Atrial contribution to cardiac function US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Atrial contribution to cardiac function. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Atrial contribution to cardiac function US Medical PG Question 1: A 73-year-old man presents to your clinic for a routine checkup. His medical history is notable for a previous myocardial infarction. He states that he has not seen a doctor in "many years". He has no complaints. When you auscultate over the cardiac apex with the bell of your stethoscope, you notice an additional sound immediately preceding S1. This extra heart sound is most likely indicative of which of the following processes?
- A. Decreased left ventricular compliance (Correct Answer)
- B. Increased left ventricular compliance
- C. Increased pulmonary compliance
- D. Decreased left ventricular filling volume
- E. Increased left ventricular filling volume
Atrial contribution to cardiac function Explanation: ***Decreased left ventricular compliance***
- An additional sound immediately preceding S1 suggests a **fourth heart sound (S4)**, which occurs during **atrial contraction** against a stiff, non-compliant ventricle.
- A myocardial infarction can lead to left ventricular hypertrophy and **fibrosis**, causing **decreased left ventricular compliance**.
*Increased left ventricular compliance*
- **Increased ventricular compliance** would allow for easier filling and would not generate an audible S4.
- This condition is typically seen in dilated ventricles, which accommodate larger volumes **without significant pressure increases**.
*Increased pulmonary compliance*
- **Pulmonary compliance** refers to the lungs' ability to stretch and expand, and it is unrelated to an additional heart sound preceding S1.
- This concept describes the **elastic properties of lung tissue** and has no direct bearing on cardiac auscultation in this context.
*Decreased left ventricular filling volume*
- A **decreased left ventricular filling volume** might reduce the intensity of heart sounds but would not, in itself, cause an S4 before S1.
- S4 is related to the **atrial kick** into a resistant ventricle, not the overall volume available for filling.
*Increased left ventricular filling volume*
- While increased filling volume can occur in conditions like **valvular regurgitation**, it does not directly lead to an S4.
- An S4 is specifically due to a forceful atrial contraction against a **non-compliant ventricle**, regardless of the absolute filling volume.
Atrial contribution to cardiac function US Medical PG Question 2: A 67-year-old male with a history of poorly controlled hypertension, COPD, and diabetes presents to his cardiologist for a routine appointment. He reports that he has no current complaints and has not noticed any significant changes in his health. On exam, the cardiologist hears an extra heart sound in late diastole that immediately precedes S1. This heart sound is most associated with which of the following?
- A. Left ventricular hypertrophy (Correct Answer)
- B. Increased filling pressures
- C. Mitral regurgitation
- D. Mitral stenosis
- E. Ventricular dilation
Atrial contribution to cardiac function Explanation: ***Left ventricular hypertrophy***
- An **S4 heart sound** in late diastole, immediately preceding S1, is typically heard with a **stiff, non-compliant left ventricle**, which is characteristic of **left ventricular hypertrophy**.
- The patient's history of **poorly controlled hypertension and diabetes** are significant risk factors for developing left ventricular hypertrophy.
*Increased filling pressures*
- While increased filling pressures can occur in heart failure, an **S4** specifically indicates **diastolic dysfunction due to a hypertrophied ventricle**, not merely high filling pressures.
- An **S3 heart sound** is more commonly associated with increased filling pressures and **ventricular dilation in systolic dysfunction**.
*Mitral regurgitation*
- **Mitral regurgitation** is typically characterized by a **holosystolic murmur**, which is a different auscultatory finding.
- While chronic mitral regurgitation can lead to ventricular hypertrophy, the **S4 sound** itself reflects the underlying **stiffness of the ventricle**, not directly the valvular insufficiency.
*Mitral stenosis*
- **Mitral stenosis** is characterized by an **opening snap** followed by a **mid-diastolic rumble**, which is distinct from an S4 heart sound.
- It involves a narrowed mitral valve orifice, causing impedance to blood flow from the left atrium to the left ventricle.
*Ventricular dilation*
- **Ventricular dilation** is typically associated with an **S3 heart sound**, which occurs in early diastole during rapid ventricular filling.
- An **S4** signifies a **non-compliant, stiff ventricle** (often hypertrophied), rather than a dilated one.
