Amyl nitrite may be used to provoke latent gradients in patients with hypertrophic cardiomyopathy (HC) without significant resting outflow tract gradients, but afterload reduction may not be comparable to a more physiologic Stressor such as symptom-limited exercise testing. This study compared the ability of amyl nitrite and exercise testing to provoke outflow tract gradients in 57 patients (40 men and 17 women, mean age ± SD 49 ± 16 years) with HC (septal thickness 19 ± 5 mm, average resting gradient 13 ± 10 mm Hg) who underwent echocardiography at rest, after amyl nitrite inhalation, and after maximal exercise. No significant gradient (< 50 mm Hg) was induced after either provocation in 26 patients (46%); in 15 patients (26%), inducibility was achieved after both stressors, in 6 (11%) after exercise only, and in 10 (18%) after amyl only. Patients with amyl-induced gradients differed from those in whom gradients were noninducible on the basis of smaller outflow tract dimensions (p < 0.001), larger resting gradients (p < 0.001), and a greater prevalence of "septal bulge" morphology (p = 0.02). Those with exercise-induced gradients were able to attain a greater workload (p = 0.07), have larger resting gradients (p = 0.02), and also tended to have a septal bulge morphology (p ≤0.01). Although outflow tract obstruction increased to similar levels after amyl nitrite (49 ± 39 mm Hg) and symptom-limited exercise (47 ± 39 mm Hg), gradients induced by exercise and amyl correlated poorly (r = 0.54). Gradients were the same (within 10%) with both stressors in 14 patients (25%), greater with exercise in 25 (44%), and greater with amyl in 18 patients (32%). Measurement of outflow tract gradients after exercise should be included in the assessment of patients with HC with suspected latent outflow obstruction, particularly in younger patients without amyl-induced outflow tract gradients.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine