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Biomedical subjects

T R Lloyd

Publications and source records attributed to T R Lloyd.

At least 55 records · Page 3Linked to original sources
PubMed1994

Hyaluronate degradation affects ventricular function of the early postlooped embryonic rat heart in situ.

Hyaluronic acid is the major glycosaminoglycan of the early cardiac extracellular matrix or "cardiac jelly," yet little is known about its role in the ontogeny of early ventricular performance. To investigate the in situ effect of hyaluronate degradation on ventricular function, whole rat embryos were cultured in rat serum alone (control embryos) or rat serum plus 20 TRU/mL of Streptomyces hyaluronidase (treatment embryos) from gestational day 9.5 (before formation of the heart tube) through initial looping of the heart. Cardiac function was measured before looping (24 hours in culture) and immediately after looping (36 hours in culture) by video motion analysis of the external wall motion of the bulbus cordis and primitive ventricle. Degradation of hyaluronic acid in the treated embryos was confirmed by Alcian blue staining at pH 2.5. Significant increases in heart rate, circumferential shortening fraction, maximum velocity of circumferential contraction, and maximum velocity of circumferential relaxation were observed with looping in both control and treatment embryos. Although there was minimal difference in ventricular performance between control and treatment embryos before looping, there was a significant increase in all parameters of ventricular performance in the hyaluronidase-treated embryos immediately after looping of the heart. Endocardial cushions were absent in hyaluronidase-treated embryos, and an additional group of embryos cultured in the presence of Streptomyces hyaluronidase for 48 to 72 hours failed to develop endocardial cushions. These experiments are the first to (1) document a quantifiable increase in ventricular performance during early cardiac looping and (2) demonstrate that hyaluronate degradation results in abnormal endocardial cushion formation and altered ventricular performance of the postlooped heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Central pulmonary artery growth patterns after the bidirectional Glenn procedure.

The changes in pulmonary artery size and hemodynamics in 30 patients with univentricular cardiac anatomy were examined before and after bidirectional Glenn procedures done between October 1989 and February 1992. Serial angiographic and hemodynamic examinations before and 17.6 +/- 1.6 months after bidirectional Glenn procedures were compared. At the follow-up study there was no significant change in diameter of the pulmonary artery ipsilateral to the bidirectional Glenn shunt, however, a significant decrease was noted in the diameter of the pulmonary artery contralateral to the bidirectional Glenn shunt (p = 0.04). There was also a 32% decrease in the Nakata index of total cross-sectional pulmonary artery area after the bidirectional Glenn procedure (p = 0.004). Total pulmonary blood flow and mean pulmonary artery pressure had decreased, and arterial oxygen saturation had increased at follow-up. These changes, however, did not correlate with the observed changes in pulmonary artery size. By linear regression analysis, a significant relationship was identified between the Nakata index before the bidirectional Glenn procedure and the absolute change in Nakata index (r = 0.83). A significant decrease in Nakata index occurred only in patients with a bidirectional Glenn shunt in place more than 15 months. Sixteen of the 30 patients subsequently underwent total cavo-pulmonary anastomosis with 7 requiring concurrent surgical pulmonary artery reconstruction. Changes in pulmonary artery size observed more than 15 months after the bidirectional Glenn procedure may have implications for subsequent Fontan repair in children with univentricular anatomy.

Arteriovenous Shunt, Surgical↗
PubMed1993

Transcatheter occlusion of patent ductus arteriosus with Gianturco coils.

BACKGROUND: Transcatheter occlusion with Gianturco coils has been attempted in a small number of patients with tiny (< or = 1.5-mm diameter) patent ductus arteriosus, and preliminary results have been encouraging. The present study extends this method to larger ductus sizes and makes recommendations for proper coil size selection. METHODS AND RESULTS: Coil occlusion was attempted in 24 consecutive patients with patent ductus arteriosus who did not require other cardiac surgery. Median patient age was 4.2 years (8 months to 30 years), and mean ductus diameter was 1.7 +/- 0.8 mm. Two instances of coil embolization occurred in the first 4 patients, with successful coil retrieval. Based on this experience, we proposed that the coil helical diameter should be twice or more the minimum ductus diameter, with coil length sufficient for three or more loops. With these recommendations, coils were successfully implanted in the subsequent 20 consecutive patients. Of the 22 patients with successful coil implantation, 15 (68%) had no residual shunting, and 7 had trace residual shunting by angiography. The continuous murmur was abolished in all 22 patients. No significant complications occurred, and all patients were discharged within 24 hours of successful coil implantation. No change in the systolic pressure gradient between main and left pulmonary artery or ascending and descending aorta was observed. CONCLUSIONS: Transcatheter occlusion of patent ductus arteriosus can be safely and effectively achieved in patients with ductus diameters up to 3.3 mm. Coil occlusion does not cause obstruction to flow in the left pulmonary artery or descending aorta. Coils should be selected to provide a helical diameter twice or more the minimum ductus diameter and a length sufficient for three or more loops.

