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Question 1
Correct
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A 24-year-old male patient arrives at the emergency department complaining of dizziness and palpitations. Upon triage, cardiac monitoring reveals supraventricular tachycardia with a heart rate of 200 beats per minute. This rapid heart rate is facilitated by the specialized cells and nerve fibers in the heart that conduct action potentials during systole.
What type of cells and nerve fibers in the heart have the highest conduction velocities?Your Answer: Purkinje fibres
Explanation:The Purkinje fibres have the fastest conduction velocities in the heart, reaching about 4m/sec. During cardiac electrical activation, the SA node generates action potentials that spread throughout the atria muscle during atrial systole, conducting at a velocity of approximately 0.5m/sec. The atrioventricular node acts as a pathway for action potentials to enter from the atria to the ventricles, also conducting at a similar velocity of about 0.5m/sec. The Bundle of His, located at the base of the ventricle, divides into the left and right bundle branches, which conduct at a faster velocity of around 2m/sec. These bundles then divide into an extensive system of Purkinje fibres that conduct the impulse throughout the ventricles at an even faster velocity of about 4m/sec.
Understanding the Cardiac Action Potential and Conduction Velocity
The cardiac action potential is a series of electrical events that occur in the heart during each heartbeat. It is responsible for the contraction of the heart muscle and the pumping of blood throughout the body. The action potential is divided into five phases, each with a specific mechanism. The first phase is rapid depolarization, which is caused by the influx of sodium ions. The second phase is early repolarization, which is caused by the efflux of potassium ions. The third phase is the plateau phase, which is caused by the slow influx of calcium ions. The fourth phase is final repolarization, which is caused by the efflux of potassium ions. The final phase is the restoration of ionic concentrations, which is achieved by the Na+/K+ ATPase pump.
Conduction velocity is the speed at which the electrical signal travels through the heart. The speed varies depending on the location of the signal. Atrial conduction spreads along ordinary atrial myocardial fibers at a speed of 1 m/sec. AV node conduction is much slower, at 0.05 m/sec. Ventricular conduction is the fastest in the heart, achieved by the large diameter of the Purkinje fibers, which can achieve velocities of 2-4 m/sec. This allows for a rapid and coordinated contraction of the ventricles, which is essential for the proper functioning of the heart. Understanding the cardiac action potential and conduction velocity is crucial for diagnosing and treating heart conditions.
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This question is part of the following fields:
- Cardiovascular System
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Question 2
Incorrect
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A 79-year-old man is admitted to the hospital after experiencing severe dizziness, vertigo, slurred speech, and nausea with vomiting. The diagnosis reveals a basilar artery stroke. Which blood vessels combine to form the affected artery?
Your Answer: Pontine arteries
Correct Answer: Vertebral arteries
Explanation:The Circle of Willis is an anastomosis formed by the internal carotid arteries and vertebral arteries on the bottom surface of the brain. It is divided into two halves and is made up of various arteries, including the anterior communicating artery, anterior cerebral artery, internal carotid artery, posterior communicating artery, and posterior cerebral arteries. The circle and its branches supply blood to important areas of the brain, such as the corpus striatum, internal capsule, diencephalon, and midbrain.
The vertebral arteries enter the cranial cavity through the foramen magnum and lie in the subarachnoid space. They then ascend on the anterior surface of the medulla oblongata and unite to form the basilar artery at the base of the pons. The basilar artery has several branches, including the anterior inferior cerebellar artery, labyrinthine artery, pontine arteries, superior cerebellar artery, and posterior cerebral artery.
The internal carotid arteries also have several branches, such as the posterior communicating artery, anterior cerebral artery, middle cerebral artery, and anterior choroid artery. These arteries supply blood to different parts of the brain, including the frontal, temporal, and parietal lobes. Overall, the Circle of Willis and its branches play a crucial role in providing oxygen and nutrients to the brain.
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This question is part of the following fields:
- Cardiovascular System
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Question 3
Incorrect
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A patient in his late 60s presents with dyspnoea, orthopnoea, paroxysmal nocturnal dyspnoea, fatigue, cyanosis. A diagnosis of acute heart failure is made. He is started on diuretics, ACE inhibitors, beta-blockers but shows minimal improvement with medications.
