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Questions and Answers
What is the primary function of heart valves in the cardiovascular system?
What is the primary function of heart valves in the cardiovascular system?
Heart valves prevent the backflow of blood, ensuring a one-way flow during heart contractions.
Define automaticity in the context of heart muscle physiology.
Define automaticity in the context of heart muscle physiology.
Automaticity is the ability of cardiac cells to initiate electrical impulses spontaneously and repetitively.
How does tachycardia differ from bradycardia in terms of heart rate?
How does tachycardia differ from bradycardia in terms of heart rate?
Tachycardia is defined as a heart rate greater than 100 beats per minute, while bradycardia is a rate less than 60 beats per minute.
What is the formula to calculate cardiac output?
What is the formula to calculate cardiac output?
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What role does excitability play in cardiac muscle function?
What role does excitability play in cardiac muscle function?
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Identify the potential causes of atrial dysrhythmias.
Identify the potential causes of atrial dysrhythmias.
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What is the expected stroke volume range for an average-sized adult?
What is the expected stroke volume range for an average-sized adult?
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Describe the pathway of impulse conduction in the heart.
Describe the pathway of impulse conduction in the heart.
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What is the significance of the sinoatrial (SA) node in the heart's electrical conduction system?
What is the significance of the sinoatrial (SA) node in the heart's electrical conduction system?
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Explain how ion movements influence contractility in cardiac muscle cells.
Explain how ion movements influence contractility in cardiac muscle cells.
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Describe the purpose of an electrocardiogram (ECG) in cardiac assessment.
Describe the purpose of an electrocardiogram (ECG) in cardiac assessment.
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What characterizes atrial fibrillation and how does it affect the heart's rhythm?
What characterizes atrial fibrillation and how does it affect the heart's rhythm?
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Identify the four major components of the heart's electrical conduction pathway.
Identify the four major components of the heart's electrical conduction pathway.
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What does the QRS wave represent in the electrocardiogram?
What does the QRS wave represent in the electrocardiogram?
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Discuss the concept of refractoriness in cardiac muscles.
Discuss the concept of refractoriness in cardiac muscles.
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How can electrolyte imbalances affect cardiac rhythm?
How can electrolyte imbalances affect cardiac rhythm?
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What is the primary pharmacological treatment for symptomatic atrial fibrillation during the initial management phase?
What is the primary pharmacological treatment for symptomatic atrial fibrillation during the initial management phase?
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What defines a premature atrial contraction (PAC) in terms of its origin?
What defines a premature atrial contraction (PAC) in terms of its origin?
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What characteristic feature distinguishes atrial flutter from other atrial dysrhythmias?
What characteristic feature distinguishes atrial flutter from other atrial dysrhythmias?
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In first-degree AV block, what is the key measurement indicated in the PR interval?
In first-degree AV block, what is the key measurement indicated in the PR interval?
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What is the recommended intervention for patients with recurrent and uncontrolled atrial fibrillation?
What is the recommended intervention for patients with recurrent and uncontrolled atrial fibrillation?
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What effect does a compensatory pause have in the context of premature atrial contractions?
What effect does a compensatory pause have in the context of premature atrial contractions?
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What is the primary indicator for using oral anticoagulants over warfarin in patients with atrial fibrillation?
What is the primary indicator for using oral anticoagulants over warfarin in patients with atrial fibrillation?
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What could be a common cause of atrioventricular (AV) blocks in patients?
What could be a common cause of atrioventricular (AV) blocks in patients?
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Study Notes
Cardiac Electrophysiology
- Conductivity: Ability of cardiac cells to transmit electrical impulses across cell membranes.
- Contractility: Ability of heart muscle cells to contract and generate force, influenced by movement of sodium, calcium and potassium ions.
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Impulse Conduction: The electrical pathway for heartbeats, consisting of four major parts:
- Sinoatrial Node (SA node): Pacemaker of the heart.
- Atrioventricular Node (AV node): Delays electrical impulse, allowing ventricles to fill with blood.
- Bundle of His: Conducts the impulse from the AV node to the ventricles.
- Purkinje fibers: Rapidly distribute the impulse throughout the ventricles.
- Action Potential: A brief change in voltage (membrane potential) across the cell membrane of heart cells, initiated by ion channel activity, leading to contraction.
- Refractoriness: The period during which heart muscle cells cannot respond to a stimulus, preventing tetanus.
Electrocardiogram (ECG)
- ECG records the electrical activity of the heart.
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Waveforms:
- P Wave: Represents atrial depolarization (contraction).
