 2. Compensated left heart failure - Patients with significant stable left HF NYHA II-III who are on optimal medical treatment for CHF and are without clinical or laboratory evidence of pulmonary congestion i.e. patients without dyspnea at rest, without rales on auscultation and with BNP levels 100 pgml. This subgroup will be recruited among inpatients andor outpatients at the Rambam campus. 