The pulmonary arterial branching pattern suggests that the early systolic forward-going compression wave (FCW) might be reflected as a backward-going expansion wave (BEW). Accordingly, in 11 open-chest anesthetized dogs we measured proximal pulmonary arterial pressure and flow (velocity) and evaluated wave reflection using wave-intensity analysis under low-volume, high-volume, high-volume + 20 cmH2O positive end-expiratory pressure (PEEP), and hypoxic conditions. We defined the reflection coefficient R as the ratio of the energy of the reflected wave (BEW [-]; backward-going compression wave, BCW [+]) to that of the incident wave (FCW [+]). We found that R = -0.07 +/- 0.02 under low-volume conditions, which increased in absolute magnitude to -0.20 +/- 0.04 (P < 0.01) under high-volume conditions. The addition of PEEP increased R further to -0.26 +/- 0.02 (P < 0.01). All of these BEWs were reflected from a site ~3 cm downstream. During hypoxia, the BEW was maintained and a BCW appeared (R = +0.09 +/- 0.03) from a closed-end site ~9 cm downstream. The normal pulmonary arterial circulation in the open-chest dog is characterized by negative wave reflection tending to facilitate right ventricular ejection; this reflection increases with increasing blood volume and PEEP.

A midsystolic plateau differentiates the pattern of fetal pulmonary trunk blood flow from aortic flow. To determine whether this plateau arises from interactions between the left (LV) and right ventricle (RV) via the ductus arteriosus or from interactions between the RV and the lung vasculature, we measured blood flows and pressures in the pulmonary trunk and aorta of eight anesthetized (ketamine and alpha-chloralose) fetal lambs. Wave-intensity analysis revealed waves of energy traveling forward, away from the LV and the RV early in systole. During midsystole, a wave of energy traveling back toward the RV decreased blood flow velocity from the RV and produced the plateau in blood flow. Calculations revealed that this backward-traveling wave originated as a forward-traveling wave generated by the RV that was reflected from the lung vasculature back toward the heart and not as a forward-traveling wave generated by the LV that crossed the ductus arteriosus. Elimination of this backward-traveling wave and its associated effect on RV flow may be an important component of the increase in RV output that accompanies birth.

. Direct and series transmission of left atrial pressure perturbations to the pulmonary artery: a study using wave-intensity analysis. Am J Physiol Heart Circ Physiol 286: H267-H275, 2004. First published September 25, 2003 10.1152/ ajpheart.00505.2002-Pressure waves are thought to travel from the left atrium (LA) to the pulmonary artery (PA) only retrogradely, via the vasculature. In seven anesthetized open-chest dogs, a balloon was placed in the LA, which was rapidly inflated and deflated during diastole, early systole, and late systole. High-fidelity pressures were measured within and around the heart. Measurements were made at low volume [LoV; left ventricular end-diastolic pressure (LVEDP) ϭ 5-9 mmHg], high volume (HiV; LVEDP ϭ 16-19 mmHg), and HiV with the pericardium removed. Wave-intensity analysis demonstrated that, except during late systole, balloon inflation created forwardgoing PA compression waves that were transmitted directly through the heart without measurable delay; backward PA compression waves were transmitted in-series through the pulmonary vasculature and arrived after delays of 90 Ϯ 3 ms (HiV) and 103 Ϯ 5 ms (LoV; P Ͻ 0.05). Direct transmission was greater during diastole, and both direct and series transmission increased with volume loading. Pressure waves from the LA arrive in the PA by two distinct routes: rapidly and directly through the heart and delayed and in-series through the pulmonary vasculature. lung; arteries; hemodynamics; wave transmission WAVE TRANSMISSION through the heart is poorly understood. Among the clinical syndromes in which wave transmission could be an important, unappreciated factor are the stiff left atrium (LA) syndrome (6, 15) and the Bernheim syndrome (1,5,24). To study the transmission of waves generated in the LA, we created a system where a backward-going wave, originating from the LA, could be detected in the proximal pulmonary artery (PA; backward and forward are defined with respect to PA flow.) To create such a wave in a controlled fashion, we used an LA counterpulsation balloon. Pressure and velocity waveforms in the proximal PA were analyzed to evaluate the effects of LA pressure (P LA ) perturbations.Most commonly, pulsatile arterial phenomena have been characterized using Fourier analysis where the observed waveforms are decomposed into sinusoidal wave trains, and the results are expressed as amplitude and phase as a function of frequency (16,17). This frequency-domain analysis has provided much information. However, wave-intensity analysis where the observed waveforms are decomposed into a succession of infinitesimal wave fronts that are described by their amplitude and time (13,19) allows the interaction of forwardand backward-going waves and their relation to primary hemodynamic parameters (pressure, flow, etc.) to be studied directly. This method utilizes changes in pressure and velocity to evaluate the direction, intensity, and type of waves and has been used recently to study the systemic (18), pulmonary (8,11,22), and coronary circulations...

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