Radiological observations on 33 cases of primary interstitial myocarditis during an outbreak in the Haifa area

The radiological observations in 33 cases of primary interstitial myocarditis in the age-group 6 months to 3 ½ years are reported.

The radiological features of the disease are presented. According to the size and shape of the heart, three stages of myopathic heart configuration are shown, presenting phases of the increasing myogenic dilatation of the heart. In cases that permitted further observation, gradual decrease of the size of the heart with eventual return to normal could be seen. The radiological appearances of passive pulmonary congestion, which were present in all but 4 cases, are discussed. Cases are presented with the typical appearances of arterial venous and lymphatic engorgement extending into the most peripheral parts of the lung fields (third zone) together with Kerley's B lines. In addition, cases are reported with a pathological interstitial pattern suggestive of diffuse interstitial pneumonia, these cases showing marked emphysema. The deduction is drawn that the combination of primary interstitial myocarditis with diffuse interstitial pneumonia must be a relatively frequent occurrence. This is supported by the fact that 11 out of 27 patients who died in 1957 showed on histopathological examination evidence of interstitial inflammatory infiltration of the lungs, in addition to interstitial myocarditis. Radiological evidence of pleural fluid was seen in 28 out of the 33 cases. Diminished or invisible cardiac pulsations may be of diagnostic aid.

The radiological differential diagnostic considerations are discussed. The most important task of the radiologist is considered to be the differentiation between acute inflammatory pulmonary disease and myocarditis, the presenting severe clinical signs in both these conditions making a clinical differentiation sometimes very difficult. The differential diagnostic features between heart failure due to myocarditis and diffuse interstitial pneumonia are described, marked emphysema with a small heart and absence of Kerley's B lines pointing in favour of the latter. In addition the pathological interstitial pattern in diffuse interstitial pneumonia is usually limited to the paramediastinal regions (leaving the outer third free).

The fine granular miliary pattern in acute bronchiolitis is thought to permit differentiation of this disease.

The radiological signs of the combination of primary interstitial myocarditis with diffuse interstitial pneumonia are discussed, the most important feature being a marked emphysema and at the same time an enlarged heart.

The differentiation from other forms of primary myocardial disease is mentioned; sub-endocardial fibro-elastosis offers no differentiating radiological signs.

The radiological appearance of secondary myocarditis due to diphtheria, poliomyelitis, meningitis, nephritis, bacterial endocarditis, etc., presents no radiological differential diagnostic features.

The differential diagnostic considerations between myocarditis and decompensated rheumatic carditis as well as decompensated congenital cardiac disease are mentioned.

An important differential diagnostic sign between primary interstitial myocarditis and pericardial effusion (pericarditis) is believed to be the rare or very late occurrence of left heart failure (passive pulmonary congestion) in the latter.