1. What does systolic heart failure primarily refer to?
Heart failure with reduced ejection fraction (<40%) caused by impaired ventricular contraction.
Обяснение
Systolic heart failure is characterized by a reduced ejection fraction (less than 40%), which indicates impaired ventricular contraction. This leads to the heart's inability to pump blood effectively. The other options describe different conditions: preserved EF with diastolic dysfunction, valvular issues, or arrhythmia-related failure, but they do not define systolic heart failure.