title: Estimating right ventricular stroke work and the pulsatile work fraction in pulmonary hypertension.
abstract: BACKGROUND
  The mean pulmonary artery pressure (mPAP) replaces mean systolic ejection pressure (msePAP) in the classic formula of right ventricular stroke work (RVSW) = (mPAP - RAP) × stroke volume, where RAP is mean right atrial pressure. Only the steady work is thus taken into account, not the pulsatile work, whereas pulmonary circulation is highly pulsatile. Our retrospective, high-fidelity pressure study tested the hypothesis that msePAP was proportional to mPAP, and looked at the implications for RVSW.
  
  
  METHODS
  Eleven patients with severe, precapillary pulmonary hypertension (PH) (six patients with idiopathic pulmonary arterial hypertension and five with chronic thromboembolic PH; mPAP = 57 ± 10 mm Hg) were studied at rest and during mild to moderate exercise. Eight non-PH control subjects were also studied at rest (mPAP = 16 ± 2 mm Hg). The msePAP was averaged from end diastole to dicrotic notch.
  
  
  RESULTS
  In the full data set (53 pressure-flow points), mPAP ranged from 14 to 99.5 mm Hg, cardiac output from 2.38 to 11.1 L/min, and heart rate from 53 to 163 beats/min. There was a linear relationship between msePAP and mPAP (r² = 0.99). The msePAP matched 1.25 mPAP (bias, -0.5 ± 2.6 mm Hg). Results were similar in the resting non-PH group and in resting and the exercising PH group. This implies that the classic formula markedly underestimates RVSW and that the pulsatile work may be a variable 20% to 55% fraction of RVSW, depending on RAP and mPAP. At rest, RVSW in patients with PH was twice as high as that of the non-PH group (P < .05), but pulsatile work fraction was similar between the two groups (26 ± 4% vs 24 ± 1%) because of the counterbalancing effects of high RAP (11 ± 5 mm Hg vs 4 ± 2 mm Hg), which increases the fraction, and high mPAP, which decreases the fraction.
  
  
  CONCLUSIONS
  Our study favored the use of an improved formula that takes into account the variable pulsatile work fraction: RVSW = (1.25 mPAP - RAP) × stroke volume. Increased RAP and increased mPAP have opposite effects on the pulsatile work fraction.
authors.affiliation: Université Paris-Sud, Faculté de Médecine, EA4533, Le Kremlin Bicêtre, France. Electronic address: denis.chemla@bct.aphp.fr.
authors.forename: Denis
authors.initials: D
authors.lastname: Chemla
authors.affiliation: Hôpitaux Universitaires de Strasbourg, Service de Reanimation Medicale, Strasbourg, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Castelain
authors.affiliation: Université Paris-Sud, Faculté de Médecine, EA4533, Le Kremlin Bicêtre, France.
authors.forename: Kaixian
authors.initials: K
authors.lastname: Zhu
authors.affiliation: Université Paris-Sud, Faculté de Médecine, EA4533, Le Kremlin Bicêtre, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Papelier
authors.affiliation: Radiology Department, Hopital Antoine Béclère, Clamart, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Creuzé
authors.affiliation: Pulmonary Division, University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Susana
authors.initials: S
authors.lastname: Hoette
authors.affiliation: AP-HP, Services des Explorations Fonctionnelles et de Pneumologie, Hôpital Bicêtre, Le Kremlin Bicêtre, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Parent
authors.affiliation: AP-HP, Services des Explorations Fonctionnelles et de Pneumologie, Hôpital Bicêtre, Le Kremlin Bicêtre, France.
authors.forename: Gérald
authors.initials: G
authors.lastname: Simonneau
authors.affiliation: AP-HP, Services des Explorations Fonctionnelles et de Pneumologie, Hôpital Bicêtre, Le Kremlin Bicêtre, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Humbert
authors.affiliation: INSERM UMR_S999, Centre Chirurgical Marie Lannelongue, Le Plessis-Robinson, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Herve
mesh_terms: D000328:Adult; D002302:Cardiac Output / Q000502:physiology; D015444:Exercise / Q000502:physiology; D005260:Female; D006339:Heart Rate; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D006976:Hypertension, Pulmonary / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D011673:Pulsatile Flow / Q000502:physiology*; D012146:Rest / Q000502:physiology; D012189:Retrospective Studies; D013318:Stroke Volume / Q000502:physiology*