The Critical Role of Pulmonary Arterial Compliance in Pulmonary Hypertension

Abstract

The normal pulmonary circulation is a low-pressure, high-compliance system. Pulmonary arterial compliance decreases in the presence of pulmonary hypertension because of increased extracellular matrix/collagen deposition in the pulmonary arteries. Loss of pulmonary arterial compliance has been consistently shown to be a predictor of increased mortality in patients with pulmonary hypertension, even more so than pulmonary vascular resistance in some studies. Decreased pulmonary arterial compliance causes premature reflection of waves from the distal pulmonary vasculature, leading to increased pulsatile right ventricular afterload and eventually right ventricular failure. Evidence suggests that decreased pulmonary arterial compliance is a cause rather than a consequence of distal small vessel proliferative vasculopathy. Pulmonary arterial compliance decreases early in the disease process even when pulmonary artery pressure and pulmonary vascular resistance are normal, potentially enabling early diagnosis of pulmonary vascular disease, especially in high-risk populations. With the recognition of the prognostic importance of pulmonary arterial compliance, its impact on right ventricular function, and its contributory role in the development and progression of distal small-vessel proliferative vasculopathy, pulmonary arterial compliance is an attractive target for the treatment of pulmonary hypertension.

Keywords: heart failure; impedance; resistance; right ventricle; stiffness.

Figure 1.

Effect of decreased pulmonary arterial compliance in pulmonary hypertension. PA = pulmonary artery; PAC = pulmonary arterial compliance; RV = right ventricle.

Figure 2.

Inverse hyperbolic relationship between resistance and compliance in the pulmonary circulation as depicted by (A) Lankhaar and colleagues (adapted by permission from Reference 62) and (B) Tedford and colleagues (adapted by permission from Reference 61). CTEPH = chronic thromboembolic pulmonary hypertension; IPAH = idiopathic pulmonary artery hypertension; NONPH = healthy control subjects.

Figure 3.

Alteration in resistance–compliance relationship in pulmonary hypertension. (A) Elevated pulmonary capillary wedge pressure shifts the PVR–PAC curve to the left as depicted by Tedford and colleagues (adapted by permission from Reference 61). (B) RC time is reduced in CTEPH patients both pre- and postendarterectomy as depicted by MacKenzie and colleagues (adapted by permission from Reference 67). CTEPH = chronic thromboembolic pulmonary hypertension; IPAH = idiopathic pulmonary artery hypertension; PCWP = pulmonary capillary wedge pressure; PEA = pulmonary endarterectomy; RC = resistance and compliance.