Podcast
Questions and Answers
What does the P wave in an ECG represent?
What does the P wave in an ECG represent?
- Atrial depolarization (correct)
- Repolarization of the papillary muscles
- Ventricular depolarization
- Ventricular repolarization
Which part of the ECG indicates complete depolarization of the heart?
Which part of the ECG indicates complete depolarization of the heart?
- ST segment (correct)
- P wave
- QRS complex
- T wave
How is the heart rate calculated from an ECG?
How is the heart rate calculated from an ECG?
- HR = 300 / Number of small squares in between each R wave
- HR = 1000 / Number of small squares between R waves
- HR = 1500 / Number of small squares between 2 successive R waves (correct)
- HR = 75 / Number of large squares between R waves
What does the QRS complex represent in an ECG?
What does the QRS complex represent in an ECG?
What does the U wave usually represent in an ECG?
What does the U wave usually represent in an ECG?
What does a heart rate exceeding 100 beats/min indicate?
What does a heart rate exceeding 100 beats/min indicate?
What is the duration of each small square on ECG paper?
What is the duration of each small square on ECG paper?
Which part of the ECG is masked by ventricular depolarization?
Which part of the ECG is masked by ventricular depolarization?
Flashcards
Electrocardiogram (ECG)
Electrocardiogram (ECG)
The electrical activity of the heart can be recorded by electrodes placed on the body's surface.
P wave
P wave
The wave representing atrial depolarization, a process where the electrical signal spreads through the atria before contraction.
QRS Complex
QRS Complex
Consists of three waves (Q, R, S) representing ventricular depolarization, where the electrical signal travels through the ventricles.
T wave
T wave
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PR Interval
PR Interval
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ST Segment
ST Segment
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Heart Rate (HR)
Heart Rate (HR)
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Normal Heart Rate Range
Normal Heart Rate Range
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Study Notes
Cardiovascular Response to Exercise
- Cardiovascular response to exercise is a broad topic.
- Electrocardiogram (ECG) analysis is used to understand this response.
Electrocardiogram (ECG)
- ECG records electrical activity of the heart.
- Depolarization and repolarization of cardiac myocytes produce electrical currents.
- Electrodes on the body (good conductors) record these currents.
- Each ECG wave has a specific shape, direction, duration, and amplitude.
ECG Apparatus
- Electrocardiograph consists of:
- A sensitive galvanometer and amplifier to amplify electrical currents from the body.
- A writing machine with a heated stylus to inscribe on treated graph paper.
- Recording paper that moves at a constant speed (25 mm/sec). The paper is marked with 1x1mm squares. 5 small squares are bounded by a heavier line.
- Each small square equals 0.04 seconds.
- Horizontal calibration shows amplitude of the waves in mV (1mV=10mm).
- Connector cables that connect electrode leads to the body surface.
ECG Machine
- A device that records and displays ECG signals.
- It includes controls for starting and stopping recordings.
ECG Wave Interpretation
- P-wave: Atrial depolarization.
- QRS complex: Ventricular depolarization.
- Q-wave: Inter-ventricular septum depolarization.
- R-wave: Ventricular depolarization simultaneous.
- S-wave: Depolarization of thick posterobasal portion of the left ventricle.
- T-wave: Ventricular repolarization.
- PR interval: Delay of AV node to enable ventricular filling. From beginning of P-wave to beginning of QRS complex.
- ST-segment: Period from the end of S wave to beginning of the T wave. Heart is isoelectric during this phase.
- QT-interval: Interval between beginning of the QRS complex to the end of the T wave.
- U wave: Repolarization of papillary muscles (often absent).
ECG Analysis – Heart Rate
- Heart rate (HR) calculation:
- HR = 1500 / number of small squares between two successive R waves.
- HR = 300 / number of large squares between two successive R waves.
- Normal heart rate ranges from 60 to 100 beats per minute.
- Tachycardia: >100 beats per minute.
- Bradycardia: <60 beats per minute.
ECG Analysis – Rhythmicity
- Measures successive R-R intervals.
- Equal intervals = regular heart rate.
- Unequal intervals = irregular heart rate.
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