Case Presentation: A 56-year-old previously healthy Caucasian woman was evaluated by a neurologist for seizure-like activity and syncope. She was placed on a Holter monitor that showed episodes of paroxysmal supraventricular tachycardia, ventricular tachycardia (VT), and third-degree AV block. She presented to the emergency department with chest pain, a new left bundle branch block, and elevated troponin. Cardiac catheterization showed non-obstructive coronary artery disease with a left ventricular ejection fraction of 30-35%. Cardiac MRI showed late gadolinium enhancement highly suggestive of cardiac sarcoidosis (image 1, 2). An implantable cardioverter-defibrillator (ICD) was placed, and she was discharged on high-dose prednisone and amiodarone. The following week she presented in volume overload requiring IV diuretics. During hospitalization, she developed hemodynamically stable VT storm refractory to lidocaine, mexiletine, and amiodarone. Attempts of atrial anti-tachycardiac pacing (A-ATP) failed. Subsequently, she developed cardiogenic shock and needed intra-aortic balloon pump placement, ventilatory and inotropic support, followed by ECMO and orthotopic cardiac transplantation. Biopsy of the explanted heart showed cardiac myocyte dropouts, granulation tissue with hemosiderin-laden macrophages, and T-cells consistent with resolving GCM with no evidence of CS (images 3 and 4). She was weaned off from ECMO and ventilatory support and was discharged on immunosuppressants, with slow recovery.

Discussion: Giant Cell Myocarditis (GCM) and Cardiac Sarcoidosis (CS) both are rare, rapidly progressing, and potentially fatal, T -Lymphocyte-mediated inflammation of the myocardium, affecting middle-aged women [1,2]. GCM and CS, due to significant clinical overlap, were thought to be spectra of the same disease, but recent research has shown that they are two separate entities [3]. Rapidly progressive heart failure, cardiac transplant, and poor prognosis are the hallmark of GCM. Arrhythmias, conduction abnormalities, and slow progression of the disease are consistent with CS [4]. Cardiac MRI and PET scan are helpful diagnostic tools but cannot differentiate between two conditions.Endomyocardial biopsy is needed for definite diagnosis and differentiation (image 5,6). The presence of out-of-proportion necrosis to inflammation rules in GCM, while the absence of well-organized granulomas rules out CS [5]. The standard treatment of CS is prednisone, while GCM has a better outcome with steroid-sparing immunosuppressants [6].

Conclusions: CS and GCM manifest many end-to-end spectrum similarities but are separate entities. As management and prognosis vary, the development of further noninvasive tests is required for early diagnosis and differentiation.

IMAGE 1: Cardiac MRI showed Late Gadolinium Enhancement consistent with Cardiac Sarcoidosis

IMAGE 2: Cardiac Biopsy showed changes consistent with resolving Giant cell Myocarditis.