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Flashcards in Cardiovascular Deck (50)
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1

A physician decides to place a patient on a calcium channel blocker for treatment of her angina. Calcium channel blockers can relax the smooth muscle of blood vessels and can also have various effects on cardiac contractility, conduction, and heart rate. Which of the following calcium channel blockers would be most effective in reducing heart rate and contractility?

Verapamil

The calcium channel blockers verapamil and diltiazem are both effective in slowing the rate and contractility of the heart. Both drugs decrease the magnitude of inward calcium current through L type calcium channels and also decrease the rate of recovery of the channel. It is this latter effect that depresses the sinus node pacemaker and slows atrioventricular conduction. Verapamil is a stronger negative inotrope than diltiazem, and therefore is more effective in decreasing heart rate and contractility.

2

A 28-year-old African-American man presents to the physician with fever, weight loss, and abdominal pain. His blood pressure is 168/92 mm Hg, his pulse is 83/min, and his respiratory rate is 18/min. On physical examination, there is palpable purpura on his lower extremities; a fundoscopic examination reveals fluffy, white spots on his retina. His past medical history is significant for a previous hepatitis B infection. An arterial biopsy is shown in the image. Which of the following is the most prominent morphologic feature of the affected arteries in this patient’s disease process?

Fibrinoid necrosis

This individual is likely suffering from polyarteritis nodosa (PAN), which is characterized by necrotizing immune complex inflammation of small or medium-sized arteries. PAN is typically associated with fever, malaise, weight loss, abdominal pain, headache, myalgias, and hypertension. There are no diagnostic serologic tests specific for PAN. Patients with classic PAN are ANCA-negative and may have low titers of rheumatoid factor or antinuclear antibodies, both of which are nonspecific findings. In patients with PAN, appropriate serologic tests for active hepatitis B infection must be performed as up to 30% of patients with PAN are positive for hepatitis B surface antigen. Histologically, the intense inflammatory infiltrate in the arterial wall and surrounding connective tissue is associated with fibrinoid necrosis and disruption of the vessel wall.

3

A 50-year-old man with diabetes receives the results of a fasting lipid profile that reveals hypercholesterolemia. To reduce the patient’s mortality risk, his physician recommends lifestyle changes and initiates therapy with a statin. Which of the following mechanisms describes the action of statins in reducing serum levels of LDL cholesterol?

Competitive inhibition of 3-hydroxy3-methylglutaryl coenzyme A reductase

3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) catalyzes the rate-limiting step in the synthesis of cholesterol. The enzyme converts 3-hydroxy-3-methylglutaryl coenzyme A (HMGCoA) to mevalonic acid, a cholesterol precursor. Statins competitively inhibit HMGR by obstructing part of the enzyme’s active site and preventing suffi cient interaction with HMGCoA to produce mevalonate. The consequent decrease in intrahepatic cholesterol causes upregulation of hepatic LDL cholesterol receptors, ultimately lowering plasma LDL cholesterol levels. Diabetes mellitus is considered a cardiac heart disease equivalent, and by the ATP III recommendations, the target LDL cholesterol of a diabetic patient is 130 mg/dL.

4

A 45-year-old man who takes spironolactone and digoxin for his congestive heart failure is admitted to the hospital because he is experiencing an altered mental status. The ECG changes shown in the image are noted on testing. Urinalysis would most likely reveal which of the following?

Low K+, high Na+, high-normal volume

The key to answering this question is realizing that it asks for electrolyte leveles in urine, not serum. The ECG shows peak T waves and widened QRS interval, which are classic changes seen in hyperkalemia. Spironolactone is the most likely medication to affect urinary electrolytes. As an inhibitor of aldosterone receptors in the collecting tubule and an inhibitor of Na+ channels, spironolactone greatly decreases the excretion of K+ and mildly increases the excretion of Na+. Urine volume will be high-normal because the diuretic will increase saltwater wasting.

5

A medical student working in the emergency department sees a female baby, born 2 weeks ago, who is brought in by her anxious mother.The mother tells the student that her baby seems “purple,” especially her fingers and toes, and looks extremely blue when crying. On physical examination the sleeping baby has mild cyanosis of the face and trunk, but moderate cyanosis of the extremities. Which of the following is the most common cause of cyanosis within the first few weeks of life?

