To determine the effects of SGLT2 inhibition with empagliflozin on cardio-respiratory fitness in patients with systolic heart failure.

The investigators hypothesize that Sodium-GLucose coTransporters (SGLT)-2 inhibition will improve cardio-respiratory fitness (CRF) in patients with systolic heart failure.

Participants treated with SGLT2 inhibitor Empagliflozin as standard of care will undergo assessments described below.

The investigators will measure CRF with a validated cardiopulmonary exercise test at baseline and after 4 weeks of treatment received as standard of care, to determine whether SGLT2 inhibition improves cardio-respiratory fitness assessed by changes in peak oxygen consumption (VO2)(mL/kg/min) and minute ventilation (VE)/carbon dioxide production (VCO2) slope, powerful independent clinical predictors of mortality in HF.

Inclusion Criteria:

• Confirmed clinical diagnosis of stable HF (NYHA class II-III) on maximally tolerated HF medical regimen including angiotensin-inhibitors, beta-adrenergic blockers, and loop diuretics
• Reduced left ventricular systolic function (LVEF<50%) documented in the prior 12 months
• Poorly controlled T2DM (HbA1c levels between 6.5% and 10.0%)
• 18 years old and older.

Exclusion Criteria:

• Type I diabetes;
• Type II diabetes with episodes of severe hypoglycemia <50 mg/dl by history, frequent changes in anti-diabetic regimen class in the past 3 months or with a prior episode of diabetic ketoacidosis (any time);
• Open label treatment with SGLT2 inhibitors (within the past month);
• Treatment with thiazolidinedione (within the past month), which may induce volume and sodium retention;
• Chronic Kidney Disease (GFR<45 ml/kg*min);
• Uncontrolled thyroid dysfunction (TSH<0.4>4.5 mcIU/ml);
• Pregnancy or of child-bearing potential;
• Active or recent (within 2 weeks) genital/urinal infection;
• Concomitant conditions or treatment which would affect completion or interpretation of the study including physical inability to walk or run on a treadmill such as decompensated HF (edema, NYHA class IV), significant ischemic heart disease, angina, arterial hypotension (BP systolic <90 mmHg), orthostatic arterial hypotension, arterial hypertension (resting BP systolic >160 mmHg), atrial fibrillation with rapid ventricular response, severe valvular disease, severe chronic obstructive or restrictive pulmonary disease, moderate- severe anemia (Hgb<10 g/dl);
• Abnormal BP or heart rate response, angina or ECG changes (ischemia or arrhy- thmias) occurring during baseline cardio-pulmonary exercise testing;
• Chronic use of oral corticosteroids;
• Inability to give informed consent.

Patients with type 2 Diabetes Mellitus and Heart Failure with reduced Ejection Fraction or Systolic Heart Failure.

The investigators plan to present the data promptly upon analysis as an abstract to a national meeting and/or a manuscript.