Heller Ch. 4 Flashcards
Fick Principle on flow
Q = (tissue consumption; X[TC]) / ([X]a-[X]v)
a=arterial
v=veinous
Ejection Fraction
Calculated from an echo
EF = SV/EDV
Normal Ejection Fraction
55-80%
Mean is 67%
End-diastolic pressure/volume relationship
Assesses cardiac contractility
How an ECG works
Electrodes record the small potential differences b/w various recording sites that vary during the cardiac cycle
T wave shape
Less peaked than QRS complex because it is less synchronized
AV nodal gap
There are too few cells to detect a dipole
Einthoven’s ECG conventions
Leads make an equilateral triangle on the thorax
Deflection indicates a voltage difference
Dipole
Points in the direction of the conduction
Patient’s left and down are positive
Mean electrical axis
Orientation of the dipole during the most intense phase of ventricular depolarization
Normal mean electrical axis
Anywhere in the patient’s lower left quadrant
Left axis deviation
In the patient’s upper left quadrant
Heart is offset to the left;
Left ventricle hypertrophy; OR
Loss of electrical activity in the right ventricle
Right axis deviation
In the patient’s lower right quadrant
Heart is offset to the right;
Right ventricle hypertrophy; OR
Loss of electrical activity in the left ventricle
ECG lead arrangement
The equilateral triangle with three inner leads from the vertices and meeting in the center (center is negative)
And then six leads from right sternum to left lat