Apical sparing pattern of left ventricular myocardial 99mTc-HMDP uptake in patients with transthyretin cardiac amyloidosis

Global and Regional Variations in Transthyretin Cardiac Amyloidosis: A Comparison of Longitudinal Strain and 99mTechnetium Pyrophosphate Imaging

Background: There is limited data on the head-to-head comparison of ^99mTc-pyrophosphate (PYP) and echocardiographic strain imaging in the assessment of transthyretin (TTR) cardiac amyloidosis. Methods: At Mayo Clinic Arizona, patients that had undergone both a ^99mTc-PYP scan and transthoracic echocardiogram (TTE) within a 90-day period were retrospectively identified for chart review and strain imaging analysis. Patients were divided into two groups according to their ^99mTc-PYP results (PYP+ and PYP -) for the comparison. A standard 17-segment model was used for segmental, regional and global longitudinal strain comparison. A p-value of <0.05 was deemed as significant. Results: A total of 64 patients were included, the mean age was 75.1 ± 13.0 years and 57(89.1%) were male. Comparing the PYP+ to the PYP- group, the left ventricular global longitudinal strain was significantly worse (PYP+ vs. PYP-: -10.5 ± 2.6 vs. -13.1 ± 4.1, P = 0.003). PYP+ patients also had worse regional basal strain (-4.6 ± 2.6 vs. -8.8±4.0, p<0.001) and a trend of worse mid-ventricular strain (-9.6 ± 4.0 vs. -11.7± 4.4, P = 0.07), however, no statistical difference in apical region (-17.6 ± 4.73 vs. -19.0 ± 6.46, P = 0.35). This is consistent with an apical sparing pattern shown by the relative apical longitudinal strain index (1.3 ±0.5 vs. 1.0 ± 0.3, P = 0.008). Segment to segment analysis demonstrated significant difference in strain between PYP+ and PYP- segments in 4 segments: basal inferior (P = 0.006), basal anterolateral (P = 0.01), apical septal (P = 0.002) and apical inferior (P = 0.001). Left ventricular diastolic dysfunction was significantly different with 17 (77.3%) patients in group PYP+ versus 15 (36.6%) in PYP- participants (P = 0.002). Conclusion: Our study suggested that PYP uptake is related to overall worse LV segmental, regional and global longitudinal strain function, as well as diastolic function compared to patients without PYP uptake. This provides important data for clinicians to know the echocardiographic function features related to ^99mTc-PYP uptake and can serve as a hypothesis-generating study for future investigators.

Diagnostic Work-Up of Cardiac Amyloidosis Using Cardiovascular Imaging: Current Standards and Practical Algorithms

Among non-ischemic cardiomyopathies, cardiac amyloidosis is one of the most common, being caused by extracellular depositions of amyloid fibrils in the myocardium. Two main forms of cardiac amyloidosis are known so far, including 1) light-chain (AL) amyloidosis caused by monoclonal production of light-chains, and 2) transthyretin (ATTR) amyloidosis, caused by dissociation of the transthyretin tetramer into monomers. Both AL and ATTR amyloidosis are progressive diseases with median survival from diagnosis of less than 6 months and 3 to 5 years, respectively, if untreated. In this regard, death occurs in most patients due to cardiac causes, mainly congestive heart failure, which can be prevented due to the presence of effective, life-saving treatment regimens. Therefore, early diagnosis of cardiac amyloidosis is crucial more than ever. However, diagnosis of cardiac amyloidosis may be challenging due to variable clinical manifestations and the perceived rarity of the disease. In this regard, clinical and laboratory reg flags are available, which may help clinicians to raise suspicion of cardiac amyloidosis. In addition, advances in cardiovascular imaging have already revealed a higher prevalence of cardiac amyloidosis in specific populations, so that the diagnosis especially of ATTR amyloidosis has experienced a >30-fold increase during the past ten years. The goal of our review article is to summarize these findings and provide a practical approach for clinicians on how to use cardiovascular imaging techniques, such as echocardiography, cardiac magnetic resonance, bone scintigraphy and, if required, organ biopsy within predefined diagnostic algorithms for the diagnostic work-up of patients with suspected cardiac amyloidosis. In addition, two clinical cases and practical tips are provided in this context.

18F-sodium fluoride PET/MRI myocardial imaging in patients with suspected cardiac amyloidosis

BACKGROUND

We evaluated the diagnostic performance of 18F-NaF PET/MRI in patients with suspected cardiac amyloidosis (CA).

