What changes in preload, afterload, heart rate, and contractility will optimize hemodynamic performance in a patient with HOCM?

What changes in preload, afterload, heart rate, and contractility will optimize hemodynamic performance in a patient with HOCM?

Determinants of the severity of the ventricular obstruc-tion in HOCM are:

·        systolic volume of the ventricle

·        force of ventricular contraction

·        transmural pressure distending the outflow tract

Large systolic volumes in the ventricle distend the out-flow tract and reduce the obstruction. Paradoxically, when ventricular contractility is increased, the outflow tract is narrowed, which increases the obstruction and decreases cardiac output. When aortic pressure (afterload) is ele-vated, there is an increased transmural pressure distending the LVOT during systole and this reduces the degree of obstruction. However, during periods of systemic vasodila-tion the outflow tract is narrowed. This results in marked decreases in cardiac output and even mitral regurgitation as the mitral valve becomes the relief point for ventricular pressure (Table 8.1).