MYOCARDITIS

 

INTRODUCTION

Background: Myocarditis is an uncommon disease of the heart characterized by inflammation. Subsequent myocardial destruction often leads to a dilated cardiomyopathy.

The acute picture is nonspecific unless overt congestive heart failure develops. Although the causes are numerous, the most common association is with that of a viral syndrome.

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Pathophysiology: Myocarditis is defined as inflammatory changes in the heart muscle and is characterized by an interstitial mononuclear cell infiltrate with attendant myocyte necrosis.

It is not known whether the infiltrate is caused by a direct invasion of the infective agents, or bya a systemic immune response.

In the chronic stage, cytotoxic T lymphocytes infiltrate the myocardium and mediate an autoimmune response with myocardial autoantibody activity directed against cardiac myosin. This autoimmune process persists long after the viral particles are no longer detected. The deleterious effects of the inflammatory response are compounded by coronary artery thrombus formation, luminal obstruction, ischemia and dysrhythmias.

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Frequency:

• In the U.S.: The true incidence of clinically apparent disease is unknown due to the many cases that are not detected at the time of the acute illness. One large study demonstrated evidence of myocarditis in 1.06% of 12,747 autopsy cases.

 

Mortality/Morbidity:

• Myocarditis is rarely fulminant or leads to death.
• Neonatal and viral myocarditis are associated with acute myocyte necrosis. It is not known if this is due to direct invasion or as a sequelae of a host response.

.Sex: The male:female ratio for myocarditis is 1.5:1

Age: The average age of patients with myocarditis is 42.

 

CLINICALPATHOPHYSIOLOGY

History:

Physical:

• Patients with mild cases have a nontoxic appearance and may simply appear to have a viral syndrome.

• Tachypnea and tachycardia are common; the latter is often out of proportion to any fever.

• The more acutely ill patient will have signs of circulatory impairment due to left ventricular failure.

• Signs of ventricular dysfunction:

• Jugular venous distention

• Bibasilar crackles

• Ascites

• Peripheral edema

• An S3 or summation gallop may be noted with significant biventricular involvement.

• S1 may be diminished in intensity.

• Cyanosis

• Hypotension, due to left ventricular dysfunction, is uncommon in the acute setting and when present is a poor prognosis.

• Cardiogenic shock is seen in fulminant cases and has a high mortality.

• Murmurs of mitral or tricuspid regurgitation may be present due to ventricular dilation.

• In cases where a dilated cardiomyopathy has developed, signs of peripheral or pulmonary thromboembolism may be found.

• Associated pericarditis may manifest a pericardial friction rub.

• Pericardial effusion is common but signs of tamponade (e.g., hypotension, jugular venous distention and muffled heart tones) are rare.
  
• A pleural friction rub might be heard since pleuritis can also occur with cases of acute myocarditis.

Causes:

WORKUP

Lab Studies:

• Cardiac Enzymes:

• Only elevated in a minority of patients

• They are helpful as they demonstrate a characteristic pattern of slow elevation and fall over a period of days, in contrast to the more abrupt rise seen in acute myocardial infarction.

• Cardiac Troponin-I may be more sensitive as it is present for longer time periods after myocardial damage from any cause.

• The erythrocyte sedimentation rate (ESR) is elevated in 60% of patients with acute myocarditis.
  
• Leukocytosis is present in 25% of cases.

Imaging Studies:

Other Tests:

• Electrocardiogram (ECG):

• The most frequent finding is a sinus tachycardia.

• ST-segment elevation without reciprocal depression, particularly when diffuse, is helpful in differentiating myocarditis from acute myocardial infarction.

• Decreased QRS amplitude and transitory Q-wave development is very suggestive of this entity.

• Up to 20% of patients will have a conduction delay, including Mobitz I, Mobitz II or complete heart block.

• Left and right bundle branch block is be seen and may persist for months.

• Viral isolation from other body sites may be supportive of the diagnosis.

