In Phase 1 of the study, all patients will be treated with optimization of medical therapy for 6 months. Thereafter, all patients will cros over to Phase 2 of the study, where they will receive transendocardial CD34+ cell therapy. Follow-up of Phase 2 will last for 6 months. At the time of enrollment (6 months before cell therapy), at time of cell therapy, and 6 months thereafter we will perform detailed clinical evaluation, laboratory assays, echocardiography, 6-minute walk test, and measure plasma levels of N-terminal pro B-type natriuretic peptide (NT-proBNP).

Electro-anatomical mapping will be performed using the Biosense NOGA system (Biosense-Webster, Diamond Bar, California). Local diastolic function will be assessed by a novel algorhithm that allows for the measuring local ventricular relaxation times at each of the sampling points. Target areas for cell delivery will be defined as the myocardial segments with the evidence of local diastolic dysfunction and myocardial hibernation. Transendocardial delivery of cell suspension in the SC Group will be performed with MyoStar® (Biosense Webster) injection catheter. Each patient will receive 20 injections of 0.3 mL of stem cell suspension.

The E/e' ratio will be calculated from early transmitral velocity divided by peak left ventricular relaxation velocity for estimation of the left ventricular filling pressure.

6-minute walk test will be performed by a blinded observer according to the standard protocol.

NT-proBNP assays will be performed at a central independent laboratory, blinded to the patient's clinical data using a commercially available kit (Roche Diagnostics, Mannheim, Germany).