Podcast
Questions and Answers
What is the primary characteristic of a sinoatrial block?
What is the primary characteristic of a sinoatrial block?
Which type of blocked conduction is characterized by a failure to transmit impulses specifically through the AV node?
Which type of blocked conduction is characterized by a failure to transmit impulses specifically through the AV node?
What is the primary consequence of Mobitz II AV block?
What is the primary consequence of Mobitz II AV block?
What is the expected heart rate for the atria in a complete (third-degree) AV block?
What is the expected heart rate for the atria in a complete (third-degree) AV block?
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Which phenomenon characterizes the accelerated conduction syndrome?
Which phenomenon characterizes the accelerated conduction syndrome?
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Which type of AV block is associated with a prolonged PQ interval and is usually undetectable?
Which type of AV block is associated with a prolonged PQ interval and is usually undetectable?
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What is a potential consequence of an intraventricular block?
What is a potential consequence of an intraventricular block?
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What is NOT a type of blocked conduction?
What is NOT a type of blocked conduction?
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What distinguishes sinus extrasystole from atrial extrasystole?
What distinguishes sinus extrasystole from atrial extrasystole?
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Which of the following arrhythmias is characterized by a heart rate of 40-60 bpm and alterations in the P wave?
Which of the following arrhythmias is characterized by a heart rate of 40-60 bpm and alterations in the P wave?
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Which mechanism primarily leads to arrhythmias associated with impaired excitability?
Which mechanism primarily leads to arrhythmias associated with impaired excitability?
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Which arrhythmia arises from the bundle of His or Purkinje fibers and is characterized by a heart rate of 20-40 bpm?
Which arrhythmia arises from the bundle of His or Purkinje fibers and is characterized by a heart rate of 20-40 bpm?
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What is a common characteristic of Heterotopic arrhythmias compared to Nomotopic arrhythmias?
What is a common characteristic of Heterotopic arrhythmias compared to Nomotopic arrhythmias?
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Which type of arrhythmia is indicated by the presence of a negative P wave after a QRS complex?
Which type of arrhythmia is indicated by the presence of a negative P wave after a QRS complex?
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What is the primary cause of Sinus node weakness syndrome?
What is the primary cause of Sinus node weakness syndrome?
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In arrhythmias associated with impaired contractility, which of the following is primarily affected?
In arrhythmias associated with impaired contractility, which of the following is primarily affected?
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Which of the following correctly describes the mechanism of atrial flutter?
Which of the following correctly describes the mechanism of atrial flutter?
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What is a characteristic feature of Wolff-Parkinson-White syndrome (WPW syndrome)?
What is a characteristic feature of Wolff-Parkinson-White syndrome (WPW syndrome)?
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In which type of accelerated conduction syndrome does the James bundle play a role?
In which type of accelerated conduction syndrome does the James bundle play a role?
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What is a key feature of ventricular flutter?
What is a key feature of ventricular flutter?
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What condition may arise due to simultaneous impairment of excitability and conduction?
What condition may arise due to simultaneous impairment of excitability and conduction?
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Which statement accurately describes Atrioventricular (AV) blocks?
Which statement accurately describes Atrioventricular (AV) blocks?
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What is the primary consequence of the accelerated conduction through the Kent-Paladino bundle?
What is the primary consequence of the accelerated conduction through the Kent-Paladino bundle?
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Which of the following is NOT indicative of Atrial fibrillation?
Which of the following is NOT indicative of Atrial fibrillation?
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What is a direct effect of Wolff-Parkinson-White syndrome on the heart's conduction system?
What is a direct effect of Wolff-Parkinson-White syndrome on the heart's conduction system?
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In which syndrome does the James bundle specifically contribute to arrhythmias?
In which syndrome does the James bundle specifically contribute to arrhythmias?
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What arrhythmia is typically characterized by the absence of P waves and irregular rhythm?
What arrhythmia is typically characterized by the absence of P waves and irregular rhythm?
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What is the primary electrophysiological mechanism causing the phenomenon of reentry in arrhythmias?
What is the primary electrophysiological mechanism causing the phenomenon of reentry in arrhythmias?
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Which of the following best describes the appearance of the QRS complex during atrial flutter?
Which of the following best describes the appearance of the QRS complex during atrial flutter?
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Which genetic defect is primarily responsible for the development of the Kent-Paladino bundle?
Which genetic defect is primarily responsible for the development of the Kent-Paladino bundle?