Tetralogy of Fallot

Tetralogy of Fallot is the most common cause of cyanosis within the fi rst few weeks of life. The skin becomes bluish because of the malformed right-to-left shunt. Infants also have worsening cyanosis with agitation, diffi culty feeding, and failure to gain weight. Patients may also have clubbing of the fi ngers and toes or even polycythemia. The four components of the teratology are (1) ventricular septal defect, (2) overriding aorta, (3) infundibular pulmonary stenosis, and (4) right ventricular hypertrophy

6

A 55-year-old man with hypertension is prescribed an antiarrhythmic agent that alters the flow of cations in myocardial tissue. The image is a trace of a myocardial action potential. Each phase is associated with the opening and or closing of various ion channels. Which of the following would be affected by an agent that affects phase 2 of the myocardial action potential?

Voltage-gated Ca2+ channels opening

Voltage-gated Ca2+ channels open slowly in response to the Na+ upstroke as increasing K+ conductance during phase 2 gradually depolarizes the cell. The result is a slow conduction velocity that prolongs the transmission from the atria to the ventricles.

7

A 48-year-old man presents to the emergency department 1.5 hours after the onset of severe substernal chest pain radiating to his left arm.The pain is accompanied by diaphoresis and shortness of breath. His blood pressure is 165/94 mm Hg, pulse is 82/min, and respiratory rate is 18/min. Which of the following tests is the most important tool in the initial evaluation of patients in whom acute myocardial infarction (MI) is suspected?

ECG

ECG is the gold standard for diagnosing MI within the fi rst 6 hours of symptom onset. ECG changes will include ST-segment elevation (signifying transmural infarct), ST-segment depression (signifying subendocardial infarct), and Q waves (signifying transmural infarct).

8

This image depicts the administration of drug X, which produces an increase in systolic, diastolic, and mean arterial pressure. Drug Y is then added, resulting in little or no change to the blood pressure. Drug X is then readministered, causing a net decrease in blood pressure. Which of the following drug combinations are drug X and drug Y, respectively?

Epinephrine, phentolamine

Epinephrine is a nonselective agonist of α and β adrenergic receptors. Administering a large dose of epinephrine causes an increase in blood pressure via an increased heart rate and contractility through stimulation of β1 receptors (the β2 effect is minimal) and increased systemic vascular resistance through α1-mediated vasoconstriction. Adding phentolamine blocks the α effects of epinephrine so readministration leaves only the β1 receptor actions (increased contractility and heart rate) and the β2-mediated increase in vasodilation, causing a net decrease in blood pressure.

9

A 56-year-old woman arrives in the emergency department complaining of dizziness and headache. Her blood pressure is 210/140 mm Hg. She is currently not taking any medications and has not seen a doctor for several years. The physician decides to address her hypertension urgently. Which of the following drugs is contraindicated in this patient?

Sublingual nifedipine

Nifedipine is a dihydropyridine class calcium channel blocker that could be used in the long-term control of hypertension. However, in the case of a hypertensive emergency, nifedipine used sublingually can cause dangerous fl uctuations in bloodpressure that are diffi cult to control and can lead to more harm than good.

10

A 65-year-old man presents to the emergency department with chest pain that he noticed after climbing a set of stairs. The emergency physician sends him for an exercise stress test. Which of the following physiologic mechanisms does the heart use to deal with increased work demand during an exercise stress test?

Increased coronary blood flow

An increase in myocardial contractility due to exercise leads to increased oxygen demand by the cardiac muscle and increased oxygen consumption, causing local hypoxia. This local hypoxia causes vasodilation of the coronary arterioles, which then produces a compensatory increase in coronary blood fl ow and oxygen delivery to meet the demands of the cardiac muscle. Oxygen extraction from heart muscle is maximized. Increased demand can be met only by increasing blood fl ow

11

A 16-year-old Japanese exchange student presents to the physician with a history of fevers, joint pain, night sweats, and muscle pain. On physical examination, the patient has extremely weak pulses in her upper extremities. Laboratory abnormalities in which of the following parameters is most likely?

Erythrocyte sedimentation rate

This individual is most likely suffering from Takayasu’s arteritis, which is also known as “pulseless disease.” It typically affects medium and large arteries, resulting in thickening of the aortic arch and/or proximal great vessels. Symptoms include fevers, arthritis, night sweats, myalgias, skin nodules, ocular disturbances, and weak pulses in the upper extremities. It is most common in young Asian females and is associated with an elevated erythrocyte sedimentation rate.

12

A 72-year-old African-American man undergoes hip surgery. On his third hospital day he experiences chest pain, tachycardia, dyspnea, and a low-grade fever. The man goes into cardiac arrest, and efforts to resuscitate him are unsuccessful. On autopsy a massive pulmonary embolus is discovered. Which of the following, if present, would most likely predispose the patient to this event?

