Regional systolic function, myocardial blood flow and glucose uptake at rest in hypertrophic cardiomyopathy

Decreased ¹⁸fluorodeoxyglucose (FDG) uptake and blood flow at rest in the ventricular septum, as compared with the lateral wall, have been reported in mildly symptomatic patients with hypertrophic cardiomyopathy (HC). To assess whether regional metabolic heterogeneity in patients with HC is related to heterogeneous regional systolic function, 10 symptomatic patients (mean age 36 ± 17 years) with HC and no coronary artery disease underwent positron emission tomography with oxygen-15-water and FDG, and nuclear magnetic resonance imaging at rest to assess regional anatomy and systolic function. Regional absolute blood flow was similar between the ventricular septum and lateral wall. In contrast, FDG activity was significantly greater in the lateral wall than in the septum (1,023 ± 588 vs 767 ± 388 nCi/ml, respectively; p < 0.01). However, regional systolic wall thickening was also significantly greater in the lateral wall than in the septum (5.3 ± 4.3 vs 2.4 ± 4.0 mm, respectively; p < 0.001). Patients were then divided into group A (n = 5) with similar regional wall thickening in the septum and lateral wall, and group B (n = 5) with greater thickening in the lateral wall than in the septum. In both groups, regional blood flow was similar between the septum and lateral wall. However, the regional septal-to-lateral FDG activity ratio was 0.97 ± 0.31 in group A, and 0.74 ± 0.25 in group B (p < 0.01); the ratio in group A did not differ from that in 5 normal subjects (1.02 ± 0.58). Thus, myocardial Mood flow is normal at rest in patients with HC and no coronary artery disease; the heterogeneity in regional glucose uptake is parallel to that of regional systolic function and does not necessarily represent a metabolic abnormality at the cellular level.