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What is an electrocardiograph (ECG) and what does it measure?
What is an electrocardiograph (ECG) and what does it measure?
An electrocardiograph (ECG) is a non-invasive device that measures the electrical activity of the heart, recording the heart's rhythm and electrical impulses.
What type of deflection is produced when an impulse travels towards a positive electrode?
What type of deflection is produced when an impulse travels towards a positive electrode?
Positive or upwards deflection
What is the characteristic of a bipolar ECG lead?
What is the characteristic of a bipolar ECG lead?
One positive electrode and one negative electrode
What does the P wave represent in physiology?
What does the P wave represent in physiology?
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In normal sinus rhythm, what is the polarity of the P wave in lead II?
In normal sinus rhythm, what is the polarity of the P wave in lead II?
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What is the significance of ST elevation in an ECG?
What is the significance of ST elevation in an ECG?
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What is the significance of ST depression in an ECG?
What is the significance of ST depression in an ECG?
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What is the characteristic of Atrial Flutter with a 3:1 conduction?
What is the characteristic of Atrial Flutter with a 3:1 conduction?
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What is the characteristic of Permanent AF?
What is the characteristic of Permanent AF?
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What is the relationship between PAC and Atrial Flutter?
What is the relationship between PAC and Atrial Flutter?
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How do you calculate the atrial rate and ventricular rate from an ECG?
How do you calculate the atrial rate and ventricular rate from an ECG?
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What is the significance of P wave morphology in an ECG?
What is the significance of P wave morphology in an ECG?
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How do you measure the PR interval on an ECG, and what is its significance?
How do you measure the PR interval on an ECG, and what is its significance?
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Study Notes
What is an ECG?
- An electrocardiograph (ECG) provides information about the heart's electrical activity.
- It does not provide information about the heart's mechanical activity or blood flow.
Electrodes
- 10 electrodes are used to sense the heart's electrical activity at the skin's surface.
- Electrodes are described as positive or negative.
- Positive electrode: recording, active or exploring.
- Negative electrode: determines the direction in which the positive electrode records.
- Current moves from negative to positive.
- Electrodes are connected to form leads.
Principles of Wave Deflection
- If an impulse travels towards a positive electrode, it produces a positive or upwards deflection.
- If an impulse travels away from a positive electrode, it produces a negative or downward deflection.
- If an impulse travels perpendicular to a positive electrode, it produces a biphasic deflection (half up, half down).
ECG Leads
- 12 leads on an ECG, 10 electrodes.
- An ECG lead records the electrical activity between two electrodes as the current passes through the heart.
- Bipolar: one positive electrode and one negative electrode.
P Wave
- Represents atrial depolarization.
- In normal sinus rhythm:
- Polarity: Upright in lead II, inverted in aVR, biphasic in V1.
- Shape: small and rounded.
- Precedes each QRS complex.
- Consistent shape in the same lead.
- Height: 2mm deep (may be a normal variant in leads III and aVR).
- > 25% of the height of the following QRS.
- Present in leads V1-V3.
R Wave Progression
- R wave is the first upward deflection after the P wave.
- R-wave progression:
- Ventricles depolarize down and toward the LEFT.
- Right-sided leads (V1) negative.
- Left-sided leads (V6) positive.
- The 'progression' means a smooth transition.
- When R>S, it is labeled the transition point.
- Normal transition point: V3-V4.
- Abnormal R wave progression in anterior MI, LVH, RVH, and other conditions.
ST Segment
- Represents no electrical activity – ventricles are depolarized.
- Normally isoelectric (flat).
- Measured from the end of the S wave (J point) to the beginning of the T wave.
- J point defines where the QRS ends & ST segment begins.
- Look for:
- Elevation.
- Depression.
- Shape: concave up (normal), concave down / horizontal (abnormal, more indicative of ischemia / infarction).
- Ischemia can cause ST elevation or depression.
- Depression is more commonly associated with ischemia.
- Elevation is more commonly associated with infarction (STEMI).
Atrial Fibrillation (AF)
- Permanent AF: duration > 1 year, resistant to treatment.
- AF uncontrolled: atrial rate is fast and irregular.
- AF controlled: atrial rate is slow and regular.
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Description
Learn about the basics of electrocardiography (ECG), what it provides, and when it's used. Understand the role of ECG in medical diagnosis and treatment.
