Mechanisms of Effort Intolerance in Patients With Heart Failure and Borderline Ejection Fraction.

Combining echocardiography and cardiopulmonary stress testing allows noninvasive assessment of hemodynamics, and oxygen extraction (A-VO difference). We evaluated mechanisms of effort intolerance in patients with heart failure with borderline (40% to 49%) left ventricular ejection fraction (EF) (HF and Borderline Ejection fraction). We included 89 consecutive patients with HF and Borderline Ejection fraction (n = 25; 63.