METHODS

Twenty-seven consecutive patients underwent myocardial PET 1 hour after injection of 4 MBq/kg 18F-NaF with simultaneous MRI including cine-MRI, T1 and T2 mapping, first-pass and late gadolinium enhancement (LGE). 18F-NaF uptake was measured visually and semi-quantitatively by calculating myocardium-to-blood pool (M/B) ratios. CA was confirmed histologically.

RESULTS

Transthyretin (TTR)-CA was diagnosed in 16 patients, light-chain (AL)-CA in 7, and no-CA in 4. Visual interpretation of 18F-NaF images revealed a relative increase in myocardial uptake in only 3 patients, all with TTR CA, and a relative decrease in 13, including 7 AL CA, 3 no-CA, and 3 TTR CA. M/B ratios were significantly higher in TTR CA (1.00 ± 0.12) than in AL CA (0.81 ± 0.06, P = 0.001) or in no-CA (0.73 ± 0.16, P = 0.006). The optimal M/B cut-off to distinguish TTR CA from AL CA was ≥ 0.90 (Fischer, P = 0.0005). By comparison, classification of patients using 99mTc-HMDP heart-to-mediastinum ratios with the previously published cut-off ≥ 1.21 reached higher significance (P < 0.0001). Among MRI parameters, myocardial T1, LGE score, and extracellular volume were higher in CA than in no-CA patients, 1409 ± 76 vs 1278 ± 35 ms (P = 0.004), 10.35 ± 5.30 vs 3.50 ± 3.42 (P = 0.03), and 46 ± 10 vs 33 ± 8 % (P = 0.01), respectively.

CONCLUSION

18F-NaF PET/MRI shows good diagnostic performance when semi-quantification is used. However, contrast is low and visual interpretation may be challenging in routine. PET/MRI could constitute a one-stop-shop evaluation of amyloid load and cardiac function in patients needing rapid work-up.

Cardiac Amyloidosis: Diagnostic Tools for a Challenging Disease

Amyloidosis is a group of diseases in which amyloid fibrils build up in tissues, leading to organ dysfunction. Cardiac involvement is observed in immunoglobulin light chain amyloidosis (AL) and transthyretin amyloidosis (ATTR) and, when it occurs, the prognosis worsens. Cardiac tissue infiltration can lead to restrictive cardiomyopathy with clinical signs of diastolic heart failure, without reduction of ejection fraction (HFpEF). The aim of multiple and less invasive diagnostic tests is to discern peculiar characteristics and reach the diagnosis without performing an invasive endomyocardial biopsy. These diagnostic tools allow early diagnosis, and they are crucial to best benefit from target therapy. In this review article, we describe the mechanism behind amyloid fibril formation, infiltration of tissues, and consequent clinical signs, focusing on the diagnostic tools and the red flags to obtain a diagnosis.

The Role of Multi-modality Imaging in the Diagnosis of Cardiac Amyloidosis: A Focused Update

Cardiac amyloidosis (CA) is a unique disease entity involving an infiltrative process, typically resulting in a restrictive cardiomyopathy with diastolic heart failure that ultimately progresses to systolic heart failure. The two most common subtypes are light-chain and transthyretin amyloidosis. Early diagnosis of this disease entity, especially light-chain CA subtype, is crucial, as it portends a poorer prognosis. This review focuses on the clinical utility of the various imaging modalities in the diagnosis and differentiation of CA subtypes. This review also aims to highlight the key advances in each of the imaging modalities in the diagnosis and prognostication of CA.

Pattern of myocardial 99mTc-HMDP uptake and impact on myocardial function in patients with transthyretin cardiac amyloidosis

AIMS

The purpose of the study was to describe the pattern of 99mTc-labeled phosphate agents myocardial uptake by scintigraphy and explore its impact on left ventricular (LV) functions in transthyretin cardiac amyloidosis (TTR-CA).

METHODS

Fifty patients with TTR-CA underwent 99mTc- hydroxymethylene-diphosphonate (99mTc-HMDP) scintigraphy and echocardiography with measure of LV thickness, longitudinal strain (LS), systolic and diastolic functions. Cardiac retention by scintigraphy was assessed by visual scoring and the heart/whole body (H/WB) ratio was calculated by dividing counts in the heart by counts in late whole-body images.

