01 - Cardiac Phys and EKG Flashcards
EKG is the recording of the hearts
Electrical activity
The heart has electrical activity known as
Action potentials
The heart acts as a _____ that generates electrical currents that can be measured on the
Pump
Skin surface
Pulmonary circulation is a ____ resistance and pressure system
Low
25/10 mmHg
Systemic circulation is a ____ resistance and pressure system
High
120/80 mmHg
Review charts
Do that
Three types of cardiac cells
Pacemaker - electrical power source
Electrical conducting - hard wiring
Myocardial - contractile machinery
At rest, the Vm of pacemaker cells is
Constant
Both the inside and outside of the cell are at constant potential
How big is a cardiac pacemaker cell?
5-10 um
During an action potential, Vm of a pacemaker cell is
Not constant
Current is flowing
Inside and outside are not constant
An action potential propagating away from the positive EKG lead produces what kind of signal?
Negative
AP produces positive signal when propagating toward positive lead
Rapid depolarization correlates to
Sodium influx
At the plateau, there is calcium
Influx
During repolarization, there is a
Potassium EFFLUX
What are the pacemakers of the heart?
SA and AV node
Which is the dominant pacemaker of the heart? What is it’s rate of impulse?
SA node
60-100 bum
How big are myocardial cells?
50-100 um
The magnitude and polarity of an EKG signal depends on
Depolarizing or repolarizing
Position and orientation of electrodes
When depolarization begins, it generates a ______ deflection
Positive
The EKG returns to baseline when the pos and neg charges are balanced
The negative deflection is formed when the wave of polarization
Recedes from the electrode
The fully depolarized cell causes the ECG to return to baseline
The effects of repolarization are similar to that of depolarization except that the charges are
Reversed
The placement of bipolar limb leads on the three lead EKG is known as
Einthoven Triangle
Augmented voltage leads (aV) utilize one bipolar limb electrode as _____, and the other two as a _______ negative lead
Positive
Combined
Describe the unipolar limb leads: aVR aVL aVF
aVR - right arm positive, left arm and leg negative
aVL- left arm positive, right arm and left leg negative
aVF - left foot positive, arms negative
Lead II yields the most information about
Ischemia in the left ventricle and septum; arrhythmias in the right atrium
Position of lead I
0
Position of lead II
60
Position of lead III
120
Position of aVL
-30
Position of aVR
-150
Position of aVF
90
The chest leads v1-v6 (precordial) are positioned in successive steps at
Right margin of the sternum to the left edge of the thorax
If v1 through v6 are imagined to be spokes of wheel, their horizontal plane cuts the body into
Top and bottom halves
Oh ok
This lead produces a mostly negative deflection
V1
This lead describes a straight line directly from the patients back through the anterior aspect of the chest
V2
What is the common wall shared by the right and left ventricles? What runs through this wall?
Interventricular septum
Right and left bundle branches
Which leads best describe conduction abnormalities of the bundle branches?
V3 and V4
What are leads V5 and V6 referred to as?
Left chest leads
They are oriented along the left axiliary lines
This six limb leads can be modified limb leads represented by which four trunk leads?
V1-V4
So that all leads can be placed on the trunk of the body
Six clinical uses of the EKG?
Detection of arrhythmias and cardiac abnormalities
Indication of myocardial damage
Detection of electrolyte disturbances
Screening tool for diagnosis of ischemic disease
Can indicate anatomic and physiological state of the heart
Diagnose some noncardiac pathology
Depolarization moves from the linings (endocardium) of the ventricular cavity _______ to the epicardial surface of the ventricle
Outward
The only conducting path between the atrium and ventricle is?
AV node
When depolarization reaches the myocardial cell, calcium released causes the cell to contract. What is this process called?
Excitation contraction coupling