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What is a hallmark ECG finding in patients with Clerc-levy-Cristesco syndrome?
What is a hallmark ECG finding in patients with Clerc-levy-Cristesco syndrome?
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Which arrhythmia is defined by a heart rate of 150-300 bpm and is a precursor to more serious conditions?
Which arrhythmia is defined by a heart rate of 150-300 bpm and is a precursor to more serious conditions?
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Which intervention is most likely to be necessary if ventricular tachycardia arises due to an accelerated conduction pathway?
Which intervention is most likely to be necessary if ventricular tachycardia arises due to an accelerated conduction pathway?
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Which of the following describes arrhythmias caused by impaired automatism?
Which of the following describes arrhythmias caused by impaired automatism?
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What defines ectopic foci in arrhythmias related to impaired excitability?
What defines ectopic foci in arrhythmias related to impaired excitability?
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Which arrhythmia is characterized by its origin within the left atrium and a heart rate of less than 70 bpm?
Which arrhythmia is characterized by its origin within the left atrium and a heart rate of less than 70 bpm?
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In cases of impaired contractility, which physiological mechanism is primarily compromised?
In cases of impaired contractility, which physiological mechanism is primarily compromised?
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Which type of extra systole is caused by a premature excitation in the SA node?
Which type of extra systole is caused by a premature excitation in the SA node?
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Which type of arrhythmia manifests with the absence of P wave and wide QRS complex?
Which type of arrhythmia manifests with the absence of P wave and wide QRS complex?
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Which arrhythmia can occur due to impaired excitability that leads to premature contractions?
Which arrhythmia can occur due to impaired excitability that leads to premature contractions?
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What characterizes the junctional rhythm in terms of heart rate?
What characterizes the junctional rhythm in terms of heart rate?
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Which of the following statements about arrhythmias due to impaired conduction is accurate?
Which of the following statements about arrhythmias due to impaired conduction is accurate?
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What is a common cause behind arrhythmias associated with impaired excitability?
What is a common cause behind arrhythmias associated with impaired excitability?
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What arrhythmia is characterized by a sudden onset with a heart rate between 160-220 bpm due to multiple foci above the ventricles?
What arrhythmia is characterized by a sudden onset with a heart rate between 160-220 bpm due to multiple foci above the ventricles?
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AV block of III degree results in what pattern of electrical activity between the atria and ventricles?
AV block of III degree results in what pattern of electrical activity between the atria and ventricles?
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Which type of block is characterized by prolonged P waves due to obstruction in the atrial conductive pathway?
Which type of block is characterized by prolonged P waves due to obstruction in the atrial conductive pathway?
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Which feature distinguishes Mobitz I from Mobitz II type of AV block?
Which feature distinguishes Mobitz I from Mobitz II type of AV block?
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What is a primary complication associated with intraventricular blocks?
What is a primary complication associated with intraventricular blocks?
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In the context of impaired excitability, which mechanism is primarily affected?
In the context of impaired excitability, which mechanism is primarily affected?
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Which type of block results from morpho-functional changes within the conductive system, specifically impacting impulse spread?
Which type of block results from morpho-functional changes within the conductive system, specifically impacting impulse spread?
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What is the typical ECG characteristic of AV block of I degree?
What is the typical ECG characteristic of AV block of I degree?
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Which condition results from the failure of impulses to be transmitted specifically through the conductive pathways of the heart?
Which condition results from the failure of impulses to be transmitted specifically through the conductive pathways of the heart?
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What is the primary physiological consequence of Mobitz II type AV block?
What is the primary physiological consequence of Mobitz II type AV block?
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Which of the following arrhythmias results from impaired heart automatism?
Which of the following arrhythmias results from impaired heart automatism?
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What primarily characterizes arrhythmias due to impaired excitability?
What primarily characterizes arrhythmias due to impaired excitability?
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Which type of arrhythmia is associated with impaired contractility?
Which type of arrhythmia is associated with impaired contractility?
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What primarily results from impaired automatism in the heart?
What primarily results from impaired automatism in the heart?
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What is the underlying issue with arrhythmias caused by impaired heart automatism?
What is the underlying issue with arrhythmias caused by impaired heart automatism?
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Which condition is most likely to occur due to impaired excitability?
Which condition is most likely to occur due to impaired excitability?
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In arrhythmias related to impaired excitability, which ion's changes across membranes are mainly responsible?
In arrhythmias related to impaired excitability, which ion's changes across membranes are mainly responsible?
