Cardiomyopathy of uncertain etiology: Complementary role of multimodality imaging with cardiac MRI and 18FDG PET.

A 59-year-old female with longstanding history of tachyarrhythmias was admitted for syncope and recurrent ventricular tachycardia. She had a past medical history of hyperlipidemia, hypothyroidism, atrial fibrillation, and wide complex tachycardia that had been attributed to Wolf-Parkinson-White syndrome. Her medications included atenolol, propafenone, synthroid, and lipitor. Her 12-lead ECG was notable for sinus rhythm with marked 1st degree heart block, right bundle branch block, and left anterior fascicular block (Figure 1). The echocardiogram on admission demonstrated a moderately dilated left ventricle with normal wall thickness. There was global left ventricular hypokinesis with an estimated ejection fraction (LVEF) of 20%. There was mild right ventricular dilatation with mild global reduction in right ventricular systolic function. Figure 1 12 lead ECG notable for Sinus rhythm (black arrow indicates p wave) with marked 1st degree heart block, right bundle branch block and left anterior fascicular block. To evaluate for possible obstructive CAD, the patient underwent invasive coronary angiography which demonstrated normal coronary artery anatomy with no evidence of atherosclerotic disease (Figure 2A, B). Figure 2 Coronary angiography found no evidence of coronary artery disease, A shows the selective catheterization and opacification of the LAD and LCX, and B the RCA. An endomyocardial biopsy from the right ventricular septum was then obtained to evaluate for infiltrative disease. Five biopsy samples were acquired. The endomyocardial biopsy demonstrated diffuse subendocardial myocyte vacuolization, which was thought to be demand-related given the tachyarrhythmias and normal coronary arteries (Figure 3). Specifically, there was no evidence of active myocarditis, granulomatous inflammation, acute or recent myocardial infarction, amyloid heart disease, or iron deposition. Figure 3 Endomyocardial biopsy shows no evidence of granulomatous disease. There is diffuse subendocardial myocyte vacuolization suggestive of chronic ischemia thought to be related to demand-related given the tachyarrhythmias and normal coronary arteries. Cardiac Magnetic Resonance (CMR) imaging was performed to find a potential cause of her cardiomyopathy and source of her ventricular tachycardia. CMR demonstrated severe reduction in global systolic function with and LVEF of 24% and RVEF of 20%. There was no myocardial edema on T2 weighted sequences and no evidence of increased myocardial iron deposition. Delayed enhancement images acquired 10 minutes after injection of 0.15 mmol/kg gadolinium demonstrated abnormal enhancement of the thinned myocardium in a near transmural pattern, was most prominent along the basal to mid anterior wall and septum (Figure 4A, B, C). Collectively, the non-coronary distribution, the septal involvement, and the subendocardial sparing were features highly suggestive of a non-ischemic cardiomyopathy and raise the possibility for myocardial infiltration with sarcoid. Figure 4 A Myocardial late gadolinium enhanced imaging of the short axis of the basal myocardium shows myocardium thinning and diffuse transmural late gadolinium enhancement which spares only the inferior and inferolateral segments. Late gadolinium enhancement ... Given the incongruous results of the CMR and endomyocardial biopsy, there was a concern for a false negative biopsy. The patient subsequently underwent a rest 82Rubidium and 18FDG PET study, which demonstrated a medium sized perfusion defect with corresponding 18FDG uptake (i.e., perfusion-metabolic mismatch) involving the mid and basal anterior and anteroseptal walls. In light of the fact that the patient had normal coronary arteries, this PET pattern was highly suspicious for an active inflammatory process (Figure 5). The whole body 18FDG PET study also showed multiple 18FDG avid lymph nodes in the cervical, mediastinal, and subdiaphragmatic regions (Figure 6). Figure 5 Resting 82Rubidium PET myocardial perfusion images showing a perfusion abnormality in the basal to mid anterior and antero septal segments (top row). This defect is matched on 18FDG PET images by focal 18FDG PET avidity in the basal to mid anterior and ... Figure 6 Coronal image from the 18FDG PET study demonstrates 18FDG avid left supra clavicular node and mediastinal nodes (white arrows) and myocardium. Subsequent biopsy of a subcarinal lymph node demonstrated histological features of sarcoidosis (Figure 7). The patient was placed on immunosuppression and an implantable defibrillator was inserted. Figure 7 A and B is a low power image of the lymph node biopsy from a subcarinal lymph node which shows effacement of normal lymph node architecture by well-formed non-necrotizing granulomata. Higher power image in B demonstrates a high power image of the granulomatous ...