Quantitative 99mTc-DPD-SPECT/CT assessment of cardiac amyloidosis

[99mTc]Tc-DPD SPECT/CT evaluation of right and left ventricular involvement in cardiac transthyretin amyloidosis

BACKGROUND

Accurate assessment of ventricular involvement in transthyretin cardiac amyloidosis (ATTR-CA) is essential for diagnosis and management. This study evaluated left and right ventricular (LV and RV) involvement in patients with ATTR-CA using single-photon emission computed tomography/computed tomography (SPECT/CT) witch Technetium-99m and 3,3-diphosphono-1,2-propanodicarboxylic acid ([99mTc]Tc-DPD).

METHODS

This prospective, single-centre study enrolled 100 adults from 2020 to 2024 (NCT05814380). Participants underwent clinical assessment, genetic testing, electrocardiography, echocardiography, and [99mTc]Tc-DPD SPECT/CT. Volumetric and regional analyses of LV and RV amyloid burden were conducted. Patients were prospectively observed for 5 years to assess all-cause mortality.

RESULTS

Overall, RV uptake was observed in 91 % of patients with ATTR-CA. Radiotracer uptake was detected in the interventricular septum of all ATTR-CA patients, with apical involvement being less common (24 % hereditary ATTR vs. 31 % wild-type ATTR, p = 0.62). Notably, RV uptake was associated with RV thickness, LV global longitudinal strain, and N-terminal pro-brain natriuretic peptide levels (p = 0.00007, p = 0.00022, p = 0.00007; respectively). Multivariate analysis identified increased LV mass index and NYHA class as predictors of RV involvement (area under curve: 0.96). Volumetric LV and RV SPECT uptake measurements and apical sparing correlated with all-cause mortality (p < 0.001).

CONCLUSIONS

The presented findings confirm that SPECT/CT evaluation provides insights into both LV and RV involvement in patients with ATTR-CA and is associated with prognosis. Detailed assessment of RV involvement, through SPECT/CT, reveals significant structural and functional changes associated with disease severity. The presence of RV uptake is associated with advanced cardiac involvement, emphasising the importance of comprehensive biventricular evaluation in this patient population.

Role of [99mTc]Tc-DPD gated-SPECT-CT in the assessment of myocardial uptake patterns in transthyretin amyloidosis (TTR-CA)

PURPOSE

To evaluate the feasibility of identifying various distribution patterns of [99mTc]Tc-DPD in patients with cardiac transthyretin amyloidosis using gated SPECT-CT.

MATERIALS AND METHODS

Gated SPECT-CT was performed in patients with a positive scintigraphy result for cardiac amyloidosis due to transthyretin (TTR-CA). Patients were categorized into several groups based on sex, degree of radiopharmaceutical uptake according to the Perugini's visual scale and ventricular ejection fraction (LVEF). Cardiac polar maps were obtained using Emory Cardiac Toolbox™ software and scored by segments according to radiopharmaceutical uptake on a scale from 0 (no uptake) to 4 (very high uptake intensity). The Mann-Whitney U and Pearson's Chi-square statistical tests were employed to identify significant differences in distribution patterns according to the different variables under study.

RESULTS

65 patients were evaluated. The gender variable determined the main statistically significant differences, highlighting distinct distribution patterns of the radiopharmaceutical at the cardiac level: while women showed lower accumulation of [99mTc]Tc-DPD in the middle anterior (p=0.035) and basal anterior (p=0.001) segments, whereas men demonstrated higher accumulation in the basal anteroseptal (p=0.009) and basal inferoseptal (p=0.009) segments, and lower scores in the lateroapical segment (p=0.039).

CONCLUSIONS

Gated SPECT-CT is an essential tool for assessing the distribution pattern of [99mTc]Tc-DPD of patients with TTR-CA, offering valuable insights into the pathophysiology of the disease.

