arterial fibrillation

Question 1

What is the definition of atrial fibrillation (A-fib)?

Answer 1

Answer: Atrial fibrillation is a supraventricular arrhythmia that originates above the ventricles and causes an irregularly irregular rhythm.

Question 2

Name five mechanisms that can contribute to the development of atrial fibrillation.
Answer:

Answer 2

• Stretching of the myocardium
• Ischemia (decreased oxygen) to the myocardium of the atria
• Inflammation of the atria or nearby areas
• Increase in sympathetic nervous system (SNS) stimulation on the atria
• Electrolyte imbalance, particularly involving calcium (Ca2+) and potassium (K+)

Question 3

What are the risk factors for atrial fibrillation?

Answer 3

Answer:
can be categorized as “cardiac causes” and “non-cardiac causes.”

The cardiac causes include congestive heart failure (CHF), dilated cardiomyopathy, valvular diseases (such as mitral stenosis and mitral regurgitation), coronary artery disease or myocardial infarction, rheumatic heart disease, and hypertension.

Question 4

How does congestive heart failure (CHF) contribute to atrial fibrillation?

Answer 4

Answer:

• Congestive heart failure (CHF) causes increased stretching and distention of the myocardium of both the ventricles and the atria.
• This stretching leads to atrial dilation and hypertrophy, changing the morphology of the atria and increasing the risk of atrial fibrillation.

Question 5

What is the mechanism behind atrial fibrillation in cases of valvular diseases?

Answer 5

Answer:

• Valvular diseases, such as mitral stenosis and mitral regurgitation, can contribute to atrial fibrillation through increased stretching of the atria.
• In mitral stenosis, the narrowed mitral valve allows less blood to flow from the atria into the ventricles, resulting in the retention of some volume in the atria and causing them to balloon up.
• Mitral regurgitation can have a similar effect, although it is less common.

Question 6

How does ischemia contribute to the development of atrial fibrillation?

Answer 6

Answer:

• Ischemia, which refers to decreased oxygen supply, can trigger the development of atrial fibrillation.
• In severe coronary artery disease or myocardial infarction, if there is an ischemic or infarcted area, the tissue in the atria near that area must undergo remodeling.
• This remodeling can lead to abnormal electrical activities in the atria, resulting in atrial fibrillation.

Question 7

What is the role of inflammation in atrial fibrillation caused by rheumatic heart disease?

Answer 7

Answer:

• In rheumatic heart disease, inflammation can affect the valves, atria, endocardium, or myocardium.
• The inflammation may be due to rheumatic fever.
• Rheumatic heart disease can lead to mitral stenosis, which ultimately increases the risk of atrial fibrillation.
• Additionally, the inflammation and atrial agitation caused by rheumatic heart disease can directly contribute to the development of atrial fibrillation.

Question 8

What are the non-cardiac causes of atrial fibrillation?

Answer 8

Answer:
The non-cardiac causes of atrial fibrillation include lung pathologies, thyrotoxicosis or hyperthyroidism, holiday heart syndrome, pheochromocytoma, drugs (such as cocaine and methamphetamines), sepsis, surgical procedures, and electrolyte abnormalities.

Question 9

How do lung pathologies contribute to atrial fibrillation?

Answer 9

Answer:

• Through ischemia caused by decreased oxygen supply (hypoxemia).
• Hypoxemia can trigger the atria to become irritable, leading to abnormal foci or reentry circuits and ischemia.
• Conditions such as chronic obstructive pulmonary disease (COPD), pneumonia, or acute onset pulmonary embolism can cause ventilation or perfusion problems, respectively, resulting in low oxygen levels.

Question 10

What is the mechanism behind atrial fibrillation in cases of thyrotoxicosis or hyperthyroidism?

Answer 10

Answer:

• In cases of thyrotoxicosis or hyperthyroidism, there is increased sympathetic nervous system (SNS) activity.
• This leads to the release of excess thyroid hormones (FT3 and FT4), which increase β-adrenergic stimulation.
• The increased sensitivity of β1-adrenergic receptors to epinephrine and norepinephrine contributes to the development of atrial fibrillation.

Question 11

What is holiday heart syndrome, and how does it lead to atrial fibrillation?

Answer 11

Answer:

• is a condition where excessive alcohol intake, such as acute alcohol binge-drinking, causes various effects on the body, including inflammation, electrolyte imbalance, and increased sympathetic nervous system (SNS) activity.
• Alcohol-induced cytotoxic effects lead to inflammation, while alterations in electrolyte levels, such as potassium (K+) and magnesium (Mg2+), can occur.
• These factors, combined with increased SNS effects on the heart, can result in atrial fibrillation.

Question 12

What is pheochromocytoma, and how does it contribute to atrial fibrillation?

Answer 12

Answer:

• is a tumor located in the adrenal medulla that releases excessive amounts of catecholamines, including epinephrine and norepinephrine.
• These catecholamines bind to β1-adrenergic receptors, increasing calcium (Ca2+) influx and cation loading.
• This hyperactive sympathetic nervous system (SNS) activity leads to atrial agitation and can contribute to the development of atrial fibrillation.

Question 13

Which drugs can increase the risk of atrial fibrillation?

Answer 13

Answer:

• Drugs such as cocaine and methamphetamines can increase the risk of atrial fibrillation.
• These drugs act as sympathomimetics, binding to the same receptors as epinephrine and norepinephrine, resulting in increased sympathetic nervous system (SNS) activity.
• This increased SNS activity leads to heightened cation loading and irritation of the atria, increasing the likelihood of atrial fibrillation.

Question 14

How does sepsis contribute to the development of atrial fibrillation?

Answer 14

Answer:

• Sepsis is a condition characterized by a systemic inflammatory response to infection. During sepsis, the body experiences vasodilation, capillary permeability, and fever.
• In response to this stressful event, the sympathetic nervous system (SNS) becomes hyperactive as part of the “Fight or Flight” response.
• The increased SNS activity, intended to counteract the negative effects of sepsis, can lead to atrial fibrillation.

Question 15

What is the relationship between surgical procedures and atrial fibrillation?

Answer 15

Answer:

• Invasive surgical procedures can cause significant post-operative stress on the body.
• This stress can trigger a catecholamine response, leading to hyperactive sympathetic nervous system (SNS) activity.
• The increased SNS activity, in turn, can contribute to the development of atrial fibrillation.

Question 16

How do electrolyte abnormalities, specifically hypokalemia and hypomagnesemia, influence the occurrence of atrial fibrillation?

Answer 16

Answer:

• Electrolyte abnormalities, such as hypokalemia (decreased potassium levels) and hypomagnesemia (decreased magnesium levels), can alter the heart’s electrical activity and increase the risk of atrial fibrillation.
• Both potassium and magnesium are important cations involved in the electrical activities of the heart.
• Insufficient levels of these electrolytes can disrupt the normal electrical conduction system, leading to atrial fibrillation or supraventricular tachyarrhythmia.

Question 17

How do the risk factors of increased stretch on the heart contribute to the pathophysiology of atrial fibrillation?

Answer 17

Answer:

• Increased stretch on the heart, as seen in conditions such as congestive heart failure (CHF), dilated cardiomyopathy, and mitral stenosis, can lead to remodeling of the myocardium.
• This remodeling can generate abnormal electrical activity in the atria, resulting in atrial fibrillation.

Question 18

What is the role of inflammation of the myocardium in the development of atrial fibrillation?

Answer 18

Answer:
Inflammation of the myocardium, as observed in rheumatic heart disease, holiday heart syndrome, and increased reactive oxygen species (ROS) production, can agitate the atria and contribute to the occurrence of atrial fibrillation.

Question 19

How does low oxygen delivery to the myocardium contribute to atrial fibrillation?

Answer 19

Answer:
Conditions such as coronary artery disease, myocardial infarction, chronic obstructive pulmonary disease (COPD), pneumonia, and acute pulmonary embolism can result in low oxygen delivery to the myocardium.

