Doppler evaluation of coronary blood flow and coronary flow reserve - Clinical and experimental studies
Sammanfattning: 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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