title: Myocardial performance index in female rats with myocardial infarction: relationship with ventricular function parameters by Doppler echocardiography.
abstract: BACKGROUND
  The aim of the study was to analyze the myocardial performance index (MPI), its relationship with the standard variables of systolic and diastolic functions, and the influence of time intervals in an experimental model of female rats with myocardial infarction (MI).
  
  
  METHODS
  Forty-one Wistar female rats were submitted to surgery to induce MI. Six weeks later, Doppler echocardiography was performed to assess infarct size (IS,%), fractional area change (FAC,%), ejection fraction biplane Simpson (EF), E/A ratio of mitral inflow, MPI and its time intervals: isovolumetric contraction (IVCT, ms) and relaxation (IVRT, ms) times, and ejection time (ET, ms); MPI = IVCT + IVRT/ET.
  
  
  RESULTS
  EF and FAC were progressively lower in rats with small, medium and large-size MI ( P < .001). E/A ratio was higher only in rats with large-size MI (6.25 +/- 2.69; P < .001). MPI was not different between control rats and small-size MI (0.37 +/- 0.03 vs 0.34 +/- 0.06, P = .87), but different between large and medium-size MI (0.69 +/- 0.08 vs 0.47 +/- 0.07; P < .001) and between these two compared to small-size MI. MPI correlated with IS (r = 0.85; P < .001), EF (r = -0.86; P < .001), FAC (r = -0.77; P < .001) and E/A ratio (r = 0.77; P < .001, non-linear). IVCT was longer in large size MI compared to medium-size MI (31.87 +/- 7.99 vs 15.92 +/- 5.88; P < .001) and correlated with IS (r = 0.85; P < .001) and MPI (r = 0.92; P < .001). ET was shorter only in large-size MI (81.07 +/- 7.23; P < .001), and correlated with IS (r = -0.70; P < .001) and MPI (r = -0.85; P < .001). IVRT was shorter only in large-size compared to medium-size MI (24.40 +/- 5.38 vs 29.69 +/- 5.92; P < .037), had borderline correlation with MPI (r = 0.34; P = .0534) and no correlation with IS (r = 0.26; p = 0.144).
  
  
  CONCLUSIONS
  The MPI increased with IS, correlated inversely with systolic function parameters and had a non-linear relationship with diastolic function. These changes were due to the increase of IVCT and a decrease of ET, without significant influence of IVRT.
authors.affiliation: Cardiovascular Laboratory, Department of Cardiology/Medicine of Universidade Federal de São Paulo, Brazil. alexandrecury@ig.com.br
authors.forename: Alexandre Ferreira
authors.initials: AF
authors.lastname: Cury
authors.forename: Andre
authors.initials: A
authors.lastname: Bonilha
authors.forename: Roberto
authors.initials: R
authors.lastname: Saraiva
authors.forename: Orlando
authors.initials: O
authors.lastname: Campos
authors.forename: Antonio Carlos C
authors.initials: AC
authors.lastname: Carvalho
authors.forename: Angelo Amato V
authors.initials: AA
authors.lastname: De Paola
authors.forename: Claudio
authors.initials: C
authors.lastname: Fischer
authors.forename: Paulo Ferreira
authors.initials: PF
authors.lastname: Tucci
authors.forename: Valdir Ambrosio
authors.initials: VA
authors.lastname: Moises
mesh_terms: D000818:Animals; D015150:Echocardiography, Doppler; D005260:Female; D006339:Heart Rate; D009203:Myocardial Infarction / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D051381:Rats