Wave Intensity Analysis Provides Novel Insights Into Pulmonary Arterial Hypertension and Chronic Thromboembolic Pulmonary Hypertension

Abstract

BackgroundIn contrast to systemic hypertension, the significance of arterial waves in pulmonary hypertension (PH) is not well understood. We hypothesized that arterial wave energy and wave reflection are augmented in PH and that wave behavior differs between patients with pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH).Methods and ResultsRight heart catheterization was performed using a pressure and Doppler flow sensor–tipped catheter to obtain simultaneous pressure and flow velocity measurements in the pulmonary artery. Wave intensity analysis was subsequently applied to the acquired data. Ten control participants, 11 patients with PAH, and 10 patients with CTEPH were studied. Wave speed and wave power were significantly greater in PH patients compared with controls, indicating increased arterial stiffness and right ventricular work, respectively. The ratio of wave power to mean right ventricular power was lower in PAH patients than CTEPH patients and controls. Wave reflection index in PH patients (PAH: ≈25%; CTEPH: ≈30%) was significantly greater compared with controls (≈4%), indicating downstream vascular impedance mismatch. Although wave speed was significantly correlated to disease severity, wave reflection indexes of patients with mildly and severely elevated pulmonary pressures were similar.ConclusionsWave reflection in the pulmonary artery increased in PH and was unrelated to severity, suggesting that vascular impedance mismatch occurs early in the development of pulmonary vascular disease. The lower wave power fraction in PAH compared with CTEPH indicates differences in the intrinsic and/or extrinsic ventricular load between the 2 diseases.

Noninvasive wave intensity analysis predicts functional worsening in children with pulmonary arterial hypertension

“…This may be partially explained by better RV functional reserve in children compared with adult patients with PAH and different disease mechanisms responsible for vascular remodeling (2). The most prominent feature of WIA spectra in our patient population was the presence of BCW, which has been previously reported in adult studies and appears to be a characteristic feature of PAH (17,23,30). The additive impact of BCW on ventricular afterload has been demonstrated in both systemic and pulmonary circulations and is typically associated with ventricular hypertrophy, eccentric remodeling, and worsening ventricularvascular coupling ratio (6,24,40).…”

“…Elevated wave speed propagation or pulse wave velocity measured in the MPA has been previously described in adult patients with PAH (17,23,30) and in association with RV afterload (6) but has not previously been described in children with PAH. In this study, we report elevated c-MPA as measured in the mid-MPA using a flow-area method that is more sensitive to locally measured stiffness properties.…”

“…With regard to the pulmonary arterial vasculature, WIA has been typically conducted using combined pressure and velocity waveforms derived from simultaneous right heart catheterization and echocardiography. This approach has been shown to be useful for characterization of adult patients with PAH and chronic thromboembolic pulmonary hypertension (17,30) but is less applicable in children with PAH because of its complexity and invasive nature. More recently, Quail et al (23) introduced noninvasive WIA methodology applicable to pulmonary arteries applying high-resolution phase-contrast MRI-derived area and flow waveforms to characterize different adult PAH populations.…”

“…All aforementioned adult studies described abnormal WIA indexes typically characterized by reduced FCW suggestive of diminished RV contractile function, elevated/present BCW indicative of elevated stiffness of the pulmonary arterial vasculature, and reduced FDW typically associated with reduced RV compliance and poor diastolic function. Furthermore, both invasive and noninvasively derived WIA differentiated between idiopathic PAH and thromboembolic pulmonary hypertension (23,30).…”

“…The cardinal feature of PAH is widespread pulmonary arterial remodeling characterized by luminal narrowing and diffuse arterial wall stiffening, which leads to increased pulmonary vascular resistance (PVR) (9,27). Recent studies evaluating pulmonary vascular stiffness in adult patients with PAH revealed that elevated abnormal wave reflections originating from pulmonary arterial branches contribute to increased right ventricular (RV) afterload (17,30). Similar studies are lacking in children with PAH partially because wave intensity analysis (WIA), which is necessary to assess vascular stiffness, requires an invasive pressure-derived waveform along with simultaneous flow measurements.…”