title: Load independence of two-dimensional speckle-tracking-derived left ventricular twist and apex-to-base rotation delay in nonischemic dilated cardiomyopathy: implications for left ventricular dyssynchrony assessment.
abstract: BACKGROUND
  Left ventricular (LV) twist mechanics are a promising, sensitive tool for assessing pathophysiologic changes in patients with systolic heart failure. Although LV twist is known to be load dependent in healthy volunteers, this has not been examined in patients with "long-standing" dilated cardiomyopathy (DCM). The aim of this study was to determine whether LV twist remains load dependent in the setting of long-standing, nonischemic DCM.
  
  
  METHODS
  Thirty-four patients with DCM with baseline LV ejection fractions (LVEFs) < 40% and 13 subjects with preserved LVEFs (≥50%) were enrolled. After baseline measurements, pneumatic compression of the lower extremities (Pcom) was used to increase LV afterload. Subsequently, sublingual nitroglycerin (SL-NG) was administered to modify preload. Conventional echocardiographic parameters, LV end-systolic wall stress, net LV twist angle, and apex-to-base-rotation delay (ABRD) were assessed under each condition.
  
  
  RESULTS
  In patients with DCM, although LV end-systolic wall stress significantly increased under Pcom (196.9 ± 64.9 g/m(2) at baseline vs 231.8 ± 78.9 g/m(2) under Pcom, P < .017) and decreased after SL-NG application (231.8 ± 78.9 g/m(2) under Pcom vs 197.4 ± 67.4 g/m(2) after SL-NG, P < .017), net LV twist angle and ABRD showed no significant changes depending on LV loading condition (for LV twist, 7.63 ± 4.47° at baseline vs 7.03 ± 4.13° under Pcom vs 7.35 ± 4.36° after SL-NG, P = 0.65; for ABRD, 16.56 ± 13.81% at baseline vs 17.19 ± 14.81% under Pcom vs 15.95 ± 13.27% after SL-NG, P = .53). Careful examination of individual patient data revealed that LV twist was load independent when patients had LV twist < 12°. ABRD was also found to be load independent, but only in patients with LVEFs < 34%. In contrast, LV twist and ABRD were load dependent in patients with preserved LVEFs.
  
  
  CONCLUSIONS
  LV twist and its component, ABRD, had relatively load insensitive properties in patients with long-standing DCM and can be used in future clinical trials as load-independent indexes of LV dyssynchrony.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Cardiovascular Center, Seoul National University Hospital, Seoul, South Korea. cardiman73@gmail.com
authors.forename: Hyung-Kwan
authors.initials: HK
authors.lastname: Kim
authors.forename: Sung-A
authors.initials: SA
authors.lastname: Chang
authors.forename: Hyo-Suk
authors.initials: HS
authors.lastname: Ahn
authors.forename: Dong-Ho
authors.initials: DH
authors.lastname: Shin
authors.forename: Ji-Hyun
authors.initials: JH
authors.lastname: Kim
authors.forename: Seung-Pyo
authors.initials: SP
authors.lastname: Lee
authors.forename: Yong-Jin
authors.initials: YJ
authors.lastname: Kim
authors.forename: Goo-Yeong
authors.initials: GY
authors.lastname: Cho
authors.forename: Dae-Won
authors.initials: DW
authors.lastname: Sohn
authors.forename: Byung-Hee
authors.initials: BH
authors.lastname: Oh
authors.forename: Young-Bae
authors.initials: YB
authors.lastname: Park
mesh_terms: D002311:Cardiomyopathy, Dilated / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D004452:Echocardiography / Q000379:methods*; D055119:Elastic Modulus; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia; D013318:Stroke Volume; D019415:Torque; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology*