title: Detection of infarct size safety threshold for left ventricular ejection fraction impairment in acute myocardial infarction successfully treated with primary percutaneous coronary intervention.
abstract: OBJECTIVE
  In acute myocardial infarction (AMI) treated by primary percutaneous coronary intervention (PCI), there is a direct relationship between myocardial damage and consequent left ventricular (LV) functional impairment. It is however unclear whether there is a safety threshold below which infarct size does not significantly affect LV ejection fraction (EF). The aim of this study was to evaluate the relationship between infarct size and LVEF in AMI patients treated by successful PCI using a specific statistical approach to identify a possible safety threshold.
  
  
  METHODS
  Among patients with recent AMI submitted to perfusion gated single photon emission computed tomography (SPECT) to define the infarct size, the data of 427 subjects with sizable infarct size were considered. The relationship between infarct size and LVEF was analysed using a simple segmented regression (SSR) model and an iterative algorithm based on robust least squares (RLS) for parameter estimation.
  
  
  RESULTS
  The RLS algorithm detected two break points in the SSR model, set at infarct size values of 11.0 and 51.5 %. Because the slope coefficients of the two extreme segments of the regression line were not significant, by constraining such segments to zero slope in the SSR model, the lower break point was identified at infarct size = 8 % and the upper one at 45 %.
  
  
  CONCLUSIONS
  Using a rigorous statistical approach, it is possible to demonstrate that below a threshold of 8 % the infarct size apparently does not affect the LVEF and therefore a safety threshold could be set at this value. Furthermore, the same analysis suggests that the relationship between infarct size and LVEF impairment is lost for an infarct size > 45 %.
authors.affiliation: Department of Clinical Physiopathology, University of Florence, Florence, Italy. r.sciagra@dfc.unifi.it
authors.forename: Roberto
authors.initials: R
authors.lastname: Sciagrà
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Cipollini
authors.forename: Valentina
authors.initials: V
authors.lastname: Berti
authors.forename: Angela
authors.initials: A
authors.lastname: Migliorini
authors.forename: David
authors.initials: D
authors.lastname: Antoniucci
authors.forename: Alberto
authors.initials: A
authors.lastname: Pupi
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy*; D062645:Percutaneous Coronary Intervention; D013318:Stroke Volume; D015899:Tomography, Emission-Computed, Single-Photon; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging / Q000628:therapy*