Lowering the Recommended Maximal Wall Thickness Threshold Improves Diagnostic Sensitivity in Asians With Hypertrophic Cardiomyopathy
Thu‐Thao Le, Benjamin Huang, Chee Jian Pua, Vineet Tornekar, Annette Schumacher-Maurer, Desiree‐Faye Toh, Jennifer Bryant, Briana Ang, Ben Corden, Sanjay Prasad, Hak-Chiaw Tang, Stuart A. Cook, Calvin Chin
Abstract
Hypertrophic cardiomyopathy (HCM) is defined as left ventricular end-diastolic maximal wall thickness (WTMax) ≥15.0 mm, without accounting for ethnicity, sex, and body size. It is well-established that Asians have smaller hearts than do Caucasians. This study aims to examine the implications of this single absolute WTMax threshold on the diagnosis of HCM in Asians. 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. WTMax was measured semiautomatically at end-diastole according to the standard 16 myocardial segments. Healthy male volunteers had increased WTMax compared with that of female volunteers (8.4 ± 1.2 mm vs 6.6 ± 1.1 mm, respectively; P < 0.001). Conversely, WTMax 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 WTMax <15.0 mm and no healthy volunteers had WTMax >15.0 mm (specificity of 100% and sensitivity of 51%). Lowering WTMax 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. The study highlights cautious application of guideline-recommended WTMax to diagnose HCM in Asians. Lowering WTMax to account for ethnicity and sex improves diagnostic sensitivity without compromising specificity.