MKSAP quiz on beta-blockers


Case 1: Recurrent palpitations

A 76-year-old man is admitted to the hospital for recurrent palpitations and dyspnea that began 4 days ago. He has hypertension and coronary artery disease, which was treated with percutaneous intervention 8 years ago. Medications are aspirin, atorvastatin, and lisinopril.

On physical examination, temperature is 36.8 °C (98.2 °F), and blood pressure is 115/62 mm Hg. The resting heart rate is 110/min with intermittent irregularity. The estimated central venous pressure is not elevated. S1 and S2 are unremarkable. The lung fields are clear, and the extremities are without edema.

An electrocardiogram obtained after the physical examination is shown.

Art 1

Which of the following is the most appropriate next step in treatment?

A. Emergent cardioversion
B. Initiate beta-blocker therapy
C. Intravenous amiodarone
D. Intravenous procainamide

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Case 2: Postdischarge follow-up

A 35-year-old woman with recently diagnosed nonischemic systolic heart failure and a left ventricular ejection fraction of 30% presents 1 week after hospital discharge with a new cough, increased exertional dyspnea, and peripheral edema. Medications are lisinopril (5 mg/d) and furosemide (40 mg/d).

On physical examination, blood pressure is 100/70 mm Hg, pulse rate is 98/min and regular, respiration rate is 13/min, and oxygen saturation on ambient air is 96%. Estimated central venous pressure is 15 cm H2O. Her weight has increased by 2.3 kg (5 lb). Cardiac examination reveals a grade 2/6 holosystolic murmur at the apex and an S3. Extremity examination reveals bilateral peripheral pitting edema.

Her electrocardiogram shows sinus rhythm and is unchanged from baseline. Serum electrolyte levels and kidney function tests are normal.

In addition to a low-sodium diet, which of the following is the most appropriate management?

A. Increase furosemide
B. Increase lisinopril
C. Start carvedilol
D. Start spironolactone

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Case 3: Perioperative medication

A 50-year-old man is evaluated in the emergency department after sustaining a complex right tibia fracture in a motor vehicle accident at 9:00 PM. He underwent splinting of the fracture and was admitted to the hospital for wound debridement and internal fixation to occur the next morning. Medical history is notable for hypertension, hyperlipidemia, and type 2 diabetes mellitus. Medications are extended-release metoprolol every morning, pravastatin every evening, and metformin twice daily. He took all of his usual medications today (both morning and evening doses). He was in his usual state of health with no symptoms prior to the accident.

On physical examination, the patient has a splint on the right lower extremity. Blood pressure is 138/86 mm Hg, and pulse rate is 78/min. The remainder of the physical examination is normal.

Laboratory studies show normal serum bicarbonate, blood urea nitrogen, serum creatinine, and serum potassium levels; random plasma glucose level is 119 mg/dL (6.6 mmol/L).

Which of the patient's medications should be taken the morning of surgery?

A. Metformin
B. Metoprolol
C. Metoprolol and metformin
D. No medications

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Case 4: Agitation and tachycardia

A 52-year-old woman is brought to the emergency department after being found walking in the middle of a freeway on-ramp. She was given intramuscular haloperidol by emergency medical personnel for agitation on the way to the hospital. Her medical history is notable for polysubstance use.

On physical examination in the emergency department, she is alert and restless but calms down with verbal reassurance. Blood pressure is 155/90 mm Hg, and pulse rate is 110/min. She is admitted to the observation unit.

One hour later, she becomes severely agitated and tries to leave. Temperature is 38.2 °C (100.8 °F), blood pressure is 210/104 mm Hg, pulse rate is 124/min, and respiration rate is 14/min. Oxygen saturation is 97% breathing ambient air. The pupils are symmetric, dilated, and reactive to light. Slight tremor of the hands is noted. No tongue fasciculations are observed. The skin is warm and diaphoretic. The chest is clear to auscultation.

Laboratory studies reveal a serum creatine kinase level of 6600 U/L, creatinine level of 1.1 mg/dL (97.2 µmol/L), and a normal troponin level.

An electrocardiogram reveals sinus tachycardia without ischemic changes.

Which of the following is the most appropriate next step in treatment?

A. Activated charcoal
B. Lorazepam
C. Physostigmine
D. Propranolol

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Answers and commentary

Case 1

Correct answer: B. Initiate beta-blocker therapy.

The most appropriate next step in treatment of this patient is to initiate beta-blocker therapy. He has paroxysmal atrial fibrillation with aberrant conduction, resulting in a wide-complex tachycardia. The electrocardiogram demonstrates a normal sinus beat followed by a run of atrial fibrillation with right bundle branch block. Note the irregularly irregular nature of the tachycardia and the QRS morphology consistent with typical right bundle branch block. Given his rapid ventricular response and his symptoms of palpitations and dyspnea, the atrial fibrillation requires treatment. Beta-blocker therapy is the preferred atrioventricular nodal blocking agent given the patient's history of coronary artery disease.

Assessment of the need for anticoagulation therapy is also indicated in this patient with atrial fibrillation. Current guidelines recommend the use of the CHA2DS2-VASc score for this purpose, replacing the CHADS2 score because of its ability to more clearly discriminate stroke risk. This patient has a CHA2DS2-VASc score of 4 (1 point for hypertension, 2 points for age, and 1 point for coronary artery disease), placing him at moderate risk for stroke. Therefore, initiation of oral anticoagulation also is appropriate.

Emergent cardioversion is not necessary because the patient is hemodynamically stable and appears to be having self-terminating paroxysms of tachycardia. If the patient had a sustained arrhythmia accompanied by hemodynamic instability, emergent cardioversion would be indicated regardless of the specific etiology of the arrhythmia (that is, supraventricular versus ventricular).

