What effect does amyl nitrate have when administered to a patient with hypertrophic obstructive cardiomyopathy (HOCM)?

When amyl nitrate is administered to a patient with hypertrophic obstructive cardiomyopathy (HOCM), it causes vasodilation by releasing nitric oxide, which can lead to a drop in cardiac preload. In HOCM, the anatomy and dynamics of the heart can lead to a situation where there is obstruction of the left ventricular outflow tract (LVOT) due to the abnormal positioning of the mitral valve as well as the dynamic nature of the left ventricle.

The administration of amyl nitrate can reduce the diastolic filling pressures and allow for a decrease in ventricular volume. As the volume in the ventricle decreases, it may induce or increase the systolic anterior motion (SAM) of the mitral valve. Systolic anterior motion refers to the movement of the mitral valve toward the left ventricular outflow tract during systole, which can worsen the outflow tract obstruction. Thus, the correct answer highlights that amyl nitrate can exacerbate the condition by increasing the motion of the mitral valve towards the outflow tract, which could further narrow the LVOT and lead to more significant symptoms or hemodynamic instability in someone with HOCM.

This understanding emphasizes the complex hemodynamics at play in patients