Lecture 7 (II): Heart Rhythmicity and Normal ECG

Question 1

Vector

Answer 1

An arrow that points in the positive direction of electrical potential generated by current flow, where length is drawn proportional to voltage of potential.

Question 2

Axis Lead I

Answer 2

R arm=negative, L arm=positive, Direction=0 degrees

Question 3

Axis Lead II

Answer 3

R arm=negative, L leg=positive, Direction=60 degrees

Question 4

Axis Lead III

Answer 4

L arm=negative, L leg=positive, Direction=120 degrees

Question 5

Mean Electrical Axis

Answer 5

59 degrees; summation of vectors during ventricular depolarization

Question 6

High Voltage ECG and most common cause

Answer 6

Sum of voltages of all QRS complexes of three standard leads is greater than 4 mV; most common cause is hypertrophy of the ventricle

Question 7

J point

Answer 7

reference point for analyzing current of injury