Empagliflozin (SGLT2 inhibitor) has demonstrated mortality benefit in heart failure with reduced ejection fraction independent of its glucose-lowering effect. Which is the most mechanistically convincing explanation?
- A Osmotic diuresis and natriuresis reduce preload; shift cardiac substrate utilization from glucose to ketones (metabolic efficiency); and lower intracellular sodium via NHE1 inhibition, reducing calcium overload ✓
- B Inhibition of SGLT1 in the myocardium directly reduces glucose uptake, forcing mitochondria to use fatty acids more efficiently
- C GLP-1 elevation secondary to SGLT2 inhibition activates cardiac GLP-1 receptors, improving myocardial contractility
- D Erythropoietin elevation due to SGLT2 inhibition increases haematocrit, enhancing myocardial oxygen delivery
Explanation
The cardioprotective mechanisms of SGLT2 inhibitors in HFrEF are multifactorial. Osmotic glycosuria and natriuresis reduce plasma volume and preload without activating the renin-angiotensin system (unlike loop diuretics). Ketonaemia induced by SGLT2 inhibition provides the ischemic/failing heart with a more oxygen-efficient fuel (ketones yield more ATP per oxygen molecule than glucose via reduced electron transport chain uncoupling). The NHE1 (sodium-hydrogen exchanger isoform 1) inhibition hypothesis: SGLT2 inhibitors may also inhibit myocardial NHE1, reducing intracellular sodium accumulation in failing cardiomyocytes, which then reduces intracellular calcium overload via the NCX (sodium-calcium exchanger), lessening diastolic dysfunction and contractile dysfunction. The EMPEROR-Reduced and DAPA-HF trials established mortality/morbidity benefit in non-diabetic HFrEF as well.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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