Atrial contribution to cardiac function US Medical PG Question 3: A 60-year-old male presents with palpitations. He reports drinking many glasses of wine over several hours at a family wedding the previous evening. An EKG reveals absent P waves and irregularly irregular rhythm. He does not take any medications. Which is most likely responsible for the patient’s symptoms?
- A. Transmural myocardial infarction
- B. Untreated hypertension
- C. Ventricular hypertrophy
- D. Torsades de pointes
- E. Atrial fibrillation (Correct Answer)
Atrial contribution to cardiac function Explanation: ***Atrial fibrillation***
- The EKG findings of **absent P waves** and an **irregularly irregular rhythm** are pathognomonic for **atrial fibrillation**.
- The history of heavy alcohol consumption, known as "holiday heart syndrome," is a common trigger for paroxysmal atrial fibrillation.
*Transmural myocardial infarction*
- A myocardial infarction (heart attack) would typically present with **chest pain**, shortness of breath, and EKG changes such as ST-segment elevation or Q waves.
- While palpitations can occur, the characteristic EKG trace described is not consistent with a transmural MI.
*Untreated hypertension*
- Chronic untreated hypertension can lead to cardiac remodeling and increase the risk of arrhythmias, including atrial fibrillation, but it doesn't directly cause absent P waves and an irregularly irregular rhythm on its own; it's a risk factor rather than the direct cause of the immediate EKG findings.
- The presenting symptoms are specifically palpitation, not necessarily those of hypertensive crisis or end-organ damage from chronic hypertension.
*Ventricular hypertrophy*
- Ventricular hypertrophy, often caused by untreated hypertension, is a structural change in the heart, not an arrhythmia itself.
- While hypertrophy can predispose to arrhythmias, it wouldn't directly manifest as absent P waves and an irregularly irregular rhythm on EKG.
*Torsades de pointes*
- Torsades de pointes is a polymorphic ventricular tachycardia characterized by a **prolonged QT interval** and QRS complexes that appear to twist around the baseline.
- The EKG description of absent P waves and irregularly irregular rhythm is not consistent with Torsades de pointes.
Atrial contribution to cardiac function US Medical PG Question 4: A 17-year-old previously healthy, athletic male suddenly falls unconscious while playing soccer. His athletic trainer comes to his aid and notes that he is pulseless. He begins performing CPR on the patient until the ambulance arrives but the teenager is pronounced dead when the paramedics arrived. Upon investigation of his primary care physician's office notes, it was found that the child had a recognized murmur that was ruled to be "benign." Which of the following conditions would have increased the intensity of the murmur?
- A. Inspiration
- B. Placing the patient in a squatting position
- C. Valsalva (Correct Answer)
- D. Passive leg raise
- E. Handgrip
Atrial contribution to cardiac function Explanation: ***Valsalva***
- The patient's sudden death after collapsing during soccer, coupled with a previously noted "benign" murmur, strongly suggests **hypertrophic obstructive cardiomyopathy (HOCM)**, which is a common cause of sudden cardiac death in young athletes. The **Valsalva maneuver** decreases preload and left ventricular volume, thereby **increasing the left ventricular outflow tract (LVOT) obstruction** and hence the intensity of the HOCM murmur.
- This maneuver reduces venous return to the heart, leading to reduced ventricular filling and decreased stroke volume. This exacerbates the obstruction in HOCM, making the murmur louder.
*Inspiration*
- **Inspiration** typically **increases venous return to the right side of the heart**, which would generally intensify right-sided murmurs (e.g., tricuspid regurgitation).
- It would have **minimal effect or slightly decrease** the intensity of a left-sided obstructive murmur like that in HOCM, as it does not directly increase the LVOT obstruction.
*Placing the patient in a squatting position*
- Squatting increases both **preload** and **afterload** by increasing systemic vascular resistance and venous return.
- This increase in ventricular volume would **reduce the outflow tract obstruction** in HOCM, thereby **decreasing the intensity of the murmur**.
*Passive leg raise*
- A **passive leg raise** increases **venous return** and thus **preload**, leading to increased ventricular filling.
- Similar to squatting, this increased left ventricular volume would **reduce the left ventricular outflow tract obstruction** associated with HOCM, thereby **decreasing the murmur's intensity**.
*Handgrip*
- The **handgrip maneuver** primarily **increases afterload** and, to some extent, preload by increasing systemic vascular resistance.
