Application Study Of MRI In Diagnosing Pulmonary Hypertention Caused By Congenital Heart Disease

Purpose: To study the value of MRI in diagnosing pulmonary hypertention(PH) in congenital heart disease(CHD) patients qualitatively and quantitatively.Materials and MethodsThe 69 subjects consisted of 15 normal volunteers(control group) and 54 patients of CHD with the left shunt to the right. All CHD patients were divided into the following five subgroups: normal pulmonary pressure, mild dynamic PH, moderate dynamic PH, severe dynamic PH and Eisenmenger syndrome.Pulmonary systolic pressure(PASP) and mean pressure(PAMP), the ratio of pulmonary to aorta systolic pressure(Pp/Ps), pulmonary resistance (PVR), the ratio of main pulmonary to aorta flow(Qp/Qs) were measured by catheterization in patients with CHD.All subjects were examined by MRI. The diameter ratio of main pulmonary artery to transverse thorax(MRA/T) and the ratio of right ventricle wall thickness to thorax transverse diameter (RVW/T) were measured according to SE images. Parameters of Qp/Qs, pulmonary distensibility(PD) , acceleration time(ACT) and pulmonary regurgitation fraction(PRF) were measured according to the velocity-encoded cine MR images. Three-dimensional dynamic contrast-enhanced MRpulmonary angiography images were used to observe the conformation of central pulmonary artery and its branches.MRI findings were analyzed among the six groups. The indexes derived from MRI were compared with PASP,PAMP, PVR obtainedfrom heart catheterization by linear regression and correlation analysis.Results1. When applying RVW/T as above 0.27 for detecting the elevated pulmonary pressure, the predicting result of PH's sensitivity was 90.4%, the specificity was 87.5% and the validity was 90%.2. Parameters of morpholog (MPA/T,RVW/T,PD) and hemodynamics (ACT, PRF) derived from MRI correlated well with PASP, PAMP and PVR obtained from heart catheterization. The difference between regressive estimated value and catheter value of PASP was lOmmHg in 62.9% cases, and 20mmHg in 90.75% cases. The difference between regressive estimated value and catheter value of PVR was 3wood in 70.3% cases, and 5wood in 90.75% cases.3. Significant differences were found in RVW/T , ventricular septal curvature, PD, PRF and Qp/Qs between the patients of severe dynamic PH and Eisenmenger syndrome(P<0.05). The following 5 parameters could be used as the standard for MR to diagnose the Eisenmenger syndrome: RVW/T>0.6, the septal curvature concaving toward the right ventricle, PD< 18% > PRF>20%, Qp/Qs<2. If the patient with CHD and severe PH had 3 or more of the above paremeters , Eisenmenger syndrome or irreversible PH should be suspected.4. MR pulmonary angiography could fairly show the size and distribution of central pulmonary artery and its branches.5. The value of Qp/Qs obtained from MRI is similar to and correlates well with which obtained from catheterization (r=0.823,P<0.01).6. MRI could accurately detect the congenital anatomic defects in patients with CHD.ConclusionAs a noninvasive and non-ionizing radiation image technique, MRI has significant value in clinical application for diagnosis of PH and its etiology, and for evaluating the information in pathologic and hemodynamic abnormalities. The parameters about heart and blood vessel morpholog and hemodynamics obtained from MRI correlate well with those obtained from catheterization, and they are useful complements to ultrasonography as well.