To determine the effect of hawthorn extract 450 mg bid vs. placebo, in addition to standard medical therapy in ambulatory patients with NYHA class II to IV chronic heart failure on submaximal exercise as measured by the 6-minute walk test

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Inclusion Criteria:

• Ambulatory individuals 18 years and older who had been diagnosed with CHF (NYHA functional classes II-IV) for > 3 months
• Left ventricular ejection fraction (LVEF) of ≤ 40 percent
• Receiving indicated standard therapy (if not contraindicated or intolerant for > 3 months) defined as a diuretic, an ACE-inhibitor or an angiotensin receptor blocker (ARB) and a beta-blocke
• Patients with NYHA class III or IV symptoms were also required to receive spironolactone. Doses of these drugs had to be stable for ≥ 3 months, except for diuretics, for which ≥ 1 month of stability was required.

Exclusion Criteria:

• Hemodynamically severe uncorrected primary valvular disease
• Active myocarditis
• Hypertrophic cardiomyopathy
• Restrictive cardiomyopathy
• Myocardial infarction, stroke, unstable angina, coronary artery bypass graft surgery, valvular surgery, or angioplasty < 3 months before randomization
• Symptomatic or sustained ventricular tachycardia not controlled by antiarrhythmic drugs or an implantable cardioverter-defibrillator
• Any condition other than heart failure that would be expected to limit exercise (e.g., angina, peripheral vascular disease, pulmonary disease, arthritis, or an orthopedic problem severe enough to limit exercise)
• Nursing mothers, pregnant women and those planning a pregnancy during the study period