Mutation in the Factor V gene

A mutation in the Factor V gene, also known as Factor V Leiden, causes resistance to deactivation of Factor V by protein C. Uninhibited Factor V activity leads to a hypercoagulable state, which can lead to deep vein thrombosis and subsequent pulmonary embolism.

13

A 70-year-old woman with a history of type 2 diabetes mellitus, a body mass index of 30 kg/m2 and an MI 10 years prior presents to the emergency department with crushing subster-nal chest pain radiating to her neck and jaw. Emergency cardiac catheterization with percutaneous coronary intervention (PCI) shows a 99% occlusion of her left anterior descending artery, and an ECG reveals an anterior wall ST segment elevation MI. The patient remains stable after PCI, and echocardiography shows a mildly impaired ejection fraction (EF) of 45%. Three days later, the patient becomes acutely hypotensive and dyspneic, and physical examination reveals a high-pitched holosystolic murmur, loudest at the apex and radiating to the axilla, that had not been heard on previous exams. An emergency echocardiogram shows an EF of 25%. This patient has developed which of the following?

Ruptured papillary muscle

This patient has suffered rupture of one of the two left ventricular papillary muscles, a complication that may occur 3–10 days after an acute MI, when the infarcted area of myocardium is replaced with granulation tissue and thus is the most weak. Without the anchor of the papillary muscle, there is severe acute mitral valve regurgitation, diagnosed by a new holosystolic “blowing murmur” that is loudest at the apex and radiates to the axilla, a severely reduced stroke volume (hypotension with EF of 25%), and evidence of pulmonary edema (dyspnea).

14

A 67-year-old woman presents to the emergency department with dizziness, syncope, and palpitations. She states she is taking a medication for “heart troubles” but cannot remember its name. Results of an ECG are shown in the image. Which of this patient’s current medications might have caused this abnormal ECG pattern?

Quinidine

The ECG shows torsades des pointes. Quinidine is a class IA antiarrhythmic agent used in the treatment of supraventricular arrhythmias. Quinidine slows conduction and can increase the QT interval, leading to torsades de pointes.

15

A 35-year-old man with no significant medical history presents to his primary care physician with a 2-week history of progressive shortness of breath that occurs with activity. He previously exercised regularly and has never had symptoms like this before, but now he finds that he can walk only one block before becoming symptomatic. He has also noticed a 7-lb (3.2-kg) weight gain during this time. He does not smoke or use alcohol or illicit drugs and has not traveled recently. In addition, he has no family history of cardiac disease and does not have any sick contacts, but recalls having an upper respiratory infection about a month ago that improved on its own. Physical examination reveals crackles in his lungs bilaterally and an S3 gallop. X-ray of the chest reveals cardiomegaly. What is the most likely mechanism causing this patient’s heart failure?

Direct cytotoxicity via receptor-mediated entry of virus into cardiac myocytes

This patient is most likely experiencing congestive heart failure (CHF) secondary to dilated cardiomyopathy (DCM), which is characterized by dilation and impaired contraction of one or both ventricles. Symptoms of CHF include dyspnea (especially on exertion), orthopnea, paroxysmal nocturnal dyspnea, and peripheral edema with weight gain. DCM may also present with arrhythmias such as atrial fi brillation, or sudden cardiac death. DCM has a variety of etiologies including idiopathic, myocarditis, ischemic, druginduced, hypertension, infi ltrative disease, HIV infection, connective tissue disease, and the chemotherapeutic agent doxorubicin. In this case the most likely cause of the patient’s DCM is viral myocarditis following his upper respiratory infection several weeks ago. Viruses known to cause myocarditis include coxsackievirus, infl uenza virus, adenovirus, echovirus, cytomegalovirus, and HIV. These viruses cause myocarditis with subsequent DCM by infl icting direct cytotoxicity via receptor-mediated entry of the virus into cardiac myocytes. Patients with myocarditis may present initially with symptoms of chest pain or arrhythmias with ECG changes; in others, symptoms of heart failure may be the initial manifestation, as in this patient..

16

A 25-year-old pregnant woman goes to her gynecologist for her 36-week checkup. She complains of light-headedness when she goes to bed at night. In the offi ce, her blood pressure is 120/70 mm Hg while sitting upright and 90/50 mm Hg while lying supine. Which of the following is the most likely cause of this hypotension?