• Polymerized chain reaction (PCR) identification of a viral infection from myocardial tissue, pericardial fluid or other body fluid sites has been helpful.
  
• If a systemic disorder, such as SLE, is suspected, antinuclear antibody (ANA) and other collagen vascular disorder laboratory investigations may be useful.

Procedures:

TREATMENT

Emergency Department Care: As many cases of myocarditis are not clinically obvious, a high degree of suspicion is required for the astute emergency physician to identify the person with acute myocarditis.
Patients with mild symptoms and no signs of cardiac failure or dysrhythmia may be treated as outpatients.

• Standard treatment includes the detection of dysrhythmia with inpatient cardiac monitoring or the placement of a Holter monitor and anticoagulation to lessen the risk of thromboembolic complications.

• Patients are advised to restrict activity since studies have shown that increased activity promotes progression of inflammation.

• Left ventricular dysfunction should be treated with low sodium diet, digoxin and vasodilators, particularly if signs of congestive heart failure are present.

• The angiotensin-converting enzyme (ACE) inhibitor class of drugs, such as captopril, has been shown to be beneficial in the treatment of significant left ventricular dysfunction.

• Cardiogenic shock should be treated with inotropic and vasodilator agents, such as a combination of dobutamine and sodium nitroprusside.
  
• If needed, intra-aortic balloon pump assistance may be life-saving.

• In general, sympathomimetic and beta blocker drugs should be avoided, as they increase the extent of myocardial necrosis and mortality.

• Patients presenting with Mobitz II or complete heart block require pacemaker placement.

• The efficacy of immunosuppressive therapy and suppression of the body's systemic inflammatory response in this condition is controversial.

• Immunosuppression has been shown to have no benefit in the acute phase and may be harmful if active viral replication is occurring. Therefore, therapy with agents such as corticosteroids or cyclosporine is NOT considered an appropriate emergent therapy.
  
• Nonsteroidal anti-inflammatory drugs (NSAIDs) are contraindicated in the early course of the disease due to inhibition of prostaglandin production, worsened myocyte function and increased myocardial necrosis.

Consultations: Those patients whose clinical picture prompts emergency room treatment for new-onset CHF, dysrhythmia or cardiogenic shock should be admitted to the hospital with continuous cardiac monitoring and cardiology consultation.

MEDICATION

The medical treatment of myocarditis is for associated complications: dysrhythmia, thromboembolism, congestive heart failure and cardiogenic shock. Treatment of these conditions is thoroughly reviewed under their separate chapter headings.

FOLLOW-UP

Further Inpatient Care:

• Those patients admitted to the hospital will be treated for the complications of myocarditis. Those suspected of having the disease will most likely undergo an endomyocardial biopsy.

• Although temporary pacemaker placement for advanced degrees of heart block is indicated, in the setting of myocarditis, these conduction disturbances are usually transitory. Therefore, permanent pacemaker placement is not usually necessary.

• Bedrest with restriction of activity and sodium intake is beneficial.
  
• Patients with fulminant heart failure may require transplantation which can be life saving. Unfortunately, these patients have a higher rate of rejection than patients without myocarditis as an underlying cause of their heart failure.

Further Outpatient Care:

• The clinician may consider the placement of a Holter monitor to recognize dysrhythmias on an outpatient basis.
  
  This may be done after the initial emergency department evaluation of a patient who shows no sign of acute dysrhythmia, congestive heart failure or other complication.
  
  It may also be done after the initial inpatient treatment.

• All patients with myocarditis should be followed by a cardiologist upon discharge from the hospital.

In/Out Patient Meds:

• Treatment of pain with a narcotic analgesic, such as acetaminophen with codeine, is appropriate. Remember to avoid NSAIDs, which are relatively contraindicated in this condition.

Complications:

• Congestive heart failure
  
• Pulmonary edema
  
• Cardiogenic shock
  
• Cardiac failure
  
• Recurrent myositis
  
• Dysrhythmias

Prognosis:

• The majority of cases are believed to be clinically silent and resolve spontaneously without sequelae, therefore, it is difficult to make accurate statements concerning the prognosis of myocarditis.

