Myocarditis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Varun Kumar, M.B.B.S.
Overview
Myocarditis is inflammation of the myocardium, the muscular part of the heart. It may present with chest pain, rapid signs of heart failure, or sudden death.
Pathophysiology
During an infection or hypersensitive reaction, the immune system produces inflammatory cells that release chemicals to fight the infection. These inflammatory cells enter the myocardium (heart muscle) where the infection resides. However, the chemicals produced by an immune response can damage the heart muscle (myocardium). As a result, the heart can become damaged, enlarged, and weak. This damage to the myocardium leads to symptoms of heart failure.
Epidemiology and Demographics
In developed countries, myocarditis is generally due to viral infections such as coxsackie B, enterovirus,adenovirus, parvovirus B19, hepatitis C, and herpes virus 6. In developing countries, myocarditis is generally due to HIV and rheumatic heart disease.
Natural History, Complications & Prognosis
Myocarditis is usually self limiting and is associated with a good prognosis especially if it is secondary to a viral infection. Patients rarely develop cardiac failure, pulmonary edema, arrhythmias or cardiogenic shock. In some instances, myocarditis may be associated with sudden death. Patients with fulminant myocarditis have a good long term prognosis if they survive the acute phase of the disease [1] . The prognosis of fulminant myocarditis is better than that of either acute myocarditis or giant cell myocarditis.
The presence of left bundle branch block, q waves, AV block, syncope and a left ventricular ejection fraction < 40% are associated with sudden death and cardiac transplantation[2].
Clinicopathological classification[3]
- Fulminant myocarditis - Fulminant myocarditis occurs following a viral prodrome. Fulminant myocarditis presents as acute severe cardiovascular compromise with ventricular dysfunction. The prognosis is good if the patient survives the acute illness[1]. On endomyocardial biopsy, there are multiple focci of inflammation.
- Acute myocarditis - Acute myocarditis presents with a less distinct onset of the illness. When the patient does present, there is already a decline in left ventricular dysfunction. Acute myocarditis may progress to dilated cardiomyopathy.
- Chronic active myocarditis Chronic active myocarditis has a less distinct onset of the illness. There are clinical and histologic relapses and the development of ventricular dysfunction. Histologically, chronic inflammatory changes with mild to moderate fibrosis may be present.
- Chronic persistent myocarditis - Chronic persistent myocarditis has a less distinct onset ff the illness. Histologically it is characterized by persistent infiltration and myocyte necrosis. Despite the presence of symptoms, ventricular dysfunction is absent.
Symptoms
The symptoms and the intensity of symptoms associated with myocarditis are variable. Myocarditis may be associated with no symptoms. If symptoms are present,they may be similar to the flu. Patients may present with chest pain as a result of the inflammatory process involving the myocardium or with symptoms of congestive heart failure. Patients may complain of palpitations, a racing heart or syncope. In fulminant myocarditis, patients present with the abrupt onset of flu-like symptoms and the abrupt onset of heart failure symptoms. In chronic and acute myocarditis, the onset of symptoms may be more insidious. Symptoms may include:
- Palpitations
- Chest pain
- Fatigue
- Fever and other signs of infection including headache, muscle aches, sore throat, diarrhea, or rashes
- Joint pain or swelling
- Pedal edema
- Shortness of breath
- Fainting, often related to irregular heart rhythms
- Low urine output
Diagnosis
Physical examination
Physical examination in patients with myocarditis may reveal tachycardia, a cardiac gallop, mitral regurgitation and pulmonary edema suggestive of cardiac failure. A pericardial friction rub may be noted in presence of concomitant pericarditis, a condition sometimes referred to as myopericarditis.
Electrocardiographic Findings
Common ECG findings in myocarditis include[4]:
- Sinus tachycardia
- Diffuse T wave inversions
- ST segment elevation may also be present
ST segment elevation may also be seen in pericarditis. PR depression is also present, however, in patients with pericarditis.
Echocardiography
Echocardiography in patients with myocarditis allows for serial assessment of left ventricular dysfunction. [5].
Endomyocardial Biopsy
Endomyocardial biopsy remains the gold standard test to evaluate for the presence of and to subclassify the type of myocarditis. A small tissue sample of the endocardium and myocardium is obtained via right sided cardiac catheterization. The sample is then evaluated by a pathologist and if necessary using immunochemistry and special staining techniques. Histopathological features include abundant edema in the myocardial interstitium and an inflammatory infiltrate which is rich in lymphocytes and macrophages. Focal destruction of myocytes as a result of the inflammatory process explains the myocardial pump failure.[4]
Coronary Angiography
Coronary angiography may be helpful in excluding either myocardial ischemia or infarction as the cause of ST segment elevation, elevated cardiac biomarkers, or left ventricular dysfunction.
Cardiac Magnetic Resonance Imaging
Myocardial inflammation associated with myocarditis appears as a high intensity signal with delayed gadolinium hyperenhancement on cardiac MRI (cMRI). [6]. While the cMRI pattern of gadolinium hyperenhancement in ST segment elevation myocardial infarction is transmural and extends from the endocardium to the epicardium, the patchy, non-segmental hyperenhancement pattern in myocarditis in contrast involves the epicardium and spares the subendocardium[7].