- While it can increase the intensity of murmurs like mitral regurgitation and ventricular septal defect, it would generally **decrease or have no significant effect** on the murmur of HOCM due to the increased ventricular volume reducing the outflow obstruction.
Atrial contribution to cardiac function US Medical PG Question 5: A 65-year-old woman comes to the physician because of a 3-month history of intermittent palpitations and shortness of breath. Cardiopulmonary examination shows no other abnormalities. An ECG shows an absence of P waves, an oscillating baseline, and irregular RR intervals at a rate of approximately 95 beats per minute. The difference between atrial and ventricular rates in this patient is most likely due to which of the following?
- A. Prolonged influx through voltage-gated Ca2+ channels in the bundle of His
- B. Transient activation of K+ current in Purkinje fibers
- C. Inhibition of the Na+/K+-ATPase pump in ventricular cells
- D. Limited speed of conduction through the left bundle branch
- E. Temporary inactivation of Na+ channels in the AV node (Correct Answer)
Atrial contribution to cardiac function Explanation: ***Temporary inactivation of Na+ channels in the AV node***
- The ECG findings are classic for **atrial fibrillation**, characterized by a rapid, irregular atrial rhythm (oscillating baseline with no P waves) and an irregularly irregular ventricular response.
- The **AV node's refractory period** and the number of sodium channels available for conduction dictate the rate at which atrial impulses can pass to the ventricles, preventing a dangerously fast ventricular rate.
*Prolonged influx through voltage-gated Ca2+ channels in the bundle of His*
- The **bundle of His** primarily conducts impulses rather than primarily regulating the rate difference between atria and ventricles through calcium channel kinetics.
- Prolonged calcium influx would generally **slow conduction** or decrease excitability, but it's not the primary mechanism explaining the ventricular rate control in atrial fibrillation.
*Transient activation of K+ current in Purkinje fibers*
- **Purkinje fibers** are involved in rapid ventricular depolarization, but their primary role is not to mediate the rate difference between atria and ventricles in atrial fibrillation.
- Activation of K+ current typically leads to **repolarization**, affecting action potential duration, not the overall filtering of atrial impulses.
*Inhibition of the Na+/K+-ATPase pump in ventricular cells*
- Inhibition of the **Na+/K+-ATPase pump** would lead to intracellular sodium accumulation and depolarization, potentially causing arrhythmias, not regulating the ventricular rate in atrial fibrillation.
- This is the mechanism of action for **digoxin**, which can slow AV nodal conduction but through a different primary pathway affecting the pump.
*Limited speed of conduction through the left bundle branch*
- While conduction system abnormalities can occur, a **limited speed of conduction** specifically in the left bundle branch would cause a wide QRS complex or bundle branch block, not the inherent rate-limiting seen in atrial fibrillation.
- The AV node is the primary regulator of ventricular response rate in atrial fibrillation due to its inherent physiological properties.
Atrial contribution to cardiac function US Medical PG Question 6: A 72-year-old woman comes to the emergency department because of a 2-week history of worsening shortness of breath, lower extremity swelling, and a 3-kg (6.6-lb) weight gain. Crackles are heard on auscultation of the chest. Cardiac examination shows a dull, low-pitched early diastolic sound at the 5th left intercostal space that becomes louder in the left lateral decubitus position at end-expiration. Which of the following is the most likely cause of these auscultation findings?
- A. Increased ventricular contractility
- B. Increased capacity of the pulmonary circulation
- C. Decreased left-ventricular filling pressure
- D. Increased left ventricular end-systolic volume
- E. Decreased left myocardial compliance (Correct Answer)
Atrial contribution to cardiac function Explanation: ***Decreased left myocardial compliance***
- A dull, low-pitched early **diastolic sound (S3 gallop)**, heard best in the left lateral decubitus position at end-expiration, indicates **rapid ventricular filling** into a ventricle with altered diastolic properties. This finding, along with worsening shortness of breath, lower extremity swelling, and weight gain, suggests **heart failure with impaired ventricular filling**.
- Decreased left myocardial compliance (increased stiffness) means the left ventricle cannot **relax and fill properly** during diastole. The S3 occurs when blood rapidly decelerates as it enters the stiff, non-compliant ventricle, creating the characteristic sound.
