Comparison of Ventricular Septal Measurements in Hypertrophic Cardiomyopathy Patients Who Underwent Surgical Myectomy Using Multimodality Imaging and Implications for Diagnosis and Management

Accurate and reproducible quantification of ventricular septal (VS) thickness in hypertrophic cardiomyopathy (HC) is essential for diagnosis, surgical planning, and risk stratification. We sought to compare VS thickness measurements using transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), and cardiac magnetic resonance (CMR) in patients with HC. Prospectively reported measurements of VS thickness were compared using analysis of variance and Bland-Altman plots in 90 consecutive patients with HC who underwent a TTE, TEE, and CMR within 3 months. A subset was re-measured on 2 separate occasions by 2 readers to assess inter- and intraobserver variability. There was modest correlation between modalities, with CMR and TTE measurements of VS thickness showing the greatest correlation (CMR vs TTE, r = 0.70; CMR vs TEE, r = 0.60; TTE vs TEE, r = 0.56). Smaller measurements were seen using CMR versus either echocardiographic technique (13% smaller vs TEE, 8% smaller vs TTE, p <0.001 for both). The variability of measurement between modalities was not correlated with the degree of VS thickness. There was significantly lower intraobserver variability with CMR versus echocardiography (p = 0.01 for both), but no difference in interobserver variability. CMR delineated a different area of maximal VS thickness other than the basal anteroseptum more frequently than echocardiography (44% of cases vs 24% for TTE and 11% for TEE). In conclusion, CMR assessment of VS thickness differs significantly from echocardiography in patients with HC, with a systemic bias toward lower measurements seen with CMR.