Atrial Fibrilation

A 78-year-old man is evaluated in the emergency department for a 1-week history of palpitations and weakness. He has had multiple similar episodes in the past year but has never sought treatment. His other medical problems include hypertension and type 2 diabetes mellitus, and his medications are lisinopril, hydrochlorothiazide, and metformin. He has no history of heart disease and had a normal electrocardiographic exercise stress test 1 year ago.

On physical examination, he is alert and in no acute distress. Blood pressure is 135/80 mm Hg, heart rate is 143/min and irregular, respiration rate is 14/min, and oxygen saturation is 98% with the patient breathing room air. On cardiac examination, there are no murmurs. Lungs are clear.

Electrocardiogram shows atrial fibrillation with a rapid ventricular rate without evidence of ischemic changes. Cardiac enzyme values are normal. His heart rate decreases to 74/min with administration of labetalol.

Which of the following is the most appropriate long-term treatment for this patient?

	A Atrioventricular nodal ablation and pacemaker implantation
	B Metoprolol and aspirin
	C Metoprolol and warfarin
	D Procainamide

Key Points

• Strategies of rate versus rhythm control for atrial fibrillation are similar with respect to symptoms, mortality, and stroke risk.
• Most patients with atrial fibrillation are treated with a combination of rate control and long-term anticoagulation.

Answer and Critique (Correct Answer = C)

This patient is best treated with rate control and anticoagulation. Atrial fibrillation is the most common clinically significant arrhythmia and accounts for the most hospitalizations for cardiac arrhythmias. It occurs in less than 1% of patients ages 60 to 65 years but in 8% to 10% of patients older than 80 years. The estimated risk for stroke in affected patients is 5% per year without anticoagulation. In patients with nonvalvular atrial fibrillation, warfarin with a target INR of 2.0 to 3.0 has been shown to decrease stroke risk by an average of 62%, compared with a 19% decrease with aspirin therapy. To determine whether the risk of stroke is high enough to warrant chronic anticoagulation, risk stratification scores have been developed. One such stratification scheme is known as CHADS₂ score: Congestive heart failure, Hypertension, Age >75 years, Diabetes, Stroke or transient ischemic attack (TIA). Patients are given 2 points for a history of stroke or TIA (the strongest risk factor) and 1 point for all other risk factors. This patient has a CHADS₂ score of 3. The risk of stroke is lowest in patients with a CHADS₂ score of 0 (1.2%). The risk is 18% for a CHADS₂ score of 6 (maximum score). Patients with a CHADS₂ score of ≥3 and patients with a history of stroke are at high risk and should be considered for chronic anticoagulation with warfarin. Patients with a CHADS₂ score of 1 or 2 should be assessed on an individual basis for aspirin versus warfarin therapy.

In patients who tolerate atrial fibrillation with few symptoms, restoration of normal sinus rhythm is not indicated. Strategies of rate versus rhythm control have been found to be similar with respect to symptoms, mortality, and stroke risk. More hospitalizations and adverse drug reactions occur in patients receiving rhythm control compared with rate control. This elderly patient would be at significant risk of drug side effects from anti-arrhythmic agents and would likely have breakthrough episodes of atrial fibrillation. Therefore, in addition to chronic anticoagulation with warfarin, this patient should receive medication to control the ventricular rate, such as a β-blocker.

Atrioventricular nodal ablation for atrial fibrillation with pacemaker placement should be reserved for those patients who do not tolerate pharmacologic therapy. New ablation strategies are being investigated and are increasingly recommended in clinical practice guidelines. These include catheter-directed ablation of the pulmonary vein ostia within the left atrium. The success rate of this procedure is as high as 88% at 6 months without requiring pacemaker placement.

