CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 8, September 2013
AFRICA
e7
An MG patient is often the subject of cardiac disease, as was
the case with our patient. According to Hofstad
et al.
,
10
16% of
patients with MG have signs of cardiac disease, which is a much
higher frequency than that found in the general population.
This strongly indicates that these otherwise unexplained signs
of heart disease are related to or caused by MG. Such findings
are more frequent among thymoma patients (50%) than among
non-thymoma patients (12%).
The histological changes in the striated muscle found in MG
are muscle fibre atrophy and varying degrees of inflammation.
10
The inflammatory lesions range from discrete accumulations
of lymphocytes without tissue destruction to extensive
myonecrosis with heavy inflammatory cell infiltration and signs
of regeneration. Hearts microscopically examined by Hofstad
et
al.
had inflammatory infiltrates in the myocardium, with varying
degrees of muscle fibre degeneration or necrosis.
10
The cardiac findings may be caused by mechanisms specific
to MG or they may represent non-specific myocardial damage.
The focal, spotty localisation of the myocardial changes
indicates that the heart pathology has a causal relationship with
MG. Moreover, clinical evaluation usually represents the first
diagnostic step for a patient with suspected MG. The evaluation
of MG-related symptoms could be difficult as the cardiac disease
may mask them.
In our case, the pre-operative clinical status was not correctly
addressed as the cardiac symptoms were predominant. Hence,
the diagnosis of myocarditis in this patient was guided by the
intra-operative and histological findings, which led to revaluation
of the pre-operative clinical conditions.
Conclusion
A dynamic hypothesis concerning the correlation between
myocarditis due to myasthenia gravis and left ventricular rupture
after mitral valve replacement is presented. Additionally, we
believe that endomyocardial biopsy should be considered in this
group of patients.
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