External counterpulsation of a systemic-to-pulmonary artery shunt increases coronary blood flow in neonatal piglets.

BACKGROUND: Systemic-to-pulmonary artery shunt (SPS) palliation reduces coronary blood flow (CBF), which may precipitate myocardial ischemia postoperatively. HYPOTHESIS: Counterpulsation (CP) of SPS augments CBF. METHODS: Seven neonatal piglets (4.3 ± 0.23 kg) underwent sternotomy and ductus ligation. With a 5-mm polytetrafluoroethylene graft, SPS was created from innominate to pulmonary artery. A rigid shell holding a 9.5-mm diameter balloon was placed around the graft for CP. Using electrocardiographic signal, CP was initiated to trigger balloon inflation/deflation during the diastolic/systolic intervals, respectively. Instantaneous proximal and distal pulmonary artery and mid-anterior descending coronary artery flow rates were measured using transit time flow probes. Blood pressure and flow rates were recorded during three states: shunt closed, shunt open, and shunt open with CP. STATISTICAL COMPARISON: Friedman's test and repeated measures analysis of variance. RESULTS: Diastolic pressure decreased significantly with the shunt open (39 ± 8.4 to 28 ± 4.5 mm Hg, P = .05), then increased with CP (33 ± 2.3 mm Hg, P = .03). Median ratio of pulmonary to systemic flow (Qp/Qs) was 1.19, 1.9, and 1.53 with shunt closed, open, and open with CP, respectively. With CP, both diastolic coronary flow per minute (P = .018) and average diastolic flow rate per diastolic interval (P = .03) increased as well as total coronary flow per minute (P = .066; 19.6% ± 11.7%, 25.2% ± 17.0%, and 15.4% ± 13.9% change from shunt open, respectively). The percentage increase in average diastolic flow rate per diastolic interval correlated strongly with Qp/Qs (R (2) = .838). CONCLUSIONS: In this model of SPS, CP increased diastolic blood pressure and CBF while maintaining significant augmentation of pulmonary blood flow (Qp/Qs). Shunt CP may aid in early postoperative management of palliative congenital heart disease.

A novel electrospinning target to improve the yield of uniaxially aligned fibers.

Electrospinning is a useful technique that can generate micro and nanometer-sized fibers. Modification of the electrospinning parameters, such as deposition target geometry, can generate uniaxially aligned fibers for use in diverse applications ranging from tissue engineering to material fabrication. For example, meshes of fibers have been shown to mimic the extracellular matrix networks for use in smooth muscle cell proliferation. Further, aligned fibers can guide neurites to grow along the direction of the fibers. Here we present a novel electrospinning deposition target that combines the benefits of two previously reported electrodes: the standard parallel electrodes and the spinning wheel with a sharpened edge. This new target design significantly improves aligned fiber yield. Specifically, the target consists of two parallel aluminum plates with sharpened edges containing a bifurcating angle of 26 degrees. Electric field computations show a larger probable area of aligned electric field vectors. This new deposition target allows fibers to deposit on a larger cross-sectional area relative to the existing parallel electrode and at least doubles the yield of uniaxially aligned fibers. Further, fiber alignment and morphology are preserved after collection from the deposition target.