Cardiopulmonary Exercise Testing Correlates with Quantitative Left Ventricular [99mTc]-DPD Uptake in Transthyretin Amyloid Cardiomyopathy

Background/Objectives: Patients with transthyretin amyloid cardiomyopathy (ATTR-CM) often experience significantly reduced functional capacity due to myocardial involvement. Cardiopulmonary exercise testing (CPET) is the gold standard to quantify functional capacity, and 99mTc-DPD scintigraphy and SPECT/CT have proven to be highly effective tools for diagnostic and disease monitoring. We aimed to investigate the complementary role and correlation between both methods, focusing on their combined potential as a strong prognostic framework for monitoring disease progression and evaluating treatment efficacy. Methods: A total of 44 patients with diagnosed ATTR-CM, who underwent 99mTc-DPD scintigraphy and SPECT/CT imaging as well as CPET, were included. All patients were divided into two groups based on the median DPD retention index (low DPD uptake: ≤5.0, n = 22; high DPD uptake: >5.0, n = 22). Results: The mean age was 78 years, with 82% of participants being male. Significant correlations were observed between peak VO2 and DPD retention index (r = -0.355, p = 0.018) as well as between peak VO2 at anaerobic threshold with DPD retention index (r = -0.391, p = 0.009). Interestingly, there was no strong correlation between VE/VCO2 slope and the retention index. A strong association was identified between cardiac biomarkers and peak VO2, specifically for NT-proBNP (r = -0.530, p < 0.001) and Troponin T (r = -0.431, p < 0.001). Conclusions: In ATTR-CM, significant correlations were observed between key CPET parameters and quantitative cardiac DPD uptake, which further reflects on disease severity and functional impairment. Our findings highlight the utility of integrating CPET and SPECT/CT for comprehensive patient assessment in ATTR-CM.

A quantitative SPECT/CT metric for diagnosing transthyretin cardiac amyloidosis: multicenter study on biopsy-confirmed cases

PURPOSE

99mTechnetium-pyrophosphate ([99mTc]Tc-PYP) scintigraphy is the gold standard for diagnosing transthyretin amyloid cardiomyopathy (ATTR-CM). Conventional metrics, such as heart-to-contralateral-chest (H/CL) ratio and visual Perugini score, can be influenced by physiological blood pool uptake, leading to false positives and additional patient burdens. This study aimed to develop and validate a simple quantitative metric widely applicable for ATTR-CM diagnosis.

METHODS

This multicenter retrospective study enrolled 253 patients who underwent [99mTc]Tc-PYP SPECT/CT between April 2021 and September 2024. SPECT/CTs were acquired 3 h post-injection of 740 MBq [99mTc]Tc-PYP. A lateral wall-to-aorta (LW/Ao) ratio was obtained by dividing the average radiotracer count in the lateral wall of the left ventricle by the average count in the ascending aorta. The diagnosis of ATTR-CM diagnosis was determined by endomyocardial biopsy. As statistical analyses, area under receiver operating characteristic (AUC) was used to compare diagnostic accuracy, and intraclass correlation coefficient (ICC) was used to assess inter-rater agreement.

RESULTS

Among 52 patients (31 men; mean age 77) whose biopsy results were available, 11 were diagnosed with ATTR-CM. LW/Ao ratio showed a sensitivity of 100% (11/11), specificity of 97.6% (40/41), and positive likelihood ratio of 41.0. LW/Ao ratio showed higher AUC (0.99; 95% CI: 0.99-1.00) compared to H/CL ratio (AUC = 0.90, p = 0.04) and visual score (AUC = 0.87, p < 0.01). The ICC of LW/Ao ratio was excellent (0.91 ≥ 0.9).

CONCLUSION

The quantitative SPECT/CT metric demonstrated superior diagnostic accuracy for ATTR-CM compared to conventional methods.

Validation of [99mTc]Tc-HMDP SPECT/CT myocardium-to-blood ratio for the detection of ATTR cardiomyopathy

BACKGROUND

This study validates the accuracy of 99mTc-hydroxymethylene diphosphonate ([99mTc]Tc-HMDP) single-photon emission tomography/computed tomography (SPECT/CT) in the diagnosis of transthyretin amyloidosis (ATTR) cardiomyopathy using myocardium-to-blood ratio (MBR).

METHODS

The final study population was 80 patients who underwent [99mTc]Tc-HMDP SPECT/CT for suspected ATTR cardiomyopathy at Helsinki University Hospital or Jorvi Central Hospital in Finland. Patients were diagnosed according to the currently accepted European Society of Cardiology criteria as either non-ATTR (n = 48) or ATTR cardiomyopathy patients (n = 32). The left ventricular (LV) MBR was calculated by dividing LV maximal myocardial uptake with maximal left atrial uptake. Right ventricular (RV) uptake was calculated as the maximal uptake ratio on the RV-free wall and right atrium. Data are presented as mean ± standard deviation.

