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Decreased time constant of the pulmonary circulation in chronic thromboembolic pulmonary hypertension

par Mackenzie Ross, Robert V;Toshner, Mark R;Soon, Elaine;Naeije, Robert ;Pepke-Zaba, Joanna
Référence American journal of physiology. Heart and circulatory physiology, 305, 2, page (259-264)
Publication Publié, 2013-05

Article révisé par les pairs

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Résumé :

This study analysed the relationship between pulmonary vascular resistance (PVR) and compliance (Ca) in patients with idiopathic pulmonary arterial hypertension (IPAH) and proximal chronic thromboembolic pulmonary hypertension (CTEPH). It has recently been shown that the time constant of the pulmonary circulation (RC-time), or PVR x Ca, remains unaltered in various forms and severities of PH, with the exception of left heart failure. We reasoned that increased wave reflection in proximal CTEPH would be another cause of decreased RC-time. We conducted a retrospective analysis of invasive pulmonary hemodynamic measurements in IPAH (n=78), proximal CTEPH (n=91) before and after pulmonary endarterectomy (PEA) and distal CTEPH (n=53). Proximal CTEPH was defined by a postoperative mean pulmonary artery pressure (mPAP) ≤ 25 mmHg. Outcome measures were the RC-time, PVR, Ca and the relationship between systolic and mean pulmonary artery pressures. The RC time for Pre-PEA CTEPH was 0.49 ± 0.11s compared with Post PEA-CTEPH 0.37 ± 0.11s (p<0.0001), IPAH 0.63 ± 0.14s (p<0.001) and Distal CTEPH 0.55 ± 0.12s (p<0.05). A shorter RC-time was associated with a disproportionate decrease in systolic PAP with respect to mPAP. We concluded that the pulmonary RC-time is decreased in proximal CTEPH compared to IPAH, before and after PEA, which may be explained by increased wave reflection but also importantly by persistent structural changes after removal of proximal obstructions. A reduced RC-time in CTEPH is in accord with a wider pulse pressure and hence greater RV work for a given mean PA pressure.