However, significantly higher RI values in the patient’s native pulmonary arteries compared with the SLTX arteries possibly reflect the elevated resistance in the vascular bed of the diseased lung. One of the drawbacks of this study is the lack of comparison of the RI to invasively assessed values of different PVR and pressure. It has been demonstrated in animals that the RI as measured by duplex Doppler sonography in renal arteries reflects renal vascular resistance. However, good correlation was demonstrated between the RI and the amount of diastolic backflow from the native pulmonary arteries itat on canadian pharmacy levitra. Thus, both parameters might reflect increased PVR. Although future studies on the value of RI measurements with invasive hemodynamic parameter correlation are mandatory, we believe that the RI might provide important noninvasive information about pulmonary hemodynamics.
Pulmonary artery distensibility is a parameter indicative of vessel compliance, which is defined as change in volume per unit change in pressure. Distensibility provides information on the stiffness of the vascular wall and indirectly reflects pulmonary artery pressure. Rogren et al studied pulmonary artery distensibility by means of MRI in volunteers and in patients with pulmonary arterial hypertension. They found a significantly reduced distensibility in their patients’ main pulmonary arteries compared with volunteers and there was no age-related increase in the stiffness of pulmonary vascular walls, as has been reported for the human aorta.
In this study, the DI of the patients’ AAOs and MPAs did not differ significantly from the values obtained in volunteers. However, the distensibility of the AAO in volunteers was slightly, but not significantly, higher than in the older patient population, thus supporting the observation by Mohiaddin et al. In our patients, the DI of the native and transplanted pulmonary artery was not significantly different despite the fact that curves of vessel area over time obtained in LTX and native arteries appear markedly different (Figs 7, 8).
FIGURE 8. Sixteen magnitude and phase images perpendicular to the native pulmonary artery (LPA) with corresponding anatomic line drawings. Top: scheme of slice orientation perpendicular to the native (left) pulmonary artery with additional anatomic structures displayed on magnitude and phase images. Center: angled coronal slice through the native pulmonary artery: magnitude images. Bottom:corresponding phase images, showing dark signal only in early systole (arrow) and gray to white signal throughout the rest of the cardiac cycle indicating retrograde blood flow (R = right, L=left).