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Which arrhythmia is characterized by the absence of P waves and a heart rate of 20-40 bpm?
Which arrhythmia is characterized by the absence of P waves and a heart rate of 20-40 bpm?
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A decrease in contractility in the heart can lead to which of the following?
A decrease in contractility in the heart can lead to which of the following?
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Which of the following best describes the effects of impaired heart automatism?
Which of the following best describes the effects of impaired heart automatism?
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What distinguishes sinus node weakness syndrome within the context of impaired automatism?
What distinguishes sinus node weakness syndrome within the context of impaired automatism?
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What is the consequence of impaired contractility in heart function?
What is the consequence of impaired contractility in heart function?
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Which of these is NOT a result of impaired contractility in arrhythmias?
Which of these is NOT a result of impaired contractility in arrhythmias?
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Which arrhythmia can be a consequence of ectopic foci generating impulses?
Which arrhythmia can be a consequence of ectopic foci generating impulses?
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In conditions of impaired excitability, which of the following arrhythmias is most likely to arise?
In conditions of impaired excitability, which of the following arrhythmias is most likely to arise?
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Which feature is typical of arrhythmias due to impaired automatism?
Which feature is typical of arrhythmias due to impaired automatism?
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Which condition is characterized by a failure of impulse transmission primarily due to impaired excitability?
Which condition is characterized by a failure of impulse transmission primarily due to impaired excitability?
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What effect does impaired automatism have on heart rate regulation?
What effect does impaired automatism have on heart rate regulation?
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What is a consequence of impaired conduction due to morpho-functional changes?
What is a consequence of impaired conduction due to morpho-functional changes?
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What is typically observed in an atrioventricular block of II degree Mobitz II?
What is typically observed in an atrioventricular block of II degree Mobitz II?
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What is a notable effect of impaired heart automatism on heart function?
What is a notable effect of impaired heart automatism on heart function?
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Which condition is associated with impaired excitability in the myocardium?
Which condition is associated with impaired excitability in the myocardium?
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How does impaired contractility primarily affect the heart's pumping ability?
How does impaired contractility primarily affect the heart's pumping ability?
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Which mechanism is primarily involved in ectopic foci production due to impaired excitability?
Which mechanism is primarily involved in ectopic foci production due to impaired excitability?
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Which arrhythmia is characterized by loss of P waves and a sawtooth appearance?
Which arrhythmia is characterized by loss of P waves and a sawtooth appearance?
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Which changes in the heart’s rhythm may occur due to impaired automatism?
Which changes in the heart’s rhythm may occur due to impaired automatism?
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What is one consequence of impaired excitability within myocardial tissues?
What is one consequence of impaired excitability within myocardial tissues?
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What type of ventricular rhythm is likely to occur due to impaired contractility?
What type of ventricular rhythm is likely to occur due to impaired contractility?
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What is a common feature of the heart when affected by impaired automatism?
What is a common feature of the heart when affected by impaired automatism?
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Which of these is commonly seen on ECG in patients with impaired contractility?
Which of these is commonly seen on ECG in patients with impaired contractility?
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Which arrhythmia develops in the SA node and includes a heart rate that is greater than 100 bpm?
Which arrhythmia develops in the SA node and includes a heart rate that is greater than 100 bpm?
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What is the primary cause of arrhythmias associated with impaired excitability?
What is the primary cause of arrhythmias associated with impaired excitability?
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In which arrhythmia is the heart rate typically between 40-60 bpm and involves alterations in the P wave?
In which arrhythmia is the heart rate typically between 40-60 bpm and involves alterations in the P wave?
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What type of arrhythmia indicates impaired contractility?
What type of arrhythmia indicates impaired contractility?
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Which condition is characterized by premature contractions that can arise at any point in the heart?
Which condition is characterized by premature contractions that can arise at any point in the heart?
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How does impaired automatism typically manifest in arrhythmias?
How does impaired automatism typically manifest in arrhythmias?
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What type of extrasystole occurs due to early stimulation within the atria, resulting in a low-amplitude P wave?
What type of extrasystole occurs due to early stimulation within the atria, resulting in a low-amplitude P wave?
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What causes the absence of a P wave in the ECG during certain arrhythmias?
What causes the absence of a P wave in the ECG during certain arrhythmias?
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What causes impaired heart automatism?
What causes impaired heart automatism?
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Which condition is primarily associated with impaired excitability of cardiac cells?