RESULTS

The LV MBR was higher in ATTR patients than in non-ATTR patients (4.6 ± 1.2 vs .9 ± .2, P < .001). The LV MBR of 1.5 identified ATTR cardiomyopathy with 100% accuracy. LV MBR was associated with LV wall thickness on echocardiography in univariable analysis but not with LV ejection fraction or E/e'. The RV MBR was higher in ATTR patients (2.9 ± 1.0 vs .8 ± .2, P < .001). Neither LV nor RV MBR were associated with the clinical severity of ATTR cardiomyopathy in univariable analysis.

CONCLUSIONS

LV myocardium-to-blood ratio (MBR) greater than 1.5 was 100% accurate for detecting ATTR cardiomyopathy using [99mTc]Tc-HMDP SPECT/CT. Left ventricular MBR was associated with wall thickness on echocardiography but not with the clinical severity of ATTR cardiomyopathy.

The Accuracy of Technetium-99 m Pyrophosphate Imaging in Diagnosing Transthyretin Cardiac Amyloidosis and Its Impact on Patient Management

PURPOSE OF REVIEW

This review evaluates recent advancements in Technetium-99 m pyrophosphate (99mTc-PYP) imaging for transthyretin amyloid cardiomyopathy (ATTR-CM). We summarize the advantages of single-photon emission computed tomography (SPECT) over planar imaging, the potential impact of quantitative methods, and emerging data for quantifying response to therapy.

RECENT FINDINGS

The current literature demonstrates the superior diagnostic accuracy of SPECT compared with planar imaging in 99mTc-PYP studies. Emerging quantitative methods, using hybrid SPECT/CT and artificial intelligence, show promise for enhancing diagnostic precision and risk assessment. Recent studies have also highlighted the potential of 99mTc-PYP quantification for monitoring treatment response. 99mTc-PYP SPECT imaging has exceptional diagnostic accuracy for ATTR-CM. Quantitative techniques, which can be facilitated by artificial intelligence, improve risk stratification and may aid in treatment monitoring. Future research should focus on clarifying the clinical role and optimal approach for quantification.

Parametric mapping using cardiovascular magnetic resonance for the differentiation of light chain amyloidosis and transthyretin-related amyloidosis

AIMS

To evaluate different cardiovascular magnetic resonance (CMR) parameters for the differentiation of light chain amyloidosis (AL) and transthyretin-related amyloidosis (ATTR).

METHODS AND RESULTS

In total, 75 patients, 53 with cardiac amyloidosis {20 patients with AL [66 ± 12 years, 14 males (70%)] and 33 patients with ATTR [78 ± 5 years, 28 males (88%)]} were retrospectively analysed regarding CMR parameters such as T1 and T2 mapping, extracellular volume (ECV), late gadolinium enhancement (LGE) distribution patterns, and myocardial strain, and compared to a control cohort with other causes of left ventricular hypertrophy {LVH; 22 patients [53 ± 16 years, 17 males (85%)]}. One-way ANOVA and receiver operating characteristic analysis were used for statistical analysis. ECV was the single best parameter to differentiate between cardiac amyloidosis and controls [area under the curve (AUC): 0.97, 95% confidence intervals (CI): 0.89-0.99, P < 0.0001, cut-off: >30%]. T2 mapping was the best single parameter to differentiate between AL and ATTR amyloidosis (AL: 63 ± 4 ms, ATTR: 58 ± 2 ms, P < 0.001, AUC: 0.86, 95% CI: 0.74-0.94, cut-off: >61 ms). Subendocardial LGE was predominantly observed in AL patients (10/20 [50%] vs. 5/33 [15%]; P = 0.002). Transmural LGE was predominantly observed in ATTR patients (23/33 [70%] vs. 2/20 [10%]; P < 0.001). The diagnostic performance of T2 mapping to differentiate between AL and ATTR amyloidosis was further increased with the inclusion of LGE patterns [AUC: 0.96, 95% CI: (0.86-0.99); P = 0.05].

CONCLUSION

ECV differentiates cardiac amyloidosis from other causes of LVH. T2 mapping combined with LGE differentiates AL from ATTR amyloidosis with high accuracy on a patient level.

