An 18-year-old man comes to the clinic for a routine physical.  The patient has no medical conditions and takes no medications.  He does not use tobacco, alcohol, or recreational drugs.  He plays on his high school football team.  Review of systems is unremarkable.  Blood pressure is 120/76 mm Hg, pulse is 68/min, and respirations are 15/min.  BMI is 28 kg/m².  Blood pressures in the upper and lower extremities are equal.  There is no jugular venous distension.  Carotid upstrokes are brisk.  A grade 2/6 midsystolic murmur is present along the left sternal border.  The murmur decreases in intensity with handgrip and passive leg elevation.  Lung sounds are normal without crackles or wheezes.  Echocardiography is most likely to demonstrate which of the following findings?

A 43-year-old man is evaluated for occasional palpitations provoked by anxiety.  The patient describes a sudden-onset pounding sensation in the chest followed by lightheadedness and shortness of breath.  He has never had syncope.  The patient has no history of heart disease, and family history is unremarkable.  After initial evaluation, he is treated with verapamil and reports marked improvement in the frequency of palpitation episodes.  The tracing below shows the electrical activity of a specific type of cardiac cell in the patient’s heart.

Which of the following effects would verapamil administration most likely have on these cells?

A 56-year-old man comes to the emergency department due to palpitations that started several hours ago.  He has not had similar symptoms before.  The patient has had no chest pain, shortness of breath, lightheadedness, or syncope.  He drinks alcohol on weekends and does not use illicit drugs.  He has no family history of heart disease.  Blood pressure is 145/78 mm Hg.  BMI is 40 kg/m².  ECG is shown in the exhibit.  The patient is treated medically in the emergency department.  He is then taken to the electrophysiology laboratory for radiofrequency catheter ablation to terminate his arrhythmia.  The ablation procedure should create a conduction block through which of the following areas?

A 53-year-old man comes to the office due to difficulty breathing and increasing fatigue.  He has shortness of breath at night and has been sleeping in a recliner to help relieve his dyspnea.  Medical history is significant for hypertension and hyperlipidemia.  Two months ago, the patient suffered a myocardial infarction that was not revascularized due to a delay in seeking treatment.  He quit smoking afterward, but had previously smoked a pack of cigarettes daily for 25 years.  On cardiac auscultation, a low-frequency diastolic heart sound is heard shortly after the second heart sound when the patient lies in the left lateral decubitus position.  Cardiac imaging shows hypokinesis of the left ventricular free wall.  Which of the following is most likely to accentuate this patient’s abnormal auscultation finding?

A 65-year-old man reports multiple episodes of lightheadedness while buttoning a tight shirt collar.  During 2 episodes, he passed out briefly but sustained no injuries.  His blood pressure was 70/40 mm Hg and pulse was 45/min during one of the episodes.  Past medical history is significant for hypertension and diet-controlled diabetes mellitus.  The patient is a lifetime nonsmoker and drinks alcohol on social occasions.  On physical examination, his blood pressure is 125/72 mm Hg and pulse is 76/min without orthostatic changes.  Stimulation of afferent sensory fibers in which of the following nerves is most likely responsible for this patient’s symptoms?

A 67-year-old man is brought to the emergency department by his son after a syncopal episode.  The son was helping his father clean out the garage when the father said he felt dizzy.  As the son was helping him into a chair, the patient lost consciousness.  He woke up spontaneously about a minute later without any disorientation or confusion.  ECG demonstrates bradycardia with a regular rhythm and narrow QRS complexes.  There is complete desynchronization between the P waves and QRS complexes.  Which of the following locations is most likely pacing this patient’s ventricles?

A 55-year-old man undergoes an elective surgery under general anesthesia.  Two hours into the surgery, his left ventricular pressure-volume loop has changed from the solid line to the dashed line, as shown in the image below (the loop is unchanged in areas where there is no dashed line):

Which of the following is most likely responsible for this patient’s hemodynamic change?

