title: Impact of differential right-to-left shunting on systemic perfusion in pulmonary arterial hypertension.
abstract: OBJECTIVE
  This study aimed at identifying the ideal right-to-left shunt-fraction to improve cardiac output (CO) and systemic perfusion in pulmonary arterial hypertension (PHT).
  
  
  BACKGROUND
  Atrial septostomy (AS) has been a high-risk therapeutic option for symptomatic drug-refractory patients with PHT. Results have been unpredictable due to limited knowledge of the optimal shunt-quantity.
  
  
  METHODS
  In nine dogs, an 8-mm shunt-prosthesis was inserted between the superior vena cava (SVC) and the left atrium. With pulmonary artery (PA) banding, mean (± SEM) systolic right ventricular pressure increased from 37 ± 1 mm Hg at baseline to 44 ± 1 mm Hg (moderate PHT, P = 0.005) and 50 ± 2 mm Hg (severe PHT, P < 0.001). Shunt-flow was adjusted by total (forcing all flow through the shunt) or partial occlusion of the SVC and partial or total clamping of the shunt. Caval-, shunt-, and aortic-flow were measured by ultrasonic flow-probes. Blood gases were drawn from the aortic root and PA.
  
  
  RESULTS
  At severe PHT, a shunt-flow of 11 ± 1% of CO (253 ± 90 mL/min) increased CO significantly by 25% (1.8 ± 0.1 to 2.4 ± 0.2 L/min, P = 0.005) causing an increase of systemic oxygen delivery index (DO2 I) by 23% (309 ± 23 to 399 ± 32 mL/min/m(2), P = 0.035). Arterial O2 -saturation did not change significantly until a shunt-flow of 18 ± 2% was exceeded, causing a drop from 96 ± 1% to 84 ± 4% (P = 0.013). At moderate PHT, CO or DO2 I did not improve significantly at any shunt-flow.
  
  
  CONCLUSIONS
  In severe PHT, a shunt-flow of 11% of CO represented the ideal shunt-fraction. Augmentation of CO compensated for declined O2 -saturation due to right-to-left shunting and improved DO2 I. In moderate PHT, AS is less promising.
authors.affiliation: Division of Cardiothoracic Surgery, Washington University School of Medicine, Barnes-Jewish Hospital, St. Louis, Missouri 63110, USA.
authors.forename: Timo
authors.initials: T
authors.lastname: Weimar
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Toshinobu
authors.initials: T
authors.lastname: Kazui
authors.forename: Urvi S
authors.initials: US
authors.lastname: Lee
authors.forename: Alessandro
authors.initials: A
authors.lastname: Montecalvo
authors.forename: Richard B
authors.initials: RB
authors.lastname: Schuessler
authors.forename: Marc R
authors.initials: MR
authors.lastname: Moon
mesh_terms: D000818:Animals; D062186:Arterial Pressure; D001783:Blood Flow Velocity; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000295:instrumentation / Q000379:methods*; D002302:Cardiac Output; D006348:Cardiac Surgical Procedures / Q000295:instrumentation / Q000379:methods*; D004195:Disease Models, Animal; D004285:Dogs; D065627:Familial Primary Pulmonary Hypertension; D005260:Female; D006325:Heart Atria / Q000503:physiopathology / Q000601:surgery; D006439:Hemodynamics; D006976:Hypertension, Pulmonary / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D010030:Ostomy / Q000379:methods*; D010100:Oxygen / Q000097:blood; D012720:Severity of Illness Index; D014683:Vena Cava, Superior / Q000503:physiopathology / Q000601:surgery*; D016278:Ventricular Function, Right; D017725:Ventricular Pressure
chemical_list: D010100:Oxygen