Laboratory Findings
Myocardial inflammation can be suspected on the basis of the clinical history along with elevations of[4]:
- Biomarkers of myocardial damage such as troponin or creatine kinase
- Antibodies against viruses known to affect the myocardium and cause myocarditis
- ESR
- C-reactive protein
- Auto antibodies such as ANA and rheumatoid factor
Differentiating Myocarditis from Pericarditis and Myocardial Infarction
Myocarditis presents with chest pain and ST segment elevation. Myocarditis must be distinguished from pericarditis and the life threatening condition of ST elevation myocardial infarction.
Differentiating Myocarditis from ST Segment Elevation Myocardial Infarction
Both diseases present with chest pain, elevated cardiac biomarkers, and focal left ventricular dysfunction. There are two studies that can be used to distinguish the two syndromes:
Coronary Angiography
Coronary angiography can be performed to distinguish myocarditis from ST segment elevation myocardial infarction. ST segment elevation myocardial infarction is associated with either complete or subtotal occlusion of an epicardial coronary artery on coronary angiography.
Cardiac Magnetic Resonance Imaging
Cardiac magnetic resonance imaging is also useful in distinguishing between the two syndromes as well. On cardiac MRI, myocarditis is associated with patchy, non-sentimental, hyperenhancement which is confined to the epicardial layer of the myocardium. In contrast, in ST segment elevation myocardial infarction there is confluent hyperenhancement extending from the endocardium in a distribution that mimics the distribution of the epicardial coronary arteries.
Differentiating Myocarditis from Pericarditis
Both diseases present with chest pain and ST segment elevation. The two conditions can be distinguished by the following studies:
Electrocardiogram
While both disorders are associated with ST segment elevation, pericarditis is also associated with PR segment depression.
Cardiac Biomarkers
Myocarditis is associated with elevations of the CK-MB and the troponin, while pericarditis is not. If pericarditis is associated with underlying inflammation of the myocardium, then this is called myopericarditis. If there is concomitant involvement of both the pericardium and myocardium in myopericarditis, then there are elevations of the cardiac biomarkers.
Echocardiography
In patients with myocarditis there will be a focal wall motion abnormalities, while these will be absent in the patient with pericarditis. There may be a pericardial effusion in the patient with pericarditis, while myocarditis is not associated with a pericardial effusion.
Treatment
Insofar as most viral infections cannot be treated with directed therapy, symptomatic treatment is the mainstay of therapy for patients with viral myocarditis. Supportive therapy includes diuretics and inotropes for left ventricular failure. ACE inhibitor therapy may aid in left ventricular remodeling after the inflammation has begun to resolve. in patients with fulminant myocarditis, placement of an intra-aortic balloon pump or a left ventricular assist device may be necessary as bridge to recovery.
According to 2010 HFSA guidelines[8], routine use of immunosuppressive therapies in management of myocarditis is not recommended (Strength of Evidence A). Immunotherapy is beneficial in giant cell myocarditis. Finally, cardiac transplantation can be performed in patients with severe myocarditis who fail to recover.
Bacterial infections are treated with antibiotics the selection of which is based upon the nature of the pathogen and its sensitivity to antibiotics.
References
- ↑ 1.0 1.1 McCarthy RE, Boehmer JP, Hruban RH, Hutchins GM, Kasper EK, Hare JM; et al. (2000). "Long-term outcome of fulminant myocarditis as compared with acute (nonfulminant) myocarditis". N Engl J Med. 342 (10): 690–5. doi:10.1056/NEJM200003093421003. PMID 10706898.
- ↑ Scartazzini R, Schneider P, Bickel H (1975). "[New beta-lactam antibiotics. Functionalisation of the cephem 3-position with sulfur or nitrogen bearing substituents (author's transl)]". Helv Chim Acta. 58 (8): 2437–50. doi:10.1002/hlca.19750580824. PMID 1194054.
- ↑ Lieberman EB, Hutchins GM, Herskowitz A, Rose NR, Baughman KL (1991). "Clinicopathologic description of myocarditis". J Am Coll Cardiol. 18 (7): 1617–26. PMID 1960305.
- ↑ 4.0 4.1 4.2 Feldman AM, McNamara D (2000). "Myocarditis". N Engl J Med. 343 (19): 1388–98. doi:10.1056/NEJM200011093431908. PMID 11070105.
- ↑ Felker GM, Boehmer JP, Hruban RH, Hutchins GM, Kasper EK, Baughman KL; et al. (2000). "Echocardiographic findings in fulminant and acute myocarditis". J Am Coll Cardiol. 36 (1): 227–32. PMID 10898439.
- ↑ Abdel-Aty H, Boyé P, Zagrosek A, Wassmuth R, Kumar A, Messroghli D; et al. (2005). "Diagnostic performance of cardiovascular magnetic resonance in patients with suspected acute myocarditis: comparison of different approaches". J Am Coll Cardiol. 45 (11): 1815–22. doi:10.1016/j.jacc.2004.11.069. PMID 15936612.
- ↑ Skouri HN, Dec GW, Friedrich MG, Cooper LT (2006). "Noninvasive imaging in myocarditis". J. Am. Coll. Cardiol. 48 (10): 2085–93. doi:10.1016/j.jacc.2006.08.017. PMID 17112998.
- ↑ Heart Failure Society of America. Lindenfeld J, Albert NM, Boehmer JP, Collins SP, Ezekowitz JA; et al. (2010). "HFSA 2010 Comprehensive Heart Failure Practice Guideline". J Card Fail. 16 (6): e1–194. doi:10.1016/j.cardfail.2010.04.004. PMID 20610207.