Cardiac Catheterization↗
PubMed1993

Intraoperative and percutaneous stenting of congenital pulmonary artery and vein stenosis.

BACKGROUND: Conventional surgical or balloon dilation therapy for pulmonary artery or vein stenosis has been unsatisfactory in many patients. Balloon-expandable stents offer a new form of treatment for these vascular stenoses and can be implanted percutaneously or intraoperatively. METHODS AND RESULTS: Between July 1991 and October 1992, 20 balloon-expandable Palmaz stents (Johnson & Johnson) were implanted in 16 children at median age and weight of 3.0 years and 12.8 kg, respectively. Stent implantation was performed intraoperatively (n = 15) if the patient was less than 1 year of age or less than 10 kg in weight, in cases where limited vascular access precluded percutaneous implantation, or as an adjunct to other intracardiac surgery. Otherwise, percutaneous stenting was performed (n = 5). Vessels were tested for distensibility by dilation with balloon catheters or vascular sounds. Stents were implanted using angioplasty catheter balloons chosen to achieve desired vessel diameter and inflated to 4 to 17 atm. Acute hemodynamic and cineangiographic studies were performed in all patients immediately after the procedure to 2 months after stenting. After pulmonary artery stent implantation, mean pulmonary artery diameter increased from 5.6 to 11.5 mm (P = .001), with a decrease in mean systolic pressure gradients from 43 to 8.0 mm Hg (P = .005). Follow-up cardiac catheterization (mean, 8.7 months) in 3 patients revealed no restenosis, thrombosis, or aneurysm formation. In patients in whom pulmonary vein stents were implanted, mean pressure gradients fell from 11 to 0.3 mm Hg (P = .03), and mean pulmonary capillary wedge pressure fell from 17 to 6.3 mm Hg (P = .03) immediately after stenting. At 2- to 6-month follow-up, cardiac catheterization documented restenosis within the stent in 2 of 3 patients. The third patient died 2 months after stenting from presumed vein reocclusion. CONCLUSIONS: When implanted intraoperatively or percutaneously, balloon-expandable endovascular stents have been efficacious in the treatment of pulmonary artery stenosis. Longer follow-up will be necessary to document the long-term effectiveness of pulmonary artery stenting. Preliminary data suggest that early restenosis is common after pulmonary vein stenting. The intraoperative approach extends stenting therapy to smaller children and to patients who have limited percutaneous access.

Angioplasty, Balloon↗
PubMed1993

Management of complications of Sideris transcatheter devices for atrial septal defect closure.

Various devices that can be inserted transvenously to close an ostium secundum atrial septal defect are undergoing clinical trials. Although these are safe and effective in most instances, they may occasionally dislodge or fail to "button" properly, causing migration and embolization. We report two cases in which the occluder and counteroccluder of the Sideris device for transvenous atrial septal defect occlusion (Custom Medical Devices, Amarillo, Tex.) failed to "button" appropriately, migrating in the right atrium in one patient and embolizing to the pulmonary artery in the second patient. An emergency operation was required to retrieve the device and repair the atrial septal defect.

Cardiac Catheterization↗
PubMed1992

Echocardiographic estimation of balloon-stretched diameter of secundum atrial septal defect for transcatheter occlusion.

Stretched diameter of the atrial septal defect (ASD), determined by balloon sizing at cardiac catheterization, is commonly used to select the sizes of the devices used for transcatheter closure of the secundum ASD. We have previously evaluated the utility of pulmonary/systemic flow ratio and angiographic and echocardiographic (echo) sizes of the ASD in estimating stretched ASD diameter in a group of 16 patients and determined that echo diameter had the best correlation with stretched diameter (r = 0.82; p less than 0.001). The stretched diameter can be estimated: 1.05 x echo diameter in millimeters + 5.49. In this study we have prospectively evaluated this formula in estimating the stretched ASD diameter by two-dimensional echo measurements obtained in two (long and short-axis) subcostal views in another group of 21 patients aged 2.5 to 29 years (median 4.5 years). The echo size of the ASD was 9.7 +/- 3.0 mm, whereas the measured stretched diameter was 15.3 +/- 4.0 mm. The predicted stretched ASD diameter was calculated according to the above formula and was 15.7 +/- 3.1 mm, not significantly different (p greater than 0.1) from the measured stretched diameter. The correlation between predicted and measured stretched ASD sizes was excellent (r = 0.9; p less than 0.001). The mean squared error was 2.4. The differences between measured and predicted values were within 2 mm in all but three patients. It is concluded that stretched ASD diameter can be estimated accurately by two-dimensional subcostal echo measurements, which in turn could be used for selection of device size for occlusion of the ASD.

Catheterization↗
PubMed1992

Accuracy of central venous pressure monitoring in the intraabdominal inferior vena cava: a canine study.