Inferior vena cava compression

Inferior vena cava (IVC) compression is common in women during the third trimester of pregnancy. The large uterus compresses the IVC, decreasing venous return to the heart. This reduction in preload reduces stroke volume, thus reducing cardiac output. Recall that mean arterial pressure = cardiac output × total peripheral resistance; an acute decrease in either of these parameters will reduce blood pressure.

17

A 48-year-old obese man presents to his primary care physician with complaints of lower leg pain that occurs after he walks a few city blocks and is relieved with rest. He has no other complaints. His blood pressure is 165/85 mm Hg, his pulse is 83/min, and his respiratory rate is 18/min. After further questioning, he admits to smoking two packs of cigarettes per day. Which of the following types of vessels is most likely involved in the pathologic process surrounding this patient’s symptoms?

Arteries

This patient is presenting with intermittent claudication. Combined with his history of smoking, this points to peripheral arterial disease, which is often the presenting sign of atherosclerosis. Peripheral atherosclerosis targets areas of high turbulence typically found at branching arterial sites; the most common sites are the abdominal aorta and iliac arteries, femoral and popliteal arteries (which is causing the calf pain in this patient), and tibial and peroneal arteries. Medical therapy with antiplatelet drugs such as aspirin has had moderate success, with surgical revascularization reserved for severe cases. Risk factors for atherosclerosis include smoking, hypertension, diabetes mellitus, hyperlipidemia, and a positive family history

18

Jugular venous pressure (JVP) curves are designed to show the pressure changes that normally take place in the right atrium throughout the cardiac cycle. A JVP curve consists of two, or sometimes three, positive waves and two negative troughs. A normal JVP curve is shown in the image. Which of the following points on the normal jugular venous tracing in the image would be most prominently affected in tricuspid regurgitation?

 C and X

In tricuspid regurgitation, blood fl ows back into the atria during ventricular systole. This would affect the C and X waves, replacing them with a large positive defl ection. This positive defl ection joins the C wave and the V wave, creating the “CV wave.” The C wave is thought to be due to pressure on the tricuspid valve during ventricular systole. If the valve allows backfl ow during ventricular systole, the pressure would drastically increase in the atria. The downward movement of the ventricle causes the X descent during ventricular systole. This would also be replaced by a positive defl ection from blood regurgitating into the atria during ventricular systole

19

A 62-year-old breast cancer survivor visits her physician because of weakness, fatigue, fever, and weight gain 5 years following her radiation therapy. The physician also elicits complaints about abdominal discomfort and exertional dyspnea. Physical examination reveals hepatomegaly and jugular venous distention that fails to subside on inspiration, but shows no evidence of hypotension or pulsus paradoxus. An echocardiogram shows reduced end-diastolic volumes and elevated diastolic pressures in both ventricles. Which of the following is the most likely diagnosis?

Constrictive pericarditis

Constrictive pericarditis interferes with the fi lling of the ventricles because of granulation tissue formation in the pericardium. It can follow purulent viral infections, trauma, neoplastic diseases, mediastinal irradiation, and other chronic diseases. Pericardial thickening and calcifi cation are sometimes apparent on CT and MRI.

20

The classic location for an abdominal aortic aneurysm is inferior to the renal arteries and extending to the bifurcation of the common iliac arteries. Repair involves resecting the diseased portion of the aorta and replacing it with a synthetic graft. Based on anatomic considerations, which of the following visceral arteries would likely be resected along with the diseased aortic tissue during the repair of an infrarenal abdominal aortic aneurysm?

Inferior mesenteric artery

The inferior mesenteric artery originates from the aorta inferior to the renal arteries and superior to the bifurcation of the aorta into the common iliac arteries. This artery may sometimes be sacrifi ced during an infrarenal aortic aneurysm repair rather than being re-attached to a healthy segment of aorta. Usually, there is enough collateral fl ow to the hindgut from the superior mesenteric artery and the hypogastric arteries that the loss of the inferior mesenteric artery does not result in colonic ischemia

21

A 52-year-old African-American man is brought to the emergency department unresponsive, and efforts to resuscitate him are unsuccessful. On autopsy, it is found that he suffered from a ruptured aneurysm of the aortic root. His dilated aorta, as seen on autopsy, is shown in the image. In addition, inspection of the man’s skin revealed several ulcerated lesions. Which of the following is most likely associated with the underlying etiology of this patient’s aneurysm?

