In the flow phantom study, correlations between absolute values of true and MRI-derived velocities and flow volumes were assessed by means of linear regression analysis. Correlations between left and right cardiac output both in volunteers and in patients and correlations of the sum of LPA and RPA flow with MPA flow, and net retrograde flow in the native lung pulmonary artery with RI were assessed by linear regression analysis itat on buy birth control. Wilcoxon’s signed-ranked test was used to compare differences in peak average systolic velocities, flow volumes, RI, and DI. These comparisons were done in volunteers and in patients, in right and left, and in native and transplanted lung pulmonary arteries, and tested for statistical significance. A p value <0.05 was considered statistically significant. Results are expressed as the mean of each group ±1 SD.
In Vitro Study
There was excellent correlation between true velocities and true flow and VEC-MRI-derived measurements with a correlation coefficient of r=0.99.
In Vivo Study
Blood Flow Volumes and Velocities: Results of flow measurements are shown in Table 1. There were good correlations between right and left cardiac output both in SLTX patients (r=0.91) and in volunteers (r=0.95, Fig 1). In addition, there were good correlations between the sum of RPA and LPA flow and MPA flow in volunteers (r=0.97) as well as in patients (r=0.94). Peak systolic average velocity (Vsyst) in the AAO and MPA was significantly lower in patients compared with volunteers (AAO: 69±9 vs 45±9 cm/s, p<0.001; MPA: 62±7 vs 39±12 cm/s, p<0.05). Vsyst in the lung transplant artery (53±11 cm/s) was significantly higher than in the native lung artery (31±19 cm/s, p<0.05).
Flow Pattern and Profile Analysis: In volunteers, blood flow was pulsatile in AAO, MPA, RPA, and LPA. In the AAO, a systolic peak was followed by some amount of retrograde flow during early diastole. The flow patterns in the pulmonary vessels in volunteers demonstrated no retrograde flow during diastole. There was no apparent difference between the flow profiles of RPA and LPA in volunteers, demonstrating almost equal perfusion of both vascular beds (Fig 2).
Table 1—Flow and Vsyst Obtained in AAO, MPA, RPA, and LPA and in LTX and Native Pulmonary Artery, Both in SLTX Patients and Normal Subjects
Figure 1. Regression correlations of blood flow in the ascending aorta with flow in the main pulmonary artery in normal subjects and in SLTX patients.
Figure 2. MRI-assessed flow profiles in the AAO, MPA, RPA, and LPA of a normal volunteer.