title: Signal-morphology impedance cardiography during incremental cardiopulmonary exercise testing in pulmonary arterial hypertension.
abstract: BACKGROUND
  Haemodynamic responses to exercise are related to physical impairment and worse prognosis in patients with pulmonary arterial hypertension (PAH). It is clinically relevant, therefore, to investigate the practical usefulness of non-invasive methods of monitoring exercise haemodynamics in this patient population.
  
  
  METHODS
  Using a novel impedance cardiography (ICG) approach that does not require basal impedance estimations and relies on a morphological analysis of the impedance signal (Signal-Morphology-ICG(™)), stroke volume (SV) and cardiac index (CI) were evaluated in 50 patients and 21 age-matched controls during a ramp-incremental cardiopulmonary exercise testing.
  
  
  RESULTS
  Technically unacceptable readings were found in 12 of 50 (24%) patients. In the remaining subjects, early decrease (N = 9) or a 'plateau' in SV (N = 8) and Δ (peak-unloaded exercise) SV <10 ml were markers of more advanced PAH (P<0.05). ΔCI ≤ 1.5-fold and early estimated lactate threshold were the only independent predictors of a severely reduced peak oxygen uptake (VO(2)) in patients (R(2) = 0.71, P<0.001). The finding of ΔCI ≤ 1.5-fold plus peak VO(2) < 50% predicted was associated with a number of clinical and functional markers of disease severity (P<0.001). In addition, abnormal SV responses and ΔCI ≤ 1.5-fold were significantly related to 1-year frequency of PAH-related adverse events (death and balloon atrial septostomy, N = 8; P<0.05).
  
  
  CONCLUSIONS
  'Qualitative' and 'semi-quantitative' signal-morphology impedance cardiography(™) (PhysioFlow(™)) during incremental exercise provided clinically useful information to estimate disease severity and short-term prognosis in patients with PAH in whom acceptable impedance signals could be obtained.
authors.affiliation: Pulmonary Function and Clinical Exercise Physiology Unit, Division of Respiratory Diseases, Department of Medicine, Federal University of Sao Paulo (UNIFESP), São Paulo, São Paulo, Brazil.
authors.forename: Eloara M
authors.initials: EM
authors.lastname: Ferreira
authors.forename: Jaquelina S
authors.initials: JS
authors.lastname: Ota-Arakaki
authors.forename: Priscila B
authors.initials: PB
authors.lastname: Barbosa
authors.forename: Ana Cristina B
authors.initials: AC
authors.lastname: Siqueira
authors.forename: Daniela M
authors.initials: DM
authors.lastname: Bravo
authors.forename: Carlos Eduardo B
authors.initials: CE
authors.lastname: Kapins
authors.forename: Célia Maria C
authors.initials: CM
authors.lastname: Silva
authors.forename: Luiz Eduardo
authors.initials: LE
authors.lastname: Nery
authors.forename: J Alberto
authors.initials: JA
authors.lastname: Neder
mesh_terms: D000328:Adult; D001938:Brazil; D002307:Cardiography, Impedance; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D015150:Echocardiography, Doppler; D004562:Electrocardiography; D005080:Exercise Test; D065627:Familial Primary Pulmonary Hypertension; D005260:Female; D006439:Hemodynamics; D006801:Humans; D006976:Hypertension, Pulmonary / Q000175:diagnosis* / Q000503:physiopathology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D011379:Prognosis; D011651:Pulmonary Artery / Q000503:physiopathology*; D012720:Severity of Illness Index; D012815:Signal Processing, Computer-Assisted; D013147:Spirometry; D013318:Stroke Volume; D013997:Time Factors