Bibliography

1. Snow V, Weiss KB, LeFevre M, McNamara R, Bass E, Green LA, Michl K, Owens DK, Susman J, Allen DI, Mottur-Pilson C; AAFP Panel on Atrial Fibrillation; ACP Panel on Atrial Fibrillation. Management of newly detected atrial fibrillation: a clinical practice guideline from the American Academy of Family Physicians and the American College of Physicians. Ann Intern Med. 2003;139:1009-17. [PMID: 14678921]
2. Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ. Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation. JAMA. 2001;285:2864-70. [PMID: 11401607]

Acute Coronary Syndrome

A 49-year-old man is evaluated in the emergency department for chest discomfort accompanied by nausea and dyspnea that began 2 hours ago. On physical examination, blood pressure is 109/78 mm Hg and heart rate is 88/min. There is no jugular venous distention and no carotid bruits. The lungs are clear. Cardiac examination shows a normal S1 and S2 and no gallops, rubs, or murmurs. The troponin level is 6 ng/mL (normal <0.5 ng/mL). Electrocardiogram shows a 1-mV ST elevation in leads II, III, and aVF.

He is treated with enoxaparin, aspirin, metoprolol, and glycoprotein receptor blockers and is taken to the cardiac catheterization laboratory. A stent is placed in a subtotally occluded right coronary artery. A follow-up echocardiogram shows normal wall motion, normal valve function, and a normal ejection fraction. By day 4, he has no complications and is prepared to be discharged.

In addition to aspirin, clopidogrel, and metoprolol, which of the following medications should be given at discharge?
A Atorvastatin
B Gemfibrozil
C Niacin
D Warfarin

Key Point
In patients with an acute coronary syndrome, statin therapy is indicated regardless of the serum cholesterol level.

Answer and Critique (Correct Answer = A)

This patient has survived a small inferior wall myocardial infarction and was successfully treated with a stent. At discharge, he should receive aspirin, metoprolol, clopidogrel for at least 180 days, and a statin regardless of his serum cholesterol level. In patients with coronary artery disease, especially those presenting with symptoms and those undergoing revascularization by either stenting or bypass graft surgery, statin therapy reduces late cardiovascular events despite having minimal or no effect on the angiographic appearance of the coronary arteries.

The PROVE IT-TIMI 22 study compared a moderate-dose statin (pravastatin, 40 mg/d) with a high-dose statin (atorvastatin, 80 mg/d) in patients hospitalized for acute coronary syndrome. The median LDL cholesterol levels achieved were 95 mg/dL by the pravastatin group and 62 mg/dL for the atorvastatin group. Those receiving atorvastatin had a 16% reduction in the composite endpoint of death from any cause, myocardial infarction, unstable angina requiring rehospitalization, coronary artery revascularization, and stroke during 2 years of follow-up. These results showed evidence of benefit from early aggressive LDL cholesterol lowering with high-dose atorvastatin.

Warfarin is not indicated after ST-elevation myocardial infarction treated by stenting unless there is another indication such as atrial fibrillation, deep venous thrombosis, or intracardiac thrombus.

Niacin for hypertriglyceridemia may be needed, but at this time the triglyceride values are not reported and may be falsely elevated early in the course of ST-elevation myocardial infarction. The first line of treatment would be statins even for normal LDL cholesterol levels in patients with documented coronary artery disease. The combination of statins with a fibrate (e.g., gemfibrozil) is attractive for patients who have both high cholesterol and triglyceride levels or for those who continue to have elevated triglyceride levels after reaching their LDL cholesterol target on statin therapy. However, in this patient, the best initial choice is a statin.
Bibliography

1. Ray KK, Cannon CP, Ganz P. Beyond lipid lowering: What have we learned about the benefits of statins from the acute coronary syndromes trials? Am J Cardiol. 2006;98:18P-25P. Epub 2006 Sep 29. [PMID: 17126675]

Acute Inferior ST-elevation Myocardial Infarction

A 64-year-old woman is evaluated in the emergency department 6 hours after the onset of severe crushing chest pain associated with diaphoresis, nausea, and vomiting. Her medical history is significant only for hyperlipidemia; her medications are atorvastatin and aspirin. On physical examination, blood pressure is 140/88 mm Hg, and heart rate is 88/min. The lungs are clear, and no cardiac murmurs are heard. Examination of the abdomen and extremities is normal. Electrocardiogram shows a 3-mV ST elevation in leads II, III, and aVF, with occasional premature ventricular contractions. The hospital does not have cardiac catheterization facilities, and the patient is therefore given fibrinolytic therapy. Her chest pain resolves; she has two episodes of 6- to 10-beat ventricular tachycardia and stable hemodynamic parameters. Electrocardiogram now shows <0.5-mV ST elevation.

