Electrocardiogram; analysis of ECG Flashcards
Electrocardiogram; ECG means?
- 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)
Explain the Einthoven´s Triangle:
- 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.
Einthoven 1:
Right arm (-) -> Left arm(+)
Einthoven 2:
Right arm(-) -> Left leg (++)
Einthoven 3:
Left arm (+) -> Left leg (++)
The heart as a Dipole:
- The oscillogram
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.
What happens if we measure the projections coming from an Symmetric atrium?
No potential difference could be detected between the two electrodes, therefore the inegral vector (dipole) is zero - no deflection on Oscilloscope.
(do not exist)
What happens if we measure the projections coming from an Aymmetric atrium?
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.
Analysis of ECG is done by:
- P-wave
- PQ- segment
- QRS-complex
- Q-wave
- R-wave
- S-wave
- ST-segment
- T-wave
- TP-segment
Explain the P-wave:
- upward (positive) deflection
- beginning og atrial depolarization
- The SA node is depolarized before, but it cant be detected.
Explain the PQ-segment:
- On the isoelectric line
- Total atrial depolarization
- AV conduction
Explain the QRS complex:
Beginning of ventricular depolarization, meanwhile repolarization of Atrium already starts.
Explain Q-wave:
- Downards
- stimulus runst from His-bundle to the septum and toward (upward) the basis of the heart.
Explain R-wave:
- Max ventricular depolarization
- The stimulus runs from endocardium to pericardium and from base to apex.
- the total ventriular mass is depolarizing
Explain S-wave:
- The end of QRS.
- mostly related to the depolarization of the right ventricle
- from endocardium to pericardium
Explain the ST segment:
- Isoelectric line on the oscilloscope (like the plateau of an individual fibers AP)
- Ventricles are totally depolarized.
Explain the T-wave:
- 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).
Explain the TP-segment:
- 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.
Types of ECG:
- Unipolar ECG
- His bundle ECG
- Esophageal ECG
- Vectocardiography
What is echocardiography?
Ultrasonography examination
