| 1. |
- Oskarsson, Gylfi
(författare)
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Coronary flow and flow reserve in children
- 2004
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Ingår i: Acta Pædiatrica. - : Wiley. - 1651-2227 .- 0803-5253. ; 93, s. 20-25
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Tidskriftsartikel (refereegranskat)abstract
- Aortic blood pressure affects coronary blood flow, but within the normal physiological blood pressure range coronary blood flow is constant. The coronary flow is pulsatile, being maximal in the early diastole. There is a smaller systolic flow component. The low systolic pressure in the right ventricle favours systolic flow. The proportion of systolic flow is greater in the right than in the left coronary artery. Heart diseases in children cause several haemodynamic and functional changes that are likely to affect myocardial perfusion. Newborns with severe valvular aortic stenosis may have a retrograde systolic flow in the left coronary artery. Children with dilated cardiomyopathy have a reduced coronary flow related to myocardial mass. Coronary flow reserve (CFR) is defined as the ratio of maximal coronary blood flow, as induced by reactive hyperaemia or administration of vasodilators, divided by resting flow. Coronary flow can normally increase 2.5-4-fold. CFR is reduced if basal flow is increased due to myocardial hypertrophy, strain or hypoxaemia. Very low CFR values measured with positron emission tomography are reported in neonates with surgically treated congenital heart disease. Measurement of coronary flow velocity with the intracoronary Doppler guide wire may be regarded as a reference or "gold standard" in the evaluation of coronary flow velocity and CFR. Conclusions: Coronary flow and CFR in children is a largely unexploited field, and has vast potential for future research.
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| 2. |
- Oskarsson, Gylfi, et al.
(författare)
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Coronary flow reserve in the newborn lamb: An intracoronary Doppler guide wire study
- 2004
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Ingår i: Pediatric Research. - 1530-0447. ; 55:2, s. 205-210
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Tidskriftsartikel (refereegranskat)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 mug/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.
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| 3. |
- Oskarsson, Gylfi
(författare)
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Doppler evaluation of coronary blood flow and coronary flow reserve - Clinical and experimental studies
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Heart diseases in children cause different combinations of myocardial hypertrophy, increased intra-ventricular pressures, volume overload and decreased oxygen saturation. This may affect basal coronary flow and the ability of the heart to maximally increase coronary flow. Transthoracic and intracoronary Doppler techniques were used to register coronary flow and coronary flow reserve (CFR) in normal subjects and in children with heart disease. The same methods were employed in experimental studies (lamb model) where CFR in the newborn was defined, and the effects of fetal asphyxia on coronary flow as compared with cerebral flow were described. Flow velocity parameters and flow volume in the left anterior descending (LAD) coronary artery in healthy neonates and infants increase with age and left ventricular mass, and are affected by both systolic and diastolic left ventricular function. In neonates with severe aortic stenosis, systolic flow reversal and increased diastolic flow velocity were observed preoperatively, but the flow normalised immediately after operation. In infants with idiopathic idiopathic dilated cardiomyopathy, all LAD flow velocity parameters and flow volume were increased compared to age matched controls, while LAD flow corrected for left ventricular mass was reduced. Children treated with arterial switch operation for transposition of the great arteries who had normal postoperative hemodynamics had normal CFR in both the LAD and the right coronary artery (RCA). However, if residual lesions causing myocardial hypertrophy were present, the basal RCA flow velocity was increased and CFR reduced. CFR in the LAD in the newborn lamb, as measured by administration of adenosine, was found to be slightly lower (3.0) than what has been reported for older subject, while the reactive CFR, the flow response to rapid severe hypoxemia, was found to be significantly higher or 4.2. The circulatory response to fetal asphyxia was characterised by a rapid short-lived 4-fold increase in RCA flow, while cerebral blood flow decreased immediately. Doppler techniques can be used to describe the effects of heart disease and abnormal hemodynamic conditions on coronary flow and CFR in children. Abnormal coronary flow dynamics and reduced CFR may be associated with increased risk of myocardial ischemia, and these concepts may aid in decision-making regarding surgical and medical treatment of children with heart disease.
