More Than Meets the Eye: Time for a New Imaging Paradigm to Test for Cardiac Amyloidosis

A compartment-based myocardial density approach helps to solve the native T1 vs. ECV paradox in cardiac amyloidosis

Cardiovascular magnetic resonance (CMR) plays an important clinical role for diagnosis and therapy monitoring of cardiac amyloidosis (CA). Previous data suggested a lower native T1 value in spite of a higher LV mass and higher extracellular volume fraction (ECV) value in wild-type transthyretin amyloidosis (ATTRwt) compared to light-chain amyloidosis (AL)-resulting in the still unsolved "native T1 vs. ECV paradox" in CA. The purpose of this study was to address this paradox. The present study comprised N = 90 patients with ATTRwt and N = 30 patients with AL who underwent multi-parametric CMR studies prior to any specific treatment. The CMR protocol comprised cine- and late-gadolinium-enhancement (LGE)-imaging as well as T2-mapping and pre-/post-contrast T1-mapping allowing to measure myocardial ECV. Left ventricular ejection fraction (LV-EF), left ventricular mass index (LVMi) and left ventricular wall thickness (LVWT) were significantly higher in ATTRwt in comparison to AL. Indexed ECV (ECVi) was also higher in ATTRwt (p = 0.041 for global and p = 0.001 for basal septal). In contrast, native T1- [1094 ms (1069-1127 ms) in ATTRwt vs. 1,122 ms (1076-1160 ms) in AL group, p = 0.040] and T2-values [57 ms (55-60 ms) vs. 60 ms (57-64 ms); p = 0.001] were higher in AL. Considering particularities in myocardial density, "total extracellular mass" (TECM) was substantially higher in ATTRwt whereas "total intracellular mass" (TICM) was rather similar between ATTRwt and AL. Consequently, the "ratio TICM/TECM" was lower in ATTRwt compared to AL (0.58 vs. 0.83; p = 0.007). Our data confirm the presence of a "native T1 vs. ECV paradox" with lower native T1 values in spite of higher myocardial mass and ECV in ATTRwt compared to AL. Importantly, this observation can be explained by particularities regarding myocardial density that result in a lower TICM/TECM "ratio" in case of ATTRwt compared to AL-since native T1 is determined by this ratio.

Diagnosis of Cardiac Involvement in Amyloid A Amyloidosis by Cardiovascular Magnetic Resonance Imaging

Background: Diagnosis of cardiac involvement in amyloid A (AA) amyloidosis is challenging since AA amyloidosis is a rare disease and cardiac involvement even less frequent. The diagnostic yield of currently available non-invasive imaging methods is not well-studied and rather limited, and invasive endomyocardial biopsy (EMB) is rarely performed due to the potential risk of this procedure. Cardiovascular magnetic resonance (CMR)-based myocardial tissue characterization by late-gadolinium-enhancement (LGE) imaging and novel-mapping approaches may increase the diagnostic yield in AA amyloidosis.

Methods: Two patients with AA amyloidosis in whom cardiac involvement was suspected based on CMR findings and subsequently proven by biopsy work-up are presented. CMR studies were performed on a 1.5-T system and comprised a cine steady-state free precession pulse sequence for ventricular function and a late-gadolinium-enhancement (LGE) sequence for detection of myocardial pathology. Moreover, a modified Look-Locker inversion recovery (MOLLI) T1-mapping sequence was applied in basal, mid and apical short-axes prior to contrast agent administration and ~20 min thereafter to determine native T1 and ECV values.

Results: Both patients showed slightly dilated left ventricles (LV) with mild to moderate LV hypertrophy and preserved systolic function. Only a very subtle pattern of LGE was observed in both patients with AA amyloidosis. However, markedly elevated native T1 (max. 1,108 and 1,112 ms, respectively) and extracellular volume fraction (ECV) values (max. 39 and 48%, respectively) were measured in the myocardium suggesting the presence of cardiac involvement - with subsequent EMB-based proof of AA amyloidosis.