Radionuclide Imaging of Cardiac Amyloidosis: An Update and Future Aspects

Cardiac amyloidosis (CA) is caused by the misfolding, accumulation and aggregation of proteins into large fibrils in the extracellular compartment of the myocardium, leading to restrictive cardiomyopathy, heart failure and death. The major forms are transthyretin (ATTR) CA and light-chain (AL) CA, based on the respective precursor protein. Each of them requires early diagnosis for a timely treatment initiation that will improve patient outcomes. For this, radionuclide imaging is essentially used as single-photon emission computed tomography (SPECT) with bone-avid radiotracers or as positron emission tomography (PET) with amyloid-binding radiotracers. Both offer unprecedented specificity for the diagnostic of CA. SPECT has even revolutionized the diagnosis of ATTR-CA by making it non-invasive. Indeed, SPECT has now entered the standard diagnostic pathway to CA and has led to earlier diagnosis of the disease. SPECT also modified the epidemiology of ATTR-CA, highlighting that the disease is much more frequent than previously believed, and showing that ATTR-CA plays a substantial role in HFpEF and aortic stenosis, particularly among elderly patients. In parallel, amyloid-binding radiotracers for PET have accumulated a substantial amount of evidence, but are not approved for clinical use in CA yet. Further studies are needed to refine acquisition protocols and validate results in broader populations. Unlike bone-avid SPECT radiotracers, PET radiotracers have been specifically created to bind to amyloid fibrils. Thus, PET is the only imaging method that is truly specific for amyloid deposits and very sensitive to any amyloid type. Indeed, PET can not only detect ATTR-CA, but also AL-CA and rare hereditary forms. For both SPECT and PET, advances in quantitation of myocardial uptake have generated more granular and reproducible findings, paving the way for progress in earlier diagnosis, risk stratification and therapeutic response monitoring. Encouraging findings have shown that SPECT and PET are sensitive to early CA when other diagnostic methods are negative. Both radionuclide imaging techniques can predict adverse outcomes, but more evidence is needed to determine how to use them in conjunction with usual prognostic staging scores. Studies on follow-up imaging after therapy suggested that SPECT and PET can capture myocardial changes in CA, but again, more data are needed to meaningfully interpret such changes. Based on all these promising results, radionuclide imaging has the potential to further impact the landscape of CA in diagnosis, prognosis and follow-up, but also to substantially contribute to the assessment of novel therapies that will improve the lives of patients with CA.

Epidemiological Changes in Transthyretin Cardiac Amyloidosis: Evidence from In Vivo Data and Autoptic Series

Cardiac amyloidosis is an infiltrative disease that causes progressive myocardial impairment secondary to amyloid fibril deposition in the extracellular space of the myocardium. Many amyloid precursors, including transthyretin protein, are known to determine cardiac damage by aggregating and precipitating in cardiac tissue. Transthyretin cardiac amyloidosis may be either caused by rare genetic mutations of the transthyretin gene in the hereditary variant, or may arise as a consequence of age-related mechanisms in the acquired form. Although it has been labeled as a rare disease, in recent years, transthyretin cardiac amyloidosis has stood out as an emerging cause of aortic stenosis, unexplained left ventricular hypertrophy and heart failure with preserved ejection fraction, particularly in the elderly. Indeed, the integration of data deriving from both in vivo imaging techniques (whose advancement in the last years has allowed to achieve an easier and more accessible non-invasive diagnosis) and forensic studies (showing a prevalence of amyloid deposition in cardiac tissue of elderly patients up to 29%) suggests that cardiac amyloidosis is a more common disease than traditionally considered. Thanks to all the improvements in non-invasive diagnostic techniques, along with the development of efficacious therapies offering improvements in survival rates, transthyretin cardiac amyloidosis has been transformed from an incurable and infrequent condition to a relatively more diffuse and treatable disease, which physicians should take into consideration in the differential diagnostic processes in daily clinical practice.

