Longitudinal Strain Imaging in Light-Chain Cardiac Amyloidosis

Diagnosis and Treatment of Cardiac Amyloidosis Related to Plasma Cell Dyscrasias

Light chain amyloidosis is a deadly disease in which a monoclonal plasma cell dyscrasia produces misfolded immunoglobulin light chains (AL) that aggregate and form rigid amyloid fibrils. The amyloid deposits infiltrate one or more organs, leading to injury and severe dysfunction. The degree of cardiac involvement is a major driver of morbidity and mortality. Early diagnosis and treatment are crucial to prevent irreversible end-organ damage and improve overall survival. Treatment of AL cardiac amyloidosis involves eliminating the underlying plasma cell dyscrasia with chemotherapy and pursuing supportive heart failure management.

Cardiac Imaging in Systemic Diseases: What the Clinician should Know

IMPORTANCE

Systemic diseases that affect the cardiovascular system constitute a diagnostic and therapeutic challenge for all specialists involved; imaging tools along with clinical suspicion play an essential role in their evaluation. These entities share neurological, immunological, renal, hematologic, oncologic, infectious and endocrine processes, all of which may have associated cardiac involvement.

OBSERVATIONS

Recent advances in cardiac ultrasound, Computed Tomography (CT), cardiac Magnetic Resonance (CMR) and nuclear scintigraphy have impacted the management of these conditions when involving the heart since they provide valuable anatomical and functional information while avoiding the use of invasive techniques. For this review, bibliographic sources were gathered from diverse databases, including PubMed, Cochrane, EBSCO and Google Scholar, concentrating on English language publications dealing with the clinical use of these tools.

CONCLUSION

Clinical suspicion should always guide the use of imaging since in many instances, these techniques only play a supportive role rather than representing a diagnostic gold standard. Early diagnosis is critical due to the fact that cardiac manifestations are commonly a late phenomenon.

The Utility of 99mTc-DPD Scintigraphy in the Diagnosis of Cardiac Amyloidosis: An Australian Experience

BACKGROUND

The uptake of bone-seeking radiotracers in the amyloid heart is well recognised. 99^mTc-DPD has been shown to be highly sensitive for cardiac transthyretin (ATTR) amyloid in an overseas population, but is not registered for use in Australia. We explored its utility as a diagnostic tool within our population.

METHODS

Patients diagnosed with AL and ATTR (wild-type and inherited) cardiac amyloidosis were prospectively recruited from the Princess Alexandra Hospital Amyloidosis Centre. Patients underwent injection with ^99mTc-DPD then planar whole body imaging was performed at 5 minutes post-injection (soft tissue phase) and 3 hours (bone phase). A myocardial SPECT and low amperage CT were acquired after the late whole-body scan. Scans were analysed by two nuclear imaging specialists. Intensity of cardiac ^99mTc-DPD uptake was graded as 0 to 3 in accordance with previous criteria, and semiquantitative analysis was performed using a heart to whole body ratio (H:WB) on the 3-hour scan. Patients also underwent electrocardiography and transthoracic echocardiography, and blood samples were taken for troponin I and brain natriuretic peptide levels, to assess for any correlation with DPD uptake.

RESULTS

Twenty-one patients (8 AL and 13 ATTR) completed the study. Median age was 58 and 70 years for AL and ATTR patients respectively, and 19 (90.5%) were male. 99^mTc-DPD scintigraphy was positive in 2 (25%) of AL, and 13 (100%) of ATTR patients. Grade of cardiac uptake, and mean H:WB (0.1249 v. 0.0794) was greater in the ATTR cohort (p-value<0.001 and 0.001 respectively). No statistically significant correlation was identified between H:WB and echocardiographic parameters. There was a significant positive correlation between H:WB and the PR interval on ECG (p=0.026).

CONCLUSIONS

99^mTc-DPD scintigraphy is highly sensitive for the diagnosis of cardiac ATTR amyloid, but less so for AL amyloid.