Which condition is primarily associated with impaired excitability of cardiac cells?
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Which arrhythmia is primarily associated with impaired contractility?
Which arrhythmia is primarily associated with impaired contractility?
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What is a consequence of impaired excitability in cardiac tissue?
What is a consequence of impaired excitability in cardiac tissue?
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Which is a typical symptom associated with impaired contractility?
Which is a typical symptom associated with impaired contractility?
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Which arrhythmia might result from the interaction of impaired automatism and impaired contractility?
Which arrhythmia might result from the interaction of impaired automatism and impaired contractility?
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Impaired excitability of cardiac cells affects which electrical property?
Impaired excitability of cardiac cells affects which electrical property?
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Impaired contractility is often characterized by which of the following?
Impaired contractility is often characterized by which of the following?
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What is a common characteristic of arrhythmias caused by impaired automatism?
What is a common characteristic of arrhythmias caused by impaired automatism?
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Which of the following describes a key feature of impaired excitability in cardiac tissues?
Which of the following describes a key feature of impaired excitability in cardiac tissues?
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In arrhythmias associated with impaired contractility, which aspect is primarily affected?
In arrhythmias associated with impaired contractility, which aspect is primarily affected?
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What primarily characterizes the arrhythmias due to impaired excitability?
What primarily characterizes the arrhythmias due to impaired excitability?
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Which mechanism is most often compromised in conditions leading to impaired contractility?
Which mechanism is most often compromised in conditions leading to impaired contractility?
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Which of the following statements about impaired automatism in cardiac arrhythmias is true?
Which of the following statements about impaired automatism in cardiac arrhythmias is true?
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How does impaired excitability influence the risk of arrhythmias?
How does impaired excitability influence the risk of arrhythmias?
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Which condition is NOT typically associated with impaired contractility?
Which condition is NOT typically associated with impaired contractility?
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Study Notes
Arrhythmias
- Any irregular heartbeat is considered an arrhythmia.
- These can be caused by problems with:
- Automaticity
- Excitability
- Conduction
- Combinations of excitability and conduction
- Contractility
Impaired Automaticity
- Occurs when the heart's natural pacemaker (SA node) malfunctions.
- Can lead to either:
- Nomotopic arrhythmias: originate from the SA node
- Heterotopic arrhythmias: originate from other parts of the heart's conduction system
Nomotopic Arrhythmias
- Originate in the SA node.
- Include:
- Sinus tachycardia: fast heart rate
- Sinus bradycardia: slow heart rate
- Sinus arrhythmia: irregular heart rhythm
- Sinus node weakness syndrome: problems with the SA node's ability to generate impulses
Heterotopic Arrhythmias
- Originate in parts of the heart other than the SA node.
- Include:
- Slow atrial rhythm: pacemaker is in the left atrium, heart rate less than 70 bpm
- AV (Junctional) rhythm: pacemaker is the AV node, characterized by altered P waves and a heart rate of 40-60 bpm.
- Idioventricular rhythm: pacemaker is the bundle of His or Purkinje fibers, characterized by absence of P waves, a heart rate of 20-40 bpm, and a wide QRS complex.
Impaired Excitability
- Occurs when other heart cells (cardiomyocytes) become overly excitable and generate their own impulses, disrupting the SA node's control.
- Typically caused by disturbances in ion balance across cell membranes, especially potassium levels.
Types of Arrhythmias from Impaired Excitability
-
Extrasystoles: premature contractions that occur in different regions of the heart
- Sinus extrasystole: originates in the SA node, shows shortened TP interval before the extrasystole
- Atrial extrasystole: originates in the atria, shows a low-amplitude P wave.
- AV extrasystole: excitation from the AV node travels in both directions, showing a negative P wave after the QRS complex.
- Ventricular extrasystole: contraction originates in the ventricles, characterized by a compensatory pause and sometimes a contraction after the extrasystole, QRS is altered due to the irregular electrical pathway.
- Paroxysmal supraventricular tachycardia (PSVT): a sudden, rapid heart rate (160-220 bpm), caused by multiple excitable foci above the ventricles.
Impaired Conduction
- Occurs when the electrical signals that control the heart's rhythm encounter blocks or delays in their travel through the conduction system.
- These blocks can be:
- Transverse: across different parts of the heart (e.g., between the atria and ventricles)
- Longitudinal: along a specific pathway (e.g., within an atrium)
- Arborization: within a branch of the conduction system
Types of Conduction Blocks
- Sinoatrial (SA) block: impulses don't travel from the SA node to the atria, resulting in a slower heart rate and longer RR intervals on an ECG.
