Cardiac resynchronization therapy indications

Synonyms and Keywords: CRT
 * : Bhaskar Purushottam, M.D. [mailto:bpurushottam@gmail.com]

Overview
Cardiac resynchronization therapy (CRT) with or without an ICD is indicated in patients who have an LVEF less than or equal to 35%, a QRS duration greater than or equal to 0.12 seconds, and normal sinus rhythm, for the treatment of NYHA functional Class III or ambulatory Class IV heart failure symptoms in patients whose medical therapy has been optimized.

Indications
==ACC / AHA Guidelines - Recommendations for Cardiac Resynchronization Therapy in Patients with Severe Systolic Heart Failure (DO NOT EDIT) == {{cquote|

Class I
1) For patients who have LVEF less than or equal to 35%, a QRS duration greater than or equal to 0.12 seconds, and sinus rhythm, CRT with or without an ICD is indicated for the treatment of NYHA functional Class III or ambulatory Class IV heart failure symptoms with optimal recommended medical therapy. (Level of Evidence: A)

Class IIa
1) For patients who have LVEF less than or equal to 35%, a QRS duration greater than or equal to 0.12 seconds, and AF, CRT with or without an ICD is reasonable for the treatment of NYHA functional Class III or ambulatory Class IV heart failure symptoms on optimal recommended medical therapy. (Level of Evidence: B)

2) For patients with LVEF less than or equal to 35% with NYHA functional Class III or ambulatory Class IV symptoms who are receiving optimal recommended medical therapy and who have frequent dependence on ventricular pacing, CRT is reasonable. (Level of Evidence: C)

Class IIb
1) For patients with LVEF less than or equal to 35% with NYHA functional Class I or II symptoms who are receiving optimal recommended medical therapy and who are undergoing implantation of a permanent pacemaker and/or ICD with anticipated frequent ventricular pacing, CRT may be considered. (Level of Evidence: C)

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Unanswered Questions
Unanswered questions regarding the indications for CRT include:
 * 1) The identification of patients who would definitely benefit from CRT (i.e. reducing the number of non-responders). Different imaging modalities and dyssynchrony parameters may accurately reveal mechanical dyssynchrony and therefore predict a CRT responder, especially in patients with a narrow QRS complex.
 * 2) Further confirmatory evidence regarding the benefit of atrioventricular ablation versus pharmacological rate control in optimizing the clinical benefits is needed. In addition to atrioventricular and Ventricular-Ventricular optimization, other device based changes need to be explored so as to optimize the benefits of CRT.