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Biomedical subjects

David Michael McMullan

Publications and source records attributed to David Michael McMullan.

6 recordsLinked to original sources
PubMed2006

Evaluation of downsized homograft conduits for right ventricle-to-pulmonary artery reconstruction.

OBJECTIVE: Although homograft conduits are frequently used to establish right ventricle-to-pulmonary artery continuity, the limited availability of small-size homografts is a significant constraint in pediatric cardiac surgery. We compared the performance of standard homograft conduits with that of surgically reduced bicuspid homograft conduits in patients undergoing repair of truncus arteriosus. METHODS: Forty infants undergoing complete repair of truncus arteriosus with either standard homografts (n = 26) or reduced-size bicuspid homografts (n = 14) were evaluated. RESULTS: The median downsized conduit diameter (13 mm) was similar to the standard homograft diameter (12 mm, P = .52). There were 6 early deaths and 5 late deaths, representing an overall 30-day mortality of 15% and a 5-year mortality of 25%. No deaths were directly related to homograft dysfunction. Four (29%) downsized conduits and 8 (31%) standard conduits required replacement at a median interval of 18.5 months and 42.4 months, respectively. Catheter-based interventions were required in 5 (36%) patients in the downsized group and in 3 (12%) patients in the standard group. There was no difference in freedom from surgical or catheter-based reintervention between the 2 groups (P = .42). Freedom from conduit failure (severe conduit stenosis, moderate or greater regurgitation) was 55.9% and 17.2% at 3 years in the downsized and standard groups, respectively. CONCLUSION: The surgically downsized homograft is an excellent option when an appropriate-sized homograft is not available and might prevent morbidity associated with the use of an oversized conduit.

Anastomosis, Surgical↗
PubMed2004

Pulmonary arteriovenous shunting in the normal fetal lung.

OBJECTIVES: We hypothesized that pulmonary arteriovenous shunting (PAVS) is normally present in fetal lungs and that cavopulmonary anastomosis-induced PAVS may represent a return to an earlier morphologic stage of development. BACKGROUND: The surgical superior cavopulmonary anastomosis is performed as part of the staged Fontan pathway to treat univentricular forms of congenital heart disease; PAVS is a known sequela after superior cavopulmonary anastomosis and may have important clinical consequences. Although the etiology and true morphology of the structures responsible for PAVS are unknown, a leading theory is that PAVS is caused by absence of normal hepatic venous drainage to the pulmonary circulation. METHODS: To determine whether normal fetal lungs demonstrate PAVS, we performed contrast echocardiograms on 13 fetal lambs, 8 neonatal lambs, 4 juvenile lambs, and 4 adult sheep using a blended mixture of saline and blood injected directly into the proximal pulmonary artery. RESULTS: Pulmonary arteriovenous shunting was detected by direct epicardial echocardiography in all fetal lambs (n = 13) and neonatal animals studied at one and three days of life (n = 4) and in two of four animals studied at six to nine days of life. Pulmonary arteriovenous shunting was not present in animals studied at four weeks of life (n = 2) and in adult sheep (n = 5). CONCLUSIONS: These studies demonstrate that PAVS is normally present in late gestation fetal and early neonatal lambs but then disappears during the later neonatal period. Furthermore, these findings suggest that PAVS associated with cavopulmonary anastomosis or other processes affecting the developing pulmonary circulation may represent a return to an earlier morphologic stage of development.

Animals↗
PubMed2004

A method for selectively limiting lumen diameter in corrosion casting.

Corrosion casting is a technique frequently used to evaluate the form and spatial relationship of three dimensional biological structures, such as vascular networks, in vitro [Scann. Microsc. 5 (1991) 1097; Schraufnagel, D.E. The lung microstructure. In: Motta, P.M., Murakami, T. Fujita, H. eds. Scanning Electron Microscopy of Vascular Casts: Methods and Applications. Boston: Kluwer Academic Publishers; 1992:123-137]. However, because corrosion casts tend to reproduce the complexity of surrounding vascular structures as well as the structures of interest, the use of this technique in highly complex vascular systems may obscure important changes such as A-V shunts because they may get lost among the myriad of capillaries. We developed a novel modification for creating vascular corrosion casts by utilizing polystyrene microspheres to selectively embolize normal capillary networks and thereby reduce the overall complexity of the cast. his technique may aid investigators in the evaluation of a variety of vascular beds and is useful in demonstrating non-capillary arteriovenous communications.

Animals↗