Baseline characteristics of the patients.

Background
Pulmonary hypertension (PH) is a common and morbid complication of left heart disease (LHD), comprising two subtypes: (1) isolated post-capillary pulmonary hypertension (Ipc-PH) and (2) combined post-capillary and pre-capillary pulmonary hypertension (Cpc-PH). Knowledge regarding the physiological characteristics that distinguish Cpc-PH, which has a worse prognosis, from Ipc-PH remains limited. Therefore, this study aimed to assess the utility of cardiopulmonary exercise testing (CPET) variables in detecting Cpc-PH.
Methods and results
Among 105 consecutive patients with LHD (age: 55 ± 13 years; male/female = 79/26) who underwent right heart catheterization and CPET, 45 (43%) were classified as PH-LHD (mean pulmonary artery pressure >20 mmHg). Ipc-PH (n = 24) was defined as pulmonary vascular resistance (PVR) ≤ 3 WU and Cpc-PH (n = 21) as PVR > 3 WU. Patients with Cpc-PH had a significantly lower peak partial pressure of carbon dioxide (PETCO2) (Non-PH/Ipc-PH/Cpc-PH = 38.2 ± 6.6 vs. 38.3 ± 6.0 vs 33.0 ± 4.4 mmHg, p = 0.006), higher VE vs. VCO2 slope (Non-PH/Ipc-PH/Cpc-PH = 33.0 [28.3, 36.6] vs. 32.5 [28.1, 37.8] vs. 40.6 [33.6, 46.1], p = 0.007), and lower ΔVO2/ΔWR (Non-PH/Ipc-PH/Cpc-PH = 8.5 ± 1.4 vs. 8.0 ± 1.7 vs. 6.8 ± 2.0 mL/min/watt, p = 0.001) than those with Ipc-PH and non-PH. Using multivariable logistic regression analysis, CPET variables were found to be independent predictors of Cpc-PH (lower peak PETCO2: odds ratio, 0.728 [95% confidence interval {CI}: 0.616–0.840], p = 0.003 and lower ΔVO2/ΔWR: odds ratio, 0.747 [95% CI: 0.575–0.872], p = 0.003).
Conclusion
From our exploratory analysis, CPET variables, especially in the lower peak PETCO2 and lower ΔVO2/ΔWR, were associated with Cpc-PH in patients with left heart disease.

背景：肺动脉高压（Pulmonary hypertension, PH）是左心疾病（left heart disease, LHD）常见且具有较高致残性的并发症，可分为两个亚型：(1) 孤立性毛细血管后肺动脉高压（isolated post-capillary pulmonary hypertension, Ipc-PH）与(2) 毛细血管前合并毛细血管后肺动脉高压（combined post-capillary and pre-capillary pulmonary hypertension, Cpc-PH）。目前针对预后更差的Cpc-PH与Ipc-PH之间的鉴别生理学特征的认知仍较为有限。因此本研究旨在评估心肺运动试验（cardiopulmonary exercise testing, CPET）相关变量在检出Cpc-PH中的应用价值。
方法与结果：本研究纳入105例连续就诊的左心疾病患者（年龄：55±13岁；男/女比例为79/26），所有患者均接受了右心导管检查与心肺运动试验，其中45例（43%）被归类为PH-LHD（平均肺动脉压＞20mmHg）。Ipc-PH组（n=24）的定义为肺血管阻力（pulmonary vascular resistance, PVR）≤3Wood单位（WU），Cpc-PH组（n=21）的定义为PVR＞3WU。相较于Ipc-PH患者与非PH患者，Cpc-PH患者的峰值呼气末二氧化碳分压（peak partial pressure of carbon dioxide, PETCO2）显著更低：非PH/Ipc-PH/Cpc-PH组分别为38.2±6.6、38.3±6.0与33.0±4.4mmHg，p=0.006；其二氧化碳通气当量斜率（VE/VCO2 slope）显著更高：非PH/Ipc-PH/Cpc-PH组分别为33.0[28.3, 36.6]、32.5[28.1, 37.8]与40.6[33.6, 46.1]，p=0.007；且氧摄取量随做功量变化的比值（ΔVO2/ΔWR）显著更低：非PH/Ipc-PH/Cpc-PH组分别为8.5±1.4、8.0±1.7与6.8±2.0mL/min/瓦，p=0.001。经多变量logistic回归分析显示，心肺运动试验相关变量是Cpc-PH的独立预测因素：更低的峰值PETCO2（优势比：0.728，95%置信区间[CI]：0.616–0.840，p=0.003）以及更低的ΔVO2/ΔWR（优势比：0.747，95%CI：0.575–0.872，p=0.003）。
结论：基于本次探索性分析，在左心疾病患者中，心肺运动试验相关变量——尤其是更低的峰值PETCO2与更低的ΔVO2/ΔWR——与Cpc-PH存在显著关联。