title: Noninvasive assessment of LV contraction patterns using CMR to identify responders to CRT.
abstract: OBJECTIVE
  Type II activation describes the U-shaped electrical activation of the left ventricle (LV) with a line of block in patients with left bundle branch block (LBBB). We sought to determine if a corresponding pattern of contraction could be identified using cardiac magnetic resonance (CMR) cine imaging and whether this predicted response to cardiac resynchronization therapy (CRT).
  
  
  BACKGROUND
  U-shaped LV electrical activation in LBBB has been shown to predict favorable response to CRT. It is not known if the degree of electromechanical coupling is such that the same is true for LV contraction patterns.
  
  
  METHODS
  A total of 52 patients (48% ischemic) scheduled for CRT implantation prospectively underwent pre-implantation CMR cine analysis using endocardial contour tracking software to generate time-volume curves and contraction propagation maps. These were analyzed to assess the contraction sequence of the LV. The effect of contraction pattern on CRT response in terms of reverse remodeling (RR) and clinical parameters (New York Heart Association functional class, 6-min walk distance and Heart Failure Questionnaire score) was assessed at 6 months.
  
  
  RESULTS
  Two types of contraction pattern were identified; homogenous spread from septum to lateral wall (type I, n = 27) and presence of block with a subsequent U-shaped contraction pattern (type II, n = 25). Rates of RR in those with a type 2 pattern were significantly greater at 6 months (80% vs. 26%, p < 0.001) as was mean increase in 6-min walk distance (126 ± 106 m vs. 55 ± 60 m; p = 0.004).
  
  
  CONCLUSIONS
  Cine CMR can identify a U-shaped pattern of contraction which predicts increased echocardiographic and clinical response rates to CRT in patients with LBBB.
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College, London, United Kingdom.
authors.forename: Manav
authors.initials: M
authors.lastname: Sohal
authors.forename: Anoop
authors.initials: A
authors.lastname: Shetty
authors.forename: Simon
authors.initials: S
authors.lastname: Duckett
authors.forename: Zhong
authors.initials: Z
authors.lastname: Chen
authors.forename: Eva
authors.initials: E
authors.lastname: Sammut
authors.forename: Sana
authors.initials: S
authors.lastname: Amraoui
authors.forename: Gerry
authors.initials: G
authors.lastname: Carr-White
authors.forename: Reza
authors.initials: R
authors.lastname: Razavi
authors.forename: Christopher Aldo
authors.initials: CA
authors.lastname: Rinaldi
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy; D005080:Exercise Test; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D018579:Patient Selection; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012984:Software; D011795:Surveys and Questionnaires; D016896:Treatment Outcome; D016277:Ventricular Function, Left; D020257:Ventricular Remodeling
keywords: CMR; CRT; ECG; ICM; LBBB; NCM; NICM; cardiac MRI; cardiac magnetic resonance; cardiac resynchronization therapy; electrocardiograph; ischemic cardiomyopathy; left bundle branch block; left ventricular contraction patterns; noncontact mapping; nonischemic cardiomyopathy