PET/CT Assessment of Symptomatic Individuals with Obstructive and Nonobstructive Hypertrophic

Patients with obstructive hypertrophic cardiomyopathy (HCM) exhibit elevated left ventricular outflow tract gradients (LVOTGs) and appear to have a worse prognosis than those with nonobstructive HCM. The aim of this study was to evaluate whether patients with obstruction, compared with nonobstruc-tive HCM, demonstrate significant differences in PET parame-ters of microvascular function.Methods: PET was performed in 33 symptomatic HCM patients at rest and during dipyridamole stress (peak) for the assessment of regional myocardial perfu-sion (rMP), left ventricular ejection fraction (LVEF), myocardial blood flow (MBF), and myocardial flow reserve (MFR). Myocar-dial wall thickness and LVOTG were measured with an echo-cardiogram. Patients were divided into the following 3 groups: nonobstructive (LVOTG, 30 mm Hg at rest and after provoca-tion test with amyl nitrite), obstructive (LVOTG $ 30 mm Hg at rest and with provocation), and latent HCM (LVOTG, 30 at rest but $ 30 mm Hg with provocation). Results: Eleven patients were classified as nonobstructive (group 1), 12 as obstructive (group 2), and 10 as latent HCM (group 3). Except for age (42 6 18 y for group 1, 586 7 y for group 2, and 586 12 y for group 3; P 5 0.01), all 3 groups had similar baseline characteristics, in-cluding maximal wall thickness (2.3 6 0.5 cm for group 1, 2.2 6 0.4 cm for group 2, and 2.1 6 0.7 cm for group 3; P 5 0.7). During peak flow, most patients in groups 1 and 2, but fewer in group 3, exhibited rMP defects (73 % for group 1, 100 % for group 2, and 40 % for group 3; P 5 0.007) and a drop in LVE