Study Of Correlation Between Aortic Compliance And Hemodynamics In Primary Hypertensive Patients With MR

Objective:To observe the local aortic stiffness parameters and hemodynamic states in primaryhypertensive patients with MRI. The correlation between them was investigated. Andthe effect of aortic stiffness on hemodynamics changes and primary hypertensivepathogenesis were discussed.Material and methods:Consecutively60clinical diagnosed primary hypertensive patients were divide into2groups: group A (isolated systolic hypertension, ISH; SBP≥140mmHg; DBP＜90mmHg)(average age55.5±3.1Y, male14), group B(non-isolated systolichypertension, NISH; SBP≥140mmHg; DBP≥90mmHg)(average age52.6±5.9Y,male15).30subjects with no hypertensive(SBP＜140mmHg; DBP＜90mmHg) wereenrolled as control group C(average age51.7±5.8Y, male15). All the subjectsunderwent MRI examination and BP was recorded simultaneously. During MRIexamination, TrueFISP sequence, PC-MRA sequence and Cine sequence wereperformed. The cross-sectional images of aorta for PC-MRA and Cine sequences wereacquired at the following3locations:①ascending aorta at pulmonary bifurcationlevel;②descending aorta at pulmonary bifurcation level;③abdominal aorta at1cmdistal to the lowest renal artery. At the aortic levels, the average cross-sectional area ofthe lumen, the average flow velocity, the average blood flow and the net flow, andcalculate partial lumen of the absolute and relative compliance were measured in onecardiac cycle with quantitative analysis of the image data.(1) Average lumencompliance, mean flow velocity, the average blood flow, the net flow were comparedat the different aortic levels.(2) Differences among3groups were discussed inaverage lumen compliance, mean flow velocity, average blood flow, net flow with corresponding aortic level.(3) Correlation between of the aortic lumen compliancewith blood pressure and blood flow index (mean flow velocity, average blood flowand net flows) were calculated.Results:Compliance (C) and Distensibility (D) were found lower in hypertension group thanthat in control group with significant difference (P<.05) over different parts of aorta.And Young s modulus (E) was found higher in hypertension group with significantdifference (P<.05). C decreased and D increased as the position of the aorta changedfrom ascending aorta to abdominal aorta (P<.05). E was found anomaly increase atabdominal aorta in Group B, while it decreased from ascending aorta to abdominalaorta in other groups.The maximum average velocity of the aorta happened at descending aorta. Peaksystolic blood flow velocity, forward flow decreased from ascending aorta toabdominal aorta, while regurgitant blood flow increased. The value of averagevelocity, peak systolic blood flow velocity were the highest in Group C. Regurgitantblood flow was more common during early diastolic phase in Group B (12/30,40.0%)than Group C (2/30,6.7%)(P<.05) at ascending aorta. At descending aorta, theincidence of regurgitation was the highest in Group B (29/30,96.7%)(P<.05), andregurgitation accrued during whole diastolic phase in30%patients. At abdominalaorta, the incidence of full-diastolic regurgitation was highest in Group B (15/30,50.0%).SBP and PP were found mild-moderate negative correlations with C and D over thewhole aorta, mild positive correlations with E over the whole aorta. DBP was found amild correlation with D and E at abdominal aorta.Conclusion:This study demonstrated that aortic elasticity decrease can reduce the blood flowvelocity in aorta. It is the reason of fluid pressure increase in the aortic lumen. Aorticregurgitation happens and prolongs in diastolic phase are very important reasons which lead to the rise of DBP. This may be interpreted with distal aortic (abdominalaorta) stiffness increase. Thus, aortic elasticity decrease is one of the generationmechanisms in primary hypertension. There must be obvious significance in maintainand restore the aortic elasticity for clinical treatment of hypertension.