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Cardiac involvement is a usual complication of PM/DM in present studies, which was demonstrated to be a poor prognostic factor.4,6,9 Because clinical manifestations of heart diseases are relatively infrequent, clinicians have not paid much attention to it.
This review suggests that heart failure is the most common clinical symptom. Any abnormalities of heart construction or function can lead to systolic or diastolic dysfunction. Because cardiac complications lack symptoms in early stages, this factor was ignored by patients and doctors. Acute or chronic heart failure is the manifestation of heart deterioration and damage that was reported by physicans.
ECG and UCG are the most often used auxiliary tests to evaluate cardiac abnormalities. In the polymorphism of the cardiac manifestations in PM/DM, conduction defects, left ventricular diastolic dysfunction, and hyperdynamic left ventricular contraction manifest relatively higher incidence. Lymphocytic infiltration, fibrosis of conduction system lesions, and active myocarditis are the pathologic foundation of the diseases listed above.8,12 The presumption of enhanced left ventricular function by Gottdiener et al15 was indicated by a reduction of afterload by arteriovenous shunting across involved skeletal muscle beds and high output state secondary, due either to increased metabolic demand of diseased skeletal muscle or to the effects of vasoactive amines released by involved muscle. It is possible that myocarditis may predispose the patient to development of congestive heart failure over a period of time or under certain circumstances. Systolic left ventricular function decrease is the concurrent outcome of persistent hyperkinetic cardiovascular state and necrosis of myocardium.
Most heart abnormalities are subclinical, and traditional techniques such as ECG, Holter, and UCG are limited by their poor sensitivity and specificity. Cardiac MRI is a noninvasive technique that has been efficiently used in early diagnosis of viral myocarditis. Allanore et al16 proposed that cardiac MRI could be used to diagnosis and monitor myocarditis sensitively in PM/DM. Although its evaluation on large scale is warranted, cardiac MRI may be of considerable potential value in this field.
Pathologic findings of myocardium with myocardial inflammatory, degenerative changes and necrosis are similar to that of skeletal muscles, which indicate that the heart is a target organ of PM/DM. Recent research demonstrated that overexpression of major histocompatibility complex in muscle fibers is related to the mechanism of PM/DM.26,27 Therefore, more detailed characterization of the cellular phenotype or localization of inflammation in myocardium should be helpful to understand the possible mechanism of cardiac involvement.
Many excluded studies demonstrated that CK-MB and cTnT may be expressed in regenerating skeletal muscles of patients with muscle disease. A study of 3 patients by Kiely et al28 suggested a noncardiac origin for CK-MB in DM. On the other hand, due to the multiple manifestations of heart damage, sometimes the level of CK-MB is normal when cardiac involvement is present.29 CK-MB was increased in 51% and cTnT in 41% of patients without clinical evidence for myocardial damage.30 Given the limited state of knowledge about cardiac troponin I(cTnI) in PM/DM at present, cTnI was only elevated in a few patients (2.5%). The correlation between cTnI and myocardial cell injury is unclear right now.
The therapy for heart complications is empirical. The effects of corticosteroids and immunosuppressants on cardiac manifestations in patients with PM/DM are conflicting. In addition, there are case reports about successful treatment with rituximab31and heart transplantation.32 Because of the pathophysiological analogy of myocardial tissue and skeletal muscle, corticosteroids should be effective for myocarditis as well as inflammation in the skeletal muscles. Therefore, carefully designed controlled studies are needed.
In the past decades, earlier diagnosis and adequate treatment regimes have become the standard for care, so survival of patients with PM/DM has improved progressively worldwide.6 Cancer, lung, and cardiovascular complications are generally cited as the most common causes of death in PM/DM patients. In the articles included, 37 patients (46.3%) died as a direct result of heart disease. Cancer-associated myositis were excluded in this review. The top 2 causes of death are heart disease and respiratory failure. Because cardiac complications were paid close attention to in this review, there may be a selection of literature bias. Therefore, the ratio of heart disease as a direct cause was as high as 46.3%, but the data also illustrated that the presence of cardiac involvement was associated with a significantly worse survival.
As stated in many articles, most cardiac involvement in PM/DM was subclinical. Also, noninvasive technologies for detection lack sensitivity. The most frequently reported clinical manifest is heart failure with poor prognosis. Therefore, we prefer ECG and UCG as routine examinations to detect subclinical heart disease. See Figure 2 for the flowchart illustrating the evaluation of heart in PM/DM patient. It is beneficial to prevent heart disease from progressing.
Some limitations of this systematic review should be acknowledged. First, due to the differences of patient selection, heart disease definition and detection methods used analyzed sources with relatively heterogeneous and cannot be systematically quantitatively evaluated. Second, case reports were excluded from this analysis.