The short and long-term characteristics and outcomes of patients with grade 1 myocardial uptake on cardiac scintigraphy

AIMS

This study aimed to characterize the final diagnosis and prognosis of patients with grade 1 myocardial scintigraphy uptake, which is an unequivocal result for the diagnosis of transthyretin cardiac amyloidosis (ATTR-CA) requiring further invasive investigation with tissue biopsy.

METHODS AND RESULTS

We retrospectively compared the clinical and imaging parameters of patients suspected for ATTR-CA (based on clinical and echocardiographic parameters) with grade 1 vs. grades 2/3 technetium pyrophosphate uptake on cardiac scintigraphy. Prospectively, grade 1 patients underwent re-evaluation for ATTR-CA at long term. Of the 132 ATTR-CA suspected patients, 89 (67%) were diagnosed as grade 1 and 43 (33%) as grades 2/3 uptake. Grade 1 vs. grades 2/3 patients were younger and female predominant with lower biomarker levels and left ventricular mass. Based on available imaging and pathology findings, only 6 out of the 89 patients with grade 1 uptake (7%) were finally diagnosed with light-chain cardiac amyloidosis, whereas no patient was diagnosed with ATTR-CA. At 2 [interquartile range (IQR) 0.75, 3.25] years of follow-up, the survival of patients with grade 1 vs. grades 2/3 uptake was significantly better [hazard ratio 0.271 (95% confidence interval 0.130 to 0.563, P = 0.0005)]. Prospectively, 30 patients with grade 1 uptake were re-evaluated at a median follow-up of 3.2 (IQR 2.2, 3.9) years. Their New York Heart Association class, biomarker levels, and echocardiography findings remained stable. No patient (0/25) demonstrated grades 2/3 uptake at repeated long-term scintigraphy.

CONCLUSIONS

Patients with suspected ATTR-CA and a grade 1 scintigraphy uptake demonstrate a stable clinical, laboratory, imaging, and scintigraphy phenotype along with a benign survival profile at long-term follow-up. Larger studies should define the optimal evaluation strategy in this population.

Long-term prognosis of patients with Perugini Grade 1 cardiac scintigraphy score

Background

A Perugini Grade 1 myocardial uptake on amyloid cardiac scintigraphy does not establish the diagnosis of amyloid transthyretin cardiomyopathy (ATTR-CA), and according to current position papers mandates an endomyocardial biopsy to rule in or rule out ATTR-CA. We aimed to investigate whether Perugini Grade 1 reflects an early stage of ATTR-CA or a false positive result thus obliviating the need for further evaluation.

Methods

Study population was comprised of consecutive ≥70 years old patients who underwent a baseline cardiac scintigraphy scan for the presumed diagnosis of ATTR-CA at our institution between the years 2017–2020 and had a Perugini Grade 1 score. Patients with Perugini Grade 2 or 3 comprised our control group. At the beginning of 2022, Perugini Grade 1 patients prospectively underwent a repeat follow-up evaluation which included clinical examination, echocardiography with strain parameters, cardiac biomarkers measurement and cardiac scintigraphy. Cardiac magnetic resonance (CMR) and genetic testing for ATTR-CA mutations were analyzed as well.

Preliminary results

Fifty patients were included in the baseline study cohort, of whom 44% (n=22) were females. A carpal tunnel syndrome history was present in 10 patients (20%). Baseline troponin T and NT pro-BNP levels were 23 (IQR 14,39) and 1557 (IQR 237, 5746) ng/L, respectively. Wall thickness by echocardiography was 12 (11, 15) mm and 8 patients (16%) had severe mitral annulus calcification. Left ventricular ejection fraction (LVEF) was 60 (IQR 50, 60)%. At a median follow-up of 31 (20, 35) months, 7 patients (14%) were diagnosed with plasma-cell dyscrasias and 6 patients (12%) were hospitalized for heart failure exacerbations. Follow-up troponin T and NT pro-BNP levels were 27 (IQR 21,46) pg/ml and 1158 (IQR 434, 7249) ng/L, respectively (p=NS compared to baseline). Wall thickness by echocardiography was 12 (12, 15) mm and LVEF was 60 (IQR 50, 60)% (p=NS compared to baseline). Follow-up cardiac scintigraphy demonstrated Perugini Grade 1 in all re-tested patients. Two patients and 14 patients (32% total) underwent an endomyocardial biopsy or CMR, respectively, for a definitive diagnosis. All 16 tests were incompatible with amyloid cardiomyopathy. Genetic data results will be added. All-cause survival was similar between patients with Perugini Grade 1 versus Grades 2 and 3 (log rank p=0.103).

Conclusion

At long-term follow-up, Perugini Grade 1 patients do not demonstrate progression of laboratory or imaging amyloid characteristics. This suggests that Perugini grade 1 reflects a false positive result for ATTR-CA rather than an early stage in the disease. Larger-scale data should further question the need for an endomyocardial biopsy in these patients.