What should be considered if he continues to fail to improve?Your Answer: High-flow oxygen
Correct Answer: Continuous positive airway pressure
Explanation:If a patient with acute heart failure does not show improvement with appropriate medication, CPAP should be considered as a viable treatment option.
Heart failure requires acute management, with recommended treatments including IV loop diuretics such as furosemide or bumetanide. Oxygen may also be given in accordance with British Thoracic Society guidelines to maintain oxygen saturations between 94-98%. Vasodilators such as nitrates should not be routinely given to all patients, but may be considered for those with concomitant myocardial ischaemia, severe hypertension, or regurgitant aortic or mitral valve disease. However, hypotension is a major side-effect and contraindication.
For patients with respiratory failure, CPAP may be used. In cases of hypotension or cardiogenic shock, treatment can be challenging as loop diuretics and nitrates may exacerbate hypotension. Inotropic agents like dobutamine may be considered for patients with severe left ventricular dysfunction and potentially reversible cardiogenic shock. Vasopressor agents like norepinephrine are typically only used if there is insufficient response to inotropes and evidence of end-organ hypoperfusion. Mechanical circulatory assistance such as intra-aortic balloon counterpulsation or ventricular assist devices may also be used.
While opiates were previously used routinely to reduce dyspnoea/distress in patients, NICE now advises against routine use due to studies suggesting increased morbidity in patients given opiates. Regular medication for heart failure such as beta-blockers and ACE-inhibitors should be continued, with beta-blockers only stopped if the patient has a heart rate less than 50 beats per minute, second or third degree atrioventricular block, or shock.
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This question is part of the following fields:
- Cardiovascular System
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Question 4
Correct
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A 63-year-old man comes to the clinic for a hypertension follow-up. He was diagnosed with high blood pressure two months ago and started on amlodipine. However, his blood pressure remained uncontrolled, so ramipril was added four weeks ago. During his visit today, his blood pressure is measured at 155/92 mmHg. You decide to prescribe indapamide, a thiazide-like diuretic. Can you explain the mechanism of action of thiazide-like diuretics?
Your Answer: Inhibit Na+ Cl- cotransporter
Explanation:Thiazide-like drugs such as indapamide work by blocking the Na+-Cl− symporter at the beginning of the distal convoluted tubule, which inhibits sodium reabsorption. Loop diuretics, on the other hand, inhibit the Na+ K+ 2Cl- cotransporters in the thick ascending loop of Henle. Amiloride, a potassium-sparing diuretic, inhibits the epithelial sodium channels in the cortical collecting ducts, while spironolactone, another potassium-sparing diuretic, blocks the action of aldosterone on aldosterone receptors and inhibits the Na+/K+ exchanger in the cortical collecting ducts.
Thiazide diuretics are medications that work by blocking the thiazide-sensitive Na+-Cl− symporter, which inhibits sodium reabsorption at the beginning of the distal convoluted tubule (DCT). This results in the loss of potassium as more sodium reaches the collecting ducts. While thiazide diuretics are useful in treating mild heart failure, loop diuretics are more effective in reducing overload. Bendroflumethiazide was previously used to manage hypertension, but recent NICE guidelines recommend other thiazide-like diuretics such as indapamide and chlorthalidone.
Common side effects of thiazide diuretics include dehydration, postural hypotension, and electrolyte imbalances such as hyponatremia, hypokalemia, and hypercalcemia. Other potential adverse effects include gout, impaired glucose tolerance, and impotence. Rare side effects may include thrombocytopenia, agranulocytosis, photosensitivity rash, and pancreatitis.
It is worth noting that while thiazide diuretics may cause hypercalcemia, they can also reduce the incidence of renal stones by decreasing urinary calcium excretion. According to current NICE guidelines, the management of hypertension involves the use of thiazide-like diuretics, along with other medications and lifestyle changes, to achieve optimal blood pressure control and reduce the risk of cardiovascular disease.
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This question is part of the following fields:
- Cardiovascular System
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Question 5
Correct
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An 85-year-old man presents to the hospital with complaints of breathlessness at rest. He has a medical history of type 2 diabetes and hypertension, for which he takes metformin, lisinopril, and metoprolol. He also smokes five cigarettes a day. On examination, he has a heart rate of 100 bpm, blood pressure of 128/90 mmHg, and a respiratory rate of 26 with oxygen saturation of 88% on 2l/minute. He has a regular, slow rising pulse, an ejection systolic murmur, crepitations at both lung bases, and oedema at the ankles and sacrum.