Intravenous amiodarone would be an appropriate treatment for recurrent ventricular tachycardia. The electrocardiogram appearance is consistent with right bundle branch block. There is an rSR pattern in lead V1 and a terminal S wave in leads I and V6. Right axis deviation is present (QRS axis 123 degrees); however, there is also evidence of left posterior fascicular block (small r waves and deep S waves in leads I and aVL; qR complexes in leads II, III, and aVF). Thus, these features are most consistent with aberrant conduction in the setting of atrial fibrillation rather than ventricular tachycardia.

Intravenous procainamide would be the agent of choice if this tachycardia were preexcited (Wolff-Parkinson-White syndrome). Preexcitation is evidenced by the presence of a delta wave. This patient's electrocardiogram does not demonstrate preexcitation in either the sinus beat or the tachycardia.

Key Point

  • Paroxysms of an irregularly irregular rhythm with a typical right bundle branch block appearance on electrocardiogram most likely represent atrial fibrillation with aberrant conduction.

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Case 2

Correct answer: A. Increase furosemide.

In this patient with recently diagnosed heart failure, the dosage of furosemide should be increased. She has signs of volume overload (elevated central venous pressure, an S3, peripheral edema, weight gain).

Given the patient's relative hypotension and volume overload, increasing her diuretic dose would be more appropriate than increasing the dose of her ACE inhibitor, which might lead to low blood pressure and would not improve her volume overload.

Although there is a mortality benefit to the use of beta-blockers in patients with systolic heart failure, these agents have negative inotropic activity, and initiation of beta-blocker therapy is relatively contraindicated in patients with evidence of decompensated heart failure. Once the patient has been appropriately diuresed, a beta-blocker can be added. Even patients with a low systolic blood pressure, once euvolemic, can often tolerate low doses of a beta-blocker.

Spironolactone is an appropriate agent to add for treatment of stable patients with New York Heart Association (NYHA) functional class II to IV heart failure. This patient, however, has acute volume overload, which should be treated before initiation of this therapy. Although spironolactone has some diuretic activity, at the usual doses prescribed for patients with heart failure (12.5-25 mg/d), it would not have sufficient diuretic effect in this patient.

This patient's presentation demonstrates the importance of an early (within 7 days) post-hospital clinic visit for patients after a hospitalization for heart failure. Recognizing volume overload at a point when it can be treated on an outpatient basis is an example of the benefit of this visit. If the patient were euvolemic, adding additional therapy, such as a beta-blocker or spironolactone, would be appropriate. This visit also allows the internist to reemphasize to the patient the importance of medication adherence and fluid restriction.

Key Point

  • In patients with acute decompensated systolic heart failure, the most appropriate treatment is to increase the diuretic dosage to remove the excess fluid.

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Case 3

Correct answer: B. Metoprolol.

This patient should take his beta-blocker, metoprolol, the morning of surgery. He takes three chronic medications, of which two are normally taken in the morning. All medications should be continued uninterrupted throughout surgery unless potential adverse effects from continuation outweigh benefits. Not only is metoprolol important for treatment of his hypertension, but withdrawal of beta-blockade in the perioperative setting may cause tachycardia and increased myocardial oxygen demand. The American College of Cardiology (ACC) and the American Heart Association (AHA) provide a level 1 recommendation for the continuation of beta-blockers throughout the perioperative period. Thus, metoprolol should be taken the morning of surgery.

Metformin has the potential for causing lactic acidosis and inducing hypoglycemia if taken during fasting. Therefore, it should not be taken on the morning of surgery. Some experts advise withholding this medication for 24 to 48 hours before surgery, although data for the specific withholding timeframe are limited.

The ACC and AHA recommend that for patients currently taking a statin and scheduled for noncardiac surgery, the statin should be continued. This recommendation is based on several systematic reviews that found an association between perioperative statin use and a reduction in postoperative acute coronary syndrome and mortality. This patient should resume his statin therapy in the evening following his operation, maintaining his usual schedule.

Key Point

  • Perioperative beta-blockade should be continued uninterrupted in patients who are already taking a beta-blocker.

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Case 4

Correct answer: B. Lorazepam.

The most appropriate next step in treatment is to start lorazepam on an as-needed basis. The combination of hypertension, tachycardia, fever, diaphoresis, mydriasis, and rhabdomyolysis is most consistent with sympathomimetic intoxication. Common causes of sympathomimetic intoxication include cocaine, amphetamines, ephedrine, and caffeine. Benzodiazepines are first-line therapy for sympathomimetic intoxication.

Activated charcoal can be used to reduce drug levels in patients with therapeutic drug overdose but generally should not be administered if the patient is at risk of aspirating or more than 1 to 2 hours have elapsed since the time of ingestion. The potential harms of activated charcoal outweigh the benefits for this patient.

Physostigmine is an antidote for anticholinergic toxicity, which also presents with agitation, mydriasis, fever, and tachycardia. However, this degree of hypertension and the presence of diaphoresis rather than anhidrosis make anticholinergic toxicity less likely in this patient.

Experience in patients with cocaine-induced hypertension suggests use of beta-blockers can paradoxically worsen hypertension due to loss of beta-mediated vascular smooth muscle relaxation. Given these concerns with cocaine, it is reasonable to avoid beta-blockers, such as propranolol, in sympathomimetic intoxication in general. Furthermore, this patient has no clear evidence of end-organ damage (for example, stroke, acute coronary syndrome, aortic dissection) that would mandate rapid, tightly controlled blood pressure reduction.

Key Point

  • The combination of hypertension, tachycardia, fever, diaphoresis, mydriasis, and rhabdomyolysis is most consistent with sympathomimetic intoxication; benzodiazepines are first-line therapy for sympathomimetic toxicity.