In addition to heparin and aspirin, which of the following approaches is the most appropriate next step in the management of this patient?
A Amiodarone
B β-Blocker
C Coronary angiography
D Lidocaine

Key Point
β-Blocker therapy reduces infarct size and the frequency of recurrent myocardial ischemia and improves short- and long-term survival.

Answer and Critique (Correct Answer = B)

This patient has features of successful reperfusion after an acute inferior ST-elevation myocardial infarction and may be treated medically until risk stratification is performed or recurrent ischemia or complications occur. The usual management consists of heparin, aspirin, β-blockers, angiotensin-converting enzyme inhibitors, and statins. Clinical trials show that β-blocker therapy reduces infarct size and the frequency of recurrent myocardial ischemia and improves short- and long-term survival.

Evidence of successful fibrinolysis involves resolution of both chest pain and ST elevation. The rapidity with which these resolve is directly related to early patency of the affected artery. Reperfusion arrhythmias, typically manifested as a transient accelerated idioventricular arrhythmia, usually do not require additional antiarrhythmic therapy with lidocaine or amiodarone.

Immediate coronary angiography is not indicated unless recurrent ischemia, persistent ST elevation, or hemodynamic instability, including heart failure, occurs.
Bibliography

1. Kopecky SL. Effect of beta blockers, particularly carvedilol, on reducing the risk of events after acute myocardial infarction. Am J Cardiol. 2006;98:1115-9. Epub 2006 Aug 31. [PMID: 17027583]

Coronary artery **

A 32-year-old woman is brought to the hospital with chest pain after a party. She has had similar pain previously, primarily in the morning and rarely with exertion. The pain usually subsides spontaneously and occasionally is associated with diaphoresis but rarely with dyspnea. She almost lost consciousness at work during the most recent episode. The patient has occasionally inhaled cocaine. She is otherwise healthy and takes no medications. She has no family history of coronary artery disease.

On physical examination, blood pressure is 128/70 mm Hg and heart rate is 72/min. There is no jugular venous distention or carotid bruits. The lungs are clear, and cardiac examination shows a normal S1 and S2 and a faint mid-systolic click but no murmur. Electrocardiogram taken during the chest pain shows a 1-mV inferior ST elevation; a subsequent electrocardiogram taken after resolution of the pain is normal. Serum troponin concentration is elevated. Therapy with heparin, aspirin, metoprolol, and nitroglycerin is begun.

The next morning, coronary angiography shows a normal angiographic appearance of the arteries and normal left ventricular wall motion.

Which of the following is the most likely diagnosis?
A Coronary artery atherosclerosis
B Coronary artery dissection
C Coronary artery vasculitis
D Coronary artery vasospasm

Key Point
Coronary artery vasospasm is treated with nitrates in the short term and calcium channel blockers in the long term.

Answer and Critique (Correct Answer = D)

This patient has a presumptive diagnosis of myocardial infarction due to vasospasm of the coronary artery. Factors favoring this diagnosis are the normal angiographic appearance of the coronary arteries, use of cocaine, chest pain after a party (implying use of cocaine), and the episodic ST elevation with spontaneous resolution in the absence of fibrinolysis.

Coronary artery atherosclerotic disease is not likely, based upon the normal coronary artery catheterization. In addition to coronary artery vasospasm, other causes of myocardial ischemia or infarction in the absence of atherosclerotic coronary artery disease include coronary artery dissection, vasculitis (scleroderma and other connective tissue diseases), thromboembolism in the settings of endocarditis or paradoxical embolism, valvular disease, and hypertrophic cardiomyopathy. Spontaneous coronary artery dissection has been reported in pregnant women with or without hypertension but coronary artery dissection is unlikely in a nonpregnant woman Vasculitis seems unlikely in the absence of any additional signs or symptoms to support a diagnosis of collagen vascular disease. Endocarditis is unlikely in the absence of fever and a heart murmur, and hypertrophic cardiomyopathy is unlikely in the absence of a murmur and the normal electrocardiogram (following resolution of the chest pain).

