• HFpEF: heart failure with preserved ejection fraction
• HFNEF: heart failure with normal ejection fraction
• The pumping percentage, or ejection fraction, is usually preserved, but the ventricle is abnormal in how it relaxes and fills.

Flow of events

1. Comorbidities cause systemic microvascular inflammation
   Common contributors include hypertension, obesity, diabetes, chronic kidney disease, aging, and atrial fibrillation. They promote inflammation and dysfunction of the small coronary blood vessels.
2. LV dysfunction develops
   LV means left ventricle, the main pumping chamber.
3. Longitudinal fibres are affected
   These subendocardial muscle fibres contribute to longitudinal contraction and the normal twisting and untwisting motion of the LV.
   During early diastole, rapid untwisting helps create suction that draws blood from the left atrium into the LV. Impaired relaxation/untwisting reduces this early filling.
4. LV diastolic dysfunction
   The LV becomes slow to relax and stiff, so it cannot accept normal blood volume without an increase in pressure. This is the central issue in HFpEF. The heart may eject a normal proportion of its contents, yet filling occurs at abnormally high pressure.
5. Compensation: LVH and reduced cavity size
   LVH means left-ventricular hypertrophy, usually thickening of the ventricular wall due to long-standing hypertension and other stressors.
   A thicker, stiffer wall often causes a smaller LV cavity. Thus even a modest volume of blood can markedly raise filling pressure.
6. ↑ LVEDP
   LVEDP is left-ventricular end-diastolic pressure, the pressure in the LV after it has filled. It rises because the stiff ventricle resists filling.
7. ↑ LAP
   LAP is left-atrial pressure. Since blood flows from the left atrium into the LV, a high LV filling pressure is transmitted backward to the left atrium.
8. Backward transmission to lungs
   High LAP raises pulmonary venous and capillary pressure, producing:
   • exertional breathlessness, later breathlessness at rest
   • pulmonary congestion or edema
   • pleural effusions
   • pulmonary hypertension over time
   This link between impaired LV relaxation/stiffness and high filling pressures is why patients can have heart-failure symptoms despite a normal LVEF. JACC review

One-line summary

• The LV muscle fibres are arranged in opposing spiral directions.
• During systole, the LV performs a wringing motion:
  • apex rotates counterclockwise
  • base rotates clockwise
    when viewed from the apex.
• This is called LV twist or torsion. It helps efficient ejection of blood.
• In early diastole, the ventricle rapidly recoils in the opposite direction, called untwisting.
• Untwisting releases stored elastic energy and produces a suction effect, helping blood move from the left atrium into the LV.