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| 4. |
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| 5. |
- Oskarsson, Gylfi, et al.
(författare)
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Normal coronary flow reserve after arterial switch operation for transposition of the great arteries: an intracoronary Doppler guidewire study.
- 2002
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Ingår i: Circulation. - 1524-4539. ; 106:13, s. 1696-1702
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Recent studies performed with positron emission tomography have suggested that coronary flow reserve (CFR) is moderately to severely reduced after the arterial switch operation (ASO). These findings are of great concern but have not been confirmed by other methods. METHODS AND RESULTS: Eleven symptom-free children were studied between 4 and 11 (median 6.0) years after the ASO. Flow velocity in the left anterior descending (LAD) and right coronary arteries (RCA) was measured with a 0.014-inch Doppler FloWire (Cardiometrics) before and after intracoronary injection of adenosine (0.5 micro g/kg) and nitroglycerin (5 micro g/kg). CFR was defined as the ratio of hyperemic to basal average peak velocity (APV). The median (range) CFR in the LAD was 3.7 (3.0 to 4.8) and 3.4 (2.9 to 4.8) in the RCA. The increase in APV after intracoronary injection of nitroglycerin was 300% (240% to 420%) in the LAD and 260% (190% to 460%) in the RCA. APV at rest was 15.0 (14.0 to 21.0) cm/s in the LAD and 16.0 (9.6 to 30.0) cm/s in the RCA. A linear relation was found between right ventricular systolic pressure and resting APV in the RCA (r=0.77, P=0.0056), and between resting APV and CFR (r=-0.61, P<0.05) in the RCA. CONCLUSIONS: The CFR and coronary vasoreactivity to nitroglycerin in children treated for transposition of the great arteries with the ASO was within normal limits. Increased right ventricular pressure and myocardial hypertrophy can cause increased resting coronary flow velocity in the RCA and affect CFR negatively.
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| 6. |
- Thorngren-Jerneck, Kristina, et al.
(författare)
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Reduced postnatal cerebral glucose metabolism measured by PET after asphyxia in near term fetal lambs
- 2001
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Ingår i: Journal of Neuroscience Research. - : Wiley. - 1097-4547 .- 0360-4012. ; 66:5, s. 844-850
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Tidskriftsartikel (refereegranskat)abstract
- The effects of fetal asphyxia on cerebral function and development, involve the transition from fetal to neonatal life. Changes in cerebral glucose metabolism may be an early postnatal indicator of fetal asphyxia. The objective is to develop an experimental lamb model involving the transition from fetal to neonatal life and to examine the effect of fetal asphyxia with cerebral hypoxic ischemia on early postnatal cerebral glucose metabolism. Fetal asphyxia was induced by total umbilical cord occlusion in eight near-term fetal lambs (134-138 days) with the ewe under isoflurane-opiate anesthesia. The mean occlusion time until cardiac arrest was 14.5 (4.2) min (SD). Lambs were immediately delivered and standardized resuscitation was instituted after 2 min asystole. At 4 hr postnatal age, [18-F]Fluoro-2-deoxy-glucose (18-FDG) was injected intravenously in eight asphyxiated lambs and in eight controls. Cerebral glucose metabolism was examined by positron emission tomography (PET). As a result the mean arterial blood pressure, acid-base values, blood glucose and serum lactate at 4 hr postnatal age did not differ significantly between lambs subjected to umbilical cord occlusion and controls. EEG was abnormal in all lambs subjected to cord occlusion and normal in the controls at 4 hr postnatal age. Global cerebral metabolic rate (CMRgl) as determined by PET was significantly lower in lambs subjected to cord occlusion mean/median (SD) 22.2/19.6 (8.4) micromol/min/100 g) than in controls mean/median (SD) 37.8/35.9 (6.1); P < 0.01). Global CMRgl is significantly reduced in newborn lambs 4 hr after fetal asphyxia induced by umbilical cord occlusion. A reduction in CMRgl is an early indicator of global hypoxic cerebral ischemia.
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