Conclusion: We recommend a multi-parametric CMR approach in patients with AA amyloidosis comprising both LGE-based contrast-imaging and T1-mapping-based ECV measurement of the myocardium for non-invasive work-up of suspected cardiac involvement. The respective CMR findings may be used as gatekeeper for additional invasive procedures (such as EMB) and as a non-invasive monitoring tool regarding assessment and modification of ongoing treatments.

Diagnostic performance of CMR, SPECT, and PET imaging for the detection of cardiac amyloidosis: a meta-analysis

Background

Noninvasive myocardial imaging modalities, such as cardiac magnetic resonance (CMR), single photon emission computed tomography (SPECT), and Positron emission tomography (PET), are well-established and extensively used to detect cardiac amyloid (CA). The purpose of this study is to directly compare CMR, SPECT, and PET scans in the diagnosis of CA, and to provide evidence for further scientific research and clinical decision-making.

Methods

PubMed, Embase, and Cochrane Library were searched. Studies used CMR, SPECT and/or PET for the diagnosis of CA were included. Pooled sensitivity, specificity, positive and negative likelihood ratio (LR), diagnostic odds ratio (DOR), their respective 95% confidence intervals (CIs) and the area under the summary receiver operating characteristic (SROC) curve (AUC) were calculated. Quality assessment of included studies was conducted.

Results

A total of 31 articles were identified for inclusion in this meta-analysis. The pooled sensitivities of CMR, SPECT and PET were 0.84, 0.98 and 0.78, respectively. Their respective overall specificities were 0.87, 0.92 and 0.95. Subgroup analysis demonstrated that ^99mTc-HMDP manifested the highest sensitivity (0.99). ^99mTc-PYP had the highest specificity (0.95). The AUC values of ^99mTc-DPD, ^99mTc-PYP, ^99mTc-HMDP were 0.89, 0.99, and 0.99, respectively. PET scan with ¹¹C-PIB demonstrated a pooled sensitivity of 0.91 and specificity of 0.97 with an AUC value of 0.98.

Conclusion

Our meta-analysis reveals that SEPCT scans present better diagnostic performance for the identification of CA as compared with other two modalities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02292-z.

Prevalence of transthyretin amyloid cardiomyopathy in male patients who underwent bilateral carpal tunnel surgery: The ACTUAL study

INTRODUCTION

Bilateral carpal tunnel syndrome (CTS), particularly in male individuals with left ventricular hypertrophy (LVH), has been recognized as a red flag for transthyretin cardiac amyloidosis (TTR-CA). Nonetheless, the opportunity of screening CTS patients for TTR has yet to be determined.

METHODS

Medical records of 1689 CTS surgeries performed at our institution between 2008 and 2018 were reviewed. Eighty-three males who underwent bilateral CTS surgery were considered eligible for the study, and offered a screening examination including electrocardiography and echocardiography. Individuals with LVH (diastolic septal wall thickness > 12 mm) were offered second-line diagnostic testing including blood testing and bone scintigraphy.

RESULTS

Study population consisted of 53 bilateral CTS male patients, with median age of 73 years. LVH was found in 6 (11%) individuals. None of them had monoclonal gammopathy or reported CTS occupational risk factors. Two declined to undergo further testing, whereas 2 had negative and 2 had positive bone scintigraphy (both Perugini 2 uptake) and tested negative for TTR gene mutations (wild-type TTR-CA).

CONCLUSIONS

Prevalence of TTR-CA in the entire study population was 4%, but among bilateral CTS patients with LVH peaked at 33%. In this latter population, screening for TTR-CA appeared feasible and effective.

Estimating cancer risk from 99mTc pyrophosphate imaging for transthyretin cardiac amyloidosis

BACKGROUND

Increasing recognition that transthyretin cardiac amyloidosis (ATTR-CA) is much more common than previously appreciated and the emergence of novel disease-modifying therapeutic agents have led to a paradigm shift in which ATTR-CA screening is considered in high-risk populations, such as patients with heart failure with preserved ejection fraction (HFpEF) or aortic stenosis. Radiation risk from 99mTc-pyrophosphate (99mTc-PYP) scintigraphy, a test with very high sensitivity and specificity for ATTR-CA, has not been previously determined.

