Podcast
Questions and Answers
What is the primary difference between the electrical and mechanical events of the heart?
What is the primary difference between the electrical and mechanical events of the heart?
- Electrical events precede mechanical events. (correct)
- Mechanical events precede electrical events.
- Electrical and mechanical events occur simultaneously.
- Mechanical events initiate electrical events.
In a junctional rhythm, the AV node paces the heart at the same rate as the SA node normally would.
In a junctional rhythm, the AV node paces the heart at the same rate as the SA node normally would.
False (B)
What is the primary treatment or cure for ventricular fibrillation, and how does it work?
What is the primary treatment or cure for ventricular fibrillation, and how does it work?
Defibrillation involves applying a high-voltage electrical shock to repolarize heart muscle cells simultaneously, interrupting the disorganized electrical activity and allowing the heart's natural pacemaker to resume control.
In the sequence of events in a regular ECG, the ______ complex represents ventricular depolarization.
In the sequence of events in a regular ECG, the ______ complex represents ventricular depolarization.
Match the ECG component with the corresponding electrical event in the heart.
Match the ECG component with the corresponding electrical event in the heart.
What does the absence of a P wave typically indicate in an ECG reading?
What does the absence of a P wave typically indicate in an ECG reading?
An ECG tracing represents the action potential of a single cardiac cell.
An ECG tracing represents the action potential of a single cardiac cell.
How does a heart block affect the relationship between P waves and QRS complexes on an ECG?
How does a heart block affect the relationship between P waves and QRS complexes on an ECG?
An extrasystole is characterized by the ______ firing early, leading to an extra heartbeat followed by a pause.
An extrasystole is characterized by the ______ firing early, leading to an extra heartbeat followed by a pause.
Relate each ECG abnormality to its underlying pathophysiology.
Relate each ECG abnormality to its underlying pathophysiology.
Which interval on an ECG represents the time from the beginning of ventricular depolarization through ventricular repolarization?
Which interval on an ECG represents the time from the beginning of ventricular depolarization through ventricular repolarization?
Ventricular fibrillation is characterized by coordinated ventricular contractions.
Ventricular fibrillation is characterized by coordinated ventricular contractions.
What physiological mechanism causes the 'thud' sensation associated with an extrasystole?
What physiological mechanism causes the 'thud' sensation associated with an extrasystole?
The S-T segment on an ECG represents the time between ventricular ______ and the start of ventricular repolarization.
The S-T segment on an ECG represents the time between ventricular ______ and the start of ventricular repolarization.
Match the location with the electrical event in the heart.
Match the location with the electrical event in the heart.
Flashcards
What is an ECG?
What is an ECG?
Composite of all action potentials generated by nodal and contractile cells.
What does the P wave represent?
What does the P wave represent?
Depolarization of the atria.
What does the QRS complex represent?
What does the QRS complex represent?
Depolarization of the ventricles.
What does the T wave represent?
What does the T wave represent?
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What is the P-R interval?
What is the P-R interval?
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What is the S-T segment?
What is the S-T segment?
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What is the Q-T interval?
What is the Q-T interval?
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What is sinus rhythm?
What is sinus rhythm?
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What is Junctional Rhythm?
What is Junctional Rhythm?
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What is a heart block?
What is a heart block?
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What is Ventricular Fibrillation?
What is Ventricular Fibrillation?
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What is extrasystole?
What is extrasystole?
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Study Notes
- The lecture discusses the sequence of events in a regular ECG, irregular ECGs and their events, and the physiology behind extrasystole.
Electrocardiogram (ECG)
- ECGs are a composite of action potentials from nodal (pacemaker) and contractile cells, and are registered at a given time.
- ECGs are not a tracing of a single action potential.
- Electrical events precede the mechanical events of contraction or relaxation.
ECG Waves and Intervals
- P wave: Represents atrial depolarization.
- QRS complex: Represents ventricular depolarization.
- T wave: Represents ventricular repolarization.
- P-R interval: Time from the beginning of atrial excitation to the start of ventricular excitation.
- S-T segment: Time between ventricular depolarization and the start of ventricular repolarization.
- Q-T interval: Period from the beginning of ventricular depolarization through ventricular repolarization.
ECG Sequence
- Atrial depolarization, initiated by the SA node, causes the P wave.
- With atrial depolarization complete, the impulse is delayed at the AV node.
- Ventricular depolarization begins at the apex, causing the QRS complex and atrial repolarization.
- Ventricular depolarization is complete.
- Ventricular repolarization starts at the apex, causing the T wave.
- Ventricular repolarization is complete.
Irregular ECGs
- Irregular ECGs are caused by a variety of arrhythmia.
Arrhythmia: Junctional Rhythm
- Occurs when the SA node is damaged, and the AV node takes over pacing the heart.
- Results in a slower heartbeat, around 40-60 BPM (SA node usually paces at 75 BPM).
- There is no P wave, and the ventricles have greater contractility.
Arrhythmia: Heart Block
- Caused by a blockage in the conductive pathway.
- AV node fails to conduct some SA node impulses.
- Heart block results in a slower heartbeat, and presence of more P waves than QRS waves.
Arrhythmia: Ventricular Fibrillation
- In ventricles, there is a continuous, disorganized action potential pattern resulting in chaotic, abnormal ECG deflections.
- Can be treated by defibrillation with high voltage, causing a simultaneous refractory period.
Arrhythmia: Extrasystole
- SA node fires early.
- Results in an extra heartbeat that is followed by a pause, often felt as a "thud."
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