Free University of Brussels, Brussels, Belgium
Dept of Internal Medicine, Justus Liebig-University, Universities of Giessen and Marburg Lung Center (UGMLC), Giessen, Germany.
Eur Respir J. 2022 Jun 16;59(6). doi: 10.1183/13993003.02334-2021. Print 2022 Jun.
Pulmonary arterial hypertension (PAH) is a rare dyspnoea-fatigue syndrome caused by a progressive increase in pulmonary vascular resistance and eventual right ventricular (RV) failure. In spite of extensive pulmonary vascular remodelling, lung function in PAH is generally well preserved, with hyperventilation and increased physiological dead space, but minimal changes in lung mechanics and only mild to moderate hypoxaemia and hypocapnia. Hypoxaemia is mainly caused by a low mixed venous oxygen tension from a decreased cardiac output. Hypocapnia is mainly caused by an increased chemosensitivity. Exercise limitation in PAH is cardiovascular rather than ventilatory or muscular. The extent of pulmonary vascular disease in PAH is defined by multipoint pulmonary vascular pressure-flow relationships with a correction for haematocrit. Pulsatile pulmonary vascular pressure-flow relationships in PAH allow for the assessment of RV hydraulic load. This analysis is possible either in the frequency domain or in the time domain. The RV in PAH adapts to increased afterload by an increased contractility to preserve its coupling to the pulmonary circulation. When this homeometric mechanism is exhausted, the RV dilates to preserve flow output by an additional heterometric mechanism. Right heart failure is then diagnosed by imaging of increased right heart dimensions and clinical systemic congestion signs and symptoms. The coupling of the RV to the pulmonary circulation is assessed by the ratio of end-systolic to arterial elastances, but these measurements are difficult. Simplified estimates of RV-pulmonary artery coupling can be obtained by magnetic resonance or echocardiographic imaging of ejection fraction.
肺动脉高压（PAH）是一种罕见的呼吸困难-疲劳综合征，由肺血管阻力的进行性增加和最终的右心室（RV）衰竭引起。尽管广泛的肺血管重塑，PAH 的肺功能通常保持良好，表现为过度通气和增加的生理无效腔，但肺力学变化极小，仅有轻度至中度低氧血症和低碳酸血症。低氧血症主要是由于心输出量降低导致混合静脉血氧张力降低引起的。低碳酸血症主要是由于化学敏感性增加引起的。PAH 中的运动受限是心血管而不是通气或肌肉。PAH 中的肺血管疾病程度通过多点肺血管压力-流量关系来定义，并对血细胞比容进行校正。PAH 中的脉动肺血管压力-流量关系允许评估 RV 水力负荷。这种分析可以在频域或时域中进行。PAH 中的 RV 通过增加收缩性来适应增加的后负荷，以保持其与肺循环的耦合。当这个等容机制用尽时，RV 通过附加的异速机制扩张以保持流量输出。然后通过影像学检查右心增大和临床全身性充血体征和症状来诊断右心衰竭。RV 与肺循环的耦合通过收缩末期到动脉弹性的比值来评估，但这些测量很困难。RV-肺动脉耦合的简化估计可以通过磁共振成像或超声心动图成像的射血分数来获得。
