Resting Echocardiographic Features of Latent Left Ventricular Outflow Obstruction in Hypertrophic Cardiomyopathy*
Section snippets
METHODS
Provocation with amyl nitrite: In our echocardiography laboratory, patients routinely undergo provocative testing with amyl nitrite inhalation if they have anatomic features of HC[8]with clinical suspicion of intermittent LV outflow tract obstruction but do not demonstrate significant obstruction at rest.[3]Amyl nitrite (Vaporole, Burroughs Wellcome, Research Triangle Park, North Carolina) is administered after crushing a 0.3-ml glass capsule. The patient inhales amyl nitrite from the capsule
RESULTS
Type of hypertrophy: There were 8 patients with asymmetric septal hypertrophy, 26 with concentric hypertrophy, and 16 with proximal septal bulge. In 3 of 8 patients (38%) with asymmetric septal hypertrophy and in 10 of 26 patients (38%) with concentric hypertrophy, LV outflow obstruction was provoked by amyl nitrite inhalation. In contrast, patients with a proximal septal bulge had a significantly higher incidence of latent obstruction; 13 of 16 patients (81%) were provocable (p <0.05 by
DISCUSSION
Effect of the site of hypertrophy: Correlation between the site of hypertrophy and the hemodynamic subgroups has been previously reported. In a study with 100 patients with HC, Wigle et al[1]demonstrated that latent obstruction was found in 72% of patients with localized subaortic hypertrophy. They also showed that when the hypertrophy involved the full-length septum, only 8% of the patients had provocable obstruction. In agreement with their findings, we showed that the incidence of latent
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This study was supported in part by a grant from the Uehara Memorial Foundation, Tokyo, Japan.