Practical 1 ECG and MAP of the heart

Question 1

what direction is the mean electrical axis recorded

Answer 1

right to left

Question 2

where is the ground electrode placed

Answer 2

left ankle

Question 3

how can we get a more accurate measure of the heart

Answer 3

more electrodes, more leads

Question 4

what factors affect the mean electrical heart axis

Answer 4

direction of waves

orientation of the heart

Question 5

what is the importance of the pericardial sac

Answer 5

acts as mechanical protection - a lubricant against heart and vessels

Question 6

how is mean electrical axis calculated

Answer 6

theta = tan^-1

finding the resultant vector

Question 7

what affects orientation of the heart

Answer 7

orientation changes when the during inhalation/exhalation when the diaphragm contracts/relaxes

Question 8

what was the hypothesis of our experiment

Answer 8

a deep inhale will deliver a more vertical electrical exis than a deep exhale

Question 9

why does the volunteer have to lie down

Answer 9

to remove the effect of skeletal muscles that would otherwise show up on the recording

Question 10

how do you measure the amplitude of the QRS complex

Answer 10

height of the R wave?

Question 11

how is cardiac axis calculated

Answer 11

using tan-1 function

this calculates the degrees from the 0deg line of lead I

• the triangle can be made by moving the AVF lead to the other side where needed - its size should not change