In the current European Guidelines, hypertrophic cardiomyopathy (HCM) is defined as a wall thickness (WT) ≥15mm. Its epidemiology is presented as such: 40-60% sarcomeric protein gene mutations, 25–30% unknown and 5–10% genetic and non-genetic causes. However, clinical practice does not necessarily confirm these values.

We sought to describe the panel of LVWT and final aetiologic diagnoses among patients referred for assessment of LVWT ≥12mm.

Consecutive patients referred to our tertiary centre since January 2017 for the assessment of LVWT ≥12mm were retrospectively included. Patients presenting with severe aortic stenosis (n=107) were excluded. 121 patients were included in the final analysis. Personal and familial history were collected for all patients and each patient underwent a complete physical examination, electrocardiogram and transthoracic echocardiography. Additional assessments were carried out based on the results of this first screening.

Median LVWT was 15mm (IQR 14 – 17). Final aetiologies were distributed as follows: 38 (31%) amyloidosis, 26 (21%) post-hypertensive, 35 (29%) sarcomeric, 4 (3%) other diagnoses and 18 (16%) undetermined. Among patients diagnosed with amyloidosis, 4 (11%) were inherited TTR, 8 (21%) wild-type TTR, 13 (34%) TTR of undetermined type, 11 (29%) light chain and 2 (6%) AA or apoA2 amyloidosis. Among patients diagnosed with sarcomeric HCMs, 4 (11%) were carriers of a mutation. 43 patients (36%) had a maximal LVWT between 12 and 15mm. 11 (26%) of them had cardiac amyloidosis, 4 (9%) sarcomeric HCM, 17 (40%) undetermined LVH, 11 (26%) post-hypertensive HCM and 2 (5%) other aetiologies.

Meaningful diagnoses of HCMs, such as cardiac amyloidosis (26%) and sarcomeric HCM (9%), could be made in the 12 to 15mm range of LVWT. Overall, sarcomeric HCM does not seem to be the main aetiology and the true prevalence of cardiac amyloidosis seems to be underestimated.