title: Over-the-wire intravascular ultrasound in an animal model of pulmonary hypertension.
abstract: BACKGROUND
  Intravascular ultrasound (IVUS) measures prognostically important pulsatile flow indexes in patients with pulmonary hypertension (PH). IVUS catheters traditionally require a guiding catheter for placement which can impact hemodynamics in small infants because the guiding catheter renders the atrioventricular valve incompetent.
  
  
  METHODS
  Domestic swine (1.4-2.2 kg) were raised in isobaric normoxia (n = 4) or hypoxia (n = 3, FiO(2) 10-12%) for 72 hr for induction of PH. Cardiac catheterization and intravascular imaging was performed using a 3.5-Fr 20-MHz Eagle Eye Gold catheter (Volcano Corp., CA, USA) over a 0.014'' guide wire. Intima-media thickness (IMT) was measured and relative area change and vascular pulsatility were calculated.
  
  
  RESULTS
  The IVUS probe was easily manipulated over a 0.014'' wire without hemodynamic compromise in all animals. The IMT was thicker in the hypoxic group than the normoxic group (0.19 ± 0.03 mm vs. 0.31 ± 0.04 mm, p = .067). Hypoxic animals had systolic PH (39.66 ± 2.51 vs. 21.75 ± 2.87 mmHg, p = .02). Systemic arterial pressures between the groups were the same (hypoxic 68 ± 10.44 vs. normoxic 79.75 ± 14.84 mmHg, p = .26). Vascular pulsatility was similar (hypoxic 24 ± 2.64 vs. 20.25 ± 0.57%, p = .18). However, the arterial wall distensibility was significantly different (0.98 ± 0.2 vs. 2.01 ± 1.38 %/mmHg, p = .04).
  
  
  CONCLUSIONS
  Monorail IVUS imaging without a guide catheter overcomes a major limitation for use in infants and small animal experimental models by avoiding hemodynamic compromise. This would be a valuable tool for assessment of PH in the research and clinical setting.
authors.affiliation: Department of Pediatrics, Division of Pediatric Cardiology, University of Iowa Children's Hospital, University of Iowa, Iowa City, Iowa 52240, USA. susan-haynes@uiowa.edu
authors.forename: Susan E
authors.initials: SE
authors.lastname: Haynes
authors.forename: Abhay A
authors.initials: AA
authors.lastname: Divekar
mesh_terms: D000818:Animals; D006328:Cardiac Catheterization / Q000295:instrumentation / Q000379:methods; D004195:Disease Models, Animal; D005240:Feasibility Studies; D006439:Hemodynamics / Q000502:physiology*; D006976:Hypertension, Pulmonary / Q000000981:diagnostic imaging* / Q000503:physiopathology; D012039:Regional Blood Flow / Q000502:physiology; D013552:Swine; D017539:Tunica Intima / Q000000981:diagnostic imaging; D017540:Tunica Media / Q000000981:diagnostic imaging; D018084:Ultrasonography, Interventional / Q000295:instrumentation* / Q000379:methods*