title: Fractional flow reserve and minimum Pd/Pa ratio during intravenous adenosine infusion: very similar but not always the same.
abstract: OBJECTIVE
  Maximum and stable hyperaemia are critical prerequisites for the accurate measurement of fractional flow reserve (FFR). However, in some patients in whom hyperaemia is induced through a central vein (IV) the minimum distal coronary pressure to aortic pressure ratio (Pd/Pa ratio) develops before the stabilisation of hyperaemia. We sought to describe the prevalence, magnitude and clinical implications of this phenomenon.
  
  
  RESULTS
  The FFR tracing archive of a single institution was reviewed and a total of 104 high-quality IV-FFR recordings from 90 patients were identified. Whenever the minimum Pd/Pa ratio was found before the onset of stable hyperaemia, a search for the lowest Pd/Pa ratio within the steady-state hyperaemic plateau was performed and labelled as FFRstable. Whilst in most cases the minimum Pd/Pa ratio developed during stable hyperaemia, in 19 cases (prevalence of 18.3% [95% CI: 12.0% to 26.8%]) this value was found before the stabilisation of the hyperaemic state. In such cases, the minimum Pd/Pa ratio stabilised later at a higher level (0.77±0.09 vs. 0.81±0.08, p<0.001) (mean difference, 0.03±0.02, range, 0.01 to 0.10). In terms of dichotomous classification of stenosis severity and if FFRstable had been used to decide on revascularisation, reclassification would have occurred in three (2.9%) cases, all presenting a minimum Pd/Pa ratio ≤0.80 with FFRstable >0.80.
  
  
  CONCLUSIONS
  During IV adenosine infusion, the minimum Pd/Pa ratio occurs before the stabilisation of hyperaemia in a significant proportion of cases. While the overall difference between the minimum Pd/Pa ratio and its FFRstable counterpart is small, reclassification of stenosis severity might occur, if choosing between the minimum and stable values of FFR within the same trace.
authors.affiliation: Hospital Clinico San Carlos and Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Madrid, Spain.
authors.forename: Mauro
authors.initials: M
authors.lastname: Echavarria-Pinto
authors.forename: Ricardo
authors.initials: R
authors.lastname: Petraco
authors.forename: Tim P
authors.initials: TP
authors.lastname: van de Hoef
authors.forename: Nieves
authors.initials: N
authors.lastname: Gonzalo
authors.forename: Sukhjinder
authors.initials: S
authors.lastname: Nijjer
authors.forename: Jason M
authors.initials: JM
authors.lastname: Tarkin
authors.forename: Borja
authors.initials: B
authors.lastname: Ibanez
authors.forename: Sayan
authors.initials: S
authors.lastname: Sen
authors.forename: Pilar
authors.initials: P
authors.lastname: Jimenez-Quevedo
authors.forename: Ivan J
authors.initials: IJ
authors.lastname: Nunez-Gil
authors.forename: Luis
authors.initials: L
authors.lastname: Nombela-Franco
authors.forename: Fernando
authors.initials: F
authors.lastname: Alfonso
authors.forename: Antonio
authors.initials: A
authors.lastname: Fernandez-Ortiz
authors.forename: Carlos
authors.initials: C
authors.lastname: Macaya
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Piek
authors.forename: Justin
authors.initials: J
authors.lastname: Davies
authors.forename: Javier
authors.initials: J
authors.lastname: Escaned
mesh_terms: D000241:Adenosine / Q000008:administration & dosage*; D000368:Aged; D001011:Aorta / Q000503:physiopathology*; D062186:Arterial Pressure; D006328:Cardiac Catheterization; D023921:Coronary Stenosis / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D003331:Coronary Vessels / Q000503:physiopathology*; D005260:Female; D053805:Fractional Flow Reserve, Myocardial; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013030:Spain; D013997:Time Factors; D014665:Vasodilator Agents / Q000008:administration & dosage*
chemical_list: D014665:Vasodilator Agents; D000241:Adenosine