Disruption of the vasa vasorum

Syphilitic aortitis is characterized by obliterative endarteritis of the vasa vasorum of the media. This disruption of the vasa vasorum can lead to aneurysm, which typically involves the ascending aorta and is a manifestation of tertiary syphilis. Luetic (syphilitic) aneurysms favor the aortic root, where they can be complicated by atherosclerosis. The patient’s skin lesions are the gummas of tertiary syphilis

22

A baby is observed at birth to be noncyanotic. The mother is known to have been infected with rubella during the pregnancy. On physical examination the patient is found to have a continuous murmur that is present in both systole and diastole. A nonsteroidal anti-inflammatory drug is prescribed, and on follow-up the murmur has disappeared. Which of the following is the most likely congenital lesion?

Patent ductus arteriosus

A patent ductus arteriosus (PDA) rarely causes cyanosis. PDAs are associated with maternal rubella infection during pregnancy. During fetal development, the ductus arteriosus remains patent through the action of prostaglandin I2 (PGI2). PDAs at birth are closed with indomethacin, a nonsteroidal anti-infl ammatory drug that inhibits PGI2 formation. Remember that there are, in general, three congenital heart lesions that cause late cyanosis due to left to right shunt: ventricular septal defect, atrial septal defect, and PDA. The classic murmur heard with PDA is a continuous machinelike murmur.

23

A 25-year-old white woman with no past medical history presents to the emergency department for “a racing heartbeat.” It is determined that she has paroxysmal supraventricular tachycardia. Which of the following is the drug of choice used for diagnosing and abolishing atrioventricular nodal arrhythmias by virtue of its effectiveness and its low toxicity?

Adenosine

Adenosine is extremely useful in abolishing atrioventricular (AV) nodal arrhythmias when given in highdose intravenous boluses. Adenosine works by hyperpolarizing AV node tissue by increasing the conductance of potassium and by reducing calcium current. As a result, the conduction through the AV node is markedly reduced. In addition to this, adenosine’s extremely short duration of action (15 seconds) limits the occurrence of its toxicities (i.e., hypotension, fl ushing, chest pain, and dyspnea).

24

A 62-year-old man was admitted to the intensive care unit for overwhelming sepsis. The patient has received 4 L of normal saline bolus fluids. Empirical antibiotics were begun with no improvement in his condition. His blood pressure is 60/30 mm Hg, pulse is 112/min, temperature is 40.6° C (105° F), and respiratory rate is 23/min. The physician orders intravenous norepinephrine. Which of the following is a direct effect of norepinephrine in this clinical scenario?

Coronary vasodilation

Norepinephrine, a potent direct-acting α-agonist and a moderate β-agonist, can be useful in cases of septic shock because it stimulates peripheral vasoconstriction. However, the coronary vasculature expresses both α- and β-adrenergic receptors, with a net effect of vasodilation of the coronary vessels when catecholamines are present in high levels. Norepinephrine also exerts a mild inotropic effect as a β1-agonist, but this effect may not be clinically relevant. Successful treatment of septic shock involves fl uids, proper antibiotics, and pressors (i.e., norepinephrine) if the blood pressure is unresponsive to fl uid resuscitation. Pressors are given to maintain tissue perfusion.

25

An 85-year-old man dies from aspiration pneumonia as a complication of Alzheimer’s disease. Autopsy reveals a small (230-g) heart that appears grossly dark brown in color. Hematoxylin and eosin staining of cardiac muscle cells reveals brownish perinuclear pigmentation. The pathologist determines this phenomenon to be a consequence of age and not a causative agent in the patient’s death. Accumulation of which of the following substances is the most likely cause of the brown pigmentation seen most often in the heart, liver, or spleen of the elderly?

Lipofuscin

The combination of an atrophic heart and lipofuscin accumulation is referred to as brown atrophy. Lipofuscin is a “wear and tear” pigment that commonly deposits within hepatocytes, splenocytes, and myocardial cells in the elderly. It is comprised of oxidized and polymerized membrane lipids of autophagocytosed organelles accumulated slowly over years.

26

A 72-year-old woman has a 1-month history of left-sided jaw pain when chewing food, head-ache, fever, and fatigue. Laboratory studies reveal an elevated erythrocyte sedimentation rate. Which of the following arteries is most likely involved?

