Department of Cardiology, St Vincent's Hospital, Darlinghurst, Australia.
The University of New South Wales, Sydney, Australia.
ESC Heart Fail. 2023 Jun;10(3):1811-1821. doi: 10.1002/ehf2.14180. Epub 2023 Mar 10.
The effect of pulmonary hypertension (PH) on right ventricular (RV) afterload is commonly defined by elevation of pulmonary artery (PA) pressure or pulmonary vascular resistance (PVR). In humans however, one-third to half of the hydraulic power in the PA is contained in pulsatile components of flow. Pulmonary impedance (Zc) expresses opposition of the PA to pulsatile blood flow. We evaluate pulmonary Zc relationships according to PH classification using a cardiac magnetic resonance (CMR)/right heart catheterization (RHC) method.
Prospective study of 70 clinically indicated patients referred for same-day CMR and RHC [60 ± 16 years; 77% females, 16 mPAP <25 mmHg (PVR <240 dynes.s.cm /mPCWP <15 mmHg), 24 pre-capillary (PrecPH), 15 isolated post-capillary (IpcPH), 15 combined pre-capillary/post-capillary (CpcPH)]. CMR provided assessment of PA flow, and RHC, central PA pressure. Pulmonary Zc was expressed as the relationship of PA pressure to flow in the frequency domain (dynes.s.cm ).
Baseline demographic characteristics were well matched. There was a significant difference in mPAP (P < 0.001), PVR (P = 0.001), and pulmonary Zc between mPAP<25 mmHg patients and those with PH (mPAP <25 mmHg: 47 ± 19 dynes.s.cm ; PrecPH 86 ± 20 dynes.s.cm ; IpcPH 66 ± 30 dynes.s.cm ; CpcPH 86 ± 39 dynes.s.cm ; P = 0.05). For all patients with PH, elevated mPAP was found to be associated with raised PVR (P < 0.001) but not with pulmonary Zc (P = 0.87), except for those with PrecPH (P < 0.001). Elevated pulmonary Zc was associated with reduced RVSWI, RVEF, and CO (all P < 0.05), whereas PVR and mPAP were not.
Raised pulmonary Zc was independent of elevated mPAP in patients with PH and more strongly predictive of maladaptive RV remodelling than PVR and mPAP. Use of this straightforward method to determine pulmonary Zc may help to better characterize pulsatile components of RV afterload in patients with PH than mPAP or PVR alone.
肺动脉高压（PH）对右心室（RV）后负荷的影响通常通过肺动脉（PA）压力或肺血管阻力（PVR）的升高来定义。然而，在人体中，PA 中的三分之一到一半的水力功率包含在脉动血流的脉动分量中。肺阻抗（Zc）表示 PA 对脉动血流的阻力。我们使用心脏磁共振（CMR）/右心导管术（RHC）方法，根据 PH 分类评估肺 Zc 关系。
前瞻性研究 70 例临床指征患者，同日行 CMR 和 RHC[60±16 岁；77%女性，16 毫米汞柱<25mmHg（PVR<240 达因.s.cm /mPCWP<15mmHg），24 例前毛细血管性（PrecPH），15 例单纯后毛细血管性（IpcPH），15 例前毛细血管/后毛细血管混合性（CpcPH）]。CMR 提供了 PA 流量评估，RHC 提供了中心 PA 压力。肺 Zc 以 PA 压力与流量在频域（达因.s.cm）的关系表示。
基线人口统计学特征匹配良好。mPAP（P<0.001）、PVR（P=0.001）和肺 Zc 在 mPAP<25mmHg 患者和 PH 患者之间存在显著差异（mPAP<25mmHg：47±19 达因.s.cm；PrecPH 86±20 达因.s.cm；IpcPH 66±30 达因.s.cm；CpcPH 86±39 达因.s.cm；P=0.05）。对于所有 PH 患者，升高的 mPAP 与升高的 PVR 相关（P<0.001），但与肺 Zc 无关（P=0.87），除了 PrecPH 患者（P<0.001）。升高的肺 Zc 与降低的 RV 射血分数、RV 射血分数和 CO 相关（均 P<0.05），而 PVR 和 mPAP 则不相关。
在 PH 患者中，升高的肺 Zc 独立于升高的 mPAP，与 PVR 和 mPAP 相比，更能预测 RV 重塑不良。使用这种简单的方法来确定肺 Zc 可能有助于比 mPAP 或 PVR 更全面地描述 PH 患者 RV 后负荷的脉动成分。
