title: Isovolumic but not ejection phase Doppler tissue indices detect left ventricular dysfunction caused by coronary stenosis.
abstract: BACKGROUND
  Isovolumic acceleration (IVA) obtained by tissue Doppler echocardiography (TDE) is a sensitive and relatively load-independent index for assessing systolic ventricular function. IVA also has the ability to describe the force-frequency relationship during incremental atrial pacing in vivo.
  
  
  OBJECTIVE
  We sought to assess the ability of IVA to detect global left ventricular (LV) dysfunction induced by coronary constriction.
  
  
  METHODS
  In 6 open-chest anesthetized pigs we examined right ventricular and LV long-axis function by TDE (4-chamber view) with simultaneous invasive measurements of intraventricular pressure, maximum dP/dt, minimum dP/dt, and tau by microtip catheter. A pneumatic cuff was placed around the proximal portion of left anterior descending coronary artery (LAD) and distal flow was monitored by transonic flow probe. Mean arterial pressures were monitored by indwelling cannula. Baseline studies assessed force-frequency relationships with TDE and invasive measurements during incremental pacing from 100 to 200/min (20/min increments every 10 minutes). The protocol was repeated 10 minutes after balloon inflation to reduce LAD blood flow by 50%.
  
  
  RESULTS
  Compared with baseline, LV pressure decreased significantly (P = .03, 2-way analysis of variance) as did maximum dP/dt (P < .004) with LAD constriction. At the same time IVA and isovolumic velocity at the LV free wall were significantly reduced (P < .002 and P = .04, respectively) and both IVA and isovolumic velocity were correlated with dP/dt (r = 0.45, P < .002, and r = 0.35, P < .02, respectively). TDE systolic indices were unchanged in the right ventricle.
  
  
  CONCLUSIONS
  IVA detects changes in global LV systolic function during LAD constriction and may be a useful clinical tool to diagnose ischemia.
authors.affiliation: Division of Cardiology, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Mikiko
authors.initials: M
authors.lastname: Shimizu
authors.forename: Masaki
authors.initials: M
authors.lastname: Nii
authors.forename: Igor E
authors.initials: IE
authors.lastname: Konstantinov
authors.forename: Jia
authors.initials: J
authors.lastname: Li
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Redington
mesh_terms: D000818:Animals; D023921:Coronary Stenosis / Q000150:complications* / Q000000981:diagnostic imaging*; D015150:Echocardiography, Doppler / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013318:Stroke Volume; D013552:Swine; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000209:etiology*