Diller Gerhard-Paul, Lammers Astrid E, Haworth Sheila G, Dimopoulos Konstantinos, Derrick Graham, Bonhoeffer Philipp, Gatzoulis Michael A, Francis Darrel P
National Heart and Lung Institute, Imperial College of Science and Medicine, London, UK.
Cardiol Young. 2010 Feb;20(1):25-32. doi: 10.1017/S1047951109991855. Epub 2010 Feb 10.
Atrial septostomy is performed in patients with severe pulmonary arterial hypertension, and has been shown to improve symptoms, quality of life and survival. Despite recognized clinical benefits, the underlying pathophysiologic mechanisms are poorly understood. We aimed to assess the effects of right-to-left shunting on arterial delivery of oxygen, mixed venous content of oxygen, and systemic cardiac output in patients with pulmonary arterial hypertension and a fixed flow of blood to the lungs. We formulated equations defining the mandatory relationship between physiologic variables and delivery of oxygen in patients with right-to-left shunting. Using calculus and computer modelling, we considered the simultaneous effects of right-to-left shunting on physiologies with different pulmonary flows, total metabolic rates, and capacities for carrying oxygen. Our study indicates that, when the flow of blood to the lungs is fixed, increasing right-to-left shunting improves systemic cardiac output, arterial blood pressure, and arterial delivery of oxygen. In contrast, the mixed venous content of oxygen, which mirrors the average state of tissue oxygenation, remains unchanged. Our model suggests that increasing the volume of right-to-left shunting cannot compensate for right ventricular failure. Atrial septostomy in the setting of pulmonary arterial hypertension, therefore, increases the arterial delivery of oxygen, but the mixed systemic saturation of oxygen, arguably the most important index of tissue oxygenation, stays constant. Our data suggest that the clinically observed beneficial effects of atrial septostomy are the result of improved flow of blood rather than augmented tissue oxygenation, provided that right ventricular function is adequate.
房间隔造口术用于治疗重度肺动脉高压患者，已被证明可改善症状、提高生活质量并延长生存期。尽管有公认的临床益处，但其潜在的病理生理机制仍知之甚少。我们旨在评估右向左分流对肺动脉高压且肺血流量固定患者的动脉氧输送、混合静脉血氧含量和体循环心输出量的影响。我们制定了定义右向左分流患者生理变量与氧输送之间强制关系的方程。使用微积分和计算机建模，我们考虑了右向左分流对不同肺血流量、总代谢率和携氧能力的生理状态的同时影响。我们的研究表明，当肺血流量固定时，增加右向左分流可改善体循环心输出量、动脉血压和动脉氧输送。相比之下，反映组织氧合平均状态的混合静脉血氧含量保持不变。我们的模型表明，增加右向左分流的量无法代偿右心室衰竭。因此，在肺动脉高压情况下进行房间隔造口术可增加动脉氧输送，但可以说组织氧合最重要指标的混合体循环血氧饱和度保持不变。我们的数据表明，只要右心室功能足够，临床上观察到的房间隔造口术的有益效果是血流改善的结果，而非组织氧合增加。
