Dallas criteria

In 1987, the Dallas criteria were drawn up and published by Aretz et al. as an international basis for work and understanding (Zajonz 2016).

The Dallas criteria represent a histopathological classification for the diagnosis of myocarditis that is still valid today. The light microscopically defined criteria are an easy to apply and simple means of analysing endomyocardial biopsies by detecting lymphocyte infiltrates and necrosis of myocytes (Zajonz2016).

The Dallas criteria, however, do not or only insufficiently allow a prediction of the prognosis of the affected patient (Erdmann 2000). Over the years, these criteria have been supplemented several times by the World Health Federation (WHF) and extended in 1999 by the inclusion of immunohistological parameters (WHF classification of 1999 [Michels 2010]).

Since the myocardium usually shows a heterogeneous infestation in the presence of myocarditis, false negative results are not uncommon despite targeted biopsy from the late-enhancement areas localized in the cardiac MRI. In patients with classic symptoms, the typical histopathological findings cannot be determined in up to 80 % - 90 % of cases. Also a specific trigger for myocarditis can only be found in rare cases. In immunohistochemistry, however, an upregulation of HLA antigens, active lymphocyte subtypes and complement components that play a role in the inflammatory reaction can be detected. However, no figures are available on specificity and sensitivity (Kasper 2015).

To standardize the examination methods and to compare myocardial changes, the so-called Lake-Louise criteria of cardiac magnetic resonance imaging were therefore established for the first time in 2009. These show a sensitivity of 67 % and a specificity of 91 % (Schuler 2017).

Histological differentiation according to the Dallas classification of 1987 (Herold 2018):

For the diagnosis of acute or active myocarditis the following evidence is required:

• inflammatory infiltrate
• Edema
• Myocytolysis

In the case of persistent myocarditis, the subsequent biopsy shows an unchanged picture:

• inflammatory infiltrate
• Edema
• Myocytolysis

With the healing myocarditis one finds:

• a receding infiltrate
• a reparative fibrosis
• a myocytolysis that is only facultative

Borderline myocarditis is characterized by:

• interspersed lymphocytes (< 14 lymphocytes / mm² [Michels 2010])
• there is no myocytolysis

The chronic or inflammatory cardiomyopathy:

• this is not defined in the Dallas criteria

The histological criteria of biopsy according to the criteria of the WHF classification of 1999 (Herold 2018; Michels 2010):

The diagnosis of acute or active myocarditis can be made immunohistologically, in

• Detection of an inflammatory infiltrate with monoclonal antibodies, immunoglobulin and complement fixation (IgM antibodies, C 3)

In persistent myocarditis are also found in the bioptate:

• an expression of HLA- I- and HLA- II- antigen
• Adhesion molecules (ICAM)

Indications of a healing myocarditis are:

• Evidence of a receding infiltrate
• Detection of a decreasing HLA- I- and HLA_ II- expression

In borderline myocarditis are detectable:

• 1- 13 lymphocytes/ mm²

A chronic myocarditis or inflammatory cardiomyopathy is diagnosed by the detection of:

• > 14 lymphocytes (up to 4 macrophages included) / mm² with CD3 positive T lymphocytes > 7/mm² , immunohistological detection of viral RNA or DNA (optional) (Herold 2018)

1. Erdmann E et al (2000) Clinical Cardiology: Diseases of the heart, circulation and the vessels near the heart. Springer publishing house 1031
2. Herold G et al (2018) Internal Medicine Herold Verlag 230
3. Kasper D L et al (2015) Harrison's Principles of Internal Medicine. Mc Graw Hill Education 1559 - 1560
4. Kasper D L et al (2015) Harrison's Internal Medicine. Georg Thieme Publishing House 1898- 1899
5. Michels G et al (2010) Clinical Manual Internal Medicine Springer Verlag 62- 64
6. Pinger S (2019) Repetitorium Kardiologie: For clinic, practice, specialist examination. German medical publisher. 434
7. Schuler G (2017) Physical activity and illness. de Gruyter Publishers 271 - 281
8. Zajonz T S (2016) Lake Louise Criteria of cardiac magnetic resonance imaging in acute and chronic myocarditis: correlation with histopathological parameters. Inaugural dissertation to obtain the degree of Doctor of Medicine of the Department of Medicine of the Justus Liebig University of Giessen