['Cardiac resynchronization therapy (CRT) is associated with improved morbidity and mortality in patients with chronic heart failure (CHF) on optimal medical therapy. The impact of CHF medication optimization following CRT, however, has never been comprehensively evaluated. In the current study, we therefore investigated the effect of CHF medication dosage on morbidity and mortality in CHF patients after CRT implantation.', 'Chronic heart failure medication was assessed in 185 patients after CRT implantation. During an overall mean follow-up of 44.6 months, 83 patients experienced a primary endpoint (death, heart transplantation, assist device implantation, or hospitalization for CHF). Treatment with higher dosages of angiotensin-converting enzyme inhibitor (ACE-I) or angiotensin receptor blockers (ARBs) (P = 0.001) and beta-blockers (P < 0.001) as well as with lower dosages of loop diuretics (P < 0.001) was associated with a reduced risk for the primary combined endpoint as well as for all-cause mortality. Echocardiographic super-responders to CRT were treated with higher average dosages of ACE-I/ARBs (68.1 vs. 52.4%, P < 0.01) and beta-blockers (59 vs. 42.2%, P < 0.01). During follow-up, the average dosage of loop diuretics was decreased by 20% in super-responders, but increased by 30% in non-super-responders (P < 0.03).'] Is treatment with higher dosages of heart failure medication associated with improved outcome following cardiac resynchronization therapy?