METHODS AND RESULTS

Radiation doses to individual organs from 99mTc-PYP were estimated using models developed by the Medical Internal Radiation Dose Committee and the International Commission on Radiological Protection. Excess future cancer risks were estimated from organ doses, using risk projection models developed by the National Academies and extended by the National Cancer Institute. Excess future risks were estimated for men and women aged 40-80 and compared to total (excess plus baseline) future risks. All-organ excess cancer risks (90% uncertainty intervals) ranged from 5.88 (2.45,11.4) to 12.2 (4.11,26.0) cases per 100,000 patients undergoing 99mTc-PYP testing, were similar for men and women, and decreased with increasing age at testing. Cancer risks were highest to the urinary bladder, and bladder risk varied nearly twofold depending on which model was used. Excess 99mTc-PYP-related cancers constituted < 1% of total future cancers to the critical organs.

CONCLUSION

Very low cancer risks associated with 99mTc-PYP testing suggest a favorable benefit-risk profile for 99mTc-PYP as a screening test for ATTR-CA in high-risk populations, such as such as patients with HFpEF or aortic stenosis.

Molecular and clinical insights into protein misfolding and associated amyloidosis

The misfolding of normally soluble proteins causes their aggregation and deposition in the tissues which disrupts the normal structure and function of the corresponding organs. The proteins with high β-sheet contents are more prone to form amyloids as they exhibit high propensity of self-aggregation. The self aggregated misfolded proteins act as template for further aggregation that leads to formation of protofilaments and eventually amyloid fibrils. More than 30 different types of proteins are known to be associated with amyloidosis related diseases. Several aspects of the amyloidogenic behavior of proteins remain elusive. The exact reason that causes misfolding of the protein and its association into amyloid fibrils is not known. These misfolded intermediates surpass the over engaged quality control system of the cell which clears the misfolded intermediates. This promotes the self-aggregation, accumulation and deposition of these misfolded species in the form of amyloids in the different parts of the body. The amyloid deposition can be localized as in Alzheimer disease or systemic as reported in most of the amyloidosis. The amyloidosis can be of acquired type or familial. The current review aims at bringing together recent updates and comprehensive information about protein amyloidosis and associated diseases at one place.

Diagnosis of cardiac amyloidosis: a systematic review on the role of imaging and biomarkers

BACKGROUND

Cardiac Amyloidosis (CA) pertains to the cardiac involvement of a group of diseases, in which misfolded proteins deposit in tissues and cause progressive organ damage. The vast majority of CA cases are caused by light chain amyloidosis (AL) and transthyretin amyloidosis (ATTR). The increased awareness of these diseases has led to an increment of newly diagnosed cases each year.

METHODS

We performed multiple searches on MEDLINE, EMBASE and the Cochrane Database of Systematic Reviews. Several search terms were used, such as "cardiac amyloidosis", "diagnostic modalities cardiac amyloidosis" and "staging cardiac amyloidosis". Emphasis was given on original articles describing novel diagnostic and staging approaches to the disease.

RESULTS

Imaging techniques are indispensable to diagnosing CA. Novel ultrasonographic techniques boast high sensitivity and specificity for the disease. Nuclear imaging has repeatedly proved its worth in the diagnostic procedure, with efforts now focusing on standardization and quantification of amyloid load. Because the latter would be invaluable for any staging system, those spearheading research in magnetic resonance imaging of the disease are also trying to come up with accurate tools to quantify amyloid burden. Staging tools are currently being developed and validated for ATTR CA, in the spirit of the acclaimed Mayo Staging System for AL.

CONCLUSION

Cardiac involvement confers significant morbidity and mortality in all types of amyloidosis. Great effort is made to reduce the time to diagnosis, as treatment in the initial stages of the disease is tied to better prognosis. The results of these efforts are highly sensitive and specific diagnostic modalities that are also reasonably cost effective.