Electrocardiogram; analysis of ECG

Question 1

Electrocardiogram; ECG means?

Answer 1

• Electrical activity of single myocytes can only be measured experimentally.

THEREFORE:
the sum of the activities of all fibers can be measured on the surface of the body (ECG)

Question 2

Explain the Einthoven´s Triangle:

Answer 2

• it is a divice to detect slight electric changes (mV). Pairs of electrodes are placed aroung the heart - as dipole - creating the “Einthovens Triangle”
• Potential differences (U) are measured between the pairs of electrodes.

Question 3

Einthoven 1:

Answer 3

Right arm (-) -> Left arm(+)

Question 4

Einthoven 2:

Answer 4

Right arm(-) -> Left leg (++)

Question 5

Einthoven 3:

Answer 5

Left arm (+) -> Left leg (++)

Question 6

The heart as a Dipole:

- The oscillogram

Answer 6

1: In rest No AP, the oscillogram is at isoelectric line.
2: If depolarization happens under the Reference electrode, there is an upstroke on oscillogram.
3: At total depolarization (plateau) we are back at isoelectric line (while heart is working with full activity)
4: When repolarization begins there is a Downward deflection on depolarization
5: At total repolarization, no potential difference, so isoelectric line in rest.

Question 7

What happens if we measure the projections coming from an Symmetric atrium?

Answer 7

No potential difference could be detected between the two electrodes, therefore the inegral vector (dipole) is zero - no deflection on Oscilloscope.

(do not exist)

Question 8

What happens if we measure the projections coming from an Aymmetric atrium?

Answer 8

The real Atrium is Asymmetric, the wall thickness will change, the SA node is not in the center -> therefore the Inegral Vector (Dipole) is not in zero, and deflection can be seen on the Oscilloscope.

Question 9

Analysis of ECG is done by:

Answer 9

• P-wave
• PQ- segment
• QRS-complex
• Q-wave
• R-wave
• S-wave
• ST-segment
• T-wave
• TP-segment

Question 10

Explain the P-wave:

Answer 10

• upward (positive) deflection
• beginning og atrial depolarization
• The SA node is depolarized before, but it cant be detected.

Question 11

Explain the PQ-segment:

Answer 11

• On the isoelectric line
• Total atrial depolarization
• AV conduction

Question 12

Explain the QRS complex:

Answer 12

Beginning of ventricular depolarization, meanwhile repolarization of Atrium already starts.

Question 13

Explain Q-wave:

Answer 13

• Downards

- stimulus runst from His-bundle to the septum and toward (upward) the basis of the heart.

Question 14

Explain R-wave:

Answer 14

• Max ventricular depolarization
• The stimulus runs from endocardium to pericardium and from base to apex.
• the total ventriular mass is depolarizing

Question 15

Explain S-wave:

Answer 15

• The end of QRS.
• mostly related to the depolarization of the right ventricle
• from endocardium to pericardium

Question 16

Explain the ST segment:

Answer 16

• Isoelectric line on the oscilloscope (like the plateau of an individual fibers AP)
• Ventricles are totally depolarized.

Question 17

Explain the T-wave:

Answer 17

• Beginning og ventricular repolarization
• in man and small animals: points upwards, other species: downwards.
• Reason: the repolarization starts where the final depolarization happened (epicardial region) and not where it began to depolarize (close to endocardium).

Question 18

Explain the TP-segment:

Answer 18

• The resting phase
• following the total repolarization, so the oscilloscope is at the Isoelectric line again.
• During TP segment all the myocytes are (+) outside, while (-) inside.

Question 19

Types of ECG:

Answer 19

• Unipolar ECG
• His bundle ECG
• Esophageal ECG
• Vectocardiography

Question 20

What is echocardiography?

Answer 20

Ultrasonography examination