Cardiology Clinical Case / MCQS / Uworld for Usmle step 2 / case 6

 Cardiology Clinical Case  / MCQS / Uworld for Usmle step 2 / case 6 with answer and explanation and references and Educational objective

A 64-year-old man with a long history of uncontrolled hypertension comes to the emergency department with chest pain for the last 12 hours. He has never been hospitalized before. Electrocardiogram shows normal sinus rhythm with ST-segment elevation in the anterior leads. Coronary angiography shows complete occlusion of the proximal left anterior descending artery and no significant disease in the other coronary arteries. No intervention is performed and the patient is started on appropriate medical therapy. The next day he reports left leg pain. On examination, the left leg is cold with a mottled appearance. There is minimal swelling with absence of distal pulses. Vascular surgery is consulted. Which of the following should also be considered in this patient?

 

A.  Chest x-ray . B.  D-dimer levels . C.  Echocardiogram . D.  Venous Doppler study. E.  Ventilation-perfusion scan .

 

Answer : C

Explanation:

This patient most likely has acute limb ischemia from arterial occlusion, which is typically caused by cardiac emboli, thrombosis (eg, vascular stents, hypercoagulable states), or trauma. Major cardiac sources of arterial emboli include:

•      Left ventricular (LV) thrombus

•      Thrombus (usually left atrial) formation due to atrial fibrillation

•      Aortic atherosclerosis

Patients with large anterior ST-elevation Ml (STEMI) are at highest risk of LV thrombus and anteroapical aneurysm formation. Such patients often have an LV ejection fraction (EF) <40%. These patients are at high risk for systemic embolization (eg, stroke, peripheral arterial occlusion) and require immediate anticoagulation and vascular surgery evaluation. In addition, transthoracic echocardiogram with echo contrast must be performed to screen for LV thrombus.

 

(Choice A) Chest x-ray can be used for diagnosis of congestive heart failure or aortic dissection (ie, widened mediastinum). However, this patient has no symptoms of dyspnea or chest pain.

(Choice B and D) Heparin-induced thrombocytopenia (HIT) typically occurs 5-10 days after initiation of heparin therapy. Patients with HIT are prone to thrombosis (venous > arterial). Venous thrombosis typically presents with warmth, erythema, swelling, and tenderness. This patient's presentation and timing of symptoms suggest acute limb ischemia from arterial embolus; therefore, D-dimer levels and venous Doppler study are not required.

 

(Choice E) Ventilation-perfusion scan is used for diagnosis of pulmonary embolus, which typically presents with dyspnea, tachypnea, pleuritic chest pain, and signs or symptoms of lower-extremity deep venous thrombosis. This patient has no such symptoms.

 

Educational objective:

Acute limb ischemia after myocardial infarction suggests possible arterial embolus from left ventricular (LV) thrombus. Management includes immediate anticoagulation, vascular surgery consultation, and transthoracic echocardiogram to screen for LV thrombus and evaluate LV function.

 

References: 1. Left ventricular thrombus in patients with acute myocardial infarction: Case report and Caribbean focused update. New link : 1. Left ventricular thrombus in patients with acute myocardial infarction: Case report and Caribbean focused update.

 

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Cardiology Clinical Case / MCQS / Uworld for Usmle step 2 / case 5

 

Cardiology Clinical Case  / MCQS / Uworld for Usmle step 2 / case 5 with answer and explanation and references and Educational objective

A 69-year-old man comes to the emergency department due to left leg pain. The patient says he used to have pain in both legs after walking a couple of blocks, but several hours ago he suddenly started having severe left leg pain while resting. He reports numbness in the left leg, and he is also experiencing intermittent palpitations. The patient has a prolonged history of hypertension and hyperlipidemia. His current medications include lisinopril, amlodipine, and rosuvastatin. He has smoked a half pack of cigarettes daily for 45 years and drinks 3-4 cans of beer weekly. His blood pressure is 130/80 mm Hg and pulse is 116/min and irregular. On examination, hair is sparse on both legs. The left leg appears pale and feels colder than the right. Distal pulses are absent on the left and diminished on the right. Sensation to light touch is decreased on the dorsum of the left foot and leg. Ankle dorsiflexion is slightly weaker on the left. Which of the following is the best first step in management of this patient?

 

A.  Ankle brachial index . B.  Arterial Doppler study . C.  Intravenous heparin infusion . D.  Nerve conduction study . E.  Transthoracic echocardiogram .

 

Answer : C

Explanation:

The patient has the classic clinical presentation of acute arterial occlusion of the left lower extremity (acute limb ischemia): pain, pallor, poikilothermia (cool extremity), paresthesia, pulselessness, and paralysis (6 Ps ). This is most likely due to thromboembolic occlusion from left atrial thrombus due to atrial fibrillation (irregular heartbeat) in a patient with preexisting peripheral vascular disease (multiple risk factors, intermittent claudication, diminished pulses).

