title: Incidence, definition, diagnosis, and management of the cardiac resynchronization therapy nonresponder.
abstract: OBJECTIVE
  Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with mild-to-severe heart failure. However, up to 40% of CRT recipients are nonresponders. This review addresses important aspects with regard to the identification and management of CRT nonresponders.
  
  
  RESULTS
  Mid-term clinical or echocardiographic nonresponse is associated with worse clinical outcomes during the extended follow-up. A number of predictors are indicative of CRT response, which include patient characteristics, electrical determinants, and imaging techniques from preimplant to postimplant period, and can be grouped as modifiable and nonmodifiable contributors to treatment response. Advanced age, male sex, ischemic cause, end-stage heart failure, inadequate electrical delay, and absence of mechanical dyssynchrony are regarded as unfavorable but nonmodifiable factors, for which considering underutilization of CRT by refining patient selection is reasonable. On the contrary, more efforts should be made to optimize patient management by correcting those modifiable factors, such as suboptimal medical therapy, uncontrolled atrial fibrillation, left ventricular lead dislodgement or inappropriate location, loss of biventricular capture, and lack of device optimization.
  
  
  CONCLUSIONS
  Proper management and careful selection of CRT recipients will transform a proportion of treatment nonresponders into responders, which is vital to improve patients' outcome.
authors.affiliation: aDepartment of Cardiology, West China Hospital, Sichuan University, Chengdu, Sichuan bDivision of Cardiology, Anzhen Hospital, Capital Medical University, Beijing cDivision of Cardiology, Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhang
authors.forename: Yujie
authors.initials: Y
authors.lastname: Zhou
authors.forename: Cheuk-Man
authors.initials: CM
authors.lastname: Yu
mesh_terms: D002304:Cardiac Pacing, Artificial / Q000379:methods / Q000401:mortality; D058406:Cardiac Resynchronization Therapy / Q000379:methods* / Q000401:mortality; D017147:Defibrillators, Implantable; D003952:Diagnostic Imaging / Q000379:methods*; D015150:Echocardiography, Doppler / Q000379:methods; D004562:Electrocardiography / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy*; D006801:Humans; D015994:Incidence; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods; D008297:Male; D010138:Pacemaker, Artificial; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D012720:Severity of Illness Index; D013318:Stroke Volume / Q000502:physiology; D015996:Survival Rate; D017211:Treatment Failure; D016896:Treatment Outcome