title: Comparison of simplified and comprehensive methods for assessing the index of microvascular resistance in heart transplant recipients.
abstract: OBJECTIVE
  The objectives of the present study were to compare a simplified and a comprehensive method of estimating the index of microvascular resistance (IMR) and assess the changes from 7-11 weeks to 1 year after heart transplant (HTx).
  
  
  BACKGROUND
  he IMR is specific to the microvasculature and reflects the status of the microcirculation in cardiac patients and can be estimated via a simplified method (IMR(s)) or a comprehensive method (IMR(c)). The calculation for the latter includes coronary wedge pressure and central venous pressure.
  
  
  METHODS
  Consecutively transplanted patients (n = 48) underwent left and right heart catheterization including physiological evaluation at two time points post-HTx. The agreement between the values of IMR obtained using the IMR(s) and IMR(c) methods were assessed using Bland-Altman analysis. The agreements and differences were assessed using mixed model analysis.
  
  
  RESULTS
  The mean bias between IMRs and IMRc was 1.3 mm Hg·s (95% limits of agreement: -1.2, 3.8 mm Hg). Between 7-11 weeks and 1 year post-HTx there was a significant decline in IMR(s) values (P = 0.03) but a smaller and statistically nonsignificant decline in IMR(c) values (P = 0.13). The significant difference (P = 0.04) between IMR(c) and IMR(s) 7-11 weeks post-HTx was no longer present at 1 year (P = 0.24).
  
  
  CONCLUSIONS
  The IMR(s) method resulted in slightly higher IMR estimates and exhibited a somewhat larger change over the 10-month follow-up period than the IMR(c) method. However, the differences between the methods were small and unlikely to be of clinical importance.
authors.affiliation: Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.|Institue of Clinical Medicine, Faculty of Medicine, University of Oslo, Norway.
authors.forename: Ole
authors.initials: O
authors.lastname: Geir Solberg
authors.affiliation: Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.
authors.forename: Lars
authors.initials: L
authors.lastname: Aaberge
authors.affiliation: Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.
authors.forename: Asgrimur
authors.initials: A
authors.lastname: Ragnarsson
authors.affiliation: Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.
authors.forename: Marit
authors.initials: M
authors.lastname: Aas
authors.affiliation: Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.
authors.forename: Knut
authors.initials: K
authors.lastname: Endresen
authors.affiliation: Institute of Clinical Medicine, Campus Ahus, University of Oslo, Oslo, Norway.|HØKH, Research Centre, Akershus University Hospital, Lørenskog, Norway.
authors.forename: Jūratė
authors.initials: J
authors.lastname: Šaltytė Benth
authors.affiliation: Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.|K.G. Jebsen Cardiac Research Centre and Centre for Heart Failure Research, Faculty of Medicine, University of Oslo, Norway.
authors.forename: Lars
authors.initials: L
authors.lastname: Gullestad
authors.affiliation: Institute of Clinical Medicine, Campus Ahus, University of Oslo, Oslo, Norway.|HØKH, Research Centre, Akershus University Hospital, Lørenskog, Norway.|Department of Pulmonary Medicine, Akershus University Hospital, Lørenskog, Norway.
authors.forename: Knut
authors.initials: K
authors.lastname: Stavem
mesh_terms: D000328:Adult; D000368:Aged; D062186:Arterial Pressure; D006328:Cardiac Catheterization; D002496:Central Venous Pressure; D003324:Coronary Artery Disease / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D003326:Coronary Circulation; D003331:Coronary Vessels / Q000503:physiopathology*; D005260:Female; D016027:Heart Transplantation / Q000009:adverse effects; D006801:Humans; D016014:Linear Models; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D008955:Models, Cardiovascular; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012537:Scandinavian and Nordic Countries; D013997:Time Factors; D016896:Treatment Outcome; D014655:Vascular Resistance
keywords: coronary microcirculation; coronary physiology; heart transplantation; mixed model