What investigation is most crucial for his immediate management?Your Answer: Electrocardiogram
Explanation:Managing Pulmonary Edema from Congestive Cardiac Failure
Pulmonary edema from congestive cardiac failure requires prompt investigation and management. The most crucial investigation is an ECG to check for a possible silent myocardial infarction. Even if the ECG is normal, a troponin test may be necessary to rule out a NSTEMI. Arterial blood gas analysis is also important to guide oxygen therapy. Additionally, stopping medications such as metformin, lisinopril, and metoprolol, and administering diuretics can help manage the condition.
It is likely that the patient has aortic stenosis, which is contributing to the cardiac failure. However, acute management of the valvular disease will be addressed separately. To learn more about heart failure and its management, refer to the ABC of heart failure articles by Millane et al. and Watson et al.
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This question is part of the following fields:
- Cardiovascular System
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Question 6
Incorrect
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A patient with a history of aortic stenosis presents with anaemia. Is there a rare association with aortic stenosis that could explain the anaemia in this patient? This is particularly relevant for elderly patients.
Your Answer: Gastric ulceration
Correct Answer: Angiodysplasia
Explanation:Aortic Stenosis and Angiodysplasia: A Possible Association
There have been numerous reports suggesting a possible link between aortic stenosis and angiodysplasia, which can result in blood loss and anemia. The exact mechanism behind this association is not yet fully understood. However, it is worth noting that replacing the stenotic valve often leads to the resolution of gastrointestinal blood loss. This finding highlights the importance of early detection and management of aortic stenosis, as it may prevent the development of angiodysplasia and its associated complications. Further research is needed to fully elucidate the relationship between these two conditions and to identify potential therapeutic targets.
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This question is part of the following fields:
- Cardiovascular System
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Question 7
Correct
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A 78-year-old man with an ST-elevation myocardial infarction receives bivalirudin, aspirin, and clopidogrel before undergoing percutaneous coronary intervention. What is the mode of action of bivalirudin?
Your Answer: Reversible direct thrombin inhibitor
Explanation:Bivalirudin inhibits thrombin directly in a reversible manner.
Warfarin prevents the conversion of vitamin K to its active hydroquinone form by acting as an antagonist.
Heparins activate antithrombin II and also form inactive complexes with other clotting factors.
Aspirin inhibits COX.
Clopidogrel functions as a/an.
Bivalirudin: An Anticoagulant for Acute Coronary Syndrome
Bivalirudin is a medication that acts as a direct thrombin inhibitor, meaning it prevents the formation of blood clots. It is commonly used as an anticoagulant in the treatment of acute coronary syndrome, a condition where blood flow to the heart is blocked or reduced. Bivalirudin is a reversible inhibitor, meaning its effects can be reversed if necessary.
Acute coronary syndrome is a serious condition that can lead to heart attack or other complications if left untreated. Bivalirudin is an effective treatment option for preventing blood clots and reducing the risk of further complications. Its reversible nature also makes it a safer option for patients who may need to undergo surgery or other procedures while on anticoagulant therapy. Overall, bivalirudin is an important medication in the management of acute coronary syndrome and plays a crucial role in improving patient outcomes.
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This question is part of the following fields:
- Cardiovascular System
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Question 8
Correct
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Abnormal conduction in the heart can result in arrhythmias, which may be caused by reduced blood flow in the coronary arteries leading to hypoxia. This can slow depolarisation in phase 0, resulting in slower conduction speeds.
What ion movement is responsible for the rapid depolarisation observed in the cardiac action potential?Your Answer: Sodium influx
Explanation:Rapid depolarization is caused by a rapid influx of sodium.
During phase 2, the plateau period, calcium influx is responsible.
To maintain the electrical gradient, there is potassium influx in phase 4, which is facilitated by inward rectifying K+ channels and the Na+/K+ ion exchange pump.
Potassium efflux mainly occurs during phases 1 and 3.