- This represents **diastolic dysfunction** (heart failure with preserved ejection fraction - HFpEF), which is common in elderly patients with hypertension and is characterized by a stiff ventricle with increased filling pressures.
*Increased ventricular contractility*
- Increased ventricular contractility would lead to a more forceful ejection of blood during systole, not an early diastolic filling sound.
- This would not explain the S3 gallop or the signs of heart failure with fluid retention.
*Increased capacity of the pulmonary circulation*
- Increased pulmonary circulation capacity would help accommodate fluid and prevent pulmonary congestion, which contradicts the symptoms of crackles and shortness of breath.
- The patient has **decreased** capacity to handle the fluid volume, leading to pulmonary edema.
*Decreased left-ventricular filling pressure*
- Decreased LV filling pressure would imply less fluid overload and better cardiac function, contrary to the clinical presentation.
- An S3 gallop and signs of heart failure (crackles, edema, weight gain) indicate **increased** filling pressures from impaired ventricular function.
*Increased left ventricular end-systolic volume*
- Increased end-systolic volume indicates **systolic dysfunction** (reduced ejection fraction), where the ventricle cannot adequately eject blood, leaving residual volume after contraction.
- While systolic dysfunction can also produce an S3 gallop due to volume overload, the specific clinical description emphasizes a **diastolic filling abnormality** (sound during early diastole in a specific position that optimizes detection of ventricular filling).
- The S3 in systolic dysfunction is primarily due to **volume overload**, whereas the S3 here is attributed to blood entering a **stiff ventricle** with impaired compliance, which is the primary pathophysiologic mechanism being tested.
Atrial contribution to cardiac function US Medical PG Question 7: A 37-year-old man is brought to the emergency department by ambulance after a motor vehicle accident. He suffered multiple deep lacerations and experienced significant blood loss during transport. In the emergency department, his temperature is 98.6°F (37°C), blood pressure is 102/68 mmHg, pulse is 112/min, and respirations are 22/min. His lacerations are sutured and he is given 2 liters of saline by large bore intravenous lines. Which of the following changes will occur in this patient's cardiac physiology due to this intervention?
- A. Increased cardiac output and unchanged right atrial pressure
- B. Decreased cardiac output and increased right atrial pressure
- C. Increased cardiac output and decreased right atrial pressure
- D. Increased cardiac output and increased right atrial pressure (Correct Answer)
- E. Decreased cardiac output and decreased right atrial pressure
Atrial contribution to cardiac function Explanation: ***Increased cardiac output and increased right atrial pressure***
- The patient experienced significant blood loss, leading to a **decreased preload** and subsequent **reduced cardiac output**. Volume resuscitation with saline directly increases the **intravascular volume** which bolsters **venous return** and **right atrial pressure**.
- According to the **Frank-Starling mechanism**, increased right atrial pressure (a measure of preload) results in an increase in ventricular stretch and a more forceful contraction, thereby increasing **stroke volume** and **cardiac output**.
*Increased cardiac output and unchanged right atrial pressure*
- While fluid administration will increase **cardiac output** by improving preload, it will also directly lead to an increase in **right atrial pressure** due to the augmented venous return.
- An unchanged right atrial pressure would imply no significant increase in central venous volume, which contradicts the effect of a large volume fluid resuscitation.
*Decreased cardiac output and increased right atrial pressure*
- This scenario is unlikely because increasing **intravascular volume** through fluid resuscitation typically aims to raise **cardiac output** by optimizing preload, not decrease it.
- A decrease in cardiac output despite increased right atrial pressure could indicate **cardiac pump failure**, which is not suggested by the clinical picture of hypovolemic shock treated with fluids.
*Increased cardiac output and decreased right atrial pressure*
- An increase in **cardiac output** as a result of fluid resuscitation is expected, but a **decreased right atrial pressure** would contradict the mechanism of increased venous return and volume expansion.
- Decreased right atrial pressure would typically indicate ongoing volume loss or inadequate fluid resuscitation to restore central venous volume.
*Decreased cardiac output and decreased right atrial pressure*
- Both decreasing **cardiac output** and decreasing **right atrial pressure** indicate a worsening state of **hypovolemia** or an inadequate response to fluid resuscitation.