• This can trigger abnormal electrical activity in the atria, leading to atrial fibrillation.

Question 20

What is the relationship between increased sympathetic activity and atrial fibrillation?

Answer 20

Answer:

Increased sympathetic activity, seen in conditions like thyrotoxicosis, pheochromocytoma, excessive alcohol intake, cocaine and methamphetamine consumption, septic reaction, and post-operative state,

can agitate the atria and contribute to the development of atrial fibrillation.

Question 21

How does electrolyte imbalance, specifically hypokalemia and hypomagnesemia, contribute to atrial fibrillation?

Answer 21

Answer:

• particularly low levels of potassium (hypokalemia) and magnesium (hypomagnesemia), can alter the heart’s electrical activity.
• This disruption in electrical conduction can lead to atrial fibrillation or supraventricular tachyarrhythmia.

Question 22

What are the two ways in which significant agitation to the myocardium can generate abnormal electrical activity?

Answer 22

Answer:

• Significant agitation to the myocardium, leading to remodeling, can result in the formation of ectopic foci in multiple areas in the myocardium of the atria.
• It can also lead to the development of re-entrant circuits, involving the alpha and beta pathways, which can generate abnormal electrical signals and contribute to atrial fibrillation.

Question 23

What are common symptoms of atrial fibrillation?

Answer 23

Answer:

Common symptoms of atrial fibrillation include

• palpitations (abnormal awareness of heartbeat),
• shortness of breath, fatigue, and episodes of
• syncope (fainting).

Question 24

How does atrial fibrillation contribute to cardiogenic shock?

Answer 24

Answer:

• In cases of tachycardia (heart rate&raquo_space;> 150), there is not enough time for the ventricles to fill adequately.
• The reduced ventricular filling time leads to a decrease in end-diastolic volume, stroke volume, cardiac output, and mean arterial pressure.
• The decrease in cardiac output and hypotension can result in cardiogenic shock, which is characterized by inadequate blood flow to meet the body’s demands.

Question 25

What is the relationship between atrial fibrillation and the formation of emboli?

Answer 25

Answer:

• Inadequate atrial contractions in atrial fibrillation lead to a decrease in the atrial kick, which is responsible for about 20-30% of blood volume entering the ventricles.
• Reduced atrial kick results in increased blood volume staying in the atria, leading to stasis (blood stagnation).
• Stasis, along with endothelial injury and hypercoagulability (Virchow’s Triad), increases the risk of clot formation.
• Clots formed in the atria or on the valves can embolize and travel to different organs through the systemic circulation.

Question 26

What are the potential complications of emboli caused by atrial fibrillation?

Answer 26

Answer:

Emboli can go to various organs, including the

• Brain: Emboli reaching the brain can cause an ischemic stroke, resulting in neurologic deficits.
• Spleen: Emboli can cause a splenic infarct, leading to pain in the left upper quadrant (LUQ) and abnormalities in the complete blood count (CBC).
• Kidney: Emboli can result in a renal infarct, causing an increase in blood urea nitrogen (BUN) and creatinine levels.
• Gut: Emboli can cause acute mesenteric ischemia, leading to abdominal pain.

Question 27

What are the criteria for classifying atrial fibrillation based on hemodynamics?

Answer 27

Answer:
Hemodynamically unstable atrial fibrillation is characterized by symptoms such as low blood pressure (hypotension), pulmonary edema (in cardiogenic shock), altered mental status, or severe chest pain.

Hemodynamically stable atrial fibrillation refers to cases where the patient does not exhibit the symptoms mentioned above. They have normal blood pressure, no pulmonary edema, normal mentation, and no significant refractory chest pain.

Question 28

How is atrial fibrillation classified based on ventricular rate?

Answer 28

Answer:
* Atrial fibrillation with rapid ventricular rate is defined by a heart rate (HR) greater than 100 bpm.

This occurs when ectopic foci are firing rapidly, reaching the AV nodes and ventricles.

• Atrial fibrillation with slow ventricular rate is characterized by a heart rate less than 60 bpm.