Management of cardiac sarcoidosis

Cardiac sarcoidosis (CS) is a form of inflammatory cardiomyopathy associated with significant clinical complications such as high-degree atrioventricular block, ventricular tachycardia, and heart failure as well as sudden cardiac death. It is therefore important to provide an expert consensus statement summarizing the role of different available diagnostic tools and emphasizing the importance of a multidisciplinary approach. By integrating clinical information and the results of diagnostic tests, an accurate, validated, and timely diagnosis can be made, while alternative diagnoses can be reasonably excluded. This clinical expert consensus statement reviews the evidence on the management of different CS manifestations and provides advice to practicing clinicians in the field on the role of immunosuppression and the treatment of cardiac complications based on limited published data and the experience of international CS experts. The monitoring and risk stratification of patients with CS is also covered, while controversies and future research needs are explored.

Deep Learning-Enabled Quantification of 99mTc-Pyrophosphate SPECT/CT for Cardiac Amyloidosis

Transthyretin cardiac amyloidosis (ATTR CA) is increasingly recognized as a cause of heart failure in older patients, with 99mTc-pyrophosphate imaging frequently used to establish the diagnosis. Visual interpretation of SPECT images is the gold standard for interpretation but is inherently subjective. Manual quantitation of SPECT myocardial 99mTc-pyrophosphate activity is time-consuming and not performed clinically. We evaluated a deep learning approach for fully automated volumetric quantitation of 99mTc-pyrophosphate using segmentation of coregistered anatomic structures from CT attenuation maps. Methods: Patients who underwent SPECT/CT 99mTc-pyrophosphate imaging for suspected ATTR CA were included. Diagnosis of ATTR CA was determined using standard criteria. Cardiac chambers and myocardium were segmented from CT attenuation maps using a foundational deep learning model and then applied to attenuation-corrected SPECT images to quantify radiotracer activity. We evaluated the diagnostic accuracy of target-to-background ratio (TBR), cardiac pyrophosphate activity (CPA), and volume of involvement (VOI) using the area under the receiver operating characteristic curve (AUC). We then evaluated associations with the composite outcome of cardiovascular death or heart failure hospitalization. Results: In total, 299 patients were included (median age, 76 y), with ATTR CA diagnosed in 83 (27.8%) patients. CPA (AUC, 0.989; 95% CI, 0.974-1.00) and VOI (AUC, 0.988; 95% CI, 0.973-1.00) had the highest prediction performance for ATTR CA. The next highest AUC was for TBR (AUC, 0.979; 95% CI, 0.964-0.995). The AUC for CPA was significantly higher than that for heart-to-contralateral ratio (AUC, 0.975; 95% CI, 0.952-0.998; P = 0.046). Twenty-three patients with ATTR CA experienced cardiovascular death or heart failure hospitalization. All methods for establishing TBR, CPA, and VOI were associated with an increased risk of events after adjustment for age, with hazard ratios ranging from 1.41 to 1.84 per SD increase. Conclusion: Deep learning segmentation of coregistered CT attenuation maps is not affected by the pattern of radiotracer uptake and allows for fully automatic quantification of hot-spot SPECT imaging such as 99mTc-pyrophosphate. This approach can be used to accurately identify patients with ATTR CA and may play a role in risk prediction.

Verification of reprojected planar images generated from a ring-configured cadmium zinc telluride gamma camera in scintigraphy for diagnosing transthyretin cardiac amyloidosis

Aims

Non-invasive diagnosis of amyloid transthyretin (ATTR) cardiac amyloidosis using planar scintigraphy and single-photon emission computed tomography-computed tomography (SPECT-CT) with [99mTc]Tc-3,3-diphosphono-1,2-propanodicarboxylic acid ([99mTc]Tc-DPD) has high specificity and sensitivity. However, the introduction of ring-configured cadmium zinc telluride (CZT) gamma cameras warrants an update in the acquisition method since these systems are not able to perform planar scintigraphy. We aimed to verify the use of reprojected planar images from SPECT-CT as a replacement for planar scintigraphy in evaluating ATTR-amyloidosis.

Methods and results

The study examined 30 patients referred for clinically indicated [99mTc]Tc-DPD scintigraphy who were scanned with both a conventional gamma camera and a ring-configured CZT gamma camera. Planar scintigraphy from the conventional gamma camera was compared with reprojected planar images from the ring-configured CZT gamma camera. The images were evaluated in regard to image quality and Perugini visual score in a blinded fashion by three nuclear medicine physicians. Heart-to-contralateral (H/CL) ratios were calculated. There were 27 patients who had an identical Perugini score in planar and reprojected planar images, yielding a strong level of agreement and inter-rater reliability among the three readers. The H/CL ratios showed a strong correlation ratio (r = 0.98, P < 0.0001). A shift towards lower image quality was seen for the reprojected images.

