N. Stuart Harris
The term cardiomyopathy is used to describe a heterogeneous group of diseases that directly alter cardiac structure, impair myocardial function, or alter myo-cardial electrical properties.
Cardiomyopathies are the third most common form of heart disease in the United States and are the second most common cause of sudden death in the adolescent population.
In a patient with CHF and associated cardiomegaly or cardiomegaly in an asymptomatic patient, one of the following five disease entities will usually be diagnosed: ischemic heart disease (see Chapters 20 and 21), hypertensive heart disease (see Chapter 24), valvular heart disease (see Chapter 25), myocarditis, or idiopathic cardiomyopathy.
Patients with cardiomyopathy may manifest primarily diastolic dysfunction (hypertrophic cardiomyopathy and restrictive cardiomyopathy) or both systolic dysfunction and diastolic dysfunction (dilated cardiomyopathy, inflammatory cardiomyopathy, or myocarditis).
DILATED CARDIOMYOPATHY
PATHOPHYSIOLOGY
Dilation and compensatory hypertrophy of the myocardium result in depressed systolic function and pump failure leading to low cardiac output.
Eighty percent of cases of dilated cardiomyopathy (DCM) are not associated with specific cardiac or systemic disorders and are considered idiopathic. Idiopathic DCM is the primary indication for cardiac transplant in the United States.
Blacks and males have a 2.5-fold increased risk compared to whites and females. The age range at time of diagnosis is typically 20 to 50 years.
CLINICAL FEATURES
Systolic pump failure leads to signs and symptoms of congestive heart failure (CHF) including dyspnea on exertion, orthopnea, and paroxysmal nocturnal dyspnea.
Chest pain due to limited coronary vascular reserve may also be present.
Mural thrombi can form from diminished ventricular contractile force, and there may be signs of peripheral embolization (eg, acute neurologic deficit, flank pain, hematuria, or a pulseless, cyanotic extremity).
A holosystolic regurgitant murmur of the tricuspid and mitral valve may be heard along the lower left sternal border or at the apex. Other findings include a summation gallop, an enlarged and pulsatile liver, bibasilar rales, and dependent edema.
DIAGNOSIS AND DIFFERENTIAL
Chest x-ray usually shows an enlarged cardiac silhouette, biventricular enlargement, and pulmonary vascular congestion (“cephalization of flow” and enlarged hila).
The electrocardiogram (ECG) shows left ventricular hypertrophy, left atrial enlargement, Q or QS waves, and poor R wave progression across the precordium. Atrial fibrillation and ventricular ectopy are frequently present.
Echocardiography confirms the diagnosis and demonstrates ventricular enlargement, increased systolic and diastolic volumes, and a decreased ejection fraction.
Differential diagnosis includes acute myocardial infarction, restrictive pericarditis, acute valvular disruption, sepsis, or any other condition that results in a low cardiac output state.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Patients with newly diagnosed, symptomatic DCM require admission to a monitored bed or intensive care unit.
Intravenous diuretics (eg, furosemide 40 milligrams intravenously) and digoxin (maximum dose 0.5 milligram intravenously) can be administered. These drugs have symptomatic benefit, but have not been shown to increase survival.
Angiotensin-converting enzyme (ACE) inhibitors (eg, enalaprilat 1.25 milligrams intravenously every 6 hours) and β-blockers (eg, carvedilol 3.125 milligrams orally) can be administered. These drugs have been shown to improve survival in DCM with CHF.
Amiodarone (loaded 150 milligrams intravenously over 10 minutes, then 1 milligram/min for 6 hours) for complex ventricular ectopy can be administered.
Anticoagulation should be considered to reduce mural thrombus formation.
MYOCARDITIS (INFLAMMATORY CARDIOMYOPATHY)
PATHOPHYSIOLOGY
Inflammation of the myocardium may be the result of a systemic disorder or an infectious agent.
Viral etiologies include coxsackie B, echovirus, influenza, parainfluenza, Epstein-Barr, and HIV.
Bacterial causes include Corynebacterium diphtheriae, Neisseria meningitidis, Mycoplasma pneumoniae, and beta-hemolytic streptococci.
Pericarditis frequently accompanies myocarditis.
CLINICAL FEATURES
Patients are usually young, have no significant past cardiac history, have few risk factors for atherosclerotic coronary arterial disease, and present with a recent, abrupt onset of symptoms during or immediately after a systemic or viral illness.
Systemic signs and symptoms predominate, and include myalgias, headache, rigors, fever, and tachycardia out of proportion to the fever.
Chest pain due to coexisting pericarditis is frequently present.
A pericardial friction rub may be heard in patients with concomitant pericarditis.
In severe cases, there may be symptoms of progressive heart failure (eg, CHF, pulmonary rales, pedal edema).
