What happens to cardiac output in hypertrophic cardiomyopathy over time?

In hypertrophic cardiomyopathy (HCM), cardiac output initially may be adequate due to the increased contractility of the heart muscle, but over time, several factors contribute to a decrease in cardiac output.

As the condition progresses, the thickening of the heart muscle can lead to a reduction in the size of the ventricular cavities, thereby impairing their ability to fill adequately during diastole. This inadequate filling can lead to decreased stroke volume, which is a key component of cardiac output. Furthermore, individuals with HCM may also develop diastolic dysfunction, where the heart's ability to relax and fill with blood is compromised.

Additionally, long-standing outflow obstruction due to the hypertrophied septum can lead to turbulent blood flow and increased gradients, contributing to the decline in cardiac performance. Over time, these factors cumulatively result in a decrease in cardiac output despite any initial compensatory mechanisms that may have been in play when the disease first manifests. Thus, the correct answer captures the progression of cardiac output from an initial increase to a subsequent decrease over time.