title: Effects on outcomes of heart rate reduction by ivabradine in patients with congestive heart failure: is there an influence of beta-blocker dose?: findings from the SHIFT (Systolic Heart failure treatment with the I(f) inhibitor ivabradine Trial) study.
abstract: OBJECTIVE
  This study used the SHIFT (Systolic Heart failure treatment with the I(f) inhibitor ivabradine Trial) database to assess the impact of background beta-blocker dose on response to ivabradine.
  
  
  BACKGROUND
  In systolic heart failure, reduction in relatively high heart rates improves clinical outcomes when achieved with beta-blockers and even more so when the sinus node inhibitor ivabradine also is added.
  
  
  METHODS
  Among patients with systolic heart failure, sinus rhythm, and heart rate ≥70 beats/min on recommended background therapy, maximally tolerated beta-blocker doses were subgrouped as no beta-blocker, <25%, 25% to <50%, 50% to <100%, and 100% of European Society of Cardiology–suggested target doses. The impact of ivabradine on cardiovascular death or heart failure hospitalization (primary endpoint) was analyzed in each subgroup as time-to-first event using Cox models adjusted for heart rate. The statistical models assessed heterogeneity and trend of the treatment effect across subgroups, and an additional analysis was made adjusting for the interaction of randomized treatment with baseline heart rate.
  
  
  RESULTS
  The primary endpoint and heart failure hospitalizations were significantly reduced by ivabradine in all subgroups with <50% of target beta-blocker dose, including no beta-blocker (p = 0.012). Despite an apparent trend to reduction in treatment-effect magnitude with increasing beta-blocker dose, no variation in treatment effect was seen in general heterogeneity interaction tests (p = 0.35). Across beta-blocker subgroups, treatment effect was borderline nonsignificant only for the primary endpoint (p = 0.056), and significance was further lost after adjusting for interaction between baseline heart rate and ivabradine effect (p = 0.14).
  
  
  CONCLUSIONS
  The magnitude of heart rate reduction by beta-blocker plus ivabradine, rather than background beta-blocker dose, primarily determines subsequent effect on outcomes. (Effects of ivabradine on cardiovascular events in patients with moderate to severe chronic heart failure and left ventricular systolic dysfunction. A three-year randomised double-blind placebo-controlled international multicentre study; ISRCTN70429960)
authors.affiliation: Department of Emergency and Cardiovascular Medicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden. karl.swedberg@gu.se
authors.forename: Karl
authors.initials: K
authors.lastname: Swedberg
authors.forename: Michel
authors.initials: M
authors.lastname: Komajda
authors.forename: Michael
authors.initials: M
authors.lastname: Böhm
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Borer
authors.forename: Michele
authors.initials: M
authors.lastname: Robertson
authors.forename: Luigi
authors.initials: L
authors.lastname: Tavazzi
authors.forename: Ian
authors.initials: I
authors.lastname: Ford
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage* / Q000627:therapeutic use; D001552:Benzazepines / Q000008:administration & dosage* / Q000627:therapeutic use; D054815:Cyclic Nucleotide-Gated Cation Channels; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004359:Drug Therapy, Combination; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D014943:Global Health; D054143:Heart Failure, Systolic / Q000188:drug therapy* / Q000401:mortality / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D000077550:Ivabradine; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012849:Sinoatrial Node / Q000187:drug effects* / Q000503:physiopathology; D015996:Survival Rate / Q000639:trends; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000188:drug therapy* / Q000401:mortality / Q000503:physiopathology
chemical_list: D000319:Adrenergic beta-Antagonists; D001552:Benzazepines; D054815:Cyclic Nucleotide-Gated Cation Channels; D000077550:Ivabradine