- Interatrial block: occurs when conductive fibers within the atria are blocked, leading to a prolonged P wave.
-
Atrioventricular (AV) blocks: blocks between the atria and ventricles
- First-degree AV block: a delay in electrical conduction, showing a prolonged PQ interval on the ECG.
- Second-degree AV block (Mobitz type I or Wenckebach): a progressive lengthening of the PQ interval with each heartbeat until one QRS complex is dropped. This is a recurring pattern, with one dropped QRS complex every 5-7 heartbeats. Typically doesn't impact blood flow much.
- Second-degree AV block (Mobitz type II): the PQ interval remains constant but multiple QRS complexes are dropped. This is more severe and can cause palpitations, fatigue, and chest pain.
- Third-degree AV block (complete heart block): a complete blockage between the atria and ventricles, resulting in an asynchronous beat. The atria beat at their own rate (usually 70 bpm), and the ventricles beat at a much slower rate (20-40 bpm), typically controlled by lower pacemaker cells. Requires immediate treatment.
- Intraventricular block: blockage within a branch of the bundle of His or Purkinje fibers. Causes the affected ventricle to contract weakly, leading to asynchronous contractions and potential heart failure. Presents as a prolonged and deformed QRS complex.
Accelerated Conduction
- Occurs when additional, "shortcut" pathways develop, causing electrical signals to travel faster than normal.
- These pathways include:
- Kent-Paladino bundle: conductive tissue develops around the AV node, bypassing it.
- Mahaim bundle: connects the upper part of the bundle of His to the ventricles.
- James bundle: connects the atria to the lower portion of the AV node or to the bundle of His.
- Wolff-Parkinson-White (WPW) syndrome: a genetic condition where the Kent bundle develops. The atria and ventricles contract simultaneously, leading to extrasystoles. It can progress to ventricular tachycardia if not managed. On ECG, there is a short PQ interval, a widened QRS complex, and the presence of a "delta wave."
- Clerc-Levy-Cristesco (CLC) syndrome: a genetic condition involving the James bundle, leading to shortened PQ intervals, premature ventricular contractions, and tachycardia.
Simultaneous Impairment of Excitability and Conduction
- These arrhythmias are based on the "reentry" phenomenon.
- Damage in a section of the myocardium creates a "circuit." Electrical impulses from other areas can enter this damaged area, causing a short circuit and a continuous loop of electrical activity.
- These loops can create new excitable foci within the heart, leading to abnormal rhythms.
Atrial Flutter
- Characterized by rapid electrical activity in the atria, with frequencies between 250-400 bpm.
- P waves are absent, giving a "sawtooth" pattern on the ECG.
- When the rate increases to 400-600 bpm, it's known as atrial fibrillation.
Atrial Fibrillation
- The most common type of arrhythmia, where the electrical signal in the atria becomes chaotic.
- There is a loss of organized P waves, irregular heart rhythm (irregularly irregular), and narrow QRS complexes on the ECG.
Ventricular Flutter
- A rare but serious condition affecting the ventricles, where they contract at a rapid rate (150-300 bpm).
- Quick progression to ventricular fibrillation is common.
