title: Chronic septal infarction confers right ventricular protection during mechanical left ventricular unloading.
abstract: OBJECTIVE
  Right ventricular failure manifests in 25% of left ventricular assist device recipients because of ventricular coupling mechanism disruption. Septal ischemia accentuates this process, but the effect of septal infarction has not been elucidated. Right ventricular response to incremental left ventricular unloading was studied in sheep with septal infarction.
  
  
  METHODS
  Septal infarction was induced in 6 sheep using ethanol delivery into the main septal perforating artery. Six shams avoided ethanol. Load-independent and in-series right ventricular response to incremental (0%-100%) left ventricular unloading was measured 4 weeks later. Dimensions of whole heart, wall thickness, and chamber volumes were obtained using sonomicrometers. Selective perfusion with triphenyltetrazolium quantified septal damage.
  
  
  RESULTS
  Right ventricular preload-recruitable-stroke-work, contractility, and ejection fraction were lower at 75% and 100% left ventricular unloading in sham compared with infarcted animals (75%: 26.3 +/- 3.4, 0.70 +/- 0.15, and 23.9 +/- 4.6 vs 37 +/- 2.6 erg *10;3, 0.99 +/- 0.18 mm Hg/mL, and 35.5% +/- 3.4%, all P < . 01, 100%: 24.8 +/- 4.5, 0.67 +/- 0.14, and 23.8 +/- 5.8 vs 36.0 +/- 4.6 erg *10;3, 0.90 +/- 0.09 mm Hg/mL, and 32.7% +/- 11.0%, all P < . 01). Central venous pressure was higher at 75% and 100% unloading in sham compared with infarcted animals (75%: 8.6 +/- 1.0 vs 4.5 +/- 1.0, 100%: 12.4 +/- 0.8 vs 3.4 +/- 1.0 mm Hg, all P < . 01). Right ventricular cardiac output was less in shams with 100% unloading (1.2 +/- 0.2 L/min vs 2.1 +/- 0.3 L/min, P < . 01). End-diastolic and end-systolic right ventricular short-axis dimension at 75% and 100% unloading was greater in sham compared with infarcted animals (75%: 34.4 +/- 5.5 mm and 29.1 +/- 5.5 mm vs 25.6 +/- 4.7 mm and 20.5 +/- 4.0 mm; 100%: 37.6 +/- 6.6 mm and 29.9 +/- 5.9 mm vs 25.5 +/- 3.9 mm and 21.1 +/- 3.8 mm, all P < .01). Prolonged diastolic relaxation (Tau) in infarcted animals was normalized with 75% and 100% unloading.
  
  
  CONCLUSIONS
  High-level (>or=75%) left ventricular unloading causes right ventricular dilatation and compromised function. Chronic septal damage, however, confers protection by preserving right ventricular dimensions.
authors: Cardiac Technology Centre, Kolling Institute, St Leonards, Australia. jmau@med.usyd.edu.au
authors: James
authors: J
authors: Mau
authors: Stuart
authors: S
authors: Menzie
authors: Yifei
authors: Y
authors: Huang
authors: Michael
authors: M
authors: Ward
authors: Stephen
authors: S
authors: Hunyor
mesh_terms: D000818:Animals; D006321:Heart / Q000503:physiopathology; D006346:Heart Septum; D006353:Heart-Assist Devices; D006439:Hemodynamics; D009203:Myocardial Infarction / Q000503:physiopathology*; D012756:Sheep; D016277:Ventricular Function, Left; D016278:Ventricular Function, Right