- The administration of 2 liters of saline is intended to correct the hypovolemia and improve cardiodynamics, not to worsen them.
Atrial contribution to cardiac function US Medical PG Question 8: A 37-year-old man with a history of schizophrenia, obesity, anxiety, recurrent pneumonia, and depression is brought to the emergency department. He was recently discharged from inpatient psychiatric care where he was treated for an acute psychotic episode with fluphenazine and started on a new antidepressant. One week after discharge, during a period of cold weather, he is found outdoors confused and poorly dressed. His rectal temperature is 93.2°F (34°C). Which of the following medications is most likely contributing to his hypothermia?
- A. Fluphenazine (Correct Answer)
- B. Valproic acid
- C. Diphenhydramine
- D. Fluoxetine
- E. Lithium
Atrial contribution to cardiac function Explanation: **Fluphenazine**
- **First-generation antipsychotics** like fluphenazine can impair the body's ability to **thermoregulate** by interfering with dopaminergic pathways in the hypothalamus, increasing susceptibility to hypothermia in cold environments.
- Given the patient's recent discharge from inpatient care and exposure to cold weather while poorly dressed, the addition of an antipsychotic affecting thermoregulation strongly contributes to his hypothermia.
*Valproic acid*
- Valproic acid is an **anticonvulsant** and **mood stabilizer** primarily used for bipolar disorder and epilepsy.
- While it can have various side effects, **hypothermia** is not a commonly reported or significant side effect of valproic acid.
*Diphenhydramine*
- Diphenhydramine is an **antihistamine** with significant **sedative** and **anticholinergic** properties.
- While it can cause sedation and anticholinergic effects that might impact a patient's awareness or ability to seek shelter, it is not directly implicated in causing hypothermia through thermoregulatory dysfunction.
*Fluoxetine*
- Fluoxetine is a **selective serotonin reuptake inhibitor (SSRI)** commonly used for depression and anxiety.
- While SSRIs can have various side effects, **hypothermia** is not a characteristic or significant side effect of fluoxetine.
*Lithium*
- Lithium is a **mood stabilizer** used primarily for bipolar disorder.
- **Hypothyroidism** is a known side effect of long-term lithium use, which could theoretically contribute to an inability to maintain body temperature, but it is less likely to cause acute hypothermia compared to antipsychotics directly affecting thermoregulation.
Atrial contribution to cardiac function US Medical PG Question 9: A 17-year-old boy is brought to the pediatrician by his mother for fatigue. The patient reports that he was supposed to try out for winter track this year, but he had to quit because his “legs just give up.” He also reports increased difficulty breathing with exercise but denies chest pain or palpitations. He has no chronic medical conditions and takes no medications. He has had no surgeries in the past. The mother reports that he met all his pediatric milestones and is an “average” student. He is up-to-date on all childhood vaccinations, including a recent flu vaccine. On physical examination, there is mild lumbar lordosis. The patient’s thighs appear thin in diameter compared to his lower leg muscles, and he walks on his toes. An electrocardiogram shows 1st degree atrioventricular nodal block. Which of the following is the most likely cause of the patient’s condition?
- A. Absent dystrophin
- B. Trinucleotide repeats
- C. Abnormal dystrophin (Correct Answer)
- D. Sarcomere protein dysfunction
- E. Peripheral nerve demyelination
Atrial contribution to cardiac function Explanation: ***Abnormal dystrophin***
* The patient's presentation with **fatigue**, exercise intolerance, muscular weakness ("legs just give up"), **lumbar lordosis**, **calf pseudohypertrophy** (thighs thin compared to lower legs), and **toe walking** are classic signs of **Becker muscular dystrophy (BMD)**.
* BMD is caused by mutations in the *DMD* gene leading to **abnormally sized or reduced, but still functional, dystrophin protein**. This allows for a milder, later-onset phenotype compared to Duchenne muscular dystrophy.
*Absent dystrophin*
* **Absent dystrophin** is characteristic of **Duchenne muscular dystrophy (DMD)**, which typically presents earlier in childhood with more severe and rapid progression of muscle weakness.
* While both BMD and DMD are X-linked dystrophinopathies, the patient's age (17 years) and milder symptoms are more consistent with the later onset and slower progression seen in BMD.
