Background-Two-dimensional echocardiography is currently the standard test for the clinical diagnosis of hypertrophic cardiomyopathy(HCM). The present study was undertaken to determine whether cardiac MRI(CMR) affords greater accuracy than echocardiography in establishing the diagnosis and assessing the magnitude of left ventricular(LV) hypertrophy in HCM. Methods and Results-Forty-eight patients(age 34±16 years) suspected of having HCM(or with a confirmed diagnosis) were imaged by both echocardiography and CMR to assess LV wall thickness in 8 anatomic segments(total n=384 segments) and compared in a blinded fashion. Maximum LV thickness was similar by echocardiography(21.7±9.1 mm) and CMR(22.5±9.6 mm; P=0.21). However, in 3(6%) of the 48 patients, echocardiography did not demonstrate LV hypertrophy, and CMR identified otherwise undetected areas of wall thickening in the anterolateral LV free wall(17 to 20 mm), which resulted in a new diagnosis of HCM. In the overall study group, compared with CMR, echocardiography also underestimated the magnitude of hypertrophy in the basal anterolateral free wall(by 20±6%; P=0001), as well as the presence of extreme LV wall thickness(≥30 mm) in 10%of patients(P< 0.05). Conclusions-CMR is capable of identifying regions of LV hypertrophy not readily recognized by echocardiography and was solely responsible for diagnosis of the HCM phenotype in an important minority of patients. CMR enhances the assessment of LV hypertrophy, particularly in the anterolateral LV free wall, and represents a powerful supplemental imaging test with distinct diagnostic advantages for selected HCM patients.
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