Conclusion

Reprojected planar images generated from a ring-configured CZT gamma camera combined with SPECT-CT can be used to score ATTR amyloidosis and extract H/CL ratios in the same way as planar images and SPECT-CT from a conventional gamma camera.

Transthyretin amyloid cardiomyopathy disease burden quantified using 99mTc-pyrophosphate SPECT/CT: volumetric parameters versus SUVmax ratio at 1 and 3 hours

BACKGROUND

Various parameters derived from technetium-99m pyrophosphate (99mTc-PYP) single-photon emission computed tomography (SPECT) correlate with the severity of transthyretin amyloid cardiomyopathy (ATTR-CM). However, the optimal metrics and image acquisition timing required to quantify the disease burden remain uncertain.

METHODS AND RESULTS

We retrospectively evaluated 99mTc-PYP SPECT/CT images of 23 patients diagnosed with ATTR-CM using endomyocardial biopsies and/or gene tests. All patients were assessed by SPECT/CT 1 hour after 99mTc-PYP injection, and 13 of them were also assessed at 3 hours. We quantified 99mTc-PYP uptake using the volumetric parameters, cardiac PYP volume (CPV) and cardiac PYP activity (CPA). We also calculated the SUVmax ratios of myocardial SUVmax/blood pool SUVmax, myocardial SUVmax/bone SUVmax, and the SUVmax retention index. We assessed the correlations between uptake parameters and the four functional parameters associated with prognosis, namely left ventricular ejection fraction, global longitudinal strain, myocardial extracellular volume, and troponin T. CPV and CPA correlated more closely than the SUVmax ratios with the four prognostic factors. Significant correlations between volumetric parameters and prognostic factors were equivalent between 1 and 3 hours.

CONCLUSIONS

The disease burden of ATTR-CM was quantified more accurately by volumetric evaluation of 99mTc-PYP SPECT/CT than SUVmax ratios and the performance was equivalent between 1 and 3 hours.

The clinical value of quantitative cardiovascular molecular imaging: a step towards precision medicine

Cardiovascular diseases (CVD) are the leading cause of death worldwide and have an increasing impact on society. Precision medicine, in which optimal care is identified for an individual or a group of individuals rather than for the average population, might provide significant health benefits for this patient group and decrease CVD morbidity and mortality. Molecular imaging provides the opportunity to assess biological processes in individuals in addition to anatomical context provided by other imaging modalities and could prove to be essential in the implementation of precision medicine in CVD. New developments in single-photon emission computed tomography (SPECT) and positron emission tomography (PET) systems, combined with rapid innovations in promising and specific radiopharmaceuticals, provide an impressive improvement of diagnostic accuracy and therapy evaluation. This may result in improved health outcomes in CVD patients, thereby reducing societal impact. Furthermore, recent technical advances have led to new possibilities for accurate image quantification, dynamic imaging, and quantification of radiotracer kinetics. This potentially allows for better evaluation of disease activity over time and treatment response monitoring. However, the clinical implementation of these new methods has been slow. This review describes the recent advances in molecular imaging and the clinical value of quantitative PET and SPECT in various fields in cardiovascular molecular imaging, such as atherosclerosis, myocardial perfusion and ischemia, infiltrative cardiomyopathies, systemic vascular diseases, and infectious cardiovascular diseases. Moreover, the challenges that need to be overcome to achieve clinical translation are addressed, and future directions are provided.

Diagnostic accuracy of bone scintigraphy imaging for transthyretin cardiac amyloidosis: systematic review and meta-analysis

BACKGROUND

Bone scintigraphy imaging is frequently used to investigate patients with suspected transthyretin cardiac amyloidosis (ATTR-CM). However, the reported accuracy for interpretation approaches has changed over time. We performed a systematic review and meta-analysis to determine the diagnostic accuracy of visual planar grading, heart-to-contralateral (HCL) ratio, and quantitative analysis of SPECT imaging and evaluate reasons for shifts in reported accuracy.

METHODS

We performed a systematic review to identify studies of the diagnostic accuracy of bone scintigraphy for ATTR-CM from 1990 until February 2023 using PUBMED and EMBASE. Studies were reviewed separately by two authors for inclusion and for risk of bias assessment. Summary receiver operating characteristic curves and operating points were determined with hierarchical modeling.

