Amyl nitrate can be given via inhalation to reduce afterload for diagnostic purposes in the cardiac catheterization laboratory to invoke an LV outflow tract gradient in hypertrophic obstructive cardiomyopathy patients.
It can also be used as a diagnostic tool during cardiac physical examination. Due to the advancement of echocardiography, it is no longer commonly used.
Amyl nitrate decreases afterload and would decrease the murmur of mitral regurgitation. When the afterload is decreased, there is less resistance to blood flow from the left ventricle through the aortic valve, and thus less blood regurgitates through the mitral valve, decreasing the intensity of the murmur.