title: Long-Term Echocardiographic Response to Cardiac Resynchronization Therapy in Initial Nonresponders.
abstract: OBJECTIVE
  The aim of this study was to investigate the frequency and clinical implications of a delayed echocardiographic response to cardiac resynchronization therapy (CRT).
  
  
  BACKGROUND
  Long-term prognosis for CRT patients is routinely based on the assessment of echocardiograms after 6 to 12 months of therapy. Some patients, however, may require a longer period of therapy before echocardiographic improvements are detectable.
  
  
  METHODS
  This observational study included all patients with heart failure (HF) receiving a CRT device at a single center from 2003 to 2011. Eligible patients met current indications and had technically adequate echocardiograms from before implantation, approximately 1 year after implantation (mid-term), and ≥3 years after implantation (long-term). A positive echocardiographic response to CRT was defined as a reduction in left ventricular end-systolic volume ≥15%. All-cause mortality was compared for patients in 3 response groups: mid-term responders, long-term responders, and nonresponders.
  
  
  RESULTS
  During this study, 294 patients met the study criteria. Of the 120 patients who were nonresponders after 1 year, 52 (43%) experienced a delayed positive response. Delayed, long-term responders had mortality and hospitalization rates similar to mid-term responders and significantly lower than nonresponders.
  
  
  CONCLUSIONS
  Among patients surviving at least 3 years after implantation of a CRT device and with echocardiographic follow-up, a significant portion of nonresponders after 1 year of CRT experience a delayed echocardiographic response after a longer period of time. Survival and hospitalization rates were similar for all echocardiographic responders, regardless of the time at which the response occurred.
authors.affiliation: United Heart & Vascular Clinic, Allina Health, St. Paul, Minnesota.
authors.forename: Kevin V
authors.initials: KV
authors.lastname: Burns
authors.affiliation: United Heart & Vascular Clinic, Allina Health, St. Paul, Minnesota.
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Gage
authors.affiliation: United Heart & Vascular Clinic, Allina Health, St. Paul, Minnesota; Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Antonia E
authors.initials: AE
authors.lastname: Curtin
authors.affiliation: United Heart & Vascular Clinic, Allina Health, St. Paul, Minnesota. Electronic address: alan.bank@allina.com.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Bank
mesh_terms: D000368:Aged; D058406:Cardiac Resynchronization Therapy / Q000379:methods* / Q000401:mortality; D002423:Cause of Death / Q000639:trends; D004452:Echocardiography / Q000379:methods*; D060731:Emergency Responders; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000628:therapy; D006801:Humans; D008297:Male; D013318:Stroke Volume / Q000502:physiology*; D015996:Survival Rate / Q000639:trends; D013997:Time Factors; D014481:United States / Q000453:epidemiology
keywords: cardiac resynchronization therapy; echocardiography; heart failure; nonresponders