Echocardiography-derived measurements of maximum left ventricular (LV) wall thickness are important for both the diagnosis and risk stratification of hypertrophic cardiomyopathy (HC). Cardiac magnetic resonance (CMR) imaging is increasingly being used in the assessment of HC; however, little is known about the relation between wall thickness measurements made by the 2 modalities. We sought to compare measurements made with echocardiography and CMR and to assess the impact of any differences on risk stratification using the current European Society of Cardiology guidelines. Maximum LV wall thickness measurements were recorded on 50 consecutive patients with HC. Sixty-nine percent of LV wall thickness measurements were recorded with echocardiography, compared with 69% from CMR (p <0.001). There was poor agreement on the location of maximum LV wall thickness; weighted-Cohen's κ 0.14 (p = 0.036) and maximum LV wall thicknesses were systematically higher with echocardiography than with CMR (mean 19.1 ± 0.4 mm vs 16.5 ± 0.3 mm, p <0.01, respectively); Bland-Altman bias 2.6 mm (95% confidence interval -9.8 to 4.6). Interobserver variability was lower for CMR (R 0.67 echocardiography, R 0.93 CMR). The mean difference in 5-year sudden cardiac death (SCD) risk between echocardiography and CMR was 0.49 ± 0.45% (p = 0.37). When classifying patients (low, intermediate, or high risk), 6 patients were reclassified when CMR was used instead of echocardiography to assess maximum LV wall thickness. These findings suggest that CMR measurements of maximum LV wall thickness can be cautiously used in the current European Society of Cardiology risk score calculations, although further long-term studies are needed to confirm this.

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