Extensive cardiac FDG uptake in a patient with AL amyloidosis

A 44-year-old male patient presented to cardiology outpatients with chest pain when cycling in the past 3 months. The pain was radiating to jaw and induced particularly on inclines. He was a fit and active person, non-smoker, teetotal, with no family history of coronary artery disease or other risk factors. The ECG showed sinus rhythm, up to 2 mm ST depressions in the lateral leads and high voltage suggestive of left ventricular (LV) hypertrophy (Figure 1). Troponin-T level was significantly raised at 1431 ng/mL. The coronary arteries were normal on angiogram and initial echocardiography showed normal biventricular systolic function and bicuspid aortic valve with mildly thickened leaflets. He was treated for myopericarditis during admission and discharged with cardiovascular magnetic resonance (CMR) planned as an outpatient.

Figure 1figure 1

12-lead ECG at presentation shows sinus rhythm at 69 bpm, ST depressions in the precordial leads V5–V6, high voltage suggestive of LV hypertrophy and a ventricular ectopic beat

Following discharge, troponin levels continued to be constantly elevated (serial troponins-1041, 731, 875, 938, 2516, and 1542 ng/mL) and patient experienced persistent exertional angina. Infectious screen, autoimmune screen (including ANCA, Ro, La, Sm, RNP, Jo-1, Scl70, dsDNA, centromere, Mi2, Ku, Tho/To, RNA polymerase III, PM-Scl, PCNA, ribosomal p protein) and lupus screen were negative. CMR showed moderately thickened interventricular septum, impaired longitudinal function with preserved LV ejection fraction (EF) of 61%, and bicuspid aortic valve with mild stenosis (cine images on supplementary movies 1–4). Native T1 values were elevated (1116 ms at 1.5 T, Figure 2 panel A) and late gadolinium (LGE) study demonstrated near circumferential subendocardial enhancement which was more prominent at the basal level (Figure 2 panel B). Edema imaging was not performed on this study.

Figure 2figure 2

A shows short axis T1 mapping image with significantly elevated values, 1116 ms at 1.5 T. Late gadolinium enhancement images on B demonstrate mild near circumferential subendocardial enhancement more prominent at the basal level

Within 8 months of presentation, patient developed NHYA Class II-III heart failure symptoms in addition to continuing central, left sided exertional chest pain. He also experienced occasional nocturnal palpitations and reported pins and needles in hands but no specific joint pains or rash. He was commenced on standard heart failure treatment with Bisoprolol 10 mg/day, Ramipril 10 mg/day, Eplerenone 50 mg, Furosemide 40 mg/day. On repeat CMR study LV function deteriorated to moderately reduced ejection fraction (42%) with dilated left ventricle (end diastolic volume 110 mL/m2), functional mitral regurgitation, and bilateral pleural effusions were seen. Native T1 values also further increased (1223 ms) compared to the previous study. LGE showed dense circumferential subendocardial enhancement at all levels and mid-wall involvement in the septum (Figure 3). Edema imaging was not diagnostic on this study due to difficulty in breath holding. The CMR findings were not typical of myocarditis, and he was referred to our tertiary center for further investigation of inflammatory cardiac conditions. Myocardial vasculitis was the working diagnosis of the referring center. Local FDG PET-CT scan was performed to exclude vasculitis (with 8 h of fast) and showed no evidence of large vessel vasculitis. However, there was diffusely increased FDG uptake in the LV and the RV. Local rheumatology review concluded that clinical presentation was not consistent with vasculitis, but empirical steroids (Prednisolone 30 mg/day) were trialed, and patient felt much better, angina settled and persistently elevated troponin values slightly improved.

Figure 3figure 3

LGE images of follow up CMR study 5 months after the initial scan show progressive infiltration with dense circumferential subendocardial LGE enhancement at all levels as well as mid-wall LGE in the septum. The LV function deteriorated, LV dilated, and native T1 values further increased compared to the previous study

Case was discussed in multi-disciplinary team of Royal Brompton Hospital. A full vasculitis workup, repeat FDG PET-CT with dedicated cardiac protocol and a myeloma screen with free light chains to rule out AL amyloid was recommended. FDG PET-CT was performed after no carbohydrate diet for 24 h and 18 h of fast. Scan showed moderate global and homogenous FDG uptake in the left ventricular myocardium with SUV max of 5.3. The intensity of FDG uptake was reduced when compared to the previous local study (previously SUVmax was15.0 in the septum). No significant FDG uptake was seen in the right ventricle or atria which was previously noted. Low grade FDG uptake was reported in muscles in the pelvis, upper thighs, shoulders, and upper arms. There was also intensive uptake in the anterior part of the soft palate and the tongue of uncertain significance. There were no FDG avid lymph nodes and no uptake in the lung parenchyma, liver spleen or abdomen (Figure 4). Concomitant 82Rb myocardial perfusion scintigraphy showed reduced viability in the septum and basal inferolateral regions with reduced resting myocardial blood flow (Figure 5). Homogenous active inflammation in the entire LV myocardium with reduced intensity compared to the previous study and resolved inflammation in the RV myocardium and atria were interpreted as favorable response to steroid therapy.

Figure 4figure 4

Half body FDG PET/CT study with strict cardiac diet preparation shows intense LV myocardial uptake not typical of cardiac inflammatory conditions or myocardial vasculitis

Figure 5figure 5

Resting 82Rb myocardial blood flow quantification shows significantly reduced flow suggestive of microvascular ischemia

Follow up echocardiography at this stage reported mildly dilated LV with moderate-severely impaired systolic function. EF was 35% by Biplane method and a global longitudinal strain (GLS) was significantly reduced at − 7.5% with apical sparing pattern (Figure 6). Wall thickness was moderately increased and there was restrictive filling pattern. Right ventricle (RV) was normal sized with preserved longitudinal function but reduced radial function and mildly thickened free wall. Both atria were dilated.

Figure 6figure 6

Echocardiography after presentation with heart failure showed dilated left ventricle, significantly reduced EF and apical sparing strain pattern typical of cardiac amyloidosis

There were delays due to Covid-19 pandemic. When investigations were eventually performed in the following 6 months the free serum lambda chain titer was very high. He underwent a bone marrow biopsy which showed 20–30% lambda restricted plasma cell infiltration with a neoplastic phenotype and presence of t(11;14) translocation. Congo-red positive amyloid deposits were typed at the UK National amyloidosis as AL lambda. He also had an abdominal fat biopsy which confirmed amyloid deposits of AL type. He was diagnosed with stage IIIb cardiac AL amyloidosis with lambda light chain myeloma.

Meanwhile the LV dysfunction progressed, and he developed arrythmias. Bisoprolol was changed to Amiodarone and Ramipril was discontinued due to hypotension and renal impairment with CKD grade 3. He was admitted locally for chemotherapy initiation and experienced in hospital ventricular fibrillation arrest followed by pulseless electrical activity. After successful resuscitation ICD was implanted and he was commenced on Cyclophosphamide, Bortezomib, and Dexamethasone chemotherapy. He also underwent cardiac transplant assessment but was declined due to renal failure. He unfortunately passed away at home two weeks after chemotherapy initiation.

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