Prevalence of transthyretin amyloidosis in patients with heart failure and no left ventricular hypertrophy

Abstract Aims As evidenced by scintigraphy imaging, the prevalence of transthyretin (TTR) cardiac amyloidosis in heart failure patients with preserved ejection fraction (HFpEF) and left ventricular hypertrophy (LVH) ranges between 13% and 19%. The natural evolution of cardiac amyloidosis begins with the deposition of amyloid material in the myocardium, with LVH ensuing at later stages. With current imaging modalities, it is possible to detect TTR cardiac amyloidosis before the hypertrophic stage. The aim of this study was to determine the prevalence of TTR cardiac amyloidosis in HFpEF patients without LVH. Methods and results The study prospectively enrolled patients admitted for HF with LV ejection fraction (LVEF) ≥ 50% and LV wall thickness <12 mm. TTR cardiac amyloidosis was diagnosed according to accepted criteria, which include positive cardiac 99‐Tc‐DPD scintigraphy in the absence of monoclonal protein expansion in blood. Transthyretin gene sequencing was performed in positive patients. From July 2017 to January 2020, 329 patients with HFpEF and LV thickness <12 mm were identified. After exclusions, 58 patients completed the study with cardiac scintigraphy (79 years, 54% men; median LVEF 60% and LV wall thickness 10.5 mm). Three patients (5.2%) were positive for TTR cardiac amyloidosis; genetic analysis excluded the presence of hereditary TTR amyloidosis. Positive patients baseline characteristics (84 years, 67% men, LVEF 60%, and LV wall thickness 11 mm) were similar to patients without TTR, except for troponin levels (0.05 vs. 0.02 ng/mL, P = 0.03) and glomerular filtration rate (82 vs. 60 mL/min, P = 0.032), which were higher in TTR patients. Conclusions In a cohort of patients with HFpEF without LVH, the prevalence of TTR cardiac amyloidosis was 5%. Early diagnosis of cardiac involvement in TTR amyloidosis (before manifest LVH) would seem recommendable because newly approved specific treatments can prevent additional deposition of amyloid material

Thickness and conductivity determination of thin coatings on ferromagnetic substrates in the case of cylindrical symmetry

An eddy current method allowing the determination of parameters of a thin nonmagnetic conductive coating on a ferromagnetic conductive substrate is reported. At a single operating frequency, two independent quantities can be determined: a permeability-to-conductivity ratio of the substrate and a thickness-conductivity product of the coating. Thus, thickness or conductivity of the coating can be determined independent of variations of the substrate magnetic and electrical parameters. A simple theoretical formula for the normalized electrical impedance of the test coil is obtained using asymptotic expansions of Bessel functions. The method was applied to the evaluation of electrogalvanized wires in the frequency range 100 kHz-1 MHz. A set of low carbon steel wires with diameter around 2.2 mm, coated with zinc layers having thicknesses in the range 2.7-64.6 mu m, was investigated using two long coils. Experimental data of the electrical impedance were compared to those predicted. Agreement between theory and experiment is excellent for coatings thicker than 12 mu m. Despite discrepancies between theory and experiment for very thin layers arising from various imperfections of the coating and interfaces, the method was applied successfully in the thickness range below 12 mu m. To do this, two parameters: an apparent conductivity of the coating and a thickness offset, were introduced. The mathematical inversion of the experimental data with the two-variable Newton-Raphson method and the asymptotic formula is extremely fast. The technique developed has an extremely low sensitivity to variations of the ferromagnetic substrate conductivity and magnetic permeability. A magnetizing field of 0-23 000 A/m, producing large variations in the substrate magnetic permeability, does not significantly influence results of the coating thickness determination. The agreement between measured thickness and that obtained by a chemical method is excellent, typically within 0.5 mu m. An uncertainty of the thickness or conductivity determination better than 1% is obtained. (C) 1997 American Institute of Physics