Assessment of Proximal Tubular Function by Tubular Maximum Phosphate Reabsorption Capacity in Heart Failure

Area of Science:

• Nephrology
• Cardiology
• Internal Medicine

Background:

• Estimated glomerular filtration rate (eGFR) is vital in heart failure, but tubular function's role is less understood.
• This study investigates tubular maximum phosphate reabsorption capacity (TmP/GFR), a proximal tubular function marker, in heart failure patients.

Purpose of the Study:

• To assess the association of TmP/GFR with kidney function decline and clinical outcomes in heart failure.
• To evaluate the effect of SGLT2 inhibition (empagliflozin) on TmP/GFR in acute heart failure.

Main Methods:

• TmP/GFR was measured in 2085 heart failure patients using the Bijvoet formula.
• Logistic and Cox regression analyses examined associations with kidney function deterioration, NGAL doubling, and clinical outcomes.
• Empagliflozin's effect on TmP/GFR was assessed in 78 acute heart failure patients.

Main Results:

• Low TmP/GFR (<0.80 mmol/L) was found in 67% of patients and associated with advanced heart failure and higher tubular damage markers.
• Lower TmP/GFR independently predicted NGAL doubling (OR 2.20) and increased risk of all-cause mortality (HR 2.80), heart failure hospitalization (HR 2.29), and combined events.
• Empagliflozin significantly increased TmP/GFR after 1 day in acute heart failure patients.

Conclusions:

• Proximal tubular function, measured by TmP/GFR, is often reduced in heart failure, particularly in advanced stages.
• Lower TmP/GFR is an independent predictor of adverse clinical outcomes and NGAL doubling, irrespective of glomerular function.
• TmP/GFR may serve as a valuable prognostic marker in heart failure management.