Characteristic changes to pulsatile and steady-state load according to pulmonary hypertension classification

Area of Science:

• Cardiovascular Physiology
• Hemodynamics
• Pulmonary Hypertension Research

Background:

• Understanding pulmonary hypertension (PH) requires quantitative assessment of systemic and pulmonary circulations.
• Characteristic impedance (Zc) quantifies opposition to pulsatile blood flow.
• Previous studies have not detailed systemic and pulmonary Zc relationships across PH classifications.

Purpose of the Study:

• To describe and compare systemic and pulmonary characteristic impedance (Zc) relationships in various pulmonary hypertension (PH) subclasses.
• To investigate how Zc differs in pre-capillary PH (Pre-cPH), combined pre- and post-capillary PH (Cpc-PH), and isolated post-capillary PH (Ipc-PH).

Main Methods:

• Prospective study of 40 patients undergoing cardiac magnetic resonance (CMR) and right heart catheterization (RHC).
• CMR assessed ascending aortic (Ao) and pulmonary arterial (PA) flow.
• RHC measured central Ao and PA pressures; Zc calculated in the frequency domain.

Main Results:

• Systemic Zc and systemic vascular resistance (SVR) were over twice pulmonary Zc and pulmonary vascular resistance (PVR) in patients with mean pulmonary arterial pressure ≤25 mmHg.
• Pre-cPH patients exhibited inverse pulsatile (systemic Zc vs. pulmonary Zc) but not steady-state relationships.
• Cpc-PH and Ipc-PH patients showed concordant pulsatile and steady-state relationships.

Conclusions:

• Systemic Zc is generally higher than pulmonary Zc across PH types.
• Newly diagnosed Pre-cPH is uniquely associated with inverse pulsatile, but not steady-state, impedance relationships.
• These findings provide novel insights into circulatory dynamics across the PH spectrum.