The effects of changes in loading conditions and modulation of inotropic state on the myocardial performance index: comparison with conductance catheter measurements.
OBJECTIVE
The myocardial performance index (MPI), or Tei index, has been shown to be useful in the assessment of global myocardial performance. There are few invasive data however, which examine its load dependence or sensitivity to acute changes in contractile function. The purpose of this study was therefore to study formally the effect of clinically relevant changes in these parameters in an animal model.


RESULTS
We examined 10 Yorkshire pigs using echocardiographic assessment and simultaneous measurements of intraventricular pressure and volume by conductance catheterization. With dobutamine infusion, there was no significant change in the MPI (0.26+/-0.13-0.22+/-0.11; p=0.42), but dP/dtmax increased significantly (1001+/-240-1569+/-532 mm Hg/s, p<0.001). Afterload increase (40% change in ventricular pressure) and preload reduction (20% change in ventricular volume) were associated with significant increases in the MPI (0.26+/-0.13-0.49+/-0.20; p<0.005 and 0.26+/-0.13-0.51+/-0.20; p<0.001, respectively) without any significant change in maximal elastance (Ees).


CONCLUSIONS
The MPI, or Tei index, is significantly affected by acute changes in loading conditions but is unable to consistently detect acute changes in contractile function.
Cheung
Michael M H
MM
Division of Cardiology, Hospital for Sick Children, 555 University Avenue, Toronto, Canada, M5G 1X8.
Smallhorn
Jeffrey F
JF
Redington
Andrew N
AN
Vogel
Michael
M
D000818:Animals; D021721:Balloon Occlusion; D006328:Cardiac Catheterization / Q000379:methods; D002316:Cardiotonic Agents; D004280:Dobutamine; D004452:Echocardiography / Q000379:methods; D006334:Heart Function Tests / Q000379:methods / Q000592:standards*; D009200:Myocardial Contraction / Q000502:physiology*; D012680:Sensitivity and Specificity; D013552:Swine; D016277:Ventricular Function, Left / Q000502:physiology*
D002316:Cardiotonic Agents; D004280:Dobutamine