In this case, re-entrant circuits or ectopic foci are not firing as fast or frequently, resulting in a slower ventricular rate.

Question 29

What are the different classifications of atrial fibrillation based on onset and duration?

Answer 29

Answer:

• New Onset Atrial Fibrillation refers to atrial fibrillation that has developed within the last 48-72 hours.
• Paroxysmal Atrial Fibrillation describes atrial fibrillation that has occurred for less than 7 days.
  Persistent Atrial Fibrillation refers to atrial fibrillation that has been present for more than 7 days.
• Long-Standing Atrial Fibrillation indicates atrial fibrillation that has been present for over a year.
• Permanent Atrial Fibrillation is diagnosed when the patient has persistent atrial fibrillation without any attempts to cardiovert them to normal sinus rhythm. It specifically refers to atrial fibrillation that has persisted for more than 7 days without a cardioversion attempt.

Question 30

What is the primary focus on an EKG when diagnosing atrial fibrillation?

Answer 30

Answer: The primary focus is on Lead V1, which shows atrial activity. If no evidence is seen on V1, other leads such as V2, V3, and aVF can be examined.

Question 31

What information can be obtained from an EKG in relation to atrial fibrillation?

Answer 31

Answer:

Presence or absence of atrial fibrillation can be determined.

• Wolff-Parkinson-White (WPW) syndrome may be identified, characterized by tachycardia (close to 200 bpm) and an irregular rhythm.
• Potential causes of atrial fibrillation, such as recent myocardial infarction, coronary artery disease, and hypertension, can be assessed.
• ST segment elevation/depression can be ruled out.
• Left ventricular hypertrophy can be detected.

Question 32

Besides the standard EKG, what other diagnostic tests can be used for monitoring atrial fibrillation?

Answer 32

Answer:

• Holter Monitoring: It is considered the gold standard and addresses the limitation of the standard EKG by monitoring the electrical activity over an extended period. It is used for outpatient monitoring.
• Loop Recorder: An implantable heart recording device that monitors the outpatient’s electrical activity. It is more invasive than Holter monitoring.
• Telemetry: It involves continuous in-patient monitoring of the heart’s electrical activity.

Question 33

What can a chest X-ray (CXR) help determine in relation to atrial fibrillation?

Answer 33

Answer:

• Presence of pneumonia.
• Presence of COPD (characterized by hyperinflated lungs, hyperlucid lungs, and flattened diaphragm).
• Presence of cardiomegaly, indicating conditions such as CHF and dilated cardiomyopathy.

Question 34

What are the two types of echocardiograms used to assess atrial fibrillation?

Answer 34

Answer:
Trans-Esophageal Echocardiogram (TEE).
Trans-Thoracic Echocardiogram (TTE).

Question 35

What can be assessed in an echocardiogram for atrial fibrillation?

Answer 35

Answer:

• Presence of an atrial thrombus, which may require urgent treatment with anticoagulants.
• Presence of mitral valve issues such as stenosis, regurgitation, or mechanical valve.
• Left Ventricular Ejection Fraction (LVEF) to determine heart failure with reduced ejection fraction.
• Presence of left ventricular hypertrophy, associated with hypertension.
• Atrial dilation, which can be diagnostic for atrial fibrillation even if not observed in other tests.

Question 36

What laboratory tests can assist in determining the triggers or causes of atrial fibrillation?

Answer 36

Answer:

• Brain natriuretic peptide (BNP) to assess for elevated levels indicating congestive heart failure (CHF).
• Troponin levels to indicate myocardial ischemia.
  Complete Blood Count (CBC) to assess for elevated white blood cell count indicating pneumonia.
• Thyroid-stimulating hormone (TSH) with reflex to FT4 to screen for hyperthyroidism and differential diagnosis of hypothyroidism.
• Blood alcohol level (etOH) to consider Holiday Heart Syndrome.
• Urine metanephrine test to detect or rule out pheochromocytoma.
• Urine toxicology test (“Tox Screen”) to detect the presence of cocaine, methamphetamine, or urinary alcohol metabolites.