Lowering the Recommended Maximal Wall Thickness Threshold Improves Diagnostic Sensitivity in Asians With Hypertrophic Cardiomyopathy

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is defined as left ventricular end-diastolic maximal wall thickness (WT(Max)) ≥15.0 mm, without accounting for ethnicity, sex, and body size. It is well-established that Asians have smaller hearts than do Caucasians. OBJECTIVES: This study aims to examine the implications of this single absolute WT(Max) threshold on the diagnosis of HCM in Asians. METHODS: The study consisted of 360 healthy volunteers (male: n = 174; age: 50 ± 12 years) and 114 genetically characterized patients with HCM (male: n = 83; age: 52 ± 13 years; genotype-positive, n = 39). All participants underwent cardiovascular magnetic resonance. WT(Max) was measured semiautomatically at end-diastole according to the standard 16 myocardial segments. RESULTS: Healthy male volunteers had increased WT(Max) compared with that of female volunteers (8.4 ± 1.2 mm vs 6.6 ± 1.1 mm, respectively; P < 0.001). Conversely, WT(Max) was similar between male and female patients with HCM (15.2 ± 3.4 mm vs 14.7 ± 3.0 mm, respectively; P = 0.484) and between those with and without a pathogenic gene variant (P = 0.828). Using the recommended diagnostic threshold of 15.0 mm, 56 patients with HCM had WT(Max) <15.0 mm and no healthy volunteers had WT(Max) >15.0 mm (specificity of 100% and sensitivity of 51%). Lowering WT(Max) thresholds to 10.0 mm in female patients and 12.0 mm in male patients did not affect specificity (100%) but significantly improved sensitivity (84%). Despite lower left ventricular mass, female patients with HCM demonstrated more features of adverse cardiac remodeling than did male patients: increased myocardial fibrosis, higher asymmetric ratio, and disproportionately worse myocardial strain. CONCLUSIONS: The study highlights cautious application of guideline-recommended WT(Max) to diagnose HCM in Asians. Lowering WT(Max) to account for ethnicity and sex improves diagnostic sensitivity without compromising specificity.