title: Effect of hyperosmotic mannitol on magnetic resonance relaxation parameters in reperfused canine myocardial infarction.
abstract: To determine how administration of a hyperosmotic agent alters regional nuclear magnetic resonance (NMR) relaxation parameters and imaging characteristics in ischemic-reperfused myocardium, 7 dogs were infused with mannitol for 15 minutes before and after the release of a 3 hour left anterior descending coronary artery (LAD) occlusion. Nine control animals received normal saline during the 3 hour occlusion and 1 hour reperfusion periods. Normal posterior left ventricular (LV) wall and the ischemic anterior LV wall (risk area) myocardium was sampled for calculation of segmental microsphere myocardial blood flow, % tissue water content, NMR relaxation times (T1, T2) and myocyte ultrastructure using electron microscopy. Mean infarct T1 values were 14% greater than normal segments in saline-treated controls, but only 5% greater after mannitol. The difference in tissue water content between infarcted and normal segments was 4% in saline-treated (83 vs. 79%) compared to 2% in mannitol-treated dogs (79 vs. 77%). T1, T2 and % water content of control infarct segments were greater than treated infarcts (p less than 0.01). T1 and T2 rose as occlusion flow fell below 0.5 ml/min/g in control hearts but did not rise until flows were reduced to 0.1 ml/min/g in mannitol-treated hearts. Areas of increased signal in T1 and T2 NMR images correlated well with histochemical infarct volume (r = 0.98, SEE = 1.1 cc) in mannitol-treated dogs, but infarct borders were qualitatively less well-defined than in controls. We concluded that mannitol (1) diminishes tissue edema and reduces NMR relaxation parameters (T1, T2) in infarcted myocardium; and (2) attenuates the rise in T1 and T2 and ultrastructural myocyte injury in ischemic-reperfused myocardium.
authors.affiliation: Department of Medicine, Massachusetts General Hospital, Boston 02114.
authors.forename: D D
authors.initials: DD
authors.lastname: Miller
authors.forename: D L
authors.initials: DL
authors.lastname: Johnston
authors.forename: D
authors.initials: D
authors.lastname: Dragotakes
authors.forename: J B
authors.initials: JB
authors.lastname: Newell
authors.forename: T
authors.initials: T
authors.lastname: Aretz
authors.forename: H L
authors.initials: HL
authors.lastname: Kantor
authors.forename: T J
authors.initials: TJ
authors.lastname: Brady
authors.forename: R D
authors.initials: RD
authors.lastname: Okada
mesh_terms: D000818:Animals; D003326:Coronary Circulation; D004285:Dogs; D008279:Magnetic Resonance Imaging; D008353:Mannitol / Q000627:therapeutic use*; D009203:Myocardial Infarction / Q000175:diagnosis*; D015425:Myocardial Reperfusion; D009206:Myocardium / Q000473:pathology*; D009994:Osmolar Concentration
chemical_list: D008353:Mannitol