A 46-year-old man comes to the office for an annual examination.  He has an uncomfortable heartbeat sensation at night that he tries to decrease by sleeping on his right side.  The patient has had mild shortness of breath with exertion over the last 6 months, but he has no chest pain.  He was told during a wellness check approximately 2 years ago that he had a heart murmur.  The patient has no other medical problems.  Physical examination reveals bounding femoral pulses and carotid pulsations that are accompanied by head bobbing.  Which of the following is the most likely diagnosis?

A 35-year-old woman comes to the office for a follow-up appointment after recent hospitalization.  The patient presented to the emergency department with fever and malaise and was diagnosed with infective endocarditis.  She underwent a prolonged course of antibiotic therapy and her last dose was 5 days ago.  She has no fever or shortness of breath and has resumed her daily activities.  The patient has no other medical problems.  Blood pressure is 128/72 mm Hg and pulse is 78/min.  Auscultatory findings recorded at the left sternal border are shown in the phonocardiogram below.

Which of the following is the most likely cause of the murmur depicted above?

A 69-year-old man is brought to the emergency department with sudden onset palpitations and dyspnea.  His medical history is significant for hypertension and gastroesophageal reflux disease.  ECG reveals a heart rate of 120/min with an irregularly irregular rhythm, narrow QRS complexes, and no organized P waves.  Which of the following physiologic factors most likely determines the ventricular contraction rate in this patient?

A 23-year-old man comes to the emergency department with sudden onset of heart palpitations that started while he was at his desk at work.  The patient has no known medical problems and does not use tobacco or illicit drugs.  He drinks alcohol occasionally on the weekends.  Initial blood pressure is 110/70 mm Hg and pulse is 160/min and regular.  Gentle neck massage just below the angle of the right mandible provides immediate improvement of his condition.  His blood pressure is now 120/80 mm Hg and pulse is 75/min.  Which of the following mechanisms is responsible for improvement of this patient’s condition?

A 48-year-old man with diet-controlled type 2 diabetes mellitus is being evaluated for occasional retrosternal chest pain.  He has no history of hypertension, and his blood pressure measurements during office visits were always within normal limits.  There is no family history of cardiovascular disease.  The patient undergoes exercise treadmill stress testing.  He walks for 7 minutes on the treadmill and stops due to fatigue but does not experience chest pain.  His ECG does not show any abnormal changes.  Heart rate ranges from 70/min at rest to 132/min at peak and mean blood pressure ranges from 95 mm Hg at rest to 112 mm Hg at peak.  Which of the following parameters was most likely decreased during peak stress compared to the resting state in this patient?

A 70-year-old woman comes to the office due to progressive exertional dyspnea over the last year.  She has no chest pain or lower-extremity swelling.  The patient has long-standing hypertension but has not always been adherent to her medical regimen.  She is a lifetime nonsmoker.  Blood pressure is 164/73 mm Hg and pulse is 88/min and regular.  An S4 is heard on cardiac auscultation.  The lungs are clear.  Echocardiogram reveals left atrial enlargement, moderate concentric left ventricular hypertrophy, and a left ventricular ejection fraction of 67%.  Which of the following changes are most likely to be seen in this patient?

A 34-year-old woman who recently emigrated from Russia comes to the physician due to weakness, exertional dyspnea, and orthopnea.  On cardiac auscultation, a snap followed by a rumbling diastolic murmur is heard over the cardiac apex.  The snap most likely occurs nearest to which of the following points on the cardiac pressure-volume loop?

A 34-year-old woman comes to the office due to exertional dyspnea.  The patient has a history of IgA nephropathy; she received hemodialysis for 2 years before undergoing kidney transplantation last month.  Chest x-ray reveals cardiomegaly and pulmonary congestion.  Further evaluation determines that her symptoms are likely due to persistence of the arteriovenous fistula that was used for hemodialysis.  Which of the following physiologic changes are most likely present in this patient due to the fistula?

A 32-year-old woman is recruited for a research study.  She is evaluated in the hospital as part of the study protocol.  Her medical history includes an uncomplicated appendectomy, and medications include oral contraceptive pills and a multivitamin.  During the evaluation, increases in heart rate and cardiac output are observed, and an arterial blood gas study taken at the same time shows normal partial pressures of arterial oxygen (PaO₂) and carbon dioxide (PaCO₂).  These changes are most likely part of an integrated response to which of the following?

A 32-year-old man is evaluated in the emergency department due to fever, night sweats, and chills over the last several days.  The patient has been using intravenous drugs recently as he is “stressed out.”  He has otherwise been in good health with no medical problems.  Temperature is 38.3 C (101 F), blood pressure is 120/80 mm Hg, and pulse is 105/min and regular.  Further evaluation reveals aortic valve endocarditis with an intracardiac abscess and small fistula formation between the aortic root and right ventricle.  Doppler ultrasound interrogation of the fistula will most likely reveal which of the following blood flow patterns?

A 54-year-old man is being evaluated for exertional dyspnea that started 6 months ago.  The patient has no associated cough or wheezing.  There is no known history of heart disease in his family.  ECG, chest x-ray, exercise stress test, and echocardiogram are obtained to evaluate his symptoms.  He subsequently undergoes right and left cardiac catheterization, and the results are as follows:

What additional information is necessary to calculate cardiac output in this patient?

In an experiment, 3 L of isotonic saline are infused intravenously into a healthy volunteer after multiple baseline physiologic parameters are recorded.  Serial blood pressure measurements show an increase in the systolic and diastolic blood pressure.  Ultrasonography reveals an increase in the left ventricular volume and engorgement of the inferior vena cava.  Blood levels of a peptide hormone have also increased compared to baseline.  This hormone is most likely to increase which of the following in this test subject?

A 78-year-old man is being evaluated for headaches that are relieved by over-the-counter acetaminophen.  He takes no other medications and is a lifelong nonsmoker.  The patient’s blood pressure is 180/70 mm Hg and pulse is 75/min and regular.  During a prior office visit, blood pressure was 175/68 mm Hg.  Physical examination shows an S4 but is otherwise unremarkable.  CT scan of the head reveals no significant abnormalities.  Which of the following age-related changes best explains this patient’s blood pressure readings?

A 44-year-old man comes to the office due to increasing shortness of breath.  While climbing the stairs to his second-floor apartment, the patient must now stop halfway to catch his breath.  He has a history of nonischemic cardiomyopathy and chronic heart failure with reduced ejection fraction.  After evaluation, treatment with a new medication is begun that improves his symptoms by increasing urine output and decreasing peripheral vascular resistance.  The medication works by inhibiting a metalloprotease to prolong the action of endogenous polypeptides.  These polypeptides are most likely secreted by which of the following cell types?

A 50-year-old man comes to the emergency department due to intermittent palpitations over the last 6 months.  The patient describes them as “very uncomfortable” and says the episodes occur randomly, last for several hours, and resolve spontaneously or with sleep.  The current episode started an hour ago and has been accompanied by lightheadedness.  He has no medical history.  Temperature is normal and blood pressure is 122/75 mm Hg.  BMI is 30 kg/m².  Chest examination reveals no murmurs and the lungs are clear on auscultation.  There is trace peripheral edema.  Cardiac rhythm strip obtained in the emergency department is shown in the exhibit.  Aberrant electrical activity in which of the following anatomic structures is the most likely trigger for this patient’s current condition?

A large pharmaceutical company is conducting research on an experimental drug that affects blood flow in diseased tissue.  A healthy 30-year-old man is enrolled in the trial, and patterns of normal blood flow through various tissues are studied.  One of the patterns is shown in the image below:

The blood flow curve was most likely obtained from tissue of which of the following?

A 56-year-old woman is evaluated for fatigue and dyspnea on exertion.  Past medical history includes hypertension and systemic sclerosis.  Blood pressure is 135/80 mm Hg and pulse is 68/min.  Cardiac examination reveals loud second heart sounds with no murmurs.  Lungs are clear to auscultation.  Further evaluation with a catheterization procedure is performed, during which a balloon-tipped catheter is advanced into the pulmonary artery.  A branch of the pulmonary artery is occluded by the balloon, and the pressure beyond the point of occlusion is measured.  The pressure reading from the procedure most likely corresponds to which of the following pressures?