T L Gentles — Page 2 | PubMed Health

PubMedDate not supplied

Wall shear stress is the primary mechanism of energy loss in the Fontan connection.

Long-term outcome following the Fontan operation may be affected by the amount of energy lost as blood flows through the anastomosis geometry. A method for detailed quantification of energy loss is applied to computational simulations of the flow in an atriopulmonary and a total cavopulmonary model. Five types of flow (near wall, slow recirculation, medium speed vortices, collision, and streamlined flow) are identified and their energy losses quantified. The presence of recirculation regions decreases the efficiency of the atriopulmonary model, and a region of increased energy loss is seen in the collision region in the total cavopulmonary model. However, the most significant energy loss is through wall shear stress, which is maximal in areas where there is rapid, near wall flow.

Adult↗

PubMedDate not supplied

Utility of intraoperative transesophageal echocardiography in the assessment of residual cardiac defects.

To investigate the accuracy of immediate postbypass transesophageal echocardiography in the assessment of residual cardiac defects, we compared intraoperative transesophageal echocardiograms with intra/postoperative data in 86 patients, aged 4 days to 30.7 years (median = 1.4 years), at risk for a total of 174 postoperative lesions: right (n = 55) or left (n = 26) ventricular outflow tract obstruction, ventricular septal defect (n = 65), aortic (n = 12) or mitral regurgitation (n = 8), or mitral stenosis (n = 8). Accuracy of intraoperative transesophageal echocardiography was evaluated based on comparison with (1) immediate post-bypass left (n = 4) or right (n = 9) ventricular outflow tract pressure gradients by pullback in the operating room, (2) direct surgical inspection of residual ventricular septal defects (n = 3), (3) pulmonary artery oxygen saturation (n = 49), (4) right ventricular outflow tract pullback gradient (n = 24), and (5) transthoracic echocardiogram (n = 51) performed within 40 days of surgery. The results indicate that intraoperative transesophageal echocardiography agreed with intra/postoperative data in 87% of patients at risk for right ventricular outflow tract obstruction, 96% at risk for left ventricular outflow tract obstruction, 97% at risk for ventricular septal defect, and 100% at risk for aortic regurgitation, mitral regurgitation, or mitral stenosis. Significant residual lesions led to immediate surgical revision in 11 cases: 3 ventricular septal defects, 6 right and 2 left ventricular outflow tract obstructions. Of these, intraoperative transesophageal echocardiography confirmed and quantified suspected residual lesions in 7 and identified unsuspected lesions in 4 cases. Immediate postbypass transesophageal echocardiography proved reliable for assessing residual ventricular septal defect, mitral stenosis, and mitral or aortic regurgitation. Although accurate for assessment of the left and right ventricular outflow tracts in most patients, transesophageal echocardiography may not reliably reflect the severity of obstruction in all cases.

Adolescent↗