Ocular surface microcirculation is better preserved with pulsatile versus continuous flow during cardiopulmonary bypass—An experimental pilot

Background: Non- pulsatile cardiopulmonary bypass (CPB) may induce micro-vascular dysregulation. In piglets, we compared ocular surface microcirculation during pulsatile versus continuous flow (CF) bypass.Methods: Ocular surface microcirculation in small tissue volumes (~0.1 mm3) at limbus (high metabolic rate) and bulbar conjunctiva (low metabolic rate) was ex-amined in a porcine model using computer assisted video microscopy and diffuse reflectance spectroscopy, before and after 3 and 6 h of pulsatile (n = 5 piglets) or CF (n = 3 piglets) CPB. Functional capillary density, capillary flow velocity and microvascular oxygen saturation were quantified.Results: At limbus, velocities improved with pulsatility (p< 0.01) and deterio-rated with CF (p< 0.01). In bulbar conjunctiva, velocities were severely reduced with CF (p< 0.01), accompanied by an increase in capillary density (p< 0.01). Microvascular oxygen saturation decreased in both groups.Conclusion: Ocular surface capillary densities and flow patterns are better pre-served with pulsatile versus CF during 6 h of CPB in sleeping piglets

Evaluation of a novel device for left atrial appendage exclusion: The second-generation atrial exclusion device

BackgroundThe left atrial appendage is a frequent source of thromboemboli in patients with atrial fibrillation. Exclusion of the left atrial appendage may reduce the risk of stroke in patients with atrial fibrillation. The atrial exclusion device, previously developed to perform left atrial appendage exclusion on a beating heart, was modified to accommodate different anatomic patterns of the human left atrial appendage and to ensure uniform pressure and occlusion. The purpose of this study was to evaluate this second-generation atrial exclusion device during a midterm period in a canine model.MethodsTen mongrel dogs (mean weight 28.9 ± 4.6 kg) were used in this study. The atrial exclusion device, constructed from two parallel and rigid titanium tubes and two nitinol springs with a knit-braided polyester fabric, was implanted at the base of the left atrial appendage through a left thoracotomy on a beating heart using a specially designed delivery tool. Dogs were evaluated at 30 days (n = 4) and 90 days (n = 6) by epicardial echocardiography, left atrial and coronary angiography, gross pathology, and histologic inspection.ResultsDevice implantation was performed without complications in all dogs. Complete left atrial appendage exclusion without device migration or hemodynamic instability was confirmed, and there was no damage to the left circumflex artery or pulmonary artery. Macroscopic and microscopic assessments revealed favorable biocompatibility during midterm follow-up.ConclusionThe atrial exclusion device enabled rapid, reliable, and safe exclusion of the left atrial appendage. Clinical application may provide a new therapeutic option for reducing the risk of stroke in patients with atrial fibrillation

Acute in vivo evaluation of a new stentless mitral valve

ObjectivesWe have developed a stentless pericardial mitral valve prosthesis in 2 configurations; the purposes of this acute study in sheep were to assess (1) valve design and implant technique; (2) valve performance; and (3) acute effects on postimplant left ventricular function.MethodsA stentless bovine pericardial bileaflet valve was developed with the intent to preserve annular–papillary muscle continuity. This valve, in 2 configurations—with (n = 5) and without (n = 5) flap chordae—was implanted in 10 sheep (mean weight 73 ± 9 kg). Epicardial echocardiography was performed to assess valve performance. Load-independent left ventricular function was also estimated before implantation (baseline), 1 hour after discontinuing cardiopulmonary bypass (rest), and during dobutamine stimulation using conductance technology.ResultsImplantation was easily accomplished for both configurations. Both configurations had low transvalvular pressure (mean 2.1 ± 1.2 mm Hg at rest; 2.2 ± 1.0 mm Hg with dobutamine stimulation with flap chordae; 1.7 ± 0.5 mm Hg and 1.6 ± 0.3 mm Hg without flap chordae). No mitral regurgitation was observed in 8 sheep, and mild regurgitation was seen in 2 sheep. Compared with baseline, slope of maximum rate of change of left ventricular pressure–end-diastolic volume relation increased with stimulation both with flap chordae (+52 ± 41 mm Hg · s−1 · mL−1, P = .0005) and without (+20 ± 12 mm Hg · s−1 · mL−1, P = .003).ConclusionsBoth configurations of this newly designed stentless mitral bioprosthesis, which preserves annular–papillary muscle continuity using different novel surgical implantation techniques, demonstrated reliable valve performance, with low transvalvular pressure gradients, minimal regurgitation, and acutely preserved postimplant left ventricular function. Further chronic study is needed to verify these results and evaluate reliability of implantation procedures, biocompatibility, and durability