title: The left ventricle responds to acute graded elevation of right ventricular afterload by augmentation of twist magnitude and untwist rate.
abstract: BACKGROUND
  The right and left ventricles share the interventricular septum, which mechanically transmits pressure gradients. The aim of this study was to investigate how acute mild or moderate right ventricular (RV) afterload affects left ventricular (LV) function.
  
  
  METHODS
  In 14 open-chest pigs (mean weight, 43 ± 4 kg) with preserved pericardium, acute mild (>35 and ≤50 mm Hg) and moderate (>50 and ≤60 mm Hg) RV pressure loading conditions were induced by constriction of the pulmonary artery. Hemodynamic parameters and LV twist and untwist were evaluated under each condition.
  
  
  RESULTS
  From baseline to mild and moderate RV afterload, the mean RV systolic pressure increased from 31.0 ± 4.3 to 41.1 ± 2.7 and 52.7 ± 3.4 mm Hg (P < .001), while LV twist magnitudes increased from 15.4 ± 5.1° to 18.5 ± 3.1° and 19.8 ± 5.0° (P = .004), respectively. Absolute values of LV untwist rate increased from -116.9 ± 64.9°/sec to -160.0 ± 53.3°/sec and -169.1 ± 47.0°/sec, respectively (P = .001). After adjusting for all variables, only the ratio of the early and atrial components of mitral inflow and RV outflow tract acceleration time was significantly associated with the LV twist magnitude and LV untwist rate.
  
  
  CONCLUSIONS
  In an acute setting, the left ventricle responds to suddenly elevated RV afterload and decreased RV stroke volume by promptly increasing its twist magnitude and untwist rate.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, St. Paul's Hospital, Catholic University of Korea, Seoul, South Korea.
authors.forename: Eun Joo
authors.initials: EJ
authors.lastname: Cho
authors.forename: Panupong
authors.initials: P
authors.lastname: Jiamsripong
authors.forename: Anna M
authors.initials: AM
authors.lastname: Calleja
authors.forename: Mohsen S
authors.initials: MS
authors.lastname: Alharthi
authors.forename: Eileen M
authors.initials: EM
authors.lastname: McMahon
authors.forename: Krishnaswamy
authors.initials: K
authors.lastname: Chandrasekaran
authors.forename: Stephen
authors.initials: S
authors.lastname: Cha
authors.forename: Anna E
authors.initials: AE
authors.lastname: Bukatina
authors.forename: Bijoy K
authors.initials: BK
authors.lastname: Khandheria
authors.forename: Marek
authors.initials: M
authors.lastname: Belohlavek
mesh_terms: D000465:Algorithms; D000818:Animals; D004195:Disease Models, Animal; D006352:Heart Ventricles / Q000503:physiopathology*; D006439:Hemodynamics; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D011651:Pulmonary Artery / Q000503:physiopathology*; D013552:Swine; D018497:Ventricular Dysfunction, Right / Q000503:physiopathology*; D017725:Ventricular Pressure; D054088:Ventricular Septum