Bone scintigraphy imaging of cardiac amyloidosis

Case Report and Literature Review of Cardiac Amyloidosis: A Not-So-Rare Cause of Heart Failure

Restrictive cardiomyopathy secondary to cardiac amyloidosis is an underdiagnosed cause of heart failure and it is associated with significant morbidity and mortality. The most common types of amyloidosis are light chain amyloidosis, transthyretin amyloidosis and secondary amyloidosis. We report the case of a 84-year-old man that presented with new onset signs and symptoms of heart failure. Multimodality imaging with echocardiogram and bone tracer cardiac scintigraphy along with biomarkers, monoclonal proteins analysis and genetic test allowed to diagnosed a wild-type transthyretin amyloidosis. We discuss the clinical and diagnostic features and review the current literature about cardiac amyloidosis. This paper aims to increase clinicians' awareness of cardiac amyloidosis to promptly recognize, diagnose and treat it.

AL-Type Amyloidosis Involving Stomach and Lungs in 99m Tc-DPD Bone Scan

ABSTRACT

Systemic AL (amyloid light-chain) amyloidosis is a relatively rare disease. 99m Tc-DPD (3,3-diphosphono-1,2-pyrophosphate) bone scan is a highly sensitive diagnostic tool for cardiac amyloidosis of ATTR (transthyretin) type. In AL amyloidosis, there have been some previous reports of extracardiac DPD uptake in liver, kidney, and spleen, but not in stomach. We present 99m Tc-DPD bone scan images of AL-type amyloidosis involving stomach and lung.

Estimation of prevalence of transthyretin (ATTR) cardiac amyloidosis in an Australian subpopulation using bone scans with echocardiography and clinical correlation

BACKGROUND

Bone scans differentiate transthyretin (ATTR) cardiac amyloidosis from light chain amyloidosis and other causes of increased left ventricular (LV) wall thickness. We examined the prevalence and implications of cardiac uptake in the general population.

METHODS

Patients were included based on having undertaken a bone scan for non-cardiac indications using Technetium 99m hydroxymethylene diphosphonate (HMDP) or Technetium 99m methylene diphosphonate (MDP). Blinded image review was undertaken. Positive was defined as cardiac uptake ≥ rib AND heart/whole body ratio (H/WB) > 0.0388. Echocardiography and clinical records were reviewed.

RESULTS

6918 patients were included. 15/3472 HMDP scans were positive (14 males, 1 female): none in individuals aged < 65; 1.44% in males and 0.17% in females ≥ 65; 6.15% in males and 1.69% in females ≥ 85. Only 1/3446 MDP scans were positive. All HMDP positive patients had increased septal wall thickness on echocardiography. H/WB correlated positively with LV mass, and negatively with LV ejection fraction. No individual had an explanation other than ATTR for their positive scan.

CONCLUSION

In this Australian subpopulation, the prevalence of positive bone scans consistent with cardiac ATTR is 0% in individuals aged < 65. Prevalence increased with age, reaching 6.15% in men ≥ 85. The amount of HMDP uptake correlated with echocardiographic features of more advanced cardiac involvement. MDP does not appear useful in ATTR.

Diagnosis and treatment of transthyretin-related amyloidosis cardiomyopathy

Transthyretin-related amyloidosis (ATTR) is a subgroup of amyloidosis that results from extracellular misassembled and toxic amyloid deposits affecting multiple organ systems, and cardiac tissues in particular. Because ATTR often presents as heart failure with preserved ejection fraction (HFpEF), it has been largely underdiagnosed. Once considered incurable with a grave prognosis, ATTR cardiomyopathy has seen the development of promising alternatives for diagnosis and treatment, with early diagnosis and treatment of ATTR cardiomyopathy highly beneficial due to its high mortality rate. For instance, diagnosing ATTR cardiomyopathy previously required a cardiac biopsy, but new modalities, such as cardiac magnetic resonance imaging and radionuclide bone scans, show promise in accurately diagnosing ATTR cardiomyopathy. Ongoing research and clinical trials have focused on identifying new treatments which primarily target amyloid fiber formation by inhibiting TTR gene expression, stabilizing the TTR tetramer, preventing oligomer aggregation, or affecting degradation of amyloid fibers. In this review, we describe the advances made in the diagnosis and treatment of ATTR in order to increase awareness of the disease and encourage a lower threshold for ATTR workup. Our review also highlights the need for improving the screening, diagnosis, and treatment guidelines for ATTR cardiomyopathy.

[Suspected cardiac amyloidosis - diagnostic steps for evaluation]

Cardiac amyloidosis is a rare cause of cardiomyopathy, however, it is part of an underdiagnosed underlying systemic disease. For transthyretin (ATTR) amyloidosis, which is caused by the deposition of incorrectly folded transthyretin, either as the wild-type (wtATTR) or mutated (mATTR) form, novel evidence-based treatment options were recently shown to reduce disease progression as well as hospitalisation rates for heart failure. Thus, it is important to establish early and reliable diagnosis of cardiac involvement with ATTR amyloidosis.Modern non-invasive imaging (cardio magnetic resonance (CMR) and scintigraphic methods) together with immune fixation with determination of free light chains allow fast and reliable clinical screening for cardiac amyloidosis, whereas endomyocardial biopsy and genetics are used for confirmation of the underlying diagnosis. Interdisciplinary teams including hemato-oncology, neurology, nephrology in addition to cardiology are essential to enable personalized targeted treatment strategies.

Incidentally detected cardiac amyloidosis on 99mTc-MDP bone scintigraphy

Cardiac amyloidosis (CA) is an important cause of restrictive cardiomyopathy and heart failure with preserved ejection fraction (HFpEF). At present, 3 bone-seeking tracers, ^99mTc-diphosphono-1,2-propanodicarboxylic acid (^99mTc-DPD), ^99mTc-pyrophosphate (^99mTc-PYP), and ^99mTc-hydroxymethylene diphosphonate (^99mTc-HMDP), have been evaluated for detecting CA, but they are not widely available. In contrast, methylene diphosphate (MDP) is widely available. However, only sporadic case reports have shown that MDP can accumulate in patients with CA. We report an 86-year-old man with multiple medical problems, including hypertension, hyperlipidemia, HFpEF, and a history of treated prostate cancer, who was referred for a ^99mTc-MDP bone scan to rule out bone metastasis. The bone scan was negative for bone metastasis, but there was mild tracer accumulation in the heart, suggestive of CA. Subsequently, CA was diagnosed on ^99mTc-PYP imaging. MDP may play a role comparable to other bone-seeking tracers in the diagnosis of CA and may be used as a noninvasive adjunct in the diagnosis of CA. Future research should compare MDP with other bone-seeking tracers for the diagnosis of CA. In addition, mechanistic studies on tracer binding to amyloid fibrils may help understand the pathophysiology of CA and facilitate the development of better and more specific tracers for CA.