What is primarily decreased in systolic dysfunction of heart failure?

In systolic dysfunction of heart failure, the primary issue is a decrease in the heart's contractility. Contractility refers to the force of heart muscle contractions and is critical for the heart's ability to pump blood effectively during systole, the phase of the heartbeat when the heart muscle contracts. In conditions such as dilated cardiomyopathy or post-myocardial infarction, the myocardial contractile function is impaired, leading to reduced ejection fraction and, consequently, inadequate systemic circulation.

The decreased contractility in systolic dysfunction results in several compensatory mechanisms that can lead to increased preload and afterload, ultimately causing further heart failure symptoms. Understanding that systolic dysfunction is fundamentally about weakened muscle contraction helps in grasping the pathophysiology of heart failure and its clinical presentations. This decline in contractility is what distinguishes it from diastolic dysfunction, where compliance and filling are primarily affected.