Thus, it may be that proximal pulmonary arterial changes leading to increased Zc and RF are predominantly the passive consequences of increased mean distending pressure, and that “fixed” proximal pulmonary arterial remodeling plays a minor role in determining RV hydraulic load. Dobutamine therapy increased cardiac output and decreased PVR, without a change in the pattern of PVZ spectrum. This observation is in keeping with experimental observations that dobutamine administration up to 10 ^g/kg/min has no flow-independent pulmonary vascular effect. A dobutamine-induced decrease in PVR probably reflects the flow dependency of this composite variable rather than structural or tone-related changes in the resistive arterioles. zithromax online
There has been interest in time-domain pressure-wave morphology analysis for the differential diagnosis of pulmonary hypertension. There are data showing earlier wave reflection in patients with chronic thromboembolic pulmonary hypertension compared to that in those with PPH,- with increased pulse pressure reported in some studies that could, however, not be confirmed in others. These differences were explained by a more proximal site of wave reflection in patients with chronic thromboembolic pulmonary hypertension. To our knowledge, there has been no report on time-domain pulmonary arterial flow wave analysis for the diagnosis of pulmonary hypertension, excepted for the estimation of mean Ppa from acceleration time.
The determination of a PVZ spectrum presents the advantage of integrating all of the information contained in both the pressure and flow waves. It offers the possibility of quantifying the contributions of resistance, elastance, and wave reflection to RV hydraulic load. Pulmonary hypertension symptomatology and prognosis are essentially dependent on RV tolerance and the adaptation to chronically increased afterload. PVZ, more than PVR, allows for the estimation of RV afterload. Thus, it is possible that PVZ calculations based on the sampling and frequency analysis of routine right heart catheterization and echocardiographic signals will prove useful in assessing responses to therapy and the prognosis of patients with severe pulmonary hypertension. However, the proof of this concept will require a prospective clinical evaluation.