 

Patients with suspected acute arterial occlusion leading to an immediately-threatened limb (sensory loss, rest pain, muscle weakness) should be immediately started on anticoagulation while further diagnostic procedures are performed. Heparin prevents further thrombus propagation and thrombosis in the distal arterial and venous circulation.

(Choice A) Ankle-brachial index (ratio of systolic pressure in ankle to that in arm) is often used as a screening and/or diagnostic tool in patients with suspected peripheral arterial disease (PAD). Although this patient likely has PAD, the more acute limb-threatening complication should be addressed first.

 

(Choice B) Arterial Doppler study or duplex ultrasonography can identify the presence and location of acute arterial occlusion; however, the clinical suspicion for acute embolic occlusion in this patient is so high that anticoagulation initiation should not be delayed while obtaining additional confirmatory testing.

 

(Choice D) This patient's abnormal neurologic findings (eg, decreased sensation) are likely the result of nerve ischemia. Therefore, nerve conduction studies would not add much value.

 

(Choice E) Transthoracic echocardiogram (TTE) can aid in identifying potential cardiac sources of emboli (eg, left atrial thrombus due to atrial fibrillation, left ventricular thrombus, infective endocarditis [septic emboli], thrombus from prosthetic valves).

However, TTE should be performed after the limb-threatening acute ischemia has been addressed.

 

Educational objective:

 

Patients with suspected acute arterial occlusion leading to an immediately-threatened limb (eg, sensory loss, rest pain, muscle weakness) should be immediately started on anticoagulation with intravenous heparin prior to further evaluation with noninvasive or invasive imaging.

 

References: 1. Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II). 2. Antithrombotic therapy in peripheral artery disease : Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.   New links : 1. Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II). 2. Antithrombotic therapy in peripheral artery disease : Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

  

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Cardiology Clinical Case / MCQS / Uworld for Usmle step 2 / case 4

 Cardiology Clinical Case  / MCQS / Uworld for Usmle step 2 / case 4 with answer and explanation and references and Educational objective

A 46-year-old man comes to the physician with exertional dyspnea and dry cough. He also has occasional episodes of suffocating nighttime cough that is only relieved by sitting up. Past medical history is significant for myocardial infarction 6 months ago and hypercholesterolemia. Current medications include metoprolol, aspirin, and rosuvastatin. The patient does not use tobacco or illicit drugs but drinks alcohol on social occasions. His father died of a stroke and his mother has type 2 diabetes mellitus. His blood pressure is 150/1 00 mm Hg and pulse is 60/min. Chest examination shows bibasilar crackles. The cardiac apex is palpated in the left sixth intercostal space.  Bilateral pitting leg edema is present. Which of the following is most likely to be associated with this patient's condition?

 

A.  Constriction of the efferent renal arterioles B.  Decreased intraglomerular pressure C.  Decreased renal venous pressure D.  Decreased plasma colloid pressure E.  High sodium delivery to the distal tubule F.   Increased renal blood flow

 

Answer : A

Explanation :

 

This patient's presentation (exertional dyspnea, paroxysmal nocturnal dyspnea, pulmonary and peripheral edema) and history of myocardial infarction suggest decompensated systolic congestive heart failure (CHF). Decreased cardiac output in such patients leads to neurohumoral adaptations, including increased sympathetic nervous system tone, activation of the renin-angiotensin-aldosterone system (RAAS), and increased secretion of antidiuretic hormone. These compensatory mechanisms attempt to maintain cardiac output and systemic pressure by increasing myocardial contractility, peripheral vasoconstriction, and expansion of extracellular fluid  volume.

 

Decreased renal perfusion seen in CHF and subsequent RAAS activation lead to increased angiotensin II levels. Angiotensin II causes numerous effects including:

 

•      Vasoconstriction of both the afferent and efferent glomerular arterioles, leading to an increase in renal vascular resistance and a net decrease in renal blood flow (Choice F).

•      Preferential vasoconstrict ion of efferent renal arterioles, which increases intraglomerular pressure (Choice B) in an attempt to maintain adequate glomerular filtration rate (GFR).

•       Direct stimulation of sodium resorption in the proximal tubules and increased secretion of aldosterone from the adrenal glands, which in turn promotes further sodium resorption in the cortical collecting tubule. These actions lead to decreased sodium delivery to the distal tubule (Choice E) and an increase in extracellular fluid volume.

 

(Choice C) Patients with systolic CHF and reduced cardiac output have an increase in renal vascular resistance and overall venous pressures due to activation of the sympathetic nervous system and RAAS.