Understanding the Cardiac Action Potential and Conduction Velocity
The cardiac action potential is a series of electrical events that occur in the heart during each heartbeat. It is responsible for the contraction of the heart muscle and the pumping of blood throughout the body. The action potential is divided into five phases, each with a specific mechanism. The first phase is rapid depolarization, which is caused by the influx of sodium ions. The second phase is early repolarization, which is caused by the efflux of potassium ions. The third phase is the plateau phase, which is caused by the slow influx of calcium ions. The fourth phase is final repolarization, which is caused by the efflux of potassium ions. The final phase is the restoration of ionic concentrations, which is achieved by the Na+/K+ ATPase pump.
Conduction velocity is the speed at which the electrical signal travels through the heart. The speed varies depending on the location of the signal. Atrial conduction spreads along ordinary atrial myocardial fibers at a speed of 1 m/sec. AV node conduction is much slower, at 0.05 m/sec. Ventricular conduction is the fastest in the heart, achieved by the large diameter of the Purkinje fibers, which can achieve velocities of 2-4 m/sec. This allows for a rapid and coordinated contraction of the ventricles, which is essential for the proper functioning of the heart. Understanding the cardiac action potential and conduction velocity is crucial for diagnosing and treating heart conditions.
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This question is part of the following fields:
- Cardiovascular System
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Question 9
Incorrect
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A 82-year-old man visits the urology department complaining of a painful swelling in his left testicle that has been present for the past month. Upon examination, it is diagnosed as a left varicocele. Further CT scans reveal enlarged lymph nodes obstructing the venous drainage in the middle portion of his abdomen. Which vein is most likely to be compressed?
Your Answer: Pampiniform plexus of veins
Correct Answer: Left renal vein
Explanation:The left renal vein collects venous blood from the left testis through the left testicular/gonadal vein.
Both the left and right testes are drained by their respective testicular/gonadal veins. The right testicular vein empties directly into the inferior vena cava, while the left testicular vein drains into the left renal vein before joining the inferior vena cava.
Anatomy of the Inferior Vena Cava
The inferior vena cava (IVC) originates from the fifth lumbar vertebrae and is formed by the merging of the left and right common iliac veins. It passes to the right of the midline and receives drainage from paired segmental lumbar veins throughout its length. The right gonadal vein empties directly into the cava, while the left gonadal vein usually empties into the left renal vein. The renal veins and hepatic veins are the next major veins that drain into the IVC. The IVC pierces the central tendon of the diaphragm at the level of T8 and empties into the right atrium of the heart.
The IVC is related anteriorly to the small bowel, the first and third parts of the duodenum, the head of the pancreas, the liver and bile duct, the right common iliac artery, and the right gonadal artery. Posteriorly, it is related to the right renal artery, the right psoas muscle, the right sympathetic chain, and the coeliac ganglion.
The IVC is divided into different levels based on the veins that drain into it. At the level of T8, it receives drainage from the hepatic vein and inferior phrenic vein before piercing the diaphragm. At the level of L1, it receives drainage from the suprarenal veins and renal vein. At the level of L2, it receives drainage from the gonadal vein, and at the level of L1-5, it receives drainage from the lumbar veins. Finally, at the level of L5, the common iliac vein merges to form the IVC.
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This question is part of the following fields:
- Cardiovascular System
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Question 10
Correct
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A 68-year-old woman has a left ankle ulcer that has been present for nine months. She had a DVT in her right leg five years ago. Upon examination, there is a 6 cm diameter slough-based ulcer on the medial malleolus without cellulitis. What investigation is required before applying compression bandaging?
Your Answer: Ankle-brachial pressure index
Explanation:Venous Ulceration and the Importance of Identifying Arterial Disease
Venous ulcerations are a common type of ulcer that affects the lower extremities. The underlying cause of venous congestion, which can promote ulceration, is venous insufficiency. The treatment for venous ulceration involves controlling oedema, treating any infection, and compression. However, compressive dressings or devices should not be applied if the arterial circulation is impaired. Therefore, it is crucial to identify any arterial disease, and the ankle-brachial pressure index is a simple way of doing this. If indicated, one may progress to a lower limb arteriogram.
It is important to note that there is no clinical sign of infection, and although a bacterial swab would help to rule out pathogens within the ulcer, arterial insufficiency is the more important issue. If there is a clinical suspicion of DVT, then duplex (or rarely a venogram) is indicated to decide on the indication for anticoagulation. By identifying arterial disease, healthcare professionals can ensure that appropriate treatment is provided and avoid potential complications from compressive dressings or devices.
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This question is part of the following fields:
- Cardiovascular System
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