The best treatment for coronary artery vasospasm is nitrates in the short term and calcium channel blockers over the long term. Angiotensin-converting enzyme inhibitors reduce mortality in patients with ST elevation myocardial infarction and in patients with a left ventricular ejection fraction <40% following an acute myocardial infarction. This patient meets neither of these criteria and is unlikely to benefit from this therapy. This patient should be strongly urged not to use cocaine.
Bibliography

1. Mirza MA. Angina like pain and normal coronary arteries. Uncovering cardiac syndromes that mimic CAD. Postgrad Med. 2005;117:41-6, 54. [PMID: 15948368]

Shock

A 53-year-old man with long-standing ischemic cardiomyopathy is admitted to the intensive care unit with hypotension following a 24-hour episode of viral gastroenteritis. He is given intravenous fluids. The following day he develops chest pain, shortness of breath, and mental status changes.

On physical examination, temperature is 38.2 °C (100.8 °F), heart rate is 100/min, blood pressure is 75/45 mm Hg, respiration rate is 12/min, and he is mildly lethargic. Jugular venous pressure is difficult to assess. The lungs are clear. Cardiac examination reveals regular rhythm, a normal S1 and S2, and the presence of an S3. There is peripheral edema bilaterally to the thighs, and the extremities are cool. A pulmonary artery catheter is placed and provides the following data.

Laboratory Studies
Central venous pressure

12 mm Hg (normal, 0-5 mm Hg)
Pulmonary artery pressure

40/15 mm Hg (normal, 20-25/5-10 mm Hg)
Pulmonary capillary wedge pressure

18 mm Hg (normal, 6-12 mm Hg)
Cardiac output

3.5 L/min (normal, 4-8 L/min)

Which of the following is the most likely diagnosis?
A Cardiogenic shock
B Hypovolemic shock
C Septic shock
D Toxic shock

Key Point
The pulmonary capillary wedge pressure is elevated and the cardiac output is low in patients with primary cardiogenic shock.

Answer and Critique (Correct Answer = A)

This patient has cardiogenic shock, manifested by hypotension and evidence of hypoperfusion (decreased mental status, cool extremities). The pulmonary artery catheter data show volume overload—central venous and pulmonary capillary wedge pressures are elevated. The volume overload and low cardiac output are most consistent with cardiogenic shock.

Septic shock and toxic shock are types of distributive shock, result from a severe decrease in systemic vascular resistance, and are often associated with an increased cardiac output and low pulmonary capillary wedge pressure. Although the patient was febrile, the hemodynamic data do not support either septic shock or toxic shock. Hypovolemic shock is associated with reduced pulmonary capillary wedge pressure, cardiac output, central venous pressure, and pulmonary artery pressure. Even though the patient had a bout of viral gastroenteritis that could result in hypovolemia, the hemodynamic data are most compatible with cardiogenic shock.
Bibliography

1. Summerhill EM, Baram M. Principles of pulmonary artery catheterization in the critically ill. Lung. 2005;183:209-19. [PMID: 16078042]

Cardiac Arrest

An elderly man collapses in an airport. A physician who witnesses the collapse checks his pulse and respirations and finds neither.

Which of the following is the most important determinant for short-term survival in this patient?
A Time to cardiopulmonary resuscitation
B Time to defibrillation
C Time to intubation
D Time to transport to the hospital


Key Point
Time to defibrillation is the most important determinant of survival in cardiac arrest.

Answer and Critique (Correct Answer = B)

Because most adults who suffer cardiac arrest initially demonstrate ventricular arrhythmias, time to defibrillation is the most important determinant of survival. Defibrillation within the first 4 minutes of ventricular fibrillation results in high survival rates, and the availability of automated external defibrillators in many public settings such as airports has made early defibrillation possible. Each minute that defibrillation is delayed reduces the chance of eventual hospital discharge by 8% to 10%.

Bystander cardiopulmonary resuscitation has been shown to improve survival, but prompt defibrillation is more important. Time to transport to the hospital does not correlate with survival—it is restoration of normal blood flow that is critical. Intubation helps provide adequate oxygenation but also is not as important as restoration of a normal cardiac rhythm.
Bibliography

1. Ali B, Zafari AM. Narrative review: cardiopulmonary resuscitation and emergency cardiovascular care: review of the current guidelines. Ann Intern Med. 2007;147:171-9. [PMID: 17679705]

Multivessel Coronary Artery Disease

A 69-year-old man has been treated medically for chronic stable angina for 7 years. Over the past 6 months, he has been noticing some mild neck discomfort brought on by playing tennis. He has a 15-year history of type 2 diabetes mellitus. His medications are metoprolol, aspirin, atorvastatin, and insulin.

