Recent years have seen a surge of scientific research examining the interdependence of one germ layer in the development of the other, both in vivo and in vitro. For example, the endoderm is believed to play a crucial role in the formation of mesoderm and subsequent maturation of cells belonging to the mesodermal lineage. Our understanding of this complex relationship is continuously growing with reinterpretation of earlier concepts and apprehension of newer hypotheses into the biology of embryonic development. Here we discuss some of the events governing the cooperative control of endoderm over mesoderm, and propose a perspective based on the existing literature and our own experience.
BackgroundThe novel coronavirus (COVID-19) global pandemic is characterized by rapid respiratory decompensation and subsequent need for endotracheal intubation and mechanical ventilation in severe cases 1,2 . Approximately 3-17% of hospitalized patients require invasive mechanical ventilation [3][4][5][6] . Current recommendations advocate for early intubation, with many also advocating the avoidance of non-invasive positive pressure ventilation such as high-flow nasal cannula, BiPAP, and bag-masking as they increase the risk of transmission through generation of aerosols [7][8][9] .
Background-Aortic valve bypass (AVB; apicoaortic conduit) surgery relieves aortic stenosis (AS) by shunting blood from the apex of the left ventricle to the descending thoracic aorta through a valved conduit. We have performed AVB surgery as an alternative to conventional aortic valve replacement for high-risk AS patients. Methods and Results-Between 2003 and 2007, 31 high-risk AS patients were treated with AVB surgery. Twenty-two patients (71%) were undergoing reoperation with patent coronary bypass grafts, and 5 (16%) had a porcelain ascending aorta. The average age was 81 years. Cardiopulmonary bypass was used for 19 of 31 patients (61%); the median duration of cardiopulmonary bypass was 19 minutes. Cross-clamp time for all patients was 0 minutes. Perioperative mortality was 13% (4 of 31 patients); no perioperative deaths occurred in the last 16 consecutive patients. One patient experienced a stroke related to intraoperative hypotension. No strokes have occurred during follow-up. Renal function was unchanged after AVB (preoperative creatinine, 1.3Ϯ0.5 mg/dL; postoperative creatinine, 1.2Ϯ0.5 mg/dL). The mean gradient across the native aortic valve decreased from 43.5Ϯ15 to 10.4Ϯ5.4 mm Hg. Echocardiographically determined conduit flow expressed as a percentage of total cardiac output was 72Ϯ12%. Conclusions-AVB surgery is an important therapeutic option for high-risk patients with symptomatic AS. Ventricular outflow is distributed in a predictable fashion between the conduit and the left ventricular outflow tract, and AVB surgery reliably relieves AS. Stroke and renal dysfunction were uncommon.
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