 

(Choice D) Decreased plasma colloid pressure is the mechanism responsible for peripheral and/or generalized edema in patients with severe proteinuria and hypoalbuminemia.

 

Educational objective:

In patients with congestive heart failure, activation of the renin-angiotensin-aldosterone system (RAAS) and production of angiotensin II causes preferential vasoconstriction of efferent renal arterioles, which increases intraglomerular pressure in order to maintain adequate glomerular filtration rate (GFR).

 

References: 1. Congestive heart failure: pathophysiologic consequences of neurohormonal activation and the potential for recovery: part I. New link : 1. Congestive heart failure: pathophysiologic consequences of neurohormonal activation and the potential for recovery: part I.

 

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Cardiology Clinical Case / MCQS / Uworld for Usmle step 2 / case 3

Cardiology Clinical Case  / MCQS / Uworld for Usmle step 2 / case 3 with answer and explanation and references and Educational objective

 

A 52-year-old man comes to the emergency department with shortness of breath and dry cough. The patient has been feeling weak over the last several days with some dyspnea on exertion, which he attributes to work -related stress and fatigue. Earlier this morning, he woke up with persistent breathing difficulty that prompted him to come to the emergency department. The patient has a history of mild intermittent asthma for which he occasionally uses an albuterol inhaler. His family history is insignificant. The patient's temperature is 37.1 C (98.8 F), blood pressure is 117/72 mm Hg, pulse is 89/min, and respirations are 18/min. Laboratory analysis reveals a markedly elevated serum brain natriuretic peptide level. Which of the following clinical signs would best correlate with this finding in this patient?

 

A Cyanosis B. Extremity edema C. Neck bruit D. Periumbilical bruit E. Third heart sound F. Wheezing

 

Answer : E

Explanation :

 

This clinical presentation - progressive dyspnea, fatigue, and elevated brain natriuretic peptide (BNP) levels- is consistent with congestive heart failure (CHF). BNP is a natriuretic hormone released from ventricular myocytes in response to high ventricular filling pressures and wall stress in patients with CHF. It is derived from the cleavage of the prohormone proBNP, which produces a biologically active BNP and an inert N-terminal proBNP (NT-proBNP). Elevated levels of circulating BNP or NT-proBNP correlate with the severity of left ventricular systolic dysfunction. Conversely, normal values have a very high negative predictive value for CHF as a cause of dyspnea and should prompt a search for noncardiac causes of dyspnea.

 

The third heart sound (S3) is a low-frequency diastolic sound produced by the passive ventricular filling during early diastole; it is best heard over the cardiac apex in the left lateral decubitus position. An abnormal S3 (louder and higher pitch, S3 gallop) is commonly heard in patients with CHF due to left ventricular systolic dysfunction (up to 99% specificity), and it correlates with elevated left atrial and/or ventricular filling pressures and serum BNP levels.

 

(Choice A) Cyanosis can occur in patients with intrinsic lung disease or congenital heart defects with right to left shunting (Eisenmenger syndrome). but it would be rare in CHF unless there is marked hypoperfusion (eg, hypotension , cold and clammy extremities) .Cyanosis would not correlate with BNP levels.

 

(Choice B) Peripheral edema is one of the signs of CHF with volume overload; however, compared to S3, it is less specific to the diagnosis of CHF and correlates less closely with BNP levels. Peri pheral edema can be seen with several noncardiac conditions, including inferior vena cava obstruction, cirrhosis, and lower extremity venous insufficiency.

 

(Choice C) Neck bruits can be present in patients with carotid artery stenosis.

 

(Choice D) An abdominal or periumbilical bruit that lateralizes to one side can be heard in patients with renal artery stenosis.

 

(Choice F) Although wheezing can sometimes be heard in patients with a CHF exacerbation due to bronchial wall edema, in general it is a sign of bronchial constriction and is present in patients with asthma or chronic obstructive pulmonary disease exacerbation. BNP levels are typically not elevated in patients with dyspnea due to pulmonary or noncardiac causes.

 

Educational objective:

Elevated brain natriuretic peptide levels and an audible third heart sound are signs of increased cardiac filling pressures and are noted in patients with congestive heart failure due to left ventricular systolic dysfunction.

 

References: 1. Natriuretic peptides (BNP and NT-proBNP): measurement and relevance in heart failure. 2. Usefulness of the third heart sound in predicting an elevated level of B-type natriuretic peptide.   New links : 1. Natriuretic peptides (BNP and NT-proBNP): measurement and relevance in heart failure. 2. Usefulness of the third heart sound in predicting an elevated level of B-type natriuretic peptide.

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