Results of the physical examination are unremarkable. An electrocardiogram shows a pattern of left ventricular hypertrophy. Cardiac catheterization is performed and shows 90% stenosis in the proximal left anterior descending coronary artery, 85% stenosis in the middle right coronary artery, and 70% stenosis in the proximal left circumflex coronary artery. The left ventricular ejection fraction at rest is 40%.

Which of the following treatments would offer this patient the greatest improvement in longevity?
A Begin clopidogrel
B Begin dipyridamole
C Coronary artery bypass graft surgery
D Implantable cardioverter-defibrillator

Key Points

* Coronary artery bypass grafting improves survival in patients with obstructive left main and/or three-vessel coronary artery disease and reduced ejection fraction.
* Coronary artery bypass grafting improves survival in comparison to percutaneous intervention in patients with diabetes mellitus and multivessel coronary artery disease.

Answer and Critique (Correct Answer = C)

This fit, elderly man with no contraindications to coronary revascularization has the clinical features (three-vessel coronary artery disease [CAD] and left ventricular dysfunction) that warrant an invasive treatment approach rather than simply adjusting his medications. Patients who have CAD with large zones of ischemia benefit the most from interventional approaches added to their existing medical treatment. Patients with obstructive left main CAD and/or three-vessel CAD with a reduced left ventricular ejection fraction (≤40%) or a moderate to large amount of myocardial ischemia have improved survival rates with coronary artery bypass grafting (CABG) in combination with medical therapy as compared with medical therapy alone. Patients with multivessel CAD and diabetes mellitus have better outcomes with CABG compared with percutaneous angioplasty. Thus, CABG is preferable to a percutaneous intervention in these patients.

The implantable cardioverter-defibrillator has emerged as an important prophylactic treatment option for reducing sudden cardiac death in selected patients with CAD. An ejection fraction ≤30% helps to identify patients likely to benefit from this procedure. In this patient, the ejection fraction was reduced but remained above 30%. In addition, in patients with an ejection fraction ≤30% who are being considered for an implantable cardioverter-defibrillator, CABG remains the primary treatment when multivessel CAD is present. Thus, placement of an implantable cardioverter-defibrillator is not the best choice for this patient.
Bibliography

1. Stone KE, Chiquette E, Chilton RJ. Diabetic endovascular disease: role of coronary artery revascularization. Am J Cardiol. 2007;99:105B-112B. [PMID: 17307063]

Acute viral pericarditis

A 26-year-old woman is evaluated for sharp left precordial chest pain preceded by 2 to 3 days of sore throat, diffuse myalgias, and malaise. The chest pain is nonradiating and is aggravated by deep breaths. She does not have cough, dyspnea, fever, dizziness, or palpitations. She has always been healthy and does not use illicit drugs. A member of her immediate family was recently diagnosed with infectious mononucleosis.

On physical examination, her temperature is 36.7 °C (98 °F), heart rate is 95/min, respiration rate is 24/min, and blood pressure is 110/60 mm Hg. No lymphadenopathy is present, and the jugular veins are not distended. Lungs are clear. Cardiac examination is notable for an intermittent systolic “squeaky” sound along the left sternal border.

An electrocardiogram shows diffuse 1 to 3 mm of ST elevation with an upwardly concave configuration. An echocardiogram shows no pericardial effusion.

Which of the following is the most appropriate initial treatment for this patient?
A Clopidogrel
B Heparin
C Indomethacin
D Prednisone


Key Point
The initial treatment for acute viral pericarditis is a high-dose nonsteroidal anti-inflammatory drug.

Answer and Critique (Correct Answer = C)

This patient's sharp, pleuritic chest pain preceded by 2 to 3 days of prodromal symptoms is characteristic of acute viral pericarditis. The pericardial friction rub is suggestive of acute pericarditis, and the presence of ST segments that are upwardly concave on electrocardiography further supports this diagnosis. The lack of a pericardial effusion on echocardiography does not exclude pericarditis, given that 40% of patients with pericarditis may not have this finding.