STUDY OBJECTIVE: To test the hypotheses that in multiple pathophysiologic settings (1) end-expiratory central venous pressure measurements in the intraabdominal inferior vena cava accurately reflect those in the superior vena cava and (2) mean central venous pressure monitoring is as reliable in the inferior vena cava as it is in the superior vena cava. DESIGN: Simultaneous inferior vena caval and superior vena caval pressures were measured during five ventilatory phases: apnea, end-expiratory mechanical ventilation, maximal inspiratory mechanical ventilation, end-expiratory spontaneous ventilation, and maximal inspiratory spontaneous ventilation. Measurements were repeated after progressive intravascular volume depletion. SUBJECTS: Eight puppies. MEASUREMENTS AND RESULTS: Simultaneous inferior vena caval and superior vena caval end-expiratory pressures did not differ significantly (mean differences 0 to 0.1 mm Hg) and the limits of agreement of these measurements were within 2 mm Hg. Differences between mean maximal inspiratory pressures in the inferior vena cava and superior vena cava during mechanical and spontaneous ventilation were -0.7 and 3.6 mm Hg, respectively (p less than 0.01), and the limits of agreement extended beyond 2 mm Hg. Furthermore, mean maximal inspiratory pressures in the superior vena cava differed from end-expiratory pressures in the superior vena cava (1.1 and -3.6 mm Hg, p less than 0.01), whereas those in the inferior vena cava did not differ from end-expiratory superior vena caval pressures. CONCLUSIONS: Under the experimental conditions studied (1) end-expiratory intraabdominal inferior vena caval pressures accurately reflected end-expiratory superior vena caval pressures and (2) mean central venous pressure monitoring was as reliable in the inferior vena cava as in the superior vena cava.

Abdomen↗
PubMed1992

Transcatheter stenting of the ductus arteriosus: evaluation as an alternative to surgical shunts.

Implantation of 3.5 mm Gianturco-Roubin coronary artery stents into the ductus arteriosus was evaluated as an alternative to surgical systemic to pulmonary arterial shunts in 3 weanling piglets. Thrombosis of the ductus occurred in all 3 animals (95% confidence limits 29-100%) within 1 hour, despite pretreatment with heparin. In each case, thrombus filled the ductus arteriosus but did not extend to any extraductal portion of the stents. Rapid, heparin-resistant thrombus formation precludes use of this stent procedure as an alternative to surgical shunts.

Animals↗
PubMed1992

Accuracy of central venous pressure measurement from the abdominal inferior vena cava.

Central venous pressure measurements in the abdominal inferior vena cava were compared with measurements in the right atrium in 10 infants and 10 children during cardiac catheterization. At end expiration, the mean pressures at these two sites were within 1 mm Hg of each other in all 20 patients, with a mean difference of 0.0 +/- 0.36 mm Hg. The abdominal inferior vena cava is a safe and convenient site for measurement of central venous pressure, and our study confirms that such measurements are accurate.

Adolescent↗
PubMed1991

Failure of color flow mapping to identify coronary artery to pulmonary artery fistula.

A case of coronary artery to pulmonary artery fistula presented with the typical clinical findings of asymptomatic precordial continuous murmur and small left-to-right shunt. Echocardiography with color flow mapping failed to demonstrate the fistula on three occasions, including one study performed after angiographic demonstration of the fistula site. This case illustrates the importance of angiography in patients with unexplained continuous murmurs, even when echocardiographic and color flow mapping results are normal.

Arterio-Arterial Fistula↗
PubMed1991

Contractile response to sympathetic innervation in neonatal ventricular cardiomyocytes of the spontaneously hypertensive rat.

Differences in cardiac development between spontaneously hypertensive rats (SHR) and their normotensive Wistar Kyoto (WKY) controls are observed before the onset of hypertension. To determine whether intrinsic differences in myocardium or autonomic neurons might be responsible for these observations, we studied primary cultures of isolated, never previously innervated ventricular cardiomyocytes from neonatal rats of both strains, and sympathetic innervation was produced by addition of neurons from thoracolumbar sympathetic ganglia. Both same-strain and cross-strain innervation were compared. Amplitude and frequency of contraction were measured from video images of spontaneously contracting cells by on-line video motion analysis. Sympathetic innervation improved contractile function by 61% in SHR cardiomyocytes (p less than 0.001), an effect qualitatively similar to that previously reported for WKY cardiomyocytes. Contractile function of SHR cardiomyocytes cultured without sympathetic explants was 25% less than that of WKY cells (p less than 0.005), but the response of SHR cardiomyocytes to sympathetic innervation was twice as great as that of WKY myocytes (p less than 0.01). Cross-strain innervation experiments showed that sympathetic neurons from both strains were equally effective; interstrain differences were confined to the cardiomyocytes. Interstrain differences in cardiomyocyte contractile function and contractile response to sympathetic innervation are present before the onset of hypertension, and may in part account for alterations in cardiac function observed in prehypertensive SHR.

Animals↗