- QRS Complex: Represents ventricular depolarization (contraction).
- T Wave: Represents ventricular repolarization (relaxation).
Atrial Dysrhythmias
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Atrial Fibrillation (AFib): Rapid and irregular beating of the atria, characterized by:
- Irregular R to R intervals.
- Most common atrial arrhythmia.
- Occurs more in older individuals.
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Premature Atrial Contractions (PACs): Early heartbeats originating outside the SA node:
- Ectopic: Originating outside the SA node.
- Narrow Complexes: Originating in the atria..
- Compensatory Pause: Delay following the contraction.
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Atrial Flutter: Rapid, coordinated beating of the atria:
- Sawtooth Baseline: Characteristic pattern on ECG.
- Narrow Complex Tachycardia: Heart rate around 150 bpm.
- No Visible P Waves: Flutter waves conceal P waves.
Sinus Dysrhythmias
- Sinus Tachycardia: Rapid heart rate, greater than 100 bpm.
- Sinus Bradycardia: Slow heart rate, less than 60 bpm.
Atrioventricular (AV) Blocks
- First Degree AV Block: Delayed conduction between atria and ventricles, characterized by prolonged PR interval (greater than 0.20 seconds).
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Second Degree AV Block: Partial blockage of electrical signals between atria and ventricles.
- Mobitz Type 1 (Wenckebach): Progressive lengthening of PR interval followed by dropped QRS complex.
- Mobitz Type 2: Sudden dropped QRS complex without progressive PR lengthening.
- Third Degree (Complete) AV Block: Complete blockage of electrical signals between atria and ventricles, resulting in independent atrial and ventricular rhythms.
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Common Causes of AV Blocks:
- Idiopathic fibrosis of conduction system.
- Ischemic heart disease.
- Medications (e.g., beta-blockers).
- Increased vagal tone.
- Valvulopathy.
- Congenital disorders.
Cardiac Function Parameters
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Heart Rate: Normal range is 60 to 100 bpm.
- Bradycardia: Heart rate less than 60 bpm.
- Tachycardia: Heart rate greater than 100 bpm.
- Stroke Volume: Amount of blood ejected with each contraction (about 60-100 ml).
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Cardiac Output (CO): Amount of blood ejected by the heart each minute (4-8 liters in adults).
- CO = (EDV - ESV) x HR (EDV is end-diastolic volume, ESV is end-systolic volume, HR is heart rate).
Management of Atrial Fibrillation
- Antiarrhythmic Drugs: Used initially to control AFib rhythm.
- Cardioversion: Electrical shock delivered to restore normal rhythm, used for symptomatic patients.
- Oral Anticoagulants: (dabigatran, rivaroxaban, apixaban, edoxaban) recommended over warfarin to prevent stroke.
- Catheter Ablation: Procedure to destroy abnormal heart tissue causing AFib, used for recurrent and uncontrolled cases.
- Percutaneous Left Atrial Appendage (LAA) Occlusion: Procedure to close off a part of the atria (LAA) associated with stroke risk.
Cardiovascular System Anatomy and Physiology
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Four Chambers:
- Two Atria: Upper chambers that receive blood from the body and lungs.
- Two Ventricles: Lower chambers that pump blood to the body and lungs.
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Four Heart Valves: Allow one-way blood flow through the heart.
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Atrioventricular Valves:
- Tricuspid valve: Between right atrium and ventricle.
- Mitral valve: Between left atrium and ventricle.
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Semilunar Valves:
- Aortic valve: Between left ventricle and aorta.
- Pulmonic valve: Between right ventricle and pulmonary artery.
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Atrioventricular Valves:
Blood Flow
- Deoxygenated blood: Flows from the body through the superior and inferior vena cava to the right atrium.
- Right ventricle: Pumps deoxygenated blood to the lungs via the pulmonary artery.
- Lungs: Oxygenate blood.
- Left atrium: Receives oxygenated blood from the lungs.
- Left ventricle: Pumps oxygenated blood to the body through the aorta.
Electrophysiologic Properties of Heart Muscles
- Automaticity (Rhythmicity): Ability of cardiac cells to initiate impulse spontaneously and repetitively.
- Excitability: Ability of cardiac cells to respond to an electrical stimulus.
- Conductivity: Ability of cardiac cells to transmit electrical impulses.
- Contractility: Ability of cardiac cells to contract and generate force.
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Description
Test your knowledge on cardiac electrophysiology, exploring key concepts such as conductivity, contractility, and impulse conduction. This quiz covers essential components like the sinoatrial node and action potential, which are crucial for understanding heart function.
