title: Validation of Noninvasive Measurement of Cardiac Output Using Inert Gas Rebreathing in a Cohort of Patients With Heart Failure and Reduced Ejection Fraction.
abstract: BACKGROUND
  Cardiac output (CO) is a key indicator of cardiac function in patients with heart failure. No completely accurate method is available for measuring CO in all patients. The objective of this study was to validate CO measurement using the inert gas rebreathing (IGR) method against other noninvasive and invasive methods of CO quantification in a cohort of patients with heart failure and reduced ejection fraction.
  
  
  RESULTS
  The study included 97 patients with heart failure and reduced ejection fraction (age 42±15.5 years; 64 patients (65.9%) had idiopathic dilated cardiomyopathy and 21 patients (21.6%) had ischemic heart disease). Median left ventricle ejection fraction was 24% (10%-36%). Patients with atrial fibrillation were excluded. CO was measured using 4 methods (IGR, cardiac magnetic resonance imaging, cardiac catheterization, and echocardiography) and indexed to body surface area (cardiac index [CI]). All studies were performed within 48 hours. Median CI measured by IGR was 1.75, by cardiac magnetic resonance imaging was 1.82, by cardiac catheterization was 1.65, and by echo was 1.7 L·min-1·m-2. There were significant modest linear correlations between IGR-derived CI and cardiac magnetic resonance imaging-derived CI (r=0.7;P<0.001), as well as cardiac catheterization-derived CI (r=0.6;P<0.001). Using Bland-Altman analysis, the agreement between the IGR method and the other methods was as good as the agreement between any 2 other methods with each other.
  
  
  CONCLUSIONS
  The IGR method is a simple, accurate, and reproducible noninvasive method for quantification of CO in patients with advanced heart failure. The prognostic value of this simple measurement needs to be studied prospectively.
authors.affiliation: From the Cardiology Department (M.H., A.E., M.F.E.) and Radiology Department (A.K.), Cairo University, Egypt; Cardiology Department (M.H., K.W., P.P.S., A.E., H.M.), Radiology Department (A.K.), Biomedical Engineering Department (A.N.), and Cardiothoracic Department (M.H.Y.), Aswan Heart Centre, Egypt; and Imperial College, London, United Kingdom (M.H.Y.).
authors.forename: Mohamed
authors.initials: M
authors.lastname: Hassan
authors.affiliation: From the Cardiology Department (M.H., A.E., M.F.E.) and Radiology Department (A.K.), Cairo University, Egypt; Cardiology Department (M.H., K.W., P.P.S., A.E., H.M.), Radiology Department (A.K.), Biomedical Engineering Department (A.N.), and Cardiothoracic Department (M.H.Y.), Aswan Heart Centre, Egypt; and Imperial College, London, United Kingdom (M.H.Y.).
authors.forename: Kerolos
authors.initials: K
authors.lastname: Wagdy
authors.affiliation: From the Cardiology Department (M.H., A.E., M.F.E.) and Radiology Department (A.K.), Cairo University, Egypt; Cardiology Department (M.H., K.W., P.P.S., A.E., H.M.), Radiology Department (A.K.), Biomedical Engineering Department (A.N.), and Cardiothoracic Department (M.H.Y.), Aswan Heart Centre, Egypt; and Imperial College, London, United Kingdom (M.H.Y.).
authors.forename: Ahmed
authors.initials: A
authors.lastname: Kharabish
authors.affiliation: From the Cardiology Department (M.H., A.E., M.F.E.) and Radiology Department (A.K.), Cairo University, Egypt; Cardiology Department (M.H., K.W., P.P.S., A.E., H.M.), Radiology Department (A.K.), Biomedical Engineering Department (A.N.), and Cardiothoracic Department (M.H.Y.), Aswan Heart Centre, Egypt; and Imperial College, London, United Kingdom (M.H.Y.).
authors.forename: Peter Philip
authors.initials: PP
authors.lastname: Selwanos
authors.affiliation: From the Cardiology Department (M.H., A.E., M.F.E.) and Radiology Department (A.K.), Cairo University, Egypt; Cardiology Department (M.H., K.W., P.P.S., A.E., H.M.), Radiology Department (A.K.), Biomedical Engineering Department (A.N.), and Cardiothoracic Department (M.H.Y.), Aswan Heart Centre, Egypt; and Imperial College, London, United Kingdom (M.H.Y.).
authors.forename: Ahmed
authors.initials: A
authors.lastname: Nabil
authors.affiliation: From the Cardiology Department (M.H., A.E., M.F.E.) and Radiology Department (A.K.), Cairo University, Egypt; Cardiology Department (M.H., K.W., P.P.S., A.E., H.M.), Radiology Department (A.K.), Biomedical Engineering Department (A.N.), and Cardiothoracic Department (M.H.Y.), Aswan Heart Centre, Egypt; and Imperial College, London, United Kingdom (M.H.Y.).
authors.forename: Ahmed
authors.initials: A
authors.lastname: Elguindy
authors.affiliation: From the Cardiology Department (M.H., A.E., M.F.E.) and Radiology Department (A.K.), Cairo University, Egypt; Cardiology Department (M.H., K.W., P.P.S., A.E., H.M.), Radiology Department (A.K.), Biomedical Engineering Department (A.N.), and Cardiothoracic Department (M.H.Y.), Aswan Heart Centre, Egypt; and Imperial College, London, United Kingdom (M.H.Y.).
authors.forename: Amr
authors.initials: A
authors.lastname: ElFaramawy
authors.affiliation: From the Cardiology Department (M.H., A.E., M.F.E.) and Radiology Department (A.K.), Cairo University, Egypt; Cardiology Department (M.H., K.W., P.P.S., A.E., H.M.), Radiology Department (A.K.), Biomedical Engineering Department (A.N.), and Cardiothoracic Department (M.H.Y.), Aswan Heart Centre, Egypt; and Imperial College, London, United Kingdom (M.H.Y.).
authors.forename: Mahmoud F
authors.initials: MF
authors.lastname: Elmahdy
authors.affiliation: From the Cardiology Department (M.H., A.E., M.F.E.) and Radiology Department (A.K.), Cairo University, Egypt; Cardiology Department (M.H., K.W., P.P.S., A.E., H.M.), Radiology Department (A.K.), Biomedical Engineering Department (A.N.), and Cardiothoracic Department (M.H.Y.), Aswan Heart Centre, Egypt; and Imperial College, London, United Kingdom (M.H.Y.).
authors.forename: Hani
authors.initials: H
authors.lastname: Mahmoud
authors.affiliation: From the Cardiology Department (M.H., A.E., M.F.E.) and Radiology Department (A.K.), Cairo University, Egypt; Cardiology Department (M.H., K.W., P.P.S., A.E., H.M.), Radiology Department (A.K.), Biomedical Engineering Department (A.N.), and Cardiothoracic Department (M.H.Y.), Aswan Heart Centre, Egypt; and Imperial College, London, United Kingdom (M.H.Y.). m.yacoub@imperial.ac.uk.
authors.forename: Magdi H
authors.initials: MH
authors.lastname: Yacoub
mesh_terms: D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D000368:Aged; D001944:Breath Tests / Q000379:methods*; D006328:Cardiac Catheterization; D002302:Cardiac Output; D002311:Cardiomyopathy, Dilated / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology; D018619:Echocardiography, Doppler, Pulsed; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology; D009609:Nitrous Oxide / Q000008:administration & dosage*; D005741:Noble Gases / Q000008:administration & dosage*; D015588:Observer Variation; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D013318:Stroke Volume; D013459:Sulfur Hexafluoride / Q000008:administration & dosage*; D016277:Ventricular Function, Left; D055815:Young Adult
chemical_list: D005741:Noble Gases; D009609:Nitrous Oxide; D013459:Sulfur Hexafluoride
keywords: cardiac output; catheterization; echocardiography; heart failure; magnetic resonance imaging