RESULTS

The mean population age was 79 ± 10 years. Mean H/WB ratio was 12 ± 7. Myocardial 99mTc-HMDP uptake on segments 5, 6, 7, 8, 11, 12, 13, 14, 16, and 17 was correlated with H/WB ratio. Mean LVEF and global LS were 51 ± 10% and - 10 ± 3%, respectively. H/WB ratio was correlated with global LS (R = 0.408, P = .003), Ea (R = - 0.566, P < .001) and mean left ventricular wall thickness (R = 0.476, P < .001) but not with LVEF (R = - 0.109, P = .453). Segmental myocardial uptake was slightly correlated with segmental LS (R = 0.152, P < .001). H/WB ratio was not correlated with NT-proBNP levels (R = 0.219, P = .148) neither E/Ea ratio (R = 0.204, P = .184).

CONCLUSION

These findings show the relationship between bone tracer myocardial uptake and LV functions in patients with TTR cardiac amyloidosis.

Quantification of myocardial 99mTc-labeled bisphosphonate uptake with cadmium zinc telluride camera in patients with transthyretin-related cardiac amyloidosis

PURPOSE

We aimed to compare different methods for semi-quantitative analysis of cardiac retention of bone tracers in patients with cardiac transthyretin amyloidosis (ATTR).

METHODS

Data from 67 patients with ATTR who underwent both conventional whole-body scan and a CZT myocardial SPECT (DSPECT, Spectrum Dynamics) 3 h after injection of ^99mTc-labeled bone tracer were analyzed. Visual scoring of cardiac retention was performed on whole-body scan according to Perugini 4-point grading system from 0 (no uptake) to 3 (strong cardiac uptake with mild/absent bone uptake). A planar heart-to-background (H:B) ratio was calculated using whole-body scan (wb-H:B). CZT SPECT was quantified using three methods: planar H:B ratio calculated from anterior reprojection (ant-H:B), left anterior oblique reprojection (LAO-H:B), and 3D-H:B ratio calculated from transaxial slices as mean counts in a VOI encompassing the heart divided by background VOI in the contralateral lung. Interventricular septal thickness was obtained using echocardiography.

RESULTS

H:Bs obtained from planar and reprojected data were not statistically different (wb-H:B, 2.05 ± 0.64, ant-H:B, 1.97 ± 0.61, LAO-H:B, 2.06 ± 0.64, all p = ns). However, 3D-H:B was increased compared to planar H:Bs (3D-H:B, 4.06 ± 1.77, all p < 0.0001 vs. wb-H:B, ant-H:B, and LAO-H:B). Bland-Altman plots demonstrated that the difference between 3D and planar H:Bs increased with the mean value of myocardial uptake. 3D-H:B was best correlated to septal thickness (r = 0.45, p < 0.001). Finally, abnormal right ventricular uptake was associated with higher values of cardiac retention.

CONCLUSION

3D semi-quantitative analysis of CZT SPECT optimized the assessment of ^99mTc-labeled bone tracer myocardial uptake in patients with cardiac amyloidosis.

Analogies and disparities among scintigraphic bone tracers in the diagnosis of cardiac and non-cardiac ATTR amyloidosis

In this issue of JNC, BW Spery and Coll report a retrospective analysis of 57 patients with transthyretin-related amyloidosis (ATTR) in an advanced phase of the disease who underwent 99mTechnetium-pyrophosphate (99mTcPYP) scintigraphy. Although relatively small and "negative," the study is relevant since it broadens our knowledge on the uptake of "bone tracers" in ATTR and contributes to understand the limitations of the clinical use of scintigraphy in this disease. The paper raises, directly or indirectly, at least three questions: To what extent are the different bone tracers interchangeable for the diagnosis of ATTR cardiac amyloidosis? Are bone tracers able to image non-cardiac ATTR amyloidosis? What is the explanation for the variable performance of the different bone tracers in the diagnosis of cardiac and extracardiac ATTR amyloidosis?

Base-to-apex gradient pattern of cardiac impairment identified on myocardial T1 mapping in cardiac amyloidosis

Late gadolinium enhancement imaging by cardiac magnetic resonance imaging (CMR) is the most reliable method for identifying cardiac involvement in patients with amyloidosis, and myocardial T1 mapping is a novel CMR technique that enables the noninvasive detection and quantification of myocardial amyloid burden. Although, base-to-apex gradient patterns of impairment in patients with cardiac amyloidosis have been reported on myocardial strain analysis using echocardiography, we could not find any other reports to demonstrate that myocardial T1 mapping on CMR can clearly identify a base-to-apex gradient pattern of cardiac impairment in a patient with cardiac amyloidosis.

