Chronic inflammatory cardiomyopathy (I-CMP) or inflammatory cardiomyopathy refers to a persistent or chronic inflammatory process of the myocardium with a symptom onset of >1 month and a hypokinetic non-dilated or dilated phenotype 1-5.
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Diagnosis
The diagnosis of chronic inflammatory cardiomyopathy is based on a combination of typical clinical features (history, ECG, laboratory data) cardiac imaging features and endomyocardial biopsy in selected cases 3-5.
In addition, a temporal criterion of symptom onset >1 month is required.
Clinical presentation
Typical symptoms of acute myocardial inflammation include chest pain, palpitations, dyspnea, fatigue, shock and in some individuals sudden cardiac death (SCD) 2,3. Chronic inflammatory cardiomyopathy specifically can present with symptoms of heart failure and can be a result of delayed diagnosis of acute myocarditis 3.
Prodromal syndromes such as fever, influenza-like and gastrointestinal symptoms are common and occur in up to 80% 3.
The following different clinical scenarios that are not explained by coronary artery disease or any other known causes have been described and are distinguished 2,3:
acute coronary syndrome-like
new onset or progressive heart failure (>2 weeks up to 3 months)
chronic heart failure (>3 months with recurrent exacerbations)
"life-threatening condition"
Troponin levels might be disproportionately elevated concerning left ventricular dysfunction 2.
Complications
Complications include the following 2-4:
worsening heart failure
cardiogenic shock
Pathology
Chronic inflammatory cardiomyopathy is pathologically characterized by myocardial inflammation in association with cardiomyocyte destruction adverse cardiac remodeling and cardiac dysfunction 5.
Etiology
Causes of chronic inflammatory cardiomyopathy are the same as for myocarditis and include diverse infectious (viral, bacterial, fungal and parasitic) as well as non-infectious (toxic, genetic and autoimmune) causes 1-4.
Macroscopic appearance
Clinical phenotypes include hypokinetic dilated or non-dilated subtypes with or without nonischemic scar tissue 5.
Microscopic appearance
Histologically inflammatory cardiomyopathy features focal or diffuse myocardial fibrosis, myocyte abnormalities and inflammatory infiltrates within the myocardium 5.
Radiographic features
Imaging features of chronic inflammatory cardiomyopathy include signs of the following:
left ventricular dysfunction (LVEF <50%)
myocardial inflammation
MRI
Whereas MRI displays high accuracy in acute myocarditis the sensitivity and accuracy in subacute or chronic cardiomyopathy-like and/or arrhythmia presentations is much lower 3-6.
Imaging features of inflammatory cardiomyopathy are those of myocardial inflammation such as myocardial edema and non-ischemic myocardial injury (including abnormal T1 mapping values, elevated extracellular volume and late gadolinium enhancement) 7.
Other than in acute myocarditis systolic left ventricular dysfunction is not only supportive but mandatory 1-4 and left ventricular dilatation might be present.
Signs of pericarditis might be present.
Treatment and prognosis
Patients with chronic inflammatory cardiomyopathy should be treated with optimal medical therapy according to the guidelines for the management of heart failure 3,8,9. The prognosis of inflammatory cardiomyopathy is considered less favorable than uncomplicated myocardial inflammation with lower recovery rates and adverse outcomes such as cardiac death or heart transplantations in up to 14.7% of cases 3.
History and etymology
Inflammatory cardiomyopathy has been recognized as a specific cardiomyopathy in the 1995 report of the World Health Organization 1.
Practical points
Due to the lower sensitivity/accuracy of MRI and the Lake Louise criteria in the setting of inflammatory cardiomyopathy a more innovative and less strict application of imaging criteria and correlation with clinical criteria is recommended.
Differential diagnosis
Differential diagnosis include non-inflammatory causes of the following conditions:
acute or chronic heart failure
non-dilated cardiomyopathy with systolic dysfunction
arrhythmogenic cardiomyopathy (especially left ventricular predominant phenotypes)
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