ASAIO journal : a peer-reviewed journal of the American Society for Artificial Internal Organs
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Comparative Study
Pulsatile and nonpulsatile flows can be quantified in terms of energy equivalent pressure during cardiopulmonary bypass for direct comparisons.
The purpose of this study was to quantify and compare pulsatile and nonpulsatile pressure and flow waveforms in terms of energy equivalent pressure (EEP) during cardiopulmonary bypass in a neonatal piglet model. EEP is the ratio of the area under the hemodynamic power curve and the flow curve. Piglets, mean weight of 3 kg, were used in physiologic pulsatile pump (n = 7), pulsatile roller pump (n = 6), and nonpulsatile roller pump (n = 7) groups. ⋯ Although there was no difference in mean pressures in all groups, EEP and the percentage increase of pressure (from mean pressure to EEP) of mean arterial pressure and preaortic cannula extracorporeal circuit pressure were higher with pulsatile perfusion compared with nonpulsatile perfusion (p < 0.001). In particular, the physiologic pulsatile pump group produced significantly higher hemodynamic energy compared with the other groups (p < 0.001). These results suggest that pulsatile and nonpulsatile flows can be quantified in terms of EEP for direct comparisons, and pulsatile flow generates higher energy, which may be beneficial for vital organ perfusion during cardiopulmonary bypass.
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Various valved and nonvalved external right ventricle (RV) to pulmonary artery (PA) conduits have been used to palliate congenital heart anomalies. The ideal conduit has not been found. Reasons for conduit failures include stenosis, thrombosis, calcification of the valve or graft wall, and development of an obstructive peel. ⋯ Valved conduits demonstrated significantly less obstruction and regurgitation. The potential clinical advantages of bovine jugular conduits are their availability, potential durability evidenced by lack of early calcification, and the advantage of not requiring a proximal extension for the RV anastomosis. The presence of a durable and functional xenograft valve in valved conduits may prevent postoperative sequelae in some patients.
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Comparative Study
A computational and experimental comparison of two outlet stators for the Nimbus LVAD. Left ventricular assist device.
Two designs of an outlet stator for the Nimbus axial flow left ventricular assist device (LVAD) are analyzed at nominal operating conditions. The original stator assembly (Design 1) has significant flow separation and reversal. A second stator assembly (Design 2) replaces the original tubular outer housing with a converging-diverging throat section with the intention of locally improving the fluid dynamics. ⋯ The computational and experimental methods indicate: 1) persistent regions of flow separation in Design 1 and improved fluid dynamics in Design 2; 2) blade-toblade velocity fields that are well organized at the blade tip yet chaotic at the blade hub for both designs; and 3) a moderate decrease in pressure recovery for Design 2 as compared with Design 1. The CFD analysis provides the necessary insight to identify a subtle, localized flow acceleration responsible for the decreased hydraulic efficiency of Design 2. In addition, the curiously low thrombogenicity of Design 1 is explained by the existence of a three-dimensional unsteady vortical flow structure that enhances boundary advection.
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A common concern in cardiomyoplasty is whether latissimus dorsi muscle (LDM) stimulation impairs diastolic function. This study determined the time course of left ventricular (LV) contraction and relaxation and their relationship to the diastolic function. Ten mongrel dogs underwent vascular delay of the left latissimus dorsi muscle 2 weeks before cardiomyoplasty. ⋯ The diastolic filling time (Tdf) was significantly longer (177.9 +/- 17.6 to 213.7 +/- 18.7* ms) during the beat immediately after LDM stimulation. These changes reflected an overall stronger contraction and faster relaxation. Our results imply that with vascular delay, stimulation of LDM not only assists systolic function but also improves diastolic function in cardiomyoplasty.
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Adding a dialysis filter to the perfusion circuit at the end of cardiopulmonary bypass (CPB) has become an accepted means of reducing potassium rapidly and safely. Rapid removal of solute requires a dialysate for diffusion, and peritoneal dialysis solutions have been the standard because of availability, although occasionally normal saline or bicarb/ saline mixtures are used. Cardioplegia solution is high in glucose as well as potassium and, with many diabetic patients undergoing CPB, it is desirable to minimize glucose loads. ⋯ The lactate dialysate (LD) group received a mean of 17.4+/-7.7 L of lactate containing dialysate versus 14.6+/-4.7 L of bicarbonate dialysate (BD) (p = 0.41). After dialysis, potassium had been reduced to a similar degree in both groups, but plasma glucose levels had increased during LD while they fell during BD, and bicarbonate levels fell during LD while they rose during BD. Use of a commercially available sterile bicarbonate dialysate can safely help to lower plasma potassium during CPB and preserve more physiologic levels of glucose and bicarbonate.