Role of cardiovascular imaging for the diagnosis and prognosis of cardiac amyloidosis

Cardiac amyloidosis (CA) describes the pathological process of amyloid protein deposition in the extracellular space of the myocardium. Unfortunately, the diagnosis of CA is often made late and when the disease process is advanced. However, advances in cardiovascular imaging have allowed for better prognostication and establishing diagnostic pathways with high sensitivity and specificity. This review discusses the role of echocardiography, cardiac MRI and nuclear cardiology in current clinical practice for diagnosis and prognosis of CA.

Simplified apical four-chamber view evaluation of relative apical sparing of longitudinal strain in diagnosing AL amyloid cardiomyopathy

AIM OF THE STUDY

To assess the diagnostic utility of a simplified approach to relative apical sparing of longitudinal strain (RAS LS) using only an apical four-chamber view (A4C) in patients with AL amyloid cardiomyopathy (ALAC).

METHODS

We retrospectively evaluated echocardiographic recordings of 20 patients with ALAC, 20 patients with Fabry disease-related cardiomyopathy (FD), and 20 patients with concentric hypertensive left ventricular hypertrophy (HLVH) matched for mean LV mean thickness. Peak segmental LS values of the interventricular septum and lateral LV wall were measured in the A4C using two-dimensional speckle-tracking echocardiography. RAS LS was calculated as average apical LS/(average basal LS + average midventricular LS).

RESULTS

Relative apical sparing of longitudinal strain values in patients with ALAC (1.23 ± 0.64) were significantly higher than those in FD patients (0.75 ± 0.19, P < 0.05) as well as in individuals with HLVH (0.75 ± 0.23, P < 0.05), but with a significant overlap. The optimal RAS LS value differentiating ALAC from FD and HLVH with 70% sensitivity and 75% specificity was 0.88 (AUC 0.79). In multivariate modeling, RAS LS was significantly additive to traditional predictors of ALAC (low QRS voltage and pseudoinfarct ECG patterns, pericardial effusion, E/e' ratio, E-wave deceleration time; P < 0.05 for all models).

CONCLUSIONS

Simplified RAS LS evaluation represents an attractive approach for diagnostics of ALAC. However, because of considerable overlap with other disorders with hypertrophic phenotype, the analysis of RAS LS in the A4C should be combined with other traditional echocardiographic and ECG predictors in differentiating ALAC from other forms of concentric LV wall thickening.

Diagnostic accuracy of bone scintigraphy in the assessment of cardiac transthyretin-related amyloidosis: a bivariate meta-analysis

PURPOSE

Cardiac transthyretin-related amyloidosis (ATTR) is a progressive and fatal cardiomyopathy. The diagnosis of this disease is frequently delayed or missed due to the limited specificity of echocardiography. An increasing amount of data in the literature demonstrate the ability of bone scintigraphy with bone-seeking radiopharmaceuticals to detect myocardial amyloid deposits, in particular in patients with ATTR. Therefore we performed a systematic review and bivariate meta-analysis of the diagnostic accuracy of bone scintigraphy in patients with suspected cardiac ATTR.

METHODS

A comprehensive computer literature search of studies published up to 30 November 2017 on the role of bone scintigraphy in patients with ATTR was performed using the following search algorithm: (a) "amyloid" OR "amyloidosis" AND (b) "TTR" OR "ATTR" OR "transthyretin" AND (c) "scintigraphy" OR "scan" OR "SPECT" OR "SPET" OR "bone" OR "skeletal" OR "skeleton" OR "PYP" OR "DPD" OR "HMDP" OR "MDP" OR "HDP". Pooled sensitivity, specificity, positive and negative likelihood ratios (LR+ and LR-) and diagnostic odds ratio (DOR) of bone scintigraphy were calculated.

RESULTS

The meta-analysis of six selected studies on bone scintigraphy in cardiac ATTR including 529 patients provided the following results: sensitivity 92.2% (95% CI 89-95%), specificity 95.4% (95% CI 77-99%), LR+ 7.02 (95% CI 3.42-14.4), LR- 0.09 (95% CI 0.06-0.14), and DOR 81.6 (95% CI 44-153). Mild heterogeneity was found among the selected studies.

CONCLUSION

Our evidence-based data demonstrate that bone scintigraphy using technetium-labelled radiotracers provides very high diagnostic accuracy in the non-invasive assessment of cardiac ATTR.