Pulsatile pulmonary artery pressure in a large animal model of chronic thromboembolic pulmonary hypertension: Similarities and differences with human data

Abstract

A striking feature of the human pulmonary circulation is that mean (mPAP) and systolic (sPAP) pulmonary artery pressures (PAPs) are strongly related and, thus, are essentially redundant. According to the empirical formula documented under normotensive and hypertensive conditions (mPAP = 0.61 sPAP + 2 mmHg), sPAP matches ~160%mPAP on average. This attests to the high pulsatility of PAP, as also witnessed by the near equality of PA pulse pressure and mPAP. Our prospective study tested if pressure redundancy and high pulsatility also apply in a piglet model of chronic thromboembolic pulmonary hypertension (CTEPH). At baseline (Week-0, W0), Sham (n = 8) and CTEPH (n = 27) had similar mPAP and stroke volume. At W6, mPAP increased in CTEPH only, with a two- to three-fold increase in PA stiffness and total pulmonary resistance. Seven CTEPH piglets were also studied at W16 at baseline, after volume loading, and after acute pulmonary embolism associated with dobutamine infusion. There was a strong linear relationship between sPAP and mPAP (1) at W0 and W6 (n = 70 data points, r² = 0.95); (2) in the subgroup studied at W16 (n = 21, r² = 0.97); and (3) when all data were pooled (n = 91, r² = 0.97, sPAP range 9-112 mmHg). The PA pulsatility was lower than that expected based on observations in humans: sPAP matched ~120%mPAP only and PA pulse pressure was markedly lower than mPAP. In conclusion, the redundancy between mPAP and sPAP seems a characteristic of the pulmonary circulation independent of the species. However, it is suggested that the sPAP thresholds used to define PH in animals are species- and/or model-dependent and thus must be validated.

Keywords: animal models; pathophysiology; pulmonary hypertension experimental; right ventricle function and dysfunction.

Figure 1

Study design. (a) In the first group of animals (n = 35), pulmonary hypertension was developed in 27 animals by left pulmonary artery (PA) ligation at Week 0 and weekly embolization of the right lower lobe (RLL) PA; the eight other animals underwent no intervention. Right heart catheterization was performed at Weeks 0 and 6 (red squares) in all animals. (b) In the second group of seven animals, pulmonary hypertension was induced similarly as in the first group. Right heart catheterization was performed at Week 16 under three conditions (red square) at baseline (rest), after volume loading with 60 ml/kg of saline infusion (VL) and after acute pulmonary embolism followed by dobutamine infusion at 5 µg/kg/min (PE + D)

Figure 2

Linear relationship between mean pulmonary artery pressure (mPAP) and systolic pulmonary artery pressure (sPAP) in pooled groups 1 and 2 (n = 91 data points)