Conduction System of the Heart
- SA node, AV node, bundle of His, and Purkinje fibers
- The SA node sets the pace for the heart’s rhythm
Arrhythmias
- Irregular heartbeat affecting the rate, rhythm, or both
- Causes of Arrhythmias:
- Impaired heart automatism
- Impaired excitability
- Impaired conduction
- Simultaneous impairment of excitability and conduction
- Impaired contractility
Arrhythmias due to Impaired Automatism
-
Nomotopic arrhythmias: originate in the SA node
- Sinus tachycardia: Fast heart rate
- Sinus bradycardia: Slow heart rate
- Sinus arrhythmia: Irregular heart rhythm
- Sinus node weakness syndrome: SA node doesn’t fire properly
-
Heterotopic arrhythmias: originate in other parts of the conduction system
- Slow atrial rhythm: Heartbeat < 70 bpm
- AV (Junctional) rhythm: Pacemaker is the AV node, HR 40-60 bpm, altered P wave
- Idioventricular rhythm: Pacemaker is the bundle of His or Purkinje fibers, HR 20-40 bpm, wide QRS complex, absent P wave
Arrhythmias due to Impaired Excitability
- Related to ectopic foci, cardiomyocytes generating their own impulses
- Main cause: Ionic changes across membranes, especially potassium
- Types:
- Extrasystole
- Paroxysmal supraventricular tachycardia (PSVT)
Extrasystole
- Premature contractions that can occur anywhere in the heart
- Sinus extrasystole: Premature excitation in the SA node, shortened TP interval
- Atrial extrasystole: Excitation in the atria, low-amplitude P wave
- AV extrasystole: Excitation from AV node, negative P wave after QRS complex
- Ventricular extrasystole: Contraction develops in ventricles, compensatory pause, altered QRS
PSVT
- Sudden, very fast heartbeat (160-220 bpm)
- Results from multiple foci above the ventricles
Arrhythmias due to Impaired Conduction
- Blocked conduction: Impulses don’t spread due to changes in conduction system
- Transverse block
- Longitudinal block
- Arborization block
- Can be sinoatrial, interatrial, atrioventricular (AV) or intraventricular
-
Blocked conduction:
- Sinoatrial block: SA node impulses don't reach atria, prolonged RR distance
- Interatrial block: Blockage between atria, prolonged P wave
-
AV Block (Transverse block): AV node doesn’t transmit impulses
- AV Block of I degree: Delay in transmission, prolonged PQ interval, usually undetectable
- AV Block of II degree: Longer PQ interval with each cycle until one QRS drops (Mobitz I), can happen every 5-7 cycles, no major hemodynamic consequences
- AV Block of II degree: PQ interval remains constant and more than one QRS drops (Mobitz II) , more severe, can cause palpitations, fatigue, chest pain.
- AV Block of III degree: Complete block between atria and ventricles, inconsistent contractions, atria 70 bpm, ventricles 20-40 bpm, very severe, requires immediate attention
Intraventricular Block
- Conduction at a branch of the bundle of His or Purkinje fibers stops
- One ventricle contracts weakly, asynchronous contractions, potentially leading to heart failure
- Presents as prolonged, deformed QRS complex
Accelerated Conduction
- New conductive pathways develop leading to tachyarrhythmias
- Additional pathways
- Kent-Paladino bundle: Bypass around AV node
- Mahaim bundle: Connection between upper bundle of His and ventricles
- James bundle: Connection between atria and lower AV node or bundle of His
Wolff-Parkinson-White Syndrome (WPW)
- Genetic condition that causes the development of the Kent-Paladone bundle
- Atria and ventricles contract simultaneously, leads to extrasystoles
- Can cause ventricular tachycardia
- ECG shows shortened PQ interval, widened QRS complex, and delta wave
Clerc-Levy-Cristesco Syndrome (CLC Syndrome)
- Genetic condition that causes the development of the James bundle
- Shortened PQ intervals, premature ventricular contractions, tachycardia
Arrhythmias due to Simultaneous Impairment of Excitability and Conduction
- Based on reentry phenomenon
- Damage to part of myocardium causes impulses to circle back and create ectopic foci, can cause whole chambers to contract
Atrial Flutter
- Fast heart rate (250-400 bpm)
- Loss of P waves, normal QRS complexes
- Sawtooth appearance
Atrial Fibrillation
- Very fast heart rate (400-600 bpm)
- No P waves
- Irregularly irregular rhythm
- Narrow QRS complexes
Ventricular Flutter
- Ventricle rate 150-300 bpm
- Less common, progresses rapidly into ventricular fibrillation
Arrhythmias
- A heart rhythm abnormality affecting heart rate, rhythm, or both
- Cause:
- Impaired heart automatism
- Impaired excitability
- Impaired conduction
- Simultaneous impairment of excitability and conduction
- Impaired contractility
Nomotopic Arrhythmias
- Originate in the SA node
- Sinus tachycardia
- Sinus bradycardia
- Sinus arrhythmia
- Sinus node weakness syndrome
Heterotopic Arrhythmias
- Originate from other parts of the conductive system
- Slow atrial rhythm
- Pacemaker in the left atrium
- Heart rate less than 70 bpm
- AV (Junctional) rhythm
- Pacemaker in the AV node
- Alternating P wave and HR of 40-60 bpm
- Idioventricular rhythm
- Pacemaker in the bundle of His or Purkinje fibers
- Absence of P wave, HR of 20-40 bpm, wide QRS complex
- Slow atrial rhythm
Arrhythmias Due to Impaired Excitability
- Caused by ectopic foci, cardiomyocytes generating their own impulses when depolarization exceeds that of the pacemaker
- Main cause: Ionic changes across membranes, primarily potassium
Types of Arrhythmias Due to Impaired Excitability
- Extrasystole
- Premature contractions that can originate anywhere in the heart
- Sinus, atrial, AV, and ventricular extrasystole
- Sinus extrasystole: Shortened TP interval before the extrasystole
- Atrial extrasystole: Low-amplitude P wave
- AV extrasystole: Negative P wave after the QRS complex
- Ventricular extrasystole: Altered QRS complex due to altered wave of excitation, compensatory pause, sometimes contraction following the extrasystole
- PSVT (Paroxysmal Supraventricular Tachycardia):
- Sudden, fast arrhythmia (160-220 bpm) with multiple foci above the ventricles
Arrhythmias Due to Impaired Conduction
- Blocked conduction
- Caused by morpho-functional changes in the conductive system, preventing impulses from spreading
- Types: Transverse, longitudinal, arborization
- Locations: Sinoatrial, interatrial, atrioventricular, intraventricular
- Sinoatrial block: Prolonged RR distance, no impulses passing from the SA node to the atria.
