VEC-MRI provides a powerful noninvasive tool for assessing blood flow velocities and volumes in the proximal pulmonary artery system as well as in the ascending and descending aorta and its major branches.
In this study, the flow patterns observed in the AAO, MPA, RPA, and LPA of volunteers were similar to those reported in the literature. Canadian family pharmacy online fully The slight amount of early diastolic retrograde blood flow in the AAO has been reported to be due to coronary filling. However, no retrograde flow was observed in the MPA of volunteers and flow profiles of the RPA and LPA were almost identical. These observations are sharply contrasted by the findings in our patient group. Whereas flow profiles in the AAO of patients were not significantly different from those of volunteers, blood flow in the MPA demonstrated a retrograde peak in early diastole in six of nine patients, indicating mild to midgrade pulmonary insufficiency. These patients also exhibited elevated pulmonary artery pressures (ranging from mild to severe) and various degrees of pulmonary regurgitation in their preoperative courses as assessed by duplex Doppler echocardiography. These findings are only descriptive to underline the fact that pulmonary regurgitation is not uncommon in postoperative patients with preoperative evidence of pulmonary hypertension. Although demonstrated in one figure, retrograde flow in the MPA as an indicator of pulmonary insufficiency was not mentioned by Mo-hiaddin et al in their VEC-MRI study of SLTX patients.
Blood flow to the transplanted lung showed a biphasic pattern with an initial large peak and a subsequent small flow peak, whereas the native pulmonary arteiy demonstrated retrograde blood flow throughout diastole, indicative of blood flowing out of the native and into the transplanted lung (Fig 7). In contrast to other investigators, we observed that type of flow pattern in all our patients. In part, this discrepancy might be explained by different preoperative pulmonary pressures and vascular resistances in the study populations.
FIGURE 7. Sixteen magnitude and phase images perpendicular to the transplanted pulmonary artery (RPA) with corresponding anatomic line drawings. Top: scheme of slice orientation perpendicular to the transplanted (right) pulmonary artery with additional anatomic structures displayed on magnitude and phase images. Center: parasagittal slice through the transplanted pulmonary artery: magnitude images. Bottom: corresponding phase images, showing black signal throughout systole and early diastole indicating antegrade blood flow (arrow, A=anterior, P=posterior).