DIAGNOSIS AND DIFFERENTIAL
The diagnosis is primarily clinical with testing that may support but may not confirm the diagnosis; confirmation of a suspected infectious cause (such as appropriate viral serology) is rarely completed in the ED if done at all.
The chest radiograph is usually normal or nondiagnostic. Cardiomegaly and pulmonary venous hypertension or pulmonary edema are present with severe disease.
ECG changes include nonspecific ST-T-wave changes, ST-segment elevation from associated pericarditis, atrioventricular block, and QRS interval prolongation.
Cardiac enzymes may be elevated.
Differential diagnosis includes cardiac ischemia or infarction, valvular disease, and sepsis.
Echocardiographic studies are also nonspecific, with myocardial depression and wall motion abnormalities in severe cases.
Newer imaging modalities include nuclear imaging with gallium67- or indium111 -labeled anti-myosin antibodies. Both of these radionuclides are taken up by injured or necrotic myocytes.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Treatment for idiopathic or viral myocarditis is supportive.
Antibiotics are needed for myocarditis complicating rheumatic fever, diphtheria, or meningococcemia; treatment in these cases is guiding by the total clinical picture not simply symptoms suggesting myocarditis.
Immunosuppressive therapy may be of value in selected patients, but large trials have not consistently demonstrated benefit.
Admission is usually indicated if the patient presents with CHF symptoms.
HYPERTROPHIC CARDIOMYOPATHY
PATHOPHYSIOLOGY
This illness is characterized by left ventricular and/or right ventricular hypertrophy that is usually asymmetrical and involves primarily the intraventricular septum without ventricular dilation.
The result is abnormal compliance of the left ventricle leading to impaired diastolic relaxation and diastolic filling. Cardiac output is usually normal.
Fifty percent of cases are hereditary. Molecular genetics demonstrate that HCM is a heterogeneous disease of the sarcomere with many mutations, most commonly involving the beta-myosin heavy chain.
The prevalence is 1 in 500; the mortality rate is 1% overall, but 4% to 6% in childhood and adolescence.
CLINICAL FEATURES
Symptom severity progresses with age.
Dyspnea on exertion is the most common symptom, followed by angina-like chest pain, palpitations, and syncope.
Patients may be aware of forceful ventricular contractions and call these palpitations.
Physical examination may reveal a fourth heart sound (S4), hyperdynamic apical impulse, a precordial lift, and a systolic ejection murmur best heard at the lower left sternal border or apex.
The murmur may be increased with Valsalva maneuver or standing after squatting. The murmur can be decreased by squatting, forceful hand gripping, or passive leg elevation with the patient supine (see Chapter 25 for contrasting murmurs).
DIAGNOSIS AND DIFFERENTIAL
The ECG demonstrates left ventricular hypertrophy in 30% of patients and left atrial enlargement in 25% to 50%. Large septal Q waves (> 0.3 mV) are present in 25%. Another ECG finding is upright T waves in those leads with QS or QR complexes (T-wave inversion in those leads would suggest ischemia).
Chest x-ray is usually normal. Echocardiography is the diagnostic study of choice, and will demonstrate disproportionate septal hypertrophy.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Symptoms of HCM may mimic ischemic heart disease and treatment of those symptoms is covered in Chapter 20. Otherwise, general supportive care is indicated. Patients who present complaining of exercise intolerance or chest pain in whom the typical murmur of HCM is heard should be referred for echocardiographic evaluation, β-blockers are the mainstay of treatment for patients with HCM and chest pain.
Patients should be discouraged from engaging in vigorous exercise. Those with suspected HCM who have syncope should be hospitalized.
RESTRICTIVE CARDIOMYOPATHY
EPIDEMIOLOGY AND PATHOPHYSIOLOGY
Restrictive cardiomyopathy is heart muscle disease that results in restricted ventricular filling, with normal or decreased diastolic volume of one or both ventricles.
Most causes are idiopathic, but systemic disorders have been implicated, including amyloidosis, sar-coidosis, hemochromatosis, scleroderma, carcinoid, hypereosinophilic syndrome, and endomyocardial fibrosis. The idiopathic form is sometimes familial.
Systolic function is usually normal, and ventricular wall thickness may be normal or increased, depending on the underlying cause.
The hemodynamic hallmarks include: (1) elevated LV and RV end-diastolic pressure, (2) normal LV systolic function (ejection fraction >50%), and (3) a marked decrease followed by a rapid rise and plateau in early-diastolic ventricular pressure.
The rapid rise and abrupt plateau in the early diastolic ventricular pressure trace produce a characteristic “square-root sign” or “dip-and-plateau” filling pattern.
This filling pattern may also be seen in constrictive pericarditis, with which restrictive cardiomyopathy is commonly confused. Differentiation between the two is critical because constrictive pericarditis can be cured surgically.