- Interatrial block: Prolonged P wave due to blocked conductive fibers in the atria
- Accelerated conduction
- New conductive pathways develop, leading to tachyarrhythmias.
- Additional pathways: Kent-Paladino bundle, Mahaim bundle, James bundle
- Wolff-Parkinson-White syndrome (WPW syndrome): Bundle of Kent development, causing simultaneous atrial and ventricular contraction, extrasystoles, and potentially ventricular tachycardia. Presents with shortened PQ interval, widened QRS complex, and delta wave.
- Clerc-levy-Cristesco syndrome (CLC syndrome): Bundle of James development, leading to shortened PQ intervals, premature ventricular contractions, and tachycardia.
Atrioventricular (AV) Blocks
- Transverse blocks
- Caused by the AV node not transmitting impulses
- Three degrees, each with distinct ECG and clinical presentations
- AV block of I degree: Minor delay in transmission, prolonged PQ, usually undetected.
- AV block of II degree (Mobitz I): Progressive PQ lengthening until a QRS drops, periodic (Wenckebach period), QRS drops every 5-7 cardiac cycles. Minimal hemodynamic impact.
- AV block of II degree (Mobitz II): No PQ lengthening, two or more QRS drops. More severe, potentially causing palpitations, fatigue, and chest pain.
- AV block of III degree: Complete mismatch of atrial and ventricular contractions, disorganized contractions, atria beat at 70 bpm, ventricles beat at 20-40 bpm. Very severe and requires immediate treatment.
Intraventricular Block
- Conduction block in a branch of the bundle of His or Purkinje fibers.
- Weak ventricular contraction on the blocked side, asynchronous ventricular contractions, potential progression to heart failure.
- Prolonged and deformed QRS complex.
Arrhythmias Due to Simultaneous Impairment of Excitability and Conduction
- Based on the reentry phenomenon: Damage in a part of the myocardium blocks impulse transmission, causing impulses from other directions to enter, short-circuit, and create continuous contractions. This leads to the formation of new ectopic foci that can cause the chambers to contract as a whole.
- Examples: Atrial flutter and atrial fibrillation.
Atrial Flutter
- Rapid heart rate (250-400 bpm)
- Loss of P waves, normal QRS complexes
- "Sawtooth" appearance on ECG.
- When the heart rate reaches 400-600 bpm, it becomes atrial fibrillation
Atrial Fibrillation
- Irregularly irregular rhythm
- No P waves, narrow QRS complexes
Ventricular Flutter
- Less common than atrial flutter, rapidly progresses into ventricular fibrillation
- Ventricles beat at 150-300 bpm.
Conductive System of the Heart
- The conductive system consists of the SA node, AV node, bundle of His, and Purkinje fibers.
Arrhythmias
- Any abnormal heart rhythm is called an arrhythmia.
- Arrhythmias can affect heart rate, rhythm, or both.
- Caused by:
- Impaired heart automatism
- Impaired excitability
- Impaired conduction
- Simultaneous impairment of excitability and conduction
- Impaired contractility
Impaired Automatism
-
Nomotopic arrhythmias: Originate in the SA node.
