Cardiovascular drug utilization post-implant is related to clinical outcome in heart failure patients receiving cardiac resynchronization therapy

Background: In select patients with heart failure, cardiac resynchronization therapy (CRT) is the most common complementary treatment besides medical treatment. We aimed to assess the association between post CRT-implant changes in cardiovascular medication and cardiovascular mortality and heart failure hospitalization. Methods: 211 patients on optimal medical therapy eligible for CRT were retrospectively included in this study (72 +/- 7 years, 80% male, 66% left bundle branch block, 48% dilated cardiomyopathy and investigated at baseline and after 6 months. Follow-up with medication, biochemical markers and echocardiography was performed and 3-year mortality data was collected. Results: At 6 months post-implant the cohort was divided into two groups; 157 patients had low dosage furosemide treatment (up to 40 mg) and 54 patients were treated with high dosage (> 40 mg). A composite endpoint of heart failure hospitalization and all-cause mortality was evaluated at 30 months (881 +/- 267 days) after the 6-month visit. In multivariate Cox regression analysis, patients in the high dose diuretics group had a higher risk of the primary endpoint (HR 1.9 [1.1-3.4], p = 0.033), but treatment with high dose diuretics was not associated with improved clinical symptoms (r = 0.031, p = 0.64). Conclusions: High dosage of loop-diuretics was associated with worse medium-term clinical outcome in CRT treated patients. It is unclear whether there is a direct causality between these associations, or if higher prescribed dosage of loop-diuretics is just a marker of more severe disease. Higher dose loop diuretics do not necessarily improve the symptoms and may be harmful to the patient. Prospective trials are warranted to further elucidate these findings.