title: Coronary flow reserve in the newborn lamb: an intracoronary Doppler guide wire study.
abstract: Recent studies indicate a severely reduced coronary flow reserve (CFR) in neonates with congenital heart disease. The significance of these studies remains debatable, as the ability of the anatomically normal neonatal heart to increase coronary flow is currently unknown. This study was designed to establish normal values for CFR in newborns after administration of adenosine [pharmacologic CFR (pCFR)] and as induced by acute hypoxemia (reactive CFR). Thirteen mechanically ventilated newborn lambs were studied. Coronary flow velocities were measured in the proximal left anterior descending coronary artery before and after adenosine injection (140 and 280 microg/kg i.v.) using an intracoronary 0.014-in Doppler flow-wire. Measurements were made at normal oxygen saturation (SaO(2)) and during progressive hypoxemia induced by lowering the fraction of inspired oxygen. CFR was defined as the ratio of hyperemic to basal average peak flow velocity. In a hemodynamically stable situation with normal SaO(2), pCFR was 3.0 +/- 0.5. pCFR decreased with increasing hypoxemia. Regression analysis showed a linear relation between SaO(2) and pCFR (R = 0.86, p < 0.0001). Reactive CFR obtained at severe hypoxemia (Sao(2) <30%) was 4.2 +/- 0.8, and no significant further increase in coronary flow velocity occurred by administration of adenosine. Newborn lambs have a similar capacity to increase coronary flow in response to both pharmacologic and reactive stimuli as older subjects. Administration of adenosine does not reveal the full capacity of the newborn coronary circulation to increase flow, however, as the flow increase caused by severe hypoxemia is significantly more pronounced.
authors: Department of Pediatrics, Divison of Pediatric Cardiology, Lund University Hospital, S-221 85 Lund, Sweden. oggylfi@hn.is
authors: Gylfi
authors: G
authors: Oskarsson
authors: Erkki
authors: E
authors: Pesonen
authors: Saemunder
authors: S
authors: Gudmundsson
authors: Jónas
authors: J
authors: Ingimarsson
authors: Staffan
authors: S
authors: Sandström
authors: Olof
authors: O
authors: Werner
mesh_terms: D000208:Acute Disease; D000241:Adenosine / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002245:Carbon Dioxide / Q000097:blood; D003326:Coronary Circulation / Q000187:drug effects / Q000502:physiology*; D004195:Disease Models, Animal; D005260:Female; D000860:Hypoxia / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000503:physiopathology*; D008297:Male; D010100:Oxygen / Q000097:blood; D012756:Sheep; D018608:Ultrasonography, Doppler; D018084:Ultrasonography, Interventional; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D014665:Vasodilator Agents; D002245:Carbon Dioxide; D000241:Adenosine; D010100:Oxygen