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Questions and Answers
What does the P wave represent in an ECG?
What does the P wave represent in an ECG?
- Ventricular repolarisation
- Electrical impulse from the SA node
- Ventricular depolarisation
- Atrial depolarisation (correct)
Which component of the ECG indicates the time taken for ventricles to depolarise and repolarise?
Which component of the ECG indicates the time taken for ventricles to depolarise and repolarise?
- QT interval (correct)
- ST segment
- PR interval
- RR interval
What is the function of the AV node in the cardiac conduction system?
What is the function of the AV node in the cardiac conduction system?
- To depolarise the ventricles
- To stimulate atrial contraction
- To initiate electrical impulses
- To connect the atria with the ventricles and delay the impulse (correct)
Which of the following correctly describes the QRS complex?
Which of the following correctly describes the QRS complex?
The T wave in an ECG signifies which of the following?
The T wave in an ECG signifies which of the following?
What role do autorhythmic cells play in the heart?
What role do autorhythmic cells play in the heart?
What does the RR interval measure in an ECG?
What does the RR interval measure in an ECG?
Which of these best describes arrhythmias?
Which of these best describes arrhythmias?
Which condition is NOT associated with an increased risk of atrial fibrillation?
Which condition is NOT associated with an increased risk of atrial fibrillation?
What characterizes persistent atrial fibrillation?
What characterizes persistent atrial fibrillation?
Which of the following is a common treatment option for unstable atrial fibrillation?
Which of the following is a common treatment option for unstable atrial fibrillation?
What is a major symptom of atrial fibrillation that indicates a possible need for intervention?
What is a major symptom of atrial fibrillation that indicates a possible need for intervention?
What is one potential complication of persistent atrial fibrillation?
What is one potential complication of persistent atrial fibrillation?
Which of the following factors can act as a trigger for atrial fibrillation?
Which of the following factors can act as a trigger for atrial fibrillation?
What is a known characteristic of atrial flutter compared to atrial fibrillation?
What is a known characteristic of atrial flutter compared to atrial fibrillation?
Which medication is specifically used to control rate in the management of atrial flutter?
Which medication is specifically used to control rate in the management of atrial flutter?
What is the role of the SA node in the heart?
What is the role of the SA node in the heart?
During which phase do Ca++ slowly enter the cardiac cell?
During which phase do Ca++ slowly enter the cardiac cell?
How is automaticity defined in cardiac cells?
How is automaticity defined in cardiac cells?
What is the voltage at the start of Phase 4 of the action potential?
What is the voltage at the start of Phase 4 of the action potential?
Which of the following ions are primarily involved in maintaining resting membrane potential?
Which of the following ions are primarily involved in maintaining resting membrane potential?
What happens during the Absolute Refractory Period?
What happens during the Absolute Refractory Period?
What is the primary ion responsible for depolarization during Phase 0?
What is the primary ion responsible for depolarization during Phase 0?
What mechanism supports the movement of Na+ and Ca++ out of the cell?
What mechanism supports the movement of Na+ and Ca++ out of the cell?
Which criteria are essential for identifying a PAC on an ECG tracing?
Which criteria are essential for identifying a PAC on an ECG tracing?
What are the criteria for identifying a Wandering Atrial Pacemaker (WAP) on an ECG tracing?
What are the criteria for identifying a Wandering Atrial Pacemaker (WAP) on an ECG tracing?
In Multifocal Atrial Tachycardia (MAT), what are the key ECG indicators?
In Multifocal Atrial Tachycardia (MAT), what are the key ECG indicators?
Which of the following is NOT a symptom of Supraventricular Tachycardia (SVT)?
Which of the following is NOT a symptom of Supraventricular Tachycardia (SVT)?
What is the typical heart rate range in an AV (Junctional) Escape Rhythm?
What is the typical heart rate range in an AV (Junctional) Escape Rhythm?
Which treatment is recommended for unstable SVTs during pre-hospital care?
Which treatment is recommended for unstable SVTs during pre-hospital care?
During a Premature Junctional Contraction, how may the P wave appear?
During a Premature Junctional Contraction, how may the P wave appear?
What is a common cause of Multifocal Atrial Tachycardia?
