Aortic pressure-diameter relationship assessed by intravascular ultrasound: experimental validation in dogs

Intravascular ultrasound (IVUS) has emerged as an important diagnostic meth od for evaluating vessel diameter and vessel wall motion. To evaluate the v alidity of NUS in assessing changes in the pressure-diameter relationship w e compared measurements of abdominal aortic diameters derived from IVUS wit h those simultaneously obtained at the same site using implanted sonomicrom eters in five chronically instrumented conscious dogs and in seven acutely instrumented anesthetized dogs. Five hundred eighty beats were analyzed to obtain peak systolic and end-diastolic diameters and to calculate aortic co mpliance at different blood pressure levels induced either by an aortic pne umatic cuff or by intravenous injections of nitroglycerin or norepinephrine . IVUS agreed closely with sonomicrometer measurements at different blood p ressure levels. However, IVUS slightly but significantly underestimated aor tic diameters by 0.6 +/- 0.7 mm for systolic diameters (P < 0.001) and by 0 .7 +/- 0.6 mm for diastolic diameters (P < 0.001) compared with the sonomic rometer measurements. We conclude that IVUS is a feasible and reliable meth od to measure dynamic changes in aortic dimensions and has the potential to provide ready access to assess aortic compliance in humans.