A 6-day-old boy in the neonatal intensive care unit has a heart murmur.  The patient was born at 27 weeks gestation and intubated due to surfactant deficiency.  Birth weight was 1.14 kg (2 lb 8 oz).  Temperature is 37 C (98.6 F), blood pressure is 66/12 mm Hg, and pulse is 182/min.  A continuous murmur with systolic accentuation is best heard at the left heart border.  There are bounding femoral and palmar pulses.  Abdominal examination is unremarkable.  Blood culture is sterile.  Elevated levels of which of the following substances is most likely contributing to this patient’s condition?

A 53-year-old man comes to the physician for a follow-up visit after an acute myocardial infarction.  His medications include metoprolol and low-dose aspirin.  He used to smoke 2 packs of cigarettes daily but quit after his myocardial infarction.  The patient’s father has hypertension and his mother has type 2 diabetes mellitus.  He currently weighs 100 kg (220 lb) and is 178 cm (70 in) tall.  Examination shows an obese male with no other abnormalities.  His total serum cholesterol level is 155 mg/dL, with an HDL level of 27 mg/dL and a triglyceride level of 92 mg/dL.  Which of the following lipid-lowering agents would be most effective for preventing future cardiovascular events in this patient?

A 79-year-old man is brought to the hospital due to confusion for the past 2 days.  The patient has had nausea, decreased appetite, and poor oral intake for several weeks.  He has also mentioned that everything around him has “a yellow tint.”  He has no abdominal pain.  Medical history includes long-standing heart failure with reduced ejection fraction and atrial fibrillation.  Medications include metoprolol, digoxin, lisinopril, and apixaban.  The patient is afebrile.  Blood pressure is 130/80 mm Hg and pulse is 58/min.  The abdomen is soft and nontender; there is no rigidity or rebound and no masses are present.  Age-related changes in which of the following factors most likely accounts for this patient’s symptoms?

A 36-year-old man comes to the office after he was found to have an abnormal lipid panel during employee wellness testing at his company.  He has no prior medical problems and takes no medications.  The patient is a software technician and has a sedentary lifestyle.  He eats mostly fast foods, rarely exercises, and drinks 2-3 cans of beer daily.  His BMI is 31 kg/m².  Physical examination is unremarkable.  Results of laboratory studies performed in the office are as follows:

Lifestyle modification with a balanced diet, regular exercise, and reduced alcohol intake is advised.  He is also started on fenofibrate therapy.  This medication is most likely to help the patient by which of the following mechanisms?

A 72-year-old man is brought to the hospital due to severe substernal chest pain and shortness of breath for the last several hours.  The pain started suddenly when he was outside working in the garden.  Medical history includes diet-controlled diabetes mellitus and hypertension.  Physical examination reveals bilateral crackles and a third heart sound.  ECG shows ST elevation in multiple leads.  The patient is diagnosed with an acute myocardial infarction complicated by acute severe heart failure.  He is started on dobutamine infusion and prepared for coronary catheterization.  Which of the following is most likely to be increased due to the medication used in this patient?

A 71-year-old woman comes to the emergency department due to progressive dyspnea and orthopnea for the last week.  She has a history of myocardial infarction and systolic heart failure with a left ventricular ejection fraction of 15%.  The patient is compliant with her medications, which include carvedilol, furosemide, aspirin, lisinopril, and atorvastatin.  Blood pressure is 118/74 mm Hg and pulse is 72/min.  Examination reveals elevated jugular venous pressure, bibasilar crackles, an S3 heart sound, and bilateral lower extremity pitting edema.  The patient is started on dobutamine infusion, which provides significant symptom relief.  Echocardiogram shows mild improvement in cardiac contractility.  Which of the following is the likely mechanism underlying this patient’s clinical improvement?

A 45-year-old man comes to the clinic due to recurrent palpitations accompanied by chest discomfort and shortness of breath.  A year ago, he was diagnosed with paroxysmal atrial fibrillation treated with rate control using a beta blocker.  Past medical history is also significant for hypertension and obesity.  Echocardiogram shows left atrial enlargement, normal left ventricular ejection fraction, and no significant valvular disease.  24-hour Holter monitoring reveals bursts of atrial fibrillation associated with the patient’s symptoms.  He is initiated on dofetilide to maintain normal sinus rhythm.  This medication exerts its main effect on which portion of the action potential curve?

A 47-year-old man comes to the office due to worsening muscle weakness and dark urine for the past several days.  Two weeks ago, the patient was evaluated for dyspepsia and found to have Helicobacter pylori infection; he was started on treatment and has had partial symptom improvement.  Medical history includes hypertension and hyperlipidemia, for which he takes amlodipine and simvastatin.  Temperature is 37.1 C (98.8 F), blood pressure is 130/80 mm Hg, and pulse is 74/min.  Physical examination shows diffuse muscle tenderness.  Laboratory evaluation reveals elevated blood urea nitrogen and serum creatinine levels.  Urine microscopy shows no red or white blood cells.  Which of the following medications most likely precipitated this patient’s current condition?

A 60-year-old man comes to the emergency department with dizziness and palpitations.  He woke up this morning with an intermittent pounding sensation in his chest.  The patient has occasionally experienced a similar sensation in the past and did not think it was serious.  Later, while mowing the lawn, he became lightheaded and had to sit down to avoid passing out.  After receiving the appropriate workup, the patient is diagnosed with a cardiac arrhythmia and started on a medication known to prolong the QT interval.  However, the drug is associated with a lower incidence of torsade de pointes than other QT-prolonging agents.  Which of the following medications was most likely used in this patient?