*Trinucleotide repeats*
* **Trinucleotide repeat disorders** like **myotonic dystrophy** or **Friedreich's ataxia** can cause muscle weakness and cardiac issues but have different clinical presentations.
* Myotonic dystrophy often involves **myotonia** (delayed muscle relaxation), frontal balding, and cataracts, which are not described here.
*Sarcomere protein dysfunction*
* **Sarcomere protein dysfunction** is primarily associated with various forms of **cardiomyopathy** (e.g., hypertrophic cardiomyopathy), which would explain the cardiac findings, but it does not typically cause the specific pattern of limb girdle weakness, calf pseudohypertrophy, and toe walking seen in this patient.
* Conditions like hereditary myopathies can involve sarcomeric proteins, but the overall clinical picture strongly points to a dystrophinopathy.
*Peripheral nerve demyelination*
* **Peripheral nerve demyelination** is characteristic of conditions like **Charcot-Marie-Tooth disease** (CMT), which affects peripheral nerves and causes distal muscle weakness and atrophy, foot deformities (e.g., pes cavus), and sensory loss.
* While CMT can cause toe walking, it typically involves significant distal muscle wasting rather than calf pseudohypertrophy, and the cardiac involvement (1st-degree AV block) is less commonly a prominent feature compared to muscular dystrophies.
Atrial contribution to cardiac function US Medical PG Question 10: A 52-year-old man presents to the emergency department because of fatigue, abdominal distension, and swelling of both legs for the last 3 weeks. His wife says that he lost some weight recently. He has had type 2 diabetes mellitus for 12 years, for which he takes metformin and sitagliptin. He has a history of Hodgkin’s lymphoma which was successfully treated with mediastinal radiation 20 years ago. He does not smoke or drink alcohol. He has a family history of type 2 diabetes in his father and elder sister. Vital signs include a blood pressure of 100/70 mm Hg, a temperature of 36.9°C (98.4°F), and a regular radial pulse of 90/min. On physical examination, there is jugular venous distension, most prominently when the patient inhales. Bilateral ankle pitting edema is present, and his abdomen is distended with shifting dullness on percussion. An early diastolic knocking sound is audible on the chest. His chest X-ray is shown in the exhibit. Which of the following is the best treatment for this patient?
- A. Pericardiectomy (Correct Answer)
- B. Percutaneous aspiration with high-flow oxygen
- C. Pleurodesis
- D. Ibuprofen, plus colchicine
- E. Pericardiocentesis
Atrial contribution to cardiac function Explanation: ***Pericardiectomy***
- This patient presents with signs and symptoms of **constrictive pericarditis**, including **fatigue**, **abdominal distension** (ascites), **bilateral leg swelling** (edema), **jugular venous distension** (Kussmaul sign), and an **early diastolic knocking sound**. The **chest X-ray** demonstrating **pericardial calcification** (arrows) is highly suggestive of this condition.
- As medical therapies are generally ineffective for constrictive pericarditis, **surgical pericardiectomy** (removal of the pericardium) is the definitive treatment to relieve the constriction and improve cardiac function.
*Percutaneous aspiration with high-flow oxygen*
- This treatment is typical for a **tension pneumothorax**, which involves air accumulation in the pleural space, compressing the lung and mediastinum.
- The patient's symptoms and imaging, especially the chest X-ray showing pericardial calcification, are inconsistent with pneumothorax.
*Pleurodesis*
- **Pleurodesis** is a procedure used to prevent recurrent **pleural effusions** or **pneumothorax** by adhering the parietal and visceral pleura.
- This patient's presentation points to pericardial, not pleural, pathology, and there is no mention of recurrent pleural effusions or pneumothorax.
*Ibuprofen, plus colchicine*
- This combination is the standard treatment for **acute pericarditis**, which is characterized by chest pain, pericardial friction rub, and EKG changes.
- The patient's chronic symptoms, signs of fluid overload, and pericardial calcification indicate **constrictive pericarditis**, not acute inflammation, making anti-inflammatory agents ineffective.
*Pericardiocentesis*
- **Pericardiocentesis** is indicated for **pericardial tamponade** or large, symptomatic **pericardial effusions** to relieve pressure.
- While fluid overload is present, the key underlying issue is chronic pericardial constriction due to calcification, not a large acute effusion amenable to simple drainage.
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