Funding Acknowledgement

Type of funding sources: None.

The Effect of Tafamidis on Circulating Endothelial Progenitor Cells in Patients with Transthyretin Cardiac Amyloidosis

AIMS

Endothelial microvascular dysfunction is a known mechanism of vascular pathology in cardiac amyloidosis (CA). Scientific evidence regarding the possible protective role of the amyloid transthyretin (ATTR) stabilizer, tafamidis, is lacking. Circulating endothelial progenitor cells (cEPCs) have an important role in the process of vascular repair. We aimed to examine the effect of tafamidis on cEPCs.

METHODS AND RESULTS

Study population included patients with ATTR-CA. cEPCs were assessed using flow cytometry by the expression of CD34⁽⁺⁾/CD133⁽⁺⁾ and vascular endothelial growth factor receptor (VEGFR)-2⁽⁺⁾ and by the formation of colony-forming units (CFUs) and production of VEGF. Tests were repeated at pre-specified time-points up to 12 months following the initiation of tafamidis. Included were 18 ATTR-CA patients at a median age of 77 (IQR 71, 85) years and male predominance (n = 15, 83%). Following the initiation of tafamidis and during 12 months of drug treatment, there was a gradual increase in the levels of CD34⁽⁺⁾/VEGFR-2⁽⁺⁾ (0.43 to 2.42% (IQR 1.53, 2.91)%, p = 0.002) and CD133⁽⁺⁾/VEGFR-2⁽⁺⁾ (0.49 to 1.64% (IQR 0.97, 2.90)%, p = 0.004). Functionally, increase in EPCs-CFUs was microscopically evident following treatment with tafamidis (from 0.5 CFUs (IQR 0.0, 1.0) to 3.0 (IQR 1.3, 3.8) p < 0.001) with a concomitant increase in EPC's viability as demonstrated by an MTT assay (from 0.12 (IQR 0.03, 0.16) to 0.30 (IQR 0.18, 0.33), p < 0.001). VEGF levels increased following treatment (from 54 (IQR 52, 72) to 107 (IQR 62, 129) pg/ml, p = 0.039).

CONCLUSIONS

Tafamidis induced the activation of the cEPCs pathway, possibly promoting endothelial repair in ATTR-CA.

Quantitative and functional evaluation of endothelial progenitor cells in patients with cardiac amyloidosis

Background

Endothelial microvascular dysfunction is a known mechanism of injury in cardiac amyloidosis (CA), but evidence regarding the level and function of endothelial progenitor cells (EPCs) in patients with CA is lacking.

Methods

Study population included patients with light-chain or transthyretin (ATTR) CA. Patients with diagnosed heart failure and preserved ejection fraction (HFpEF) without monoclonal gammopathy and a 99mTc-DPD scan incompatible with TTR were used as controls. Blood circulating EPCs were assessed quantitatively by the expression of VEGFR-2(+), CD34(+) and CD133(+) using flow cytometry, and functionally by the formation of colony forming units (CFUs). MTT assay was used to demonstrate cell viability. Tests were repeated 3 months following the initiation of amyloid-suppressive therapies (either ATTR-stabilizer or targeted chemotherapy) in CA patients.

Results

Our preliminary cohort included 14 CA patients (median age 74 years, 62% ATTR CA).

Patients with CA vs. patients with HFpEF (n=8) demonstrated lower expression of CD34(+)/VEGFR-2(+) cells [0.51% (IQR 0.4, 0.7) vs. 1.03% (IQR 0.6, 1.4), P=0.043] and CD133(+)/VEGFR-2(+) cells [0.35% (IQR 0.23, 0.52) to 1.07% (IQR 0.6, 1.5), P=0.003]. Functionally, no differences were noted between groups. Following the initiation of amyloid-suppressive therapies in CA patients, we observed the up-regulation of CD34(+)/VEGFR-2(+) cells [2.47% (IQR 2.1, 2.7), P&lt;0.001] and CD133(+)/VEGFR-2(+) cells [1.38% (IQR 1.1, 1.7), P=0.003]. Moreover, functionally, active EPCs were evident microscopically by their ability to form colonies (from 0.5 CFUs [IQR 0, 1.5) to 2 CFUs (IQR 1, 3.5), P=0.023]. EPCs' viability was demonstrated by an MTT assay [0.12 (IQR 0.04, 0.12) to 0.24 (IQR 0.16, 0.3), p=0.014].

Conclusions

These preliminary results demonstrate reduced EPCs levels in CA patients indicating significant microvascular impairment. Amyloid-targeted therapies induce the activation of EPCs, thus possibly promoting endothelial regeneration. These findings may represent a novel mechanism of action of amyloid-suppressive therapies

EPCs in CA patients and during therapy

Funding Acknowledgement

Type of funding source: None