The diagnosis of restrictive cardiomyopathy should be considered in a patient presenting with CHF but no evidence of cardiomegaly or systolic dysfunction.
CLINICAL FEATURES
Symptoms of CHF predominate, including dyspnea, orthopnea, and pedal edema. Chest pain is uncommon.
Physical examination may reveal an S3 or S4 cardiac gallop, pulmonary rales, jugular venous distension, Kussmaul’s sign (inspiratory jugular venous distension), hepatomegaly, pedal edema, and ascites.
DIAGNOSIS AND DIFFERENTIAL
Chest x-ray may show signs of CHF without cardiomegaly.
Nonspecific ECG changes are most likely. However, in cases of amyloidosis or sarcoidosis, conduction disturbances and low-voltage QRS complexes are common.
Differential diagnosis includes constrictive pericarditis and diastolic left ventricular dysfunction (most commonly due to ischemic or hypertensive heart disease). Differentiating between restrictive cardiomyopathy and constrictive pericarditis is critical, because constrictive pericarditis can be cured surgically.
Doppler echocardiographic studies and cardiac cath-eterization with hemodynamic assessment are often required for specific diagnosis. CT and MRI of the heart can differentiate constrictive pericarditis from restrictive cardiomyopathy.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Treatment is symptom-directed with the use of diuretics and ACE inhibitors.
Corticosteroid therapy is indicated for sarcoidosis. Chelation is used for the treatment of hemochromatosis.
Admission is determined by the severity of the symptoms and the availability of prompt subspecialty follow-up.
ACUTE PERICARDITIS
PATHOPHYSIOLOGY
The pericardium consists of a loose fibrous membrane (visceral pericardium) overlying the epicardium, and a dense collagenous sac (parietal pericardium) surrounding the heart. The space between these layers may contain up to 50 mL of fluid under normal conditions. Intrapericardial pressure is usually subat-mospheric.
Inflammation of the pericardium may be the result of viral infection (eg, coxsackie virus, echo-virus, HIV), bacterial infection (eg, Staphylococcus, Streptococcus pneumoniae, beta-hemolytic Streptococcus, Mycobacterium tuberculosis), fungal infection (eg, Histoplasma capsulatum), malignancy (leukemia, lymphoma, melanoma, metastatic breast cancer), drugs (procainamide and hydralazine), radiation, connective tissue disease, uremia, myxedema, postmyocardial infarction (Dressler’s syndrome), or may be idiopathic.
CLINICAL FEATURES
The most common symptom is sudden or gradual onset of sharp or stabbing chest pain that radiates to the back, neck, left shoulder, or arm. Radiation to the left trapezial ridge (due to inflammation of the adjoining diaphragmatic pleura) is particularly distinguishing.
The pain may be aggravated by movement or inspiration. Typically, chest pain is made most severe by lying supine and is often relieved by sitting up and leaning forward.
Associated symptoms include low-grade intermittent fever, dyspnea, and dysphagia.
A transient, intermittent friction rub heard best at the lower left sternal border or apex is the most common physical finding. This rub is characteristically transient (eg, heard one hour and not the next).
DIAGNOSIS AND DIFFERENTIAL
ECG changes of acute pericarditis and its convalescence have been divided into four stages. During stage 1, or the acute phase, there is ST-segment elevation in leads I, V5, and V6, with PR-segment depression in leads II, aVF, and V4 through V6. As the disease resolves (stage 2), the ST segment normalizes and T-wave amplitude decreases. In stage 3, inverted T waves appear in leads previously showing ST elevations. The final phase, stage 4, is characterized by the resolution of repolarization abnormalities and a return to a normal ECG.
When sequential ECGs are not available, it can be difficult to distinguish pericarditis from the normal variant with “early repolarization.” In these cases, a simple criterion offers considerable diagnostic utility: an ST segment: T-wave amplitude ratio greater than 0.25 in leads I, V5, or V6 is indicative of acute pericarditis.
Pericarditis without other underlying cardiac disease does not typically produce dysrhythmias.
Chest x-ray is of limited value. It is usually normal, but should be done to rule out other disease.
Echocardiography is the best diagnostic test (Fig. 26-1) to assess for pericardial effusion.
Other tests that may be of value in establishing etio-logic diagnosis include complete blood cell count with differential, blood urea nitrogen and creatinine levels (to rule out uremia), streptococcal serology, appropriate viral serology, other serology (eg, antinuclear and anti-DNA antibodies), thyroid function studies, eryth-rocyte sedimentation rate, and creatinine kinase levels with isoenzymes (to assess for myocarditis).
