Correlation of hemodynamic impact and morphologic degree of renal artery stenosis in a canine model.
In a noninvasive comprehensive magnetic resonance (MR) examination, the morphologic degree of renal artery stenosis was correlated to corresponding changes in renal artery flow dynamics. Different degrees of stenosis were created with the use of a chronically implanted inflatable arterial cuff in seven dogs. For each degree of stenosis, an ultrafast three-dimensional gadolinium MR angiography with high spatial resolution was performed, followed by cardiac-gated MR flow measurements with high temporal resolution for determination of pulsatile flow profiles and mean flow. Flow was also measured by a chronically implanted flow probe. In three of the dogs, trans-stenotic pressure gradients (DeltaP) also were measured via implanted catheters. Five different degrees of stenosis could be differentiated in the MR angiograms (0%, 30%, 50%, 80%, >90%). The MR flow data agreed with the flow probe within +/-20%. Stenoses between 30 and 80% gradually reduced the early systolic peak (Max(1)) of the flow profile but only minimally affected the midsystolic peak (Max(2)) or mean flow. Stenoses of more than 90% significantly depressed mean flow by more than 50%. The ratio between Max(1) and Max(2) (Rmax(1/2)) gradually fell with the degree of stenosis. The onset of significant mean flow reduction and DeltaP was indicated by a drop of Rmax(1/2) below 1 to 1.2. Thus, the analysis of high-resolution flow profiles allows detection of early hemodynamic changes even at degrees of stenoses not associated with a reduction of mean flow. Rmax(1/2) allows differentiation of the grade of hemodynamic compromise for a given morphologic stenosis independent of mean flow in a single comprehensive MR examination.
Schoenberg
Stefan O
SO
Department of Radiology, German Cancer Research Center, Germany.
Bock
Michael
M
Department of Radiology, German Cancer Research Center, Germany.
Kallinowski
Friedrich
F
Department of Surgery, University Hospitals, University of Heidelberg, Heidelberg, Germany.
Just
Armin
A
Institut für Physiologie und Pathophysiologie, University of Heidelberg, Heidelberg, Germany.
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging / Q000473:pathology; D001794:Blood Pressure / Q000187:drug effects; D004285:Dogs; D005682:Gadolinium; D006439:Hemodynamics; D018810:Magnetic Resonance Angiography; D012077:Renal Artery / Q000000981:diagnostic imaging / Q000473:pathology; D012078:Renal Artery Obstruction / Q000175:diagnosis* / Q000503:physiopathology*; D012079:Renal Circulation / Q000187:drug effects; D018084:Ultrasonography, Interventional; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D005682:Gadolinium