title: Importance of diastolic fractional flow reserve and dobutamine challenge in physiologic assessment of myocardial bridging.
abstract: OBJECTIVE
  This study reports a comparative assessment of the hemodynamic relevance of myocardial bridges (MB) using two modalities of fractional flow reserve (FFR), with and without concomitant inotropic challenge.
  
  
  BACKGROUND
  Extravascular coronary compression by means of MB is modulated by myocardial inotropism and causes intracoronary systolic pressure overshooting and negative systolic gradients across the MB. The former characteristic suggests that adequate hemodynamic assessment of MB should include inotropic stimulation. The latter characteristic might interfere with FFR by decreasing the mean pressure gradient.
  
  
  METHODS
  We compared the hemodynamic relevance of 12 lone MB in symptomatic patients using conventional (mean) and diastolic FFR. Diastolic FFR was obtained from post-processed, digitally acquired electrocardiogram and pressure signals. Previously validated cut off values of 0.75 (mean FFR) and 0.76 (diastolic FFR) for hemodynamic relevance were used. Measurements were performed at baseline and after incremental intravenous dobutamine doses.
  
  
  RESULTS
  Fractional flow reserve decreased during dobutamine challenge: mean FFR was 0.90 +/- 0.04 at baseline and 0.84 +/- 0.06 after dobutamine (p = 0.0008); similarly, diastolic FFR was 0.88 +/- 0.05 and 0.77 +/- 0.10 before and after dobutamine, respectively (p = 0.0006). Diastolic FFR identified hemodynamic relevance in five patients, whereas mean FFR did so in only one patient. The discrepancy between mean FFR and diastolic FFR increased with dobutamine challenge: the ratio of mean FFR/diastolic FFR was 1.03 at baseline and 1.09 after dobutamine (p = 0.02). During the administration of dobutamine, the discrepancy was inversely related to the systolic pressure gradient (r = 0.58, P = 0.04).
  
  
  CONCLUSIONS
  Physiologic assessment of MB should include dobutamine challenge. Because the overshooting of systolic pressure interferes with and is a cause of error in FFR measurements based on mean pressures, diastolic FFR appears to be the technique of choice for MB assessment, whereas mean FFR should be used with caution.
authors.affiliation: Interventional Cardiology Service, Cardiovascular Institute, Hospital Clínico San Carlos, Madrid, Spain. jescaned.hcsc@salud.madrid.org
authors.forename: Javier
authors.initials: J
authors.lastname: Escaned
authors.forename: Jorge
authors.initials: J
authors.lastname: Cortés
authors.forename: Alex
authors.initials: A
authors.lastname: Flores
authors.forename: Javier
authors.initials: J
authors.lastname: Goicolea
authors.forename: Fernando
authors.initials: F
authors.lastname: Alfonso
authors.forename: Rosana
authors.initials: R
authors.lastname: Hernández
authors.forename: Antonio
authors.initials: A
authors.lastname: Fernández-Ortiz
authors.forename: Manel
authors.initials: M
authors.lastname: Sabaté
authors.forename: Camino
authors.initials: C
authors.lastname: Bañuelos
authors.forename: Carlos
authors.initials: C
authors.lastname: Macaya
mesh_terms: D000241:Adenosine; D000368:Aged; D000787:Angina Pectoris / Q000209:etiology; D015982:Bias; D001783:Blood Flow Velocity; D001794:Blood Pressure; D006328:Cardiac Catheterization / Q000379:methods* / Q000592:standards; D002316:Cardiotonic Agents; D017023:Coronary Angiography / Q000379:methods* / Q000592:standards; D003330:Coronary Vessel Anomalies / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D003971:Diastole; D004280:Dobutamine; D004562:Electrocardiography; D005260:Female; D006801:Humans; D016018:Least-Squares Analysis; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D011237:Predictive Value of Tests; D012720:Severity of Illness Index; D012815:Signal Processing, Computer-Assisted; D013599:Systole; D014665:Vasodilator Agents
chemical_list: D002316:Cardiotonic Agents; D014665:Vasodilator Agents; D004280:Dobutamine; D000241:Adenosine