• The patient manifesting with congestive heart failure will experience morbidity and mortality based on the degree of left ventricular dysfunction.

• Of patients presenting with cardiogenic shock, the elderly and patients with giant cell arteritis have a poor prognosis.

• It is important to note that one-half of the patients presenting with new onset CHF experience considerable improvement of cardiac function with treatment.

• One-fourth of patients presenting with CHF stabilize with compromised cardiac function.

• The remaining one-fourth of patients will continue to deteriorate.

• Those patients requiring transplantation have an increased risk of recurrent myocarditis and graft rejection.
  

MISCELLANEOUS

Medical/Legal Pitfalls:

• Myocarditis may present subtly but should be considered in the patient who presents with dyspnea and chest discomfort, particularly if there is a history of a recent viral illness.
  
  

  • A careful physical examination, looking for signs of congestive heart failure and pericarditis is helpful. Electrocardiography, erythrocyte sedimentation rate and cardiac enzymes are useful screening tools.
    
  • Patients with evidence of dysrhythmia, congestive heart failure or thromboembolism must be admitted. .

BIBLIOGRAPHY

• Billingham ME : The diagnostic criteria of myocarditis by endomyocardial biopsy, in Myocarditis and related disorders: proceedings of the International Symposium on Cardiomyopathy and Myocarditis; Sekiguchi M, Olsen EGJ, Goodwin JF, editors. Springer-Verlag , New York 1985; 133-137.
• Fujii J, Sato H, Sawada H et al: Echocardiographic assessment of left ventricular wall motion in myocarditis, in Myocarditis and related disorders: proceedings of the International Symposium on Cardiomyopathy and Myocarditis; Sekiguchi M, Olsen EGJ, Goodwin JF, editors. Springer-Verlag , New York 1985; 116-121.
• Mason JW, O'Connell JB, Herskowitz A et al: A clinical trial of immunosuppressive therapy for myocarditis. The Myocarditis Treatment Trial Investigators. N Engl J Med 1995; 333: 269-75.
• O'Conell JB, Costanzo-Nordin MR, Engelmeier RS et al: Prognosis and treatment of cardiomyopathy and myocarditis, in Myocarditis and related disorders: proceedings of the International Symposium on Cardiomyopathy and Myocarditis; Sekiguchi M, Olsen EGJ, Goodwin JF, editors. Springer-Verlag, New York 1985; 175-179.
• O'Connell JB, Renlund DG: Myocarditis and Specific Myocardial Diseases, in Hurst 's The Heart: Arteries and Veins, 8th edition; Schlant RC, Alexander RW, editors. McGraw-Hill , New York 1994; 1591-1598.
• O'Connell JB, Robinson JA, Gunnar RM et al: Clinical aspects of virus/immune myocarditis, in Myocarditis and related disorders: proceedings of the International Symposium on Cardiomyopathy and Myocarditis; Sekiguchi M, Olsen EGJ, Goodwin JF, editors. Springer-Verlag , New York 1985; 102-106.
• Pisani B, Taylor DO, Mason JW: Inflammatory myocardial diseases and cardiomyopathies. Am J Med 1997; 102: 459-469.
• Richardson PJ: Clinical aspects of myocarditis, in Myocarditis and related disorders: proceedings of the International Symposium on Cardiomyopathy and Myocarditis; Sekiguchi M, Olsen EGJ, Goodwin JF, editors. Springer-Verlag , New York 1985; 97-100.
• Stevens LW: Diseases of the Myocardium, Cecil Textbook of Medicine, 20th edition, Bennett JC, Plum F, editors. WB Saunders Co, Philadelphia 1996; 328-331.
• Toshima H: Clinical aspects of myocarditis and pericarditis, in Myocarditis and related disorders: proceedings of the International Symposium on Cardiomyopathy and Myocarditis; Sekiguchi M, Olsen EGJ, Goodwin JF, editors. Springer-Verlag, New York 1985; 101.