Wave Propagation Patterns in Main Pulmonary Artery Using Wave Intensity (WI) Analysis: Comparison of Pulmonary and Aortic WI Waveforms

Objectives: This study compared and contrasted the wave propagation patterns of the main pulmonary trunk with those of the ascending aorta in the same subjects using WI analysis. Methods: Flow velocity (V) and pressure (P) at the same site in the main pulmonary trunk and ascending aorta were recorded using a multisensor catheter in 5 control subjects without hypertension and evidence of pulmonary disease and in one patient with mild pulmonary hypertension (PH) with mitral regurgitation. WI was calculated from the following equation. WI=(dP/dt)(dV/dt), where dP/dt and dV/dt are the derivatives of blood pressure and velocity with respect to time. To determine the nature and direction of waves during the cardiac cycle, data were analyzed by calculating the following parameters. Positive peak WI (W₁) in early systole, positive peak WI (W₂) in late systole, W₁/W₂, negative peak WI (NW) in midsystole and ∫PW/∫NW (area ratio of positive and negative WI waveform in systole). Results: All parameters, especially NW and ∫PW/∫NW reflecting the amount of reflection, in aorta of control subjects were significantly higher than those in main pulmonary artery (p<0.05) except for peak W₂. NW was observed in aorta of all subjects except for one juvenile control subject. But no NW was observed in main pulmonary artery of all control subjects. NW was only observed in main pulmonary trunk in the patient with mild PH. Conclusions: The differences in the physical characteristics between the aorta as a resistance vessel and the main pulmonary trunk as a capacitance vessel can be illustrated by WI analysis. WI analysis may offer further detailed insight into the understanding of pulmonary diseases such as mild PH, in which initial minimum changes in peripheral resistance could alter the amount of reflection significantly because of its physical characteristics of negligible development of wave reflection in normal pulmonary artery.