RESULTS

Out of a total of 428 identified studies, 119 were reviewed in detail and 23 were included in the final analysis. The studies included a total of 3954 patients, with ATTR-CM diagnosed in 1337 (39.6%) patients and prevalence ranging from 21 to 73%. Visual planar grading and quantitative analysis had higher diagnostic accuracy (.99) than HCL ratio (.96). Quantitative analysis of SPECT imaging had the highest specificity (97%) followed by planar visual grade (96%) and HCL ratio (93%). ATTR-CM prevalence accounted for some of the observed between study heterogeneity.

CONCLUSIONS

Bone scintigraphy imaging is highly accurate for identifying patients with ATTR-CM, with between study heterogeneity in part explained by differences in disease prevalence. We identified small differences in specificity, which may have important clinical implications when applied to low-risk screening populations.

Cardiac DPD-uptake time dependency in ATTR patients verified by quantitative SPECT/CT and semiquantitative planar parameters

BACKGROUND

Bone scintigraphy plays an important role in the diagnosis of cardiac Transthyretin-Related Amyloidosis (ATTR). The mechanism of myocardial tracer accumulation and its dependence over time are not fully understood. Recently, a scintigraphic quantification of the cardiac amyloid deposition has been discussed. Nevertheless, little is known regarding the right time of quantitative imaging.

METHODS

The geometrical mean of decay corrected total counts over the heart and the heart/whole-body ratio (H/WB) were evaluated in 23 patients undergoing DPD-bone scan with planar whole-body images 1 and 3 hours post injection (p.i.). Myocardial standard uptake values (SUV)peak were assessed in another 15 patients with quantitative SPECT/CT imaging 1 hours and 3 hours p.i..

RESULTS

Total counts over the heart (1 hours p.i.: 81,676 cts, range 69,887 to 93,091 cts and 3 hours p.i.: 64,819 cts, range 52,048 to 86,123 cts, P = .0005) and H/WB ratio (1 hours p.i.:0.076 ± 0.020 and 3 hours p.i. 0.070 ± 0.022; P = .0003) were significantly increased 1 hours p.i.. Furthermore median myocardial SUVpeak (1 hours p.i.:12.2, range 9.6 to 18.9 and 3 hours p.i.: 9.6, range 8.2 to 15.0, P = 0.0012) was also significantly higher after 1 hours p.i. compared to 3 hours p.i..

CONCLUSION

Cardiac DPD activity and myocardial SUVpeak are time-dependent, which should be considered when using quantitative bone scintigraphy in ATTR patients.

Direct comparison of diagnostic and clinical values between Tc-99 m DPD and Tc-99 m PYP scintigraphy in patients with cardiac amyloidosis

BACKGROUND

Technetium-99 m 3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) and technetium-99 m sodium pyrophosphate (PYP) are the two most commonly used radiotracers for cardiac amyloidosis (CA), but no studies have directly compared them. Therefore, in this study, we directly compared the diagnostic and clinical utility of DPD and PYP scintigraphy in patients with CA.

METHODS

Ten patients with CA were enrolled. Eight clinical variables and 12 scintigraphic parameters were used. Clinical variables were age, sex, estimated glomerular filtration rate (eGFR), N-terminal pro brain natriuretic peptide (NT-proBNP), and the results of electromyography (EMG), a sensory test, electrocardiogram, and echocardiography (EchoCG). Four heart retention ratios (heart/whole-body profile, heart/pelvis, heart/skull, and heart/contralateral lung) were calculated from the DPD and PYP scans and two visual scoring systems (Perugini and Dorbala systems) were used. Comparative analyses were performed between radiotracers and between visual scoring systems using clinical variables and scintigraphic parameters.

RESULTS

Twenty DPD parameters and nine PYP parameters had significant associations with age, eGFR, NT-proBNP, EchoCG, and EMG. DPD parameters had more frequent significant associations with clinical variables than PYP parameters. Compared to visual scores in the DPD scan, the proportion of patients with higher visual scores in the PYP scan was relatively greater than those with lower visual scores, and there were more patients with a visual score of 2 or higher in PYP scans than DPD scans.

CONCLUSIONS

DPD scintigraphy may reflect the disease severity of CA better than PYP scintigraphy, whereas PYP scintigraphy may be a more sensitive imaging modality for identifying CA involvement.