The recommended initial treatment for acute viral pericarditis is a high-dose nonsteroidal anti-inflammatory drug such as indomethacin or ibuprofen. Indomethacin is rapidly tapered after 5 to 7 days because of the potential for toxicity with long-term use. Aspirin may also be used, although the high doses required may cause gastrointestinal problems.

If severe chest pain remains after 2 to 3 days of nonsteroidal anti-inflammatory drug treatment in patients with acute pericarditis, a 7- to 10-day tapering course of corticosteroids should be considered. However, corticosteroids such as prednisone have associated toxicity and are not recommended as first-line agents in the treatment of uncomplicated acute pericarditis. Low-dose colchicine may be used as an alternative to corticosteroids.

An acute myocardial infarction should always be considered in the setting of chest pain with ST elevation on electrocardiography. However, this patient's young age, viral prodrome, quality of the pain, and friction rub point to a diagnosis of acute pericarditis, and anticoagulation in a patient with known acute pericarditis is contraindicated because of the potential for hemopericardium.

Clopidogrel has no benefit as an anti-inflammatory agent for the treatment of acute pericarditis and is not indicated.
Bibliography

1. Lange RA, Hillis LD. Clinical practice. Acute pericarditis. N Engl J Med. 2004;351:2195-202. Erratum in: N Engl J Med. 2005;352:1163. [PMID: 15548780]

Arterial ischemia

A 72-year-old man is evaluated in the office for bilateral leg pain and cramping after walking briskly up an incline. The pain is in the distal thigh and calf and is worse on the right side. He has no pain when walking downhill. The patient has a 100-pack-year smoking history, type 2 diabetes mellitus, hypertension, and heart failure. His medications are captopril, furosemide, atenolol, atorvastatin, metformin, and aspirin.

On physical examination, the blood pressure is 146/68 mm Hg and heart rate 82/min and regular. The lungs are clear. Cardiac examination reveals an S4. There is a right femoral artery bruit with absent pulses and mild dependent rubor. Ankle-brachial index is 0.8.

Which of the following is the most likely cause of this patient's symptoms?
A Arterial ischemia
B Osteoarthritis
C Peripheral neuropathy
D Right popliteal venous thrombosis
E Spinal stenosis

Key Points

* Most patients with peripheral vascular disease have an ankle-brachial index (ABI) <0.9, and those with severe disease (rest ischemia) have an ABI <0.4.
* An ABI >1.3 indicates vascular calcification.

Answer and Critique (Correct Answer = A)

The patient's history of exercise-induced leg pain, its relief with rest or walking downhill, vascular bruit and absent pulses on physical examination, dependent rubor, and several major risk factors for atherosclerotic artery disease all point to arterial ischemia as the cause of his symptoms. Determination of the ankle-brachial index (ABI) is a common initial test in the evaluation for peripheral vascular disease. With a Doppler probe, the ABI is measured as the ratio of the highest right/left dorsalis pedis/posterior tibial artery systolic pressure divided by the highest right/left brachial artery systolic pressure. A normal ABI is 1.0 to 1.3. Most patients with peripheral vascular disease have an ABI <0.9, and those with severe disease (rest ischemia) have an ABI of <0.4. An ABI >1.3 suggests a calcified, noncompressible vessel, most commonly seen in patients with long-standing diabetes mellitus and hypertension.

Peripheral neuropathy would be unlikely to present as pain with exercise. Spinal stenosis commonly presents as pain with standing and after walking a variable distance, most prominently with spinal extension, and is usually relieved by flexing forward, sitting, or lying down. Like spinal stenosis, osteoarthritis may cause pain on walking but is usually independent of grade; neither condition can account for the patient's other findings including bruit, diminished pulses, dependent rubor, and abnormal ABI. Popliteal venous thrombosis may present with localized pain and erythema, but the pain would not be exertional and cannot account for bilateral pain or the physical examination findings.

Bibliography
1. Khan NA, Rahim SA, Anand SS, Simel DL, Panju A. Does the clinical examination predict lower extremity peripheral arterial disease? JAMA. 2006;295:536-46