Approximately 1.5 million of the 44 million Blacks in the United States are carriers of the valine-to-isoleucine substitution at position 122 (V122I) in the transthyretin (TTR) protein. Virtually exclusive to Blacks, this is the most common cause of hereditary cardiac amyloidosis (hATTR-CA) worldwide. hATTR-CA leads to worsening heart failure (HF) and premature death. Fortunately, new therapies that stabilize TTR improve morbidity and mortality in hATTR-CA, especially when prescribed early in the disease. However, hATTR-CA is often diagnosed at an advanced stage and conventional diagnostic tools lack diagnostic specificity to detect early disease.
The overall objectives of this study are to determine the presence of subclinical hATTR-CA and to identify biomarkers that indicate amyloid progression in V122I TTR carriers. The central hypothesis of this proposal is that hATTR-CA has a long latency period that will be detected through subclinical amyloidosis imaging and biomarker phenotyping.
The central hypothesis will be tested by pursuing 2 specific aims: Aim 1) determine the association of V122I TTR carrier status with CMRI evidence of amyloid infiltration; Sub-aim 1) determine the association of V122I TTR carrier status with cardiac reserve; Aim 2) determine the association between amyloid-specific biomarkers and V122I TTR carrier status; and Sub-aim 2) determine the association of amyloid-specific biomarkers with imaging-based parameters and evaluate their diagnostic utility for identifying subclinical hATTR-CA. In Aim 1, CMRI will be used to compare metrics associated with cardiac amyloid infiltration between a cohort of V122I TTR carriers without HF formed by cascade genetic testing and age-, sex-, and race-matched non-carrier controls. For Sub-Aim 1, a sub-sample of carriers and non-carrier controls enrolled in Aim 1 will undergo novel exercise CMRI to measure and compare cardiac systolic and diastolic reserve. Aim 2 involves measuring and comparing amyloid-specific biomarkers in V122I TTR carriers without HF with samples matched non-carriers (both from Aim 1) and individuals with symptomatic V122I hATTR-CA from our clinical sites. These biomarkers detect and quantify different processes of TTR amyloidogenesis and include circulating TTR, retinol binding protein 4, TTR kinetic stability, and misfolded TTR oligomers. Sub-aim 2 will establish the role of these biomarkers to detect imaging evidence of subclinical hATTR-CA disease.
Men and women ages 30-80 who are carriers of pathogenic TTR alleles (or matched non-carriers) without history of HF (this will be assessed by study personnel) and defined as: a) No history of hospitalization within the previous 12 months for management of HF; b) Without an elevated B-type natriuretic peptide level ≥100 pg/mL or NT-proBNP ≥360 pg/mL within the previous 12 months; or c) No clinical diagnosis of HF from a treating clinician
Signed informed consent
A self-reported history or clinical history of HF
Other known causes of cardiomyopathy
History of light-chain cardiac amyloidosis
Prior type 1 myocardial infarction (non-ST segment elevation myocardial Infarction {NSTEMI} or ST-elevation myocardial infarction {STEMI})
For Aim 1, the will be a cross-sectional cohort study of 200 pathogenic TTR allele carriers and 200 age-, sex- and race-matched non-carrier controls without heart failure. For Sub-aim 1, this will be a cross-sectional sub-study of the 2 groups enrolled in Aim 1 at UT Southwestern. For Aim 2, this will be a cross-sectional cohort study of 200 pathogenic TTR allele carriers without HF (see Aim 1, Approach), 200 age-, sex-, and race-matched controls (see Aim 1), and 100 patients with symptomatic hATTR-CA who will undergo detailed biomarker assessments.
Case-control
Cross-sectional
Not listed
(Aim 1) Evidence of amyloid infiltration as measured by ECV
ECV expansion represents interstitial expansion from amyloid infiltration and greater levels can distinguish amyloidosis from other hypertrophic cardiomyopathies and correlate with cardiac amyloidosis disease severity.
(Sub-aim 1) Δ stroke volume index (ΔSVi)
We will measure and compare ΔSVi (%) from rest to peak stress in V122I TTR carriers and non-carrier controls. Participants will exercise within the bore of the magnet using an MR compatible ergometer with adjustable electronic resistance (Ergospect Cardio-Stepper, Ergospect). Cardiac imaging will be performed at rest and during exercise at 25% (low intensity), 50% (moderate intensity), and 66% (heavy intensity) of maximal predicted work rate. Workloads will be maintained for \~5 min at each stage - 3 min to achieve a physiological steady-state and then 2 minutes for image acquisition.
(Aim 1) Late gadolinium enhancement
We will use a PSIR sequence, limiting operator-dependency. Global subendocardial enhancement, transmural LGE, and focal, patchy LGE are all features of cardiac amyloidosis, representing interstitial expansion. In cardiac amyloidosis, unlike other cardiomyopathies, LGE is correlated to amyloid infiltration not interstitial fibrosis.
(Aim 1) Native T1 and T2 mapping
Native T1 and T2 mapping represent diffuse interstitial expansion and myocardial edema, respectively. Native T1 measurements are abnormally elevated in amyloidosis and much higher in comparison with other cardiomyopathies that may be associated with interstitial expansion.
(Aim 1) Post-gadolinium T1 signal intensity
Post-gadolinium T1 signal intensity changes characteristically with myocardial signal nulling before the blood pool signal in amyloidosis (opposite of non-amyloid hearts). We will test for this characteristic pattern using a Look-Locker "TI Scout" sequence.
(Aim 1) High resolution cardiac cine imaging for cardiac morphology
High resolution cardiac cine imaging will measure cardiac morphology in all 4 chambers of the heart.
(Sub-aim 2) Associations between each biomarker from Aim 2 and CMRI measurements from Aim 1 and Sub-aim 1
To achieve this, we will employ multivariable generalized linear mixed models to determine the independent association between these biomarkers and CMRI measurements in V122I TTR carriers without HF. Additionally, after determining the univariable association between each biomarker and outcome from Aim 1 and Sub-aim 1, we will employ a backwards selection algorithm from a list of confounders (eGFR, sex, age, hypertension, and BMI) and each biomarker to determine the biomarker(s) most closely associated with subclinical hATTR-CA.
Click on the lead sponsor to view all of their trials.
University of Texas Southwestern Medical Center
Lead sponsor
The Cleveland Clinic
Collaborator
Columbia University
Collaborator
The University of Texas at Arlington
Collaborator
National Heart, Lung, and Blood Institute (NHLBI)
Collaborator
