Clin Res Cardiol (2022). https://doi.org/10.1007/s00392-022-02002-5

Surrogates for cardiac amyloidosis among patients with suspicious echocardiography
R. Albrecht1, A. Hamadanchi1, M. Franz1, J. G. Westphal1, P. Aftanski1, C. Schulze1, S. Otto1
1Klinik für Innere Medizin I - Kardiologie, Universitätsklinikum Jena, Jena;

Background: Cardiac amyloidosis (CA) is a progressive infiltrative cardiomyopathy that leads to severe heart failure. There are two leading pathogenetic causes (light chains, AL-CA and ATTR-CA). CA is underdiagnosed due to diagnostic challenging work up and more importantly, missing awareness of health care professionals for this disease.  Beyond the need of epidemiological data, diagnostic pathways have to be refined since novel therapies are now available.
Aim:  We aimed to verify currently discussed disease surrogates, and evaluate suggested and possible novel echocardiography parameters in a population of patients with proven and suspicious CA.  
Methods: A retro- and prospective database over an 8.5 year period (03/2009 and 09/2021) was established. During this time, 41,375 cardiac and non-cardiac patients underwent at least one echo exam for a broad indication at our echo lab of a maximum care hospital. Patients with suspicious echocardiograms were selected. Clinical and laboratory parameters, comorbidities, ECG and echo data were collected for all CA suspected cases. Comprehensive re-analysis of echo studies were done with TomTec®-software including measurements of cavities, wall dimensions, functional parameters, diastolic function and strain analysis among others.  

Results:
While 128 patients were suspected, the diagnosis was falsified in 16 and proven in 47 patients (Light chain n=16, ATTR n= 31). During the aforementioned time frame of 101 months, we saw an incidence of suspicious echocardiography of 1 per 328 patients (or 31 per 10,000), and an incidence of proven cases of 1 per 880 echo patients (or 11.3 per 10,000). The baseline characteristics show an overrepresented male sex (78,8%) and highly overrepresented comorbidities as shown in table 1. As discussed in several papers and position statements ([1], [2], [3], [4]) cardiac biomarkers were severely elevated (table 1), whereas we saw a low voltage pattern in roughly half of the patients  (22 of 43 patients; cut off: ≤0,5mV in limb leads).  Echocardiographic parameters (table 2 and 3) are in line with proposed CA-parameters, such as thickened walls (especially septum wall), dilated atriums and an only slightly reduced LVEF. Our novel parameter “diastolic thickness of the free right ventricular wall” (RVfWd), examined in the subxiphoid view, is with a mean of 8,4 ± 1,9 mm highly pathologic (reference value: 3-5mm) in our patient cohort, and represents the infiltration of both ventricles. Comparing the specific indices with the current scientific evidence as shown in table 3, we see severely impaired longitudinal strain while the circumferential strain remains unimpaired, as known. The shown ratios (RWT, LVMI, MCF, EFSR and SVI) of our cohort are in excellent agreement with the comparator groups from the literature. Also, the modified RAISE- score [4] was applied by using the cut- off values of local assays for troponin. Our cohort had a mean mRAISE-score of 3.0 ± 1.6 (range: 1 to 7), and therefore a high specificity and sensitivity for CA.      

Conclusion:
Echocardiography is a useful tool for identifying CA patients undergoing echo examination for all indications. Non-invasive diagnosis of advanced CA can mostly be established by combining echocardiographic surrogates as well as clinical and laboratory parameters.


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