Regression of Myocardial 99mTc-DPD Uptake After Tafamidis Treatment of Cardiac Transthyretin Amyloidosis

Cardiac transthyretin amyloidosis is an infiltrative cardiomyopathy with high mortality. To date, there are no specific biomarkers to directly assess disease activity and response to specific treatments. Our aim was to evaluate scintigraphic changes after treatment with the transthyretin stabilizer tafamidis. Methods: We included patients who had undergone ^99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (^99mTc-DPD) scintigraphy before tafamidis initiation and after at least 9 mo. Tracer activity was assessed visually and quantitatively as SUV_max Results: The study included 14 patients who were on tafamidis for 44 ± 14 mo. We observed regression of Perugini grade in 5 patients, unchanged grade in 9 patients, and regression of mean heart-to-contralateral-lung ratio (P = 0.015) and SUV_max (P = 0.005). There were no changes in N-terminal pro-B-type natriuretic peptide or echocardiographic measures. Conclusion: Treatment with tafamidis results in regression of myocardial ^99mTc-DPD uptake. ^99mTc-DPD scintigraphy may provide useful imaging biomarkers to assess response to treatment.

Quantitative SPECT/CT Parameters in the Assessment of Transthyretin Cardiac Amyloidosis-A New Dimension of Molecular Imaging

AIMS

Cardiac transthyretin amyloidosis (ATTR) represents the accumulation of misfolded transthyretin in the heart interstitium. Planar scintigraphy with bone-seeking tracers has long been established as one of the three main steps in the non-invasive diagnosis of ATTR, but lately, single-photon emission computed tomography (SPECT) has gained wide recognition for its abilities to exclude false positive results and offer a possibility for amyloid burden quantitation. We performed a systematic review of the existing literature to provide an overview of the available SPECT-based parameters and their diagnostic performances in the assessment of cardiac ATTR. Methods and Methods: Among the 43 papers initially identified, 27 articles were screened for eligibility and 10 met the inclusion criteria. We summarised the available literature based on radiotracer, SPECT acquisition protocol, analysed parameters and their correlation to planar semi-quantitative indices.

RESULTS

Ten articles provided accurate details about SPECT-derived parameters in cardiac ATTR and their diagnostic potential. Five studies performed phantom studies for accurate calibration of the gamma cameras. All papers described good correlation of quantitative parameters to the Perugini grading system.

CONCLUSIONS

Despite little published literature on quantitative SPECT in the assessment of cardiac ATTR, this method offers good prospects in the appraisal of cardiac amyloid burden and treatment monitoring.

Follow-up Tc-99 m pyrophosphate cardiac scan for patients with transthyretin cardiac amyloidosis treated with tafamidis

BACKGROUND

Tafamidis has been used for treatment of transthyretin cardiac amyloidosis (ATTR-CA). However, Tc-99 m pyrophosphate (PYP) cardiac scan for follow-up after tafamidis therapy has not been reported.

METHODS

From May 2017 to March 2022, five patients with or without tafamidis therapy had received two Tc-99 m PYP cardiac scans. Tc-99 m PYP cardiac scan was performed with planar image and single photon emission computed tomography/computed tomography (SPECT/CT) 3 h after administration of Tc-99 m PYP. Perugini grading system was applied to determine positive or negative result of the scan. Heart to contralateral lung (H/CL) ratio as well as the difference of H/CL ratio between first and second Tc-99 m PYP cardiac scans (ΔH/CL ratio) was calculated.

RESULTS

In the five patients participated in this study, three received tafamidis therapy and H/CL ratio was significantly decreased (p = 0.02) after tafamidis therapy. Besides, the ΔH/CL ratio was larger in patients with tafamidis therapy than that in those without tafamidis therapy, albeit not reaching statistical significance (p = 0.2).

CONCLUSION

A decrease in H/CL ratio was found after tafamidis therapy in patients with ATTR-CA, albeit the magnitude of changes in the H/CL ratio (ΔH/CL ratio) was not significantly different from that of patients without tafamidis therapy. Future study with larger population might be required to further clarify the effect of tafamidis therapy on myocardial uptake of Tc-99 m PYP.

CLINICAL TRIAL REGISTRATION

No clinical trial was conducted in our retrospective study.