title: Mechanical dispersion assessed by myocardial strain in patients after myocardial infarction for risk prediction of ventricular arrhythmia.
abstract: OBJECTIVE
  The aim of this study was to investigate whether myocardial strain echocardiography can predict ventricular arrhythmias in patients after myocardial infarction (MI).
  
  
  BACKGROUND
  Left ventricular (LV) ejection fraction (EF) is insufficient for selecting patients for implantable cardioverter-defibrillator (ICD) therapy after MI. Electrical dispersion in infarcted myocardium facilitates malignant arrhythmia. Myocardial strain by echocardiography can quantify detailed regional and global myocardial function and timing. We hypothesized that electrical abnormalities in patients after MI will lead to LV mechanical dispersion, which can be measured as regional heterogeneity of contraction by myocardial strain.
  
  
  METHODS
  We prospectively included 85 post-MI patients, 44 meeting primary and 41 meeting secondary ICD prevention criteria. After 2.3 years (range 0.6 to 5.5 years) of follow-up, 47 patients had no and 38 patients had 1 or more recorded arrhythmias requiring appropriate ICD therapy. Longitudinal strain was measured by speckle tracking echocardiography. The SD of time to maximum myocardial shortening in a 16-segment LV model was calculated as a parameter of mechanical dispersion. Global strain was calculated as average strain in a 16-segment LV model.
  
  
  RESULTS
  The EF did not differ between ICD patients with and without arrhythmias occurring during follow-up (34 +/- 11% vs. 35 +/- 9%, p = 0.70). Mechanical dispersion was greater in ICD patients with recorded ventricular arrhythmias compared with those without (85 +/- 29 ms vs. 56 +/- 13 ms, p < 0.001). By Cox regression, mechanical dispersion was a strong and independent predictor of arrhythmias requiring ICD therapy (hazard ratio: 1.25 per 10-ms increase, 95% confidence interval: 1.1 to 1.4, p < 0.001). In patients with an EF >35%, global strain showed better LV function in those without recorded arrhythmias (-14.0% +/- 4.0% vs. -12.0 +/- 3.0%, p = 0.05), whereas the EF did not differ (44 +/- 8% vs. 41 +/- 5%, p = 0.23).
  
  
  CONCLUSIONS
  Mechanical dispersion was more pronounced in post-MI patients with recurrent arrhythmias. Global strain was a marker of arrhythmias in post-MI patients with relatively preserved ventricular function. These novel parameters assessed by myocardial strain may add important information about susceptibility for ventricular arrhythmias after MI.
authors.affiliation: Department of Cardiology, Rikshospitalet University Hospital and University of Oslo, Oslo, Norway.
authors.forename: Kristina H
authors.initials: KH
authors.lastname: Haugaa
authors.forename: Marit Kristine
authors.initials: MK
authors.lastname: Smedsrud
authors.forename: Torkel
authors.initials: T
authors.lastname: Steen
authors.forename: Erik
authors.initials: E
authors.lastname: Kongsgaard
authors.forename: Jan Pål
authors.initials: JP
authors.lastname: Loennechen
authors.forename: Terje
authors.initials: T
authors.lastname: Skjaerpe
authors.forename: Jens-Uwe
authors.initials: JU
authors.lastname: Voigt
authors.forename: Rik
authors.initials: R
authors.lastname: Willems
authors.forename: Gunnar
authors.initials: G
authors.lastname: Smith
authors.forename: Otto A
authors.initials: OA
authors.lastname: Smiseth
authors.forename: Jan P
authors.initials: JP
authors.lastname: Amlie
authors.forename: Thor
authors.initials: T
authors.lastname: Edvardsen
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D001530:Belgium; D016022:Case-Control Studies; D017147:Defibrillators, Implantable; D004452:Echocardiography; D004554:Electric Countershock / Q000295:instrumentation; D004562:Electrocardiography; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D009203:Myocardial Infarction / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D009664:Norway; D011237:Predictive Value of Tests; D011322:Primary Prevention; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012008:Recurrence; D018570:Risk Assessment; D012307:Risk Factors; D055502:Secondary Prevention; D016277:Ventricular Function, Left