Superficial temporal artery

This individual is likely suffering from giant cell (temporal) arteritis (GCA), the most common systemic vasculitis in adults. GCA, which affects large to small arteries, typically presents in people >50 years old and is more common in women. Patients commonly present with constitutional symptoms (anorexia, fatigue, weight loss), unilateral temporal or occipital headache with overlying scalp tenderness, jaw claudication, and impaired vision. The superficial temporal artery is the most commonly affected artery in patients with GCA and is affected in this patient. On biopsy, affected arteries are characterized by nodular thickening that reduces the size of the lumen, granulomatous infl ammation with mononuclear and giant cells, and fragmentation of the internal elastic membrane. GCA is treated with high-dose corticosteroids to reduce infl ammation rapidly and prevent permanent blindness

27

A 67-year-old woman with a long history of poorly controlled diabetes mellitus and chronic renal failure is admitted to the hospital for treatment of cellulitis. Two days into her hospital stay she complains of chest pain that is relieved when she leans forward. An ECG shows diffuse ST segment elevations with PR depressions; her echocardiogram is normal. Which of the following is the most appropriate treatment at this time?

Dialysis

The patient is experiencing pericarditis due to uremia secondary to chronic kidney disease in the setting of longstanding diabetes mellitus. Pericarditis presents with pleuritic, positional chest pain that is often relieved by sitting forward and with a pericardial friction rub on physical examination. Diffuse ST segment elevations may be found on ECG, while an echocardiogram may be normal unless an effusion is also present. Pericarditis has multiple etiologies, including viral (coxsackievirus, echovirus, adenovirus, and HIV), bacterial (tuberculosis or Streptococcus pneumoniae or Staphylococcus aureus in the setting of endocarditis, pneumonia, or postcardiac surgery), neoplastic, autoimmune, uremic, cardiovascular, or idiopathic. Treatment of pericarditis secondary to uremia is dialysis.

28

A 75-year-old woman arrives at the emergency department and states that her left arm is numb. She is diaphoretic. Laboratory studies show an elevated troponin I level and the patient is treated for an acute MI. A subsequent echocardiogram shows a wall motion abnormality of the posterior interventricular septum. Stenosis of which of the following arteries would most likely cause this condition?

Posterior descending artery

The posterior descending artery is a branch of the right coronary artery on the posterior surface of the heart. It courses along the posterior interventricular groove, extending toward the apex of the heart. It has posterior septal perforator branches that run anteriorly in the ventricular septum and supply the posterior one-third of the ventricular septal myocardium.

29

A 24-year-old man presents to the emergency department with a fever, chills, night sweats, malaise, and fatigue that started 3 days ago. In the past day he has also become short of breath. He admits to using intravenous drugs regularly. At presentation, the patient is shaking and appears pale. Physical examination is remarkable for a temperature of 39.4° C (103°F), hypoxia to 88% on room air, jugular venous distention, bilaterally decreased breath sounds at the bases with dullness to percussion at the bases, and a grade III/VI systolic murmur heard best at the lower left sternal border. The patient states that he never had anything wrong with his heart before. Which pathogen is most likely responsible for this patient’s condition?

Staphylococcus aureus

This patient is presenting with a classic case of acute bacterial endocarditis (ABE). Endocarditis is often characterized by constitutional symptoms (fever, malaise, chills), new-onset cardiac murmur, and a combination of other signs and symptoms (e.g., Janeway lesions, Osler nodes, and Roth spots). Acute and subacute endocarditis can be differentiated based on history, as the acute case will have a more severe and sudden onset, as in this patient. ABE is also most often seen in cases of intravenous drug use and indwelling catheters, and Staphylococcus aureus is the most common bacterial pathogen isolated in these cases because it is part of the skin fl ora and enters the blood at needle sites. This patient’s history of intravenous drug abuse as well as auscultation of a murmur consistent with tricuspid regurgitation both point to a right-sided ABE infection. In right-sided endocarditis, septic emboli to the lungs leading to bilateral infi ltrates are seen more often. This patient is manifesting signs of bilateral infi ltrates with signs of hypoxia, decreased breath sounds, and dullness to percussion. It is important to note that many of the classic signs of endocarditis, such as Janeway lesions, Osler nodes, and Roth spots, are mostly seen as a complication of left-sided endocarditis, in which septic emboli leave the heart and enter the systemic circulation

30

Drugs such as cholestyramine and colestipol have been shown to decrease circulating serum LDL cholesterol and to slightly elevate triglycerides. These drugs work by which of the following mechanisms?

Binding and excretion of bile-soluble lipids

Cholestyramine and colestipol are bile acid resins that promote binding and excretion of dietary fats that are bile-soluble. This prevents such fats from entering the blood stream effectively. They decrease serum LDL and total cholesterol levels.