What is a common cause of Multifocal Atrial Tachycardia?
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Study Notes
Cardiac Action Potentials
- Action Potential: Initiated by the SA node; spreads through atria leading to contraction, with delay at AV node relaying impulse to Bundle of His and Purkinje Fibres.
- Ventricular Contraction: Purkinje Fibres stimulate ventricular myocardium following signal transmission.
12 Lead ECG Overview
- Electrocardiogram (ECG): Evaluates electrical currents in the heart, measuring myocardium depolarisation and repolarisation.
ECG Components
- P Waves: Indicate atrial depolarisation; one P wave precedes each QRS complex in healthy individuals.
- PR Interval: Time from the beginning of the P wave to the start of the Q wave, reflecting atrial to ventricular conduction.
- QRS Complex: Represents ventricular depolarisation, appearing as interlinked Q, R, and S waves.
- ST Segment: Isoelectric line from the end of the S wave to the beginning of the T wave, indicating the transition phase of ventricles.
- T Wave: Shows ventricular repolarisation; appears after the QRS complex.
- RR Interval: Duration from one R wave peak to the next, indicating time between QRS complexes.
- QT Interval: Time from the start of the QRS complex to the end of the T wave, reflecting ventricular depolarisation and repolarisation.
Cardiac Myocytes and Action Potentials
- Arrhythmias: Abnormal heartbeat timing or pattern.
- Cardiac Myocytes: Contractile cells generating force to pump blood from heart chambers.
- Autorhythmic Cells: Pacemaker cells conducting impulses for mechanical action, located in the SA and AV nodes.
- Automaticity: Cardiac cells can initiate impulses spontaneously without external stimulation.
Phases of Action Potential in Cardiomyocytes
- Phase 0: Influx of Na+, initiating depolarisation (approx. -90mV).
- Phase 1: Na+ channels close; K+ efflux occurs (approx. +20-30mV).
- Phase 2: Ca++ enters cell; K+ efflux continues (approx. 0mV).
- Phase 3: Ca++ channels close; K+ continues to exit (approx. 0mV).
- Phase 4: Na+ and K+ pumps activated; maintains resting voltage at -90mV.
Blood Flow in the Heart
- Understanding blood circulation through heart chambers into pulmonary and systemic circulation is crucial for physiological and pathological conditions.
Importance of Refractory Period
- The absolute refractory period ensures complete contraction and relaxation before another action potential is generated.
Atrial Arrhythmias
- Atrial Fibrillation: Characterized by irregular electrical activity; common in older males, those with heart disease, and conditions like hypertension and diabetes.
- Symptoms: Palpitations, syncope, shortness of breath, chest pain, and hypotension.
- Management Options: Rate or rhythm control medications (beta blockers), anticoagulants, and potentially ablation.
Types of Atrial Fibrillation
- Persistent AF: Lasts longer than 7 days.
- Paroxysmal AF: Episodic in nature; triggers include substance use and stress.
Atrial Flutter
- Often linked to conditions like thyrotoxicosis and sleep apnoea; presents symptoms similar to AF.
- Treatment: Rate control with beta-blockers, ablation, and anticoagulants.
Premature Atrial Contractions (PAC)
- Ectopic beats causing different-shaped P waves, while QRS complexes remain normal.
Wandering Atrial Pacemaker (WAP)
- Characterized by multiple depolarisation sources; ECG shows different P wave morphologies at a rate less than 100 BPM.
Multifocal Atrial Tachycardia (MAT)
- Caused by autonomic foci, characterized by heart rates over 100 BPM, varied P wave forms, and irregular PR intervals.
Atrioventricular Re-entrant Tachycardia (AVRT)
- Symptoms vary based on ventricular rates; management involves Valsalva maneuvers or cardioversion.
AV Nodal Re-entrant Tachycardia (AVNRT)
- Similar to AVRT; management strategies align with patient stability and response.
Signs and Symptoms of SVT
- Includes rapid heartbeat, dizziness, palpitations, and possible syncope.
Premature Junctional Contraction
- Characterized by ectopic focus in AV junction; the P wave may be inverted or absent.
AV Escape Rhythms
- Regular rhythm at 40-60 BPM with inverted P waves possibly present before, during, or after QRS complexes.
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