Relation Between NLR and IMR in STEMI Patients
Condition: Myocardial Infarction; Death
MeSH terms: Myocardial Infarction; Infarction
Study type: Observational

Summary: 
      The neutrophil-to-lymphocyte ratio (NLR) has been proven to be reliable inflammatory marker
      for atherosclerotic process and predictor for clinical outcomes in patients with various
      cardiovascular diseases. Recent study reported elevated NLR was associated with impaired
      myocardial perfusion in ST-segment elevation myocardial infarction (STEMI) patients. The
      investigators sought to determine whether NLR is associated with coronary microcirculation
      assessed by index of microcirculatory resistance (IMR) in STEMI patients who undergone
      primary percutaneous coronary intervention (PCI). A total of 123 patients with STEMI
      underwent successful primary PCI were consecutively enrolled. NLR at admission was
      calculated, and the patients were divided into three groups according to NLR tertiles. IMR
      was measured by intracoronary thermodilution-derived method immediately after index PCI.
    

Detailed description: 
      A total of 123 consecutive STEMI patients who underwent successful primary PCI and coronary
      physiologic study immediately after PCI were retrospectively enrolled in the study. All
      patients underwent index PCI between May 2009 and October 2014 at INHA university hospital.
      The definition of STEMI was determined by the current guidelines.

      Complete blood counts, including total and differential WBC counts, were obtained at the time
      of admission. Total counts of WBC, neutrophils, and lymphocytes were assessed using an
      automated blood cell counter (XE-2100, Sysmex Inc., Japan). NLR was calculated as the ratio
      of the neutrophil counts to the lymphocyte counts. All patients were divided into 3 groups
      according to the NLR tertiles.

      The IMR was assessed shortly after primary PCI by using thermodilution-derived method. After
      successful interventional reperfusion, intracoronary nitroglycerin (100~200μg) was
      administered and coronary pressure guidewire (Radi Pressure Wire 5, Radi Medical Systems,
      Uppsala, Sweden) was calibrated outside the patient. The guidewire was equalized at the
      distal tip of guiding catheter, and then advanced towards the distal third of infarct related
      artery (IRA). Three times of saline injection (3~5 ml) were administered to IRA and baseline
      mean transit time was assessed. Microcirculatory hyperemia was induced by using an adenosine
      infusion (140 μg/kg.min) administered via peripheral venous line. During maximal hyperemia,
      hyperemic mean transit time (Tmn) was measured using same method as prior separate saline
      injections. Mean aortic (Pa) and distal coronary pressures (Pd) was measured during
      hyperemia. The IMR was calculated the formula as follows: IMR = Pd x hyperemic Tmn.
      Fractional flow reserve (FFR) was calculated by ratio of Pd to Pa during maximal hyperemic
      status. Coronary flow reserve (CFR) was derived from dividing the resting Tmn by hyperemic
      Tmn.

      Continuous variables were presented as mean ± standard deviation (SD) and categorical
      variables as the number of patients (percentages). The one way analysis of variance (ANOVA)
      was used for comparing continuous variables. Additionally, post-hoc analysis was performed
      for evaluating to be significant by ANOVA. The Pearson's chi-square test or Fisher's exact
      test was used for analyzing categorical variables. Linear regression analysis was performed
      for investigating the association between NLR and variables using clinical, laboratory,
      echocardiographic, and angiographic data. A p value <0.05 was regarded statistically
      significant. All statistical analyses were carried out with SPSS version 19.0 (SPSS inc.,
      Chicago, Illinois, USA).
    

Observational model: Cohort
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        A total of 123 consecutive STEMI patients who underwent successful primary PCI and coronary
        physiologic study immediately after PCI were retrospectively enrolled in the study. All
        patients underwent index PCI between May 2009 and October 2014 at INHA university hospital.