Patients with unexplained stress dyspnea ( ≥ stage 2 NYHA), no significant underlying lung disease, with an ejection fraction > 50%, normal resting filling pressures, NTproBNP < 220 pg/ml in < 75 years, and < 450 pg/ml in ≥ 75 years will be studied with stress echocardiography and cardiometabolic stress test (VO2). These patients may have abnormal adaptation during exercise, suggesting that chronic symptoms may be related to a heart failure with preserved ejection fraction (HFPEF). More accurate and earlier diagnosis of HFPEF using stress echocardiography and VO2 may better manage stress dyspnea in patients and prevent progression of HFPEF.

A clinical assessment will be offered to people with unexplained stress dyspnea. The procedures and products used in this study are usually used as part of HFpEF's diagnostic strategy. During this assessment, carried out on an outpatient basis, an anamnesis collection, a cardiovascular clinical examination, an evaluation of dyspnea by the NYHA functional class and by 2 questionnaires, an electrocardiogram will be carried out, a 6-minute walk test, a biological blood test, a trans thoracic rest and stress cardiac ultrasound, respiratory functional tests (with diffusion capacity of lung for carbon monoxide (DLCO) and blood gas), and a metabolic stress test. A follow-up at 1 and 2 years is planned (visit, sampling and resting echocardiography).

Inclusion Criteria:

• Patient over 40 years of age, and under 80 years of age with unexplained effort dyspnea, able to pedal.
• Echocardiographic ejection fraction > 50%
• NTproBNP < 220 pg/ml in < 75 years, and < 450 pg/ml in ≥ 75 years

Exclusion Criteria:

• Patient with coronary, valve, hypertrophic, hypertensive, infiltrative, constrictive, or rhythmic, significant and/or progressive heart disease.

BMI > 35 kg/m².

• Unstable patient (systolic blood pressure < 90 mmHg, resting pulse > 100 BPM) or clinically congested (edema of the lower limbs, crackling in the lungs).
• Patient with Pulmonary function testing (EFR) showing significant respiratory disease (FEV1/ vital capacity (CV) max < 0.7, total lung capacities (CPT)< LIN)
• Chronic renal failure with creatinine clearance < 30 ml/min (MDRD) or dialysis
• Patient with anemia (Hb < 12 g/dl)
• Patient with hypo or hyperthyroidism on thyreostimulating hormone (TSH) value
• Patient under justice safeguard measure or guardianship

All referred patients for unexplained dyspnea that must be assessed