 - Stable standard heart failure HF therapy including intermediate to high dose β-blocker with either 95 mg metoprolol succinate controlled release tablet, 5mg Bisoprolol immediate release IR -tablet or 5mg Nebivolol IR tablet for at least 4 weeks. Additional intake of angiotensin-converting enzyme ACE inhibitors or angiotensin receptor blockers and optional aldosterone-receptor antagonists, diuretics or digitalis is allowed 