heart muscle
Extreme right axis deviation or No man’s land
Emphysema Hyperkalemia.
Lead transposition Ventricular pacing Ventricular arrhythmia
What are the causes of Right axis deviation?
Right Ventricular hypertrophy
(Right ventricle is enlarged and generate more electrical activity) Heart axis pulled to the right Loss of tissue of left ventricle Pulmonary embolism (obstruction in pulmonary artery - the right ventricle generate greater pressure to pump blood in PA - greater electrical activity)
Extreme right axis deviation or No man’s land
Emphysema Hyperkalemia.
Lead transposition Ventricular pacing Ventricular arrhythmia
What are the causes of Right axis deviation?
Right Ventricular hypertrophy
(Right ventricle is enlarged and generate more electrical activity) Heart axis pulled to the right Loss of tissue of left ventricle Pulmonary embolism (obstruction in pulmonary artery - the right ventricle generate greater pressure to pump blood in PA - greater electrical activity)
Left axis deviation
Past inferior MI Left anterior fascicular block Ventricular pacing Emphysema Hyperkalemia WPW Tricuspid atresia Ostium primum atrial septum defect
What do clinics use?
3 auxiliary leads
Where are the precordual leads placed?
Sternum travelling in a posterior direction
V1
Fourth intercostal space, on the right sternal border
V2
Opposite v1, on the left sternal border
v3
Between v2 and v4
V4
Fifth intercostal space, on mid-clavicular line
V5
Same level as v4, anterior axillary line
V6
Same level as v4, mid axillary line
Lead I
0 degrees +-180 degree
Lead II
+60 degree -120 degree
Lead III
+120 degree -60 degree
Lead avR
+30 degree -150 degree
Lead avL
-30 degree +150 degree
Lead avF
+90 degree -90 degree
