Prognostic Value of Myocardial Damage in Patients With Sarcoidosis
Is Cardiac Magnetic Resonance What We Need?
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Sarcoidosis is a granulomatous disease of unknown pathogenesis that can affect virtually any organ system. Cardiac involvement results in significant morbidity and mortality, with some studies reporting that cardiac involvement accounts for up to 25% of all deaths from sarcoidosis in the United States and more than half of all deaths in Japan.1–3 Many deaths seem to be arrhythmic in nature and are potentially preventable. For example, recent studies4,5 in patients with cardiac sarcoidosis (CS) and an implantable cardioverter-defibrillator show high rates of appropriate implantable cardioverter-defibrillator discharges (≈10%–15% per year for primary prevention patients), which are more than double that reported in large randomized trials of heart failure patients.6
See Article by Hulten et al
Unfortunately, the diagnosis of cardiac involvement is difficult because the extent of disease is often limited and focal in nature. Necropsy studies have shown that patients with CS frequently have lesions that are small and patchy, leaving much of the myocardium uninvolved.1,7,8 Hence, although a positive endomyocardial biopsy is confirmatory, a negative biopsy cannot exclude CS because the false-negative rate may be as high as 80%.9
Guidelines such as those from the Japanese Ministry of Health and Welfare (JMH)10 and, more recently, from the Heart Rhythm Society (HRS),11 have been published for the diagnosis of CS. Unfortunately, the recommendations rely heavily on expert opinion because the level of evidence is low. A particular limitation of the guidelines is that the diagnosis of CS requires the histological confirmation of sarcoidosis—either in the heart or outside the heart. Hence, in the absence of a positive myocardial biopsy, the guidelines do not provide a pathway to diagnose sarcoidosis confined to the heart. This is important because there is growing evidence that isolated CS …