A 66-year-old man comes to the emergency department due to several episodes of lightheadedness and a recent fall.  The symptoms are especially pronounced in the morning when he gets up from bed.  The patient takes medications for hypertension, stable angina pectoris, gout, and benign prostate hyperplasia.  He also has osteoarthritis of the right knee and takes occasional nonsteroidal anti-inflammatory drugs.  His blood pressure is 120/80 mm Hg and pulse is 70/min in the supine position, and 90/60 mm Hg and 87/min on standing, respectively.  Cardiopulmonary examination is normal.  Blockade of which of the following receptors is most likely contributing to this patient’s current condition?

A 50-year-old man is brought to the ER with severe dizziness and confusion.  He states that he had an episode of chest pain and took several tablets of nitroglycerin.  His current medications include a daily aspirin for heart attack prevention, an occasional acetaminophen for headaches and occasionally tadalafil for erectile dysfunction.  His blood pressure is 50/20 mmHg and his heart rate is 120 beats/min.  Which of the following cellular changes is most likely responsible for this patient’s symptoms?

A 47-year-old man with known coronary artery disease comes to the emergency department with chest tightness, sweating, and palpitations.  His symptoms began abruptly 2 hours ago while he was at work.  Six months ago, the patient underwent percutaneous angioplasty of the right coronary artery.  Past medical history also includes anxiety and panic attacks.  Blood pressure is 180/90 mm Hg and pulse is 110/min with a regular rhythm.  An esmolol infusion produces rapid symptom relief and heart rate slowing.  Which of the following portions of the ECG will be affected most significantly by the medication?

A 64-year-old man with a long-standing history of hypertension is brought to the emergency department with a dry cough and shortness of breath.  The patient has been unable to sleep in the flat position for the past 2 days.  Blood pressure is 192/102 mm Hg and pulse is 92/min and regular.  Physical examination reveals an S4 and bibasilar crackles.  He is started on intravenous nitroglycerin infusion and soon after reports significant symptomatic relief.  Which of the following physiologic changes are most likely to occur following administration of this medication?

A 65-year-old immigrant from Eastern Europe comes to the physician because of a four-week history of low-grade fever, multiple joint pains, and a well-demarcated erythematous rash on his face and trunk.  The patient denies hair loss, mucosal ulceration, or photosensitivity.  His serum test is positive for the presence of anti-nuclear antibody (ANA) in very high titers.  The patient reports a past medical history of coronary artery disease, congestive heart failure, and “cardiac rhythm abnormalities.”  This patient should be specifically questioned about the intake of which of the following medications?

A 60-year-old man is diagnosed with exertional angina.  His treatment regimen includes metoprolol, isosorbide dinitrate and aspirin.  He takes isosorbide dinitrate early in the morning and again in the afternoon, but he does not take an evening dose.  Such a pattern of drug administration is intended to decrease which of the following?

A 44-year-old man reports exertional shortness of breath and palpitations.  On examination, he has a systolic murmur at the left sternal border and cardiac apex, which gets louder when he stands up.  He is diagnosed with obstructive hypertrophic cardiomyopathy and paroxysmal atrial fibrillation, and is started on a medication.  Changes in the action potential of ventricular muscle cells before and after administration of medication are shown in the image below

Black curve = Before administration of medication
Red curve = After administration of medication

The patient is most likely being treated with which of the following medications?

A 60-year-old man who was recently diagnosed with hypertension comes to the office for follow-up.  He was treated with lisinopril but stopped a week ago due to a dry, nagging cough.  Past medical history is notable for type 2 diabetes mellitus with moderately increased albuminuria but normal creatinine clearance.  His other medications include metformin and rosuvastatin.  The patient does not smoke or drink alcohol.  His blood pressure is 150/92 mm Hg.  BMI is 31 kg/m².  Physical examination, including the heart and lungs, is unremarkable.  Which of the following is the best treatment for this patient’s hypertension?

A 54-year-old man with nonischemic cardiomyopathy comes to the office for a follow-up visit.  He has been hospitalized frequently for acute decompensated heart failure, and currently has dyspnea on mild exertion.  The patient also has a history of hypertension and takes multiple medications.  Blood pressure is 116/70 mm Hg, and pulse is 72/min and regular.  Physical examination shows elevated jugular venous pressure, bibasilar lung crackles, and lower extremity edema.  Serum creatinine is 1.0 mg/dL and serum potassium is 4.2 mEq/L.  Three weeks after starting digoxin therapy, the patient reports symptomatic improvement.  Which of the following is the initial cellular event triggering this response to the new medication?

A 56-year-old man comes to the emergency department due to palpitations and lightheadedness over the last 2 hours.  He has a history of hypertension but no other cardiac conditions and never before had similar symptoms.  The patient drinks 1 to 2 alcoholic beverages daily but does not smoke cigarettes or use illicit drugs.  Blood pressure is 132/76 mm Hg and pulse is 116/min and irregular.  Cardiopulmonary examination is normal, except for tachycardia.  Resting ECG shows atrial fibrillation.  The patient undergoes transesophageal echocardiography, which reveals normal cardiac anatomy and no intracardiac thrombi.  Electrical cardioversion is performed.  After the intervention, sinus rhythm is restored, and amiodarone therapy is begun to maintain normal sinus rhythm.  Which of the following cardiac electrophysiologic changes are most likely to occur in this patient due to the medication?