- Sinus tachycardia
- Sinus bradycardia
- Sinus arrhythmia
- Sinus node weakness syndrome
-
Heterotopic arrhythmias: Originate in other parts of the conductive system.
- Slow atrial rhythm:
- Pacemaker in left atrium
- Heart rate less than 70 bpm
- AV (Junctional) rhythm
- Pacemaker in the AV node
- Alternating P wave
- Heart rate 40-60 bpm
- Idioventricular rhythm
- Pacemaker in the bundle of His or Purkinje fibers
- Absent P wave
- Heart rate 20-40 bpm
- Wide QRS complex
- Slow atrial rhythm:
Impaired Excitability
- Related to ectopic foci, cardiomyocytes generating their own impulses.
- Main cause is ionic changes; potassium is especially important.
-
Extrasystole: Premature contractions.
- Sinus extrasystole
- Premature excitation in SA node
- Shortened TP interval before extrasystole
- Atrial extrasystole
- Excitation in the atria
- Low-amplitude P wave
- AV extrasystole
- Excitation from the AV node
- Negative P wave after the QRS complex
- Ventricular extrasystole
- Contraction in the ventricles
- Compensatory pause
- Altered QRS complex
- Sinus extrasystole
-
Paroxysmal supraventricular tachycardia (PSVT)
- Sudden, fast arrhythmia (160-220 bpm)
- Multiple foci above the ventricles
Impaired Conduction
-
Blocked conduction: Impulses don't spread due to morpho-functional changes.
- Transverse
- Longitudinal
- Arborization
- Sinoatrial block: Impulses don't pass from SA node to atria.
- Prolonged RR distance.
- Interatrial block: Conduction fibers in atria are blocked.
- Prolonged P wave.
-
Atrioventricular block (AV block): The AV node doesn't transmit impulses.
- AV block of I degree:
- Delayed transmission
- Prolonged PQ interval
- AV block of II degree (Mobitz I):
- PQ lengthens with each cycle until one QRS falls.
- Wenckebach period
- Fall of QRS happens every 5-7 cardiac cycles.
- Minimal hemodynamic effect.
- AV block of II degree (Mobitz II):
- PQ doesn't lengthen
- Two or more QRS falls
- More severe, can cause palpitations, fatigue, and chest pain.
- AV block of III degree
- Total mismatch of atrial and ventricular contractions
- Atria beat at 70 bpm, ventricles at 20-40 bpm.
- Very severe, requires immediate treatment.
- AV block of I degree:
-
Intraventricular block: Conduction in the bundle of His or Purkinje fibers stops.
- Weak ventricle contraction
- Asynchronous contractions
- Can progress to heart failure
- Prolonged and deformed QRS complex
-
Accelerated conduction: New conductive pathways develop.
- Kent-Paladino bundle
- Develops around AV node
- Bypasses AV node
- Mahaim bundle
- Connects upper bundle of His to ventricles
- James bundle
- Connects atria to lower section of AV node or bundle of His
-
Wolff-Parkinson-White syndrome (WPW Syndrome):
- Genetic disease caused by the development of the Kent bundle.
- Atria and ventricles contract simultaneously.
- Extrasystoles occur.
- Can lead to ventricular tachycardia.
- Shortened PQ interval
- Expanded QRS complex
- Delta wave
-
Clerc-Levy-Cristesco syndrome (CLC Syndrome):
- Genetic disease caused by the development of the James bundle.
- Shortened PQ intervals
- Premature ventricular contractions
- Tachycardia.
- Kent-Paladino bundle
Simultaneous Impairment of Excitability and Conduction
- Relates to the phenomenon of reentry
- Damage to myocardium
- Impulses don't pass through damaged area
- Short-circuiting of impulses from other directions, leading to continuous contractions.
- New ectopic foci form
- Chambers contract as a whole.
Atrial Flutter & Fibrillation
-
Atrial flutter:
- 250-400 bpm heart rate
- Loss of P waves
- Normal QRS complexes
- "Sawtooth" appearance on ECG.
-
Atrial fibrillation:
- 400-600 bpm
- No P waves
- Irregularly irregular rhythm
- Narrow QRS complexes
Ventricular Flutter
- Ventricular beat rate 150-300 bpm
- Less common
- Quickly progresses to ventricular fibrillation.
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Description
This quiz covers the fundamentals of arrhythmias, including their causes and classifications. You will learn about the differences between nomotopic and heterotopic arrhythmias and how they affect heart function. Test your knowledge on heart rhythm irregularities and their implications.