FIG. 26-1. Pericardial effusion on parasternal long-axis view. Ant Eff = anterior effusion; AV = aortic valve; LA = left atrium; LV = left ventricle; Post Eff = posterior effusion; RV = right ventricle. (Reprinted with permission from Reardon RF, Joing SA: Cardiac. In: Ma OJ, Mateer JR, Blaivas M. eds. Emergency Ultrasound, 2nd edition. The McGraw-Hill Companies, Inc., all rights reserved. Figure 6–24A. 2008.)
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Patients with idiopathic or presumed viral etiologies are treated as outpatients with nonsteroidal anti-inflammatory agents (eg, ibuprofen 400–600 milligrams orally four times daily) for 1 to 3 weeks.
Patients should be treated for a specific cause if one is identified.
Indicators of a poor prognosis include: temperature >38°C (100.4°F), subacute onset over weeks, immu-nosuppression, history of oral anticoagulant use, associated myocarditis (elevated cardiac biomarkers, symptoms of CHF), and a large pericardial effusion (an echo-free space >20 mm).
In general, patients with these risk factors or with an enlarged cardiac silhouette on chest radiograph should be admitted for early echocardiography and monitoring.
NONTRAUMATIC CARDIAC TAMPONADE
PATHOPHYSIOLOGY
Tamponade occurs when the pressure in the pericardial sac exceeds the normal filling pressure of the right ventricle, resulting in restricted filling and decreased cardiac output.
Causes include metastatic malignancy, uremia, hemorrhage (over-anticoagulation), idiopathic disorders, bacterial or tubercular disorders, chronic pericarditis, and others (eg, systemic lupus erythematosus, postradiation, myxedema).
CLINICAL FEATURES
The most common complaints are dyspnea and decreased exercise tolerance. Other nonspecific symptoms include weight loss, pedal edema, and ascites.
Physical findings include tachycardia, low systolic blood pressure, and a narrow pulse pressure. Pulsus paradoxus (apparent dropped beats in the peripheral pulse during inspiration), neck vein distension, distant heart sounds, and right upper quadrant pain (due to hepatic congestion) may also be present. Pulmonary rales are usually absent.
DIAGNOSIS AND DIFFERENTIAL
Low-voltage QRS complexes and ST-segment elevation with PR-segment depression may be present on the ECG. Electrical alternans (beat-to-beat variability in the amplitude of the P and R waves unrelated to inspiratory cycle) is a classic but uncommon finding (about 20% of cases). Chest x-ray may or may not reveal an enlarged cardiac silhouette. Echocardiography is the diagnostic test of choice.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
An intravenous fluid bolus of 500 to 1000 mL of normal saline will increase intravascular volume, facilitate right heart filling, and increase cardiac output and arterial pressure. However, it is a temporary measure.
Pericardiocentesis is both therapeutic and diagnostic. This procedure is optimally performed in the cardiac catheterization laboratory using echocardiographic guidance to avoid cardiac perforation and coronary artery laceration. In addition, a pigtail catheter can be inserted to allow continuous fluid drainage and prevention of re-accumulation.
If there is hemodynamic instability, emergency pericardiocentesis is indicated in the ED.
These patients require admission to an intensive care unit or monitored setting.
CONSTRICTIVE PERICARDITIS
PATHOPHYSIOLOGY
Constriction occurs when fibrous thickening and loss of elasticity of the pericardium results in interference with diastolic filling. Cardiac trauma, pericardiotomy (open-heart surgery), intrapericardial hemorrhage, fungal or bacterial pericarditis, and uremic pericarditis are the most common causes.
CLINICAL FEATURES
Symptoms develop gradually and mimic those of restrictive cardiomyopathy, including CHF, exertional dyspnea, and decreased exercise tolerance. Chest pain, orthopnea, and paroxysmal nocturnal dyspnea are uncommon.
On physical examination, patients may have pedal edema, hepatomegaly, ascites, jugular venous distension, and Kussmaul’s sign. A pericardial “knock” (an early diastolic sound) may be heard at the apex. There is usually no friction rub.
DIAGNOSIS AND DIFFERENTIAL
The ECG is not usually helpful, but may show low-voltage QRS complexes and inverted T waves.
Pericardial calcification is seen in up to 50% of patients on the lateral chest x-ray, but is not diagnostic of constrictive pericarditis.
Doppler echocardiography, cardiac CT, and MRI are diagnostic.
Other diseases that should be considered include acute pericarditis or myocarditis, exacerbation of chronic ventricular dysfunction, or a systemic process resulting in decreased cardiac performance (eg, sepsis).
EMERGENCY DEPARTMENT CARE AND DISPOSITION
General supportive care is the initial treatment. Symptomatic patients will require hospitalization and pericardiectomy.
For further reading in Emergency Medicine: A Comprehensive Study Guide, 7th edition., see Chapter 55, “The Cardiomyopathies, Myocarditis, and Pericardial Disease,” by James T. Niemann.