When would you consider referring a patient with suspected cardiac sarcoidosis based on PET and MRI for endomyocardial biopsy given degree of patchy involvement, as opposed to initiating empiric immunosuppressive therapies?

I would avoid initiating empiric immunosuppressive therapies without a firm diagnosis of sarcoidosis. I will mention however that the latest Japanese Circulation Society criteria for the diagnosis of sarcoidosis do include criterion for the non-invasive diagnosis of likely cardiac sarcoidosis based on imaging which includes cardiac involvement by imaging criteria (MRI and/or PET scan) as well as evidence of likely extra-cardiac involvement (mediastinal lymphadenopathy, other organ involvement) also by imaging.

Endomyocardial biopsy can be extremely useful for the diagnosis if there is clear evidence of involvement of the RV side of the septum, which is the site of the usual myocardial biopsy. However, many, if not most, cases of cardiac sa...

Very fascinating question!

So it seems that my practice and experience seems to differ a lot from many others. I commonly start immunosuppression empirically in patients with cardiac (including isolated cardiac) sarcoidosis, and very rarely do I get biopsies.

Most commonly, when I do get biopsies, I didn't end up getting much information from the biopsy that changed the management plan, as we continue to use immunosuppressants. In several patients who have failed immunosuppression, I have tried obtaining a biopsy, and frequently did not see granulomas on the biopsy. After cardiac transplant, I recalled several cases in which biopsy was negative, but the heart after removal was consistent with cardiac sarcoidosis.

On the other hand, I am ver...

An endomyocardial biopsy being negative does not rule out disease, given there can be patchy involvement of the myocardium that is missed on biopsy. Thus, if there is evidence of extracardiac sarcoidosis involving other organ systems (biopsy proven) and a compatible clinical picture (with exclusion of mimics), endomyocardial biopsy is often not necessary, and patients can be empirically treated for cardiac sarcoidosis.

If this is a new presentation with question of cardiac sarcoidosis without a known baseline diagnosis of sarcoid, would search for extra-cardiac involvement (e.g. CT or full body PET, not just cardiac MRI or cardiac PET) for lymphadenopathy or mediastinal/pulmonary involvement and pursue biopsy to confirm tissue diagnosis.

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