M L Royall | PubMed Health

PubMed2001

In vitro evaluation of the effect of aortic compliance on pediatric intra-aortic balloon pumping.

OBJECTIVES: To evaluate the effect of aortic compliance on pediatric intra-aortic balloon pumping (IABP). DESIGN: In vitro study using a mechanical model of the pediatric left heart circulation. SETTING: Cardiovascular fluid dynamics research laboratory. SUBJECT: Pulsatile flow system simulating the pediatric left heart circulation and two different aortas with compliances comparable to those of the pediatric aorta (0.12 and 0.07 mL/mm Hg). INTERVENTIONS: Measurements were made at a baseline peak aortic flow of 4 L/min, at simulated shock (1.7 L/min), and with 1:1 IABP (rates, 130 and 150 bpm; balloon volumes, 2.5 and 5.0 mL). MEASUREMENTS AND MAIN RESULTS: Peak flow rates were measured in the ascending aorta, coronary arterial system, and brachiocephalic arterial systems. Aortic pressure was measured in the ascending aorta. For both aortas (0.12 and 0.07 mL/mm Hg), IABP resulted in diastolic augmentation (38 +/- 8 and 43 +/- 16 mm Hg) and afterload reduction (4 +/- 2 and 6 +/- 3 mm Hg). For both aortas, compared to shock, IABP resulted in significant increases in coronary arterial and brachiocephalic arterial flow and aortic pressure for both aortas. Aortic flow significantly increased only in the less-compliant aorta. CONCLUSIONS: In a laboratory model of pediatric left heart circulation, IABP results in diastolic augmentation, afterload reduction, and improved hemodynamics, even in aortas of greater compliance.

Journal Article↗

PubMed1996

Relationships between bilayer structure and phospholipase A2 activity: interactions among temperature, diacylglycerol, lysolecithin, palmitic acid, and dipalmitoylphosphatidylcholine.

Bilayers composed of phosphatidylcholine initially resist catalysis by phospholipase A2. However, after a latency period, they become susceptible when sufficient reaction products (lysolecithin and fatty acid) accumulate in the membrane. Temperatures near the main bilayer phase transition and saturated long-chain diacylglycerol in the bilayer modulate the effectiveness of the reaction products. The purpose of this study was to identify possible mechanisms for these effects of temperature and diacylglycerol. Various fluorescent probes were used to asses changes in the ability of the reaction products to perturb the bilayer and promote enzyme binding to he membrane surface. Temperature appeared to cause three effects. First, the degree of binding of enzyme at the end of the latency period was greatest near the phase transition temperature where the latency was shortest. Second, the bilayer was more sensitive to perturbation by reaction products near the transition. Third, the disturbance provoked by the products was confined to the membrane surface below the transition but affected deeper regions at higher temperature where the latency period was greater. The latter two effects of temperature required the presence of calcium. Diacylglycerol promoted lateral segregation of reaction products in the bilayer. This effect corresponded with the tendency of diacylglycerol to reduce the length of the latency period at temperature below the phase transition. Therefore, it appeared that temperature affects the latency period by alternating the binding of the enzyme and the depth and magnitude of the bilayer perturbation caused by reaction products. Alternatively, diacylglycerol may enhance the effectiveness of reaction products by inducing them to segregate in the bilayer and thus create local regions of increased impact on the bilayer surface.

1,2-Dipalmitoylphosphatidylcholine↗