title: Can strain rate and strain quantify changes in regional systolic function during dobutamine infusion, B-blockade, and atrial pacing--implications for quantitative stress echocardiography.
abstract: BACKGROUND
  We investigated the ability of ultrasonic strain rate (SR) and strain (epsilon) to quantify the changes in normal myocardial function at varying inotropic states and heart rates (HR) in an attempt to determine whether these new regional function indices are potentially robust enough to quantitate stress echocardiography.
  
  
  RESULTS
  Twenty closed-chest pigs underwent incremental atrial pacing (AP: 120-180/min, n = 7), dobutamine infusion (DI: 2.5-20 microg/kg/min, n = 7) or esmolol infusion with subsequent pacing (EI: 0.5 +/- 0.15 mg/kg/min with pacing 120-180/min, n = 6). Radial deformation of the left ventricular posterior wall was interrogated using the parasternal short-axis view to derive regional systolic SR and epsilon values. At baseline SR and epsilon averaged 5.0 +/- 0.4 s(-1) and 60% +/- 4%, respectively. SR remained unchanged during AP and increased linearly with DI (at 2.5 microg/kg/min = 6.2 +/- 0.3 s(-1), P <.05 vs baseline; at 20 microg/kg/min = 9.9 +/- 0.7 s(-1), P <.0001 vs baseline), whereas EI resulted in a constant decrease of 30% +/- 4% in SR (P <.05). SR and left ventricular dP/dt(MAX) correlated linearly over the induced change in inotropic states and HR (r = 0.82; P <.0001). Conversely, epsilon values decreased during AP (at 180/min = 36% +/- 2%, P <.001). During DI, epsilon initially increased at 2.5 and 5 microg/kg/min (at 5 microg/kg/min = 77% +/- 6%, P <.05) and decreased for higher doses because of increasing HR. EI resulted in a decrease of 30% +/- 4% in epsilon with a further decrease during subsequent pacing. epsilon correlated linearly with left ventricular ejection fraction (r = 0.87; P <.0001).
  
  
  CONCLUSIONS
  Both SR and epsilon can quantify the changes in myocardial function during a range of inotropic challenges and over the range of physiologic HRs encountered during clinical stress echocardiography. SR may reflect regional contractile function, whereas epsilon reflects changes in ventricular geometry. This study would suggest that for quantitative stress echocardiography SR is better in quantification of changes in contractile function being relatively independent of HR.
authors.affiliation: Department of Cardiology, University Hospital Gasthuisberg, Leuven, Belgium.
authors.forename: Frank
authors.initials: F
authors.lastname: Weidemann
authors.forename: Fadi
authors.initials: F
authors.lastname: Jamal
authors.forename: Miroslaw
authors.initials: M
authors.lastname: Kowalski
authors.forename: Tomasz
authors.initials: T
authors.lastname: Kukulski
authors.forename: Jan
authors.initials: J
authors.lastname: D'Hooge
authors.forename: Bart
authors.initials: B
authors.lastname: Bijnens
authors.forename: Liv
authors.initials: L
authors.lastname: Hatle
authors.forename: Ivan
authors.initials: I
authors.lastname: De Scheerder
authors.forename: George R
authors.initials: GR
authors.lastname: Sutherland
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D016275:Atrial Function; D002304:Cardiac Pacing, Artificial; D002316:Cardiotonic Agents / Q000494:pharmacology*; D004280:Dobutamine / Q000494:pharmacology*; D025401:Echocardiography, Stress; D006339:Heart Rate / Q000502:physiology; D009200:Myocardial Contraction / Q000502:physiology; D011412:Propanolamines / Q000494:pharmacology; D013552:Swine
chemical_list: D000319:Adrenergic beta-Antagonists; D002316:Cardiotonic Agents; D011412:Propanolamines; D004280:Dobutamine; C036604:esmolol