title: The impact of hematocrit on oxygenation-sensitive cardiovascular magnetic resonance.
abstract: Oxygenation-sensitive (OS) Cardiovascular Magnetic Resonance (CMR) is a promising utility in the diagnosis of heart disease. Contrast in OS-CMR images is generated through deoxyhemoglobin in the tissue, which is negatively correlated with the signal intensity (SI). Thus, changing hematocrit levels may be a confounder in the interpretation of OS-CMR results. We hypothesized that hemodilution confounds the observed signal intensity in OS-CMR images.
  
  
  
  Venous and arterial blood from five pigs was diluted with lactated Ringer solution in 10 % increments to 50 %. The changes in signal intensity (SI) were compared to changes in blood gases and hemoglobin concentration. We performed an OS-CMR scan in 21 healthy volunteers using vasoactive breathing stimuli at baseline, which was then repeated after rapid infusion of 1 L of lactated Ringer's solution within 5-8 min. Changes of SI were measured and compared between the hydration states.
  
  
  
  The % change in SI from baseline for arterial (r = -0.67, p < 0.0001) and venous blood (r = -0.55, p = 0.002) were negatively correlated with the changes in hemoglobin (Hb). SI changes in venous blood were also associated with SO2 (r = 0.68, p < 0.0001) and deoxyHb concentration (-0.65, p < 0.0001). In healthy volunteers, rapid infusion resulted in a significant drop in the hemoglobin concentration (142.5 ± 15.2 g/L vs. 128.8 ± 15.2 g/L; p < 0.0001). Baseline myocardial SI increased by 3.0 ± 5.7 % (p = 0.026) following rapid infusion, and in males there was a strong association between the change in hemoglobin concentration and % changes in SI (r = 0.82, p = 0.002). After hyperhydration, the SI response after hyperventilation was attenuated (HV, p = 0.037), as was the maximum SI increase during apnea (p = 0.012). The extent of SI attenuation was correlated with the reduction in hemoglobin concentration at the end of apnea (r = 0.55, p = 0.012) for all subjects and at maximal SI (r = 0.63, p = 0.037) and the end of breath-hold (r = 0.68, p = 0.016) for males only.
  
  
  
  In dynamic studies using oxygenation-sensitive CMR, the hematocrit level affects baseline signal intensity and the observed signal intensity response. Thus, the hydration status of the patient may be a confounder for OS-CMR image analysis.
authors.affiliation: Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Montreal, QC, Canada. dominik.guensch@gmail.com.|Department of Anesthesiology and Pain Therapy, Inselspital, Bern University Hospital, University of Bern, Freiburgstrasse, 3010, Bern, Switzerland. dominik.guensch@gmail.com.|Instutite of Diagnostic, Interventional and Pediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland. dominik.guensch@gmail.com.
authors.forename: Dominik P
authors.initials: DP
authors.lastname: Guensch
authors.affiliation: Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Montreal, QC, Canada.
authors.forename: Gobinath
authors.initials: G
authors.lastname: Nadeshalingam
authors.affiliation: Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Montreal, QC, Canada.|Department of Anesthesiology and Pain Therapy, Inselspital, Bern University Hospital, University of Bern, Freiburgstrasse, 3010, Bern, Switzerland.
authors.forename: Kady
authors.initials: K
authors.lastname: Fischer
authors.affiliation: Siemens Healthcare GmbH, Erlangen, Germany.
authors.forename: Aurelien F
authors.initials: AF
authors.lastname: Stalder
authors.affiliation: Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Montreal, QC, Canada.|Department of Medicine, Heidelberg University, Heidelberg, Germany.|Departments of Cardiac Sciences and Radiology, University of Calgary, Calgary, AB, Canada.|Department of Radiology, Université de Montréal, Montreal, QC, Canada.|Departments of Medicine and Radiology, McGill University Health Centre, Montreal, QC, Canada.
authors.forename: Matthias G
authors.initials: MG
authors.lastname: Friedrich
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D005260:Female; D064368:Healthy Volunteers; D006321:Heart / Q000000981:diagnostic imaging*; D006339:Heart Rate; D006400:Hematocrit; D006438:Hemodilution / Q000379:methods*; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007262:Infusions, Intravenous; D007552:Isotonic Solutions / Q000008:administration & dosage*; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010100:Oxygen / Q000097:blood*; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D000077325:Ringer's Lactate; D034421:Sus scrofa; D014882:Water-Electrolyte Balance; D055815:Young Adult
chemical_list: D015415:Biomarkers; D006454:Hemoglobins; D007552:Isotonic Solutions; D000077325:Ringer's Lactate; C100003:deoxyhemoglobin; D010100:Oxygen
keywords: BOLD-CMR; Hematocrit; Hemodilution; Hemoglobin; OS-CMR; T2*