Effective arterial elastance as an index of pulmonary vascular load

Abstract

Morimont P, Lambermont B, Ghuysen A, Gerard P, Kolh P, Lancellotti P, Tchana-Sato V, Desaive T, D'Orio V. Effective arterial elastance as an index of pulmonary vascular load. Am J Physiol Heart Circ Physiol 294: H2736-H2742, 2008. First published April 18, 2008 doi:10.1152/ajpheart.00796.2007.-The aim of this study was to test whether the simple ratio of right ventricular (RV) endsystolic pressure (Pes) to stroke volume (SV), known as the effective arterial elastance (E a), provides a valid assessment of pulmonary arterial load in case of pulmonary embolism-or endotoxin-induced pulmonary hypertension. Ventricular pressure-volume (PV) data (obtained with conductance catheters) and invasive pulmonary arterial pressure and flow waveforms were simultaneously recorded in two groups of six pure Pietran pigs, submitted either to pulmonary embolism (group A) or endotoxic shock (group B). Measurements were obtained at baseline and each 30 min after injection of autologous blood clots (0.3 g/kg) in the superior vena cava in group A and after endotoxin infusion in group B. Two methods of calculation of pulmonary arterial load were compared. On one hand, Ea provided by using three-element windkessel model (WK) of the pulmonary arterial system [Ea(WK)] was referred to as standard computation. On the other hand, similar to the systemic circulation, Ea was assessed as the ratio of RV Pes to SV [Ea(PV) ϭ Pes/SV]. In both groups, although the correlation between Ea(PV) and Ea(WK) was excellent over a broad range of altered conditions, Ea(PV) systematically overestimated Ea(WK). This offset disappeared when left atrial pressure (Pla) was incorporated into Ea [Ea ‫ء‬ (PV) ϭ (Pes Ϫ Pla)/SV]. Thus Ea ‫ء‬ (PV), defined as the ratio of RV Pes minus Pla to SV, provides a convenient, useful, and simple method to assess the pulmonary arterial load and its impact on the RV function.hemodynamics; pulmonary hypertension; right ventricle; ventriculoarterial coupling IN CURRENT CLINICAL practice, pulmonary arterial load [or right ventricular (RV) afterload] is usually expressed as the mean pulmonary vascular resistance, computed as the ratio of the pressure drop through the pulmonary circulation [difference between mean pulmonary arterial pressure (PAP mean ) and left atrial pressure (Pla)] to the mean pulmonary blood flow [cardiac output (CO)]. Such an evaluation ignores the pulsatile nature of both pressure and flow. Although oscillatory components of the pulmonary arterial load are low, and mean resistance may be a valuable index of the pulmonary vascular load, the pulsatile nature of the load may be prominent in numerous pathological situations. Wave reflections play an important role and should be taken into account in pulmonary hypertension resulting from several pathological conditions, like pulmonary embolism and septic shock (1,2,5,14). In this way, the pulmonary arterial impedance spectrum, which is defined in the frequency domain, provides a more precise and complete description of the pulmonary vascular load (12, 17). However, be...

Right ventricular reserve in a piglet model of chronic pulmonary hypertension

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“…It has been suggested that subtraction of left atrial (or pulmonary capillary wedge pressure) gives a better estimate of R5Ea6T [34]. However, it has not been shown which estimate of Ea is best for estimation of coupling (i.e.…”

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