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Angiotensin-Converting Enzyme Inhibitor-Enhanced Phase-Contrast MR Imaging to Measure Renal Artery Velocity Waveforms in Patients with Suspected Renovascular Hypertension

¹ All authors: Department of Radiology, New York University Medical Center, 530 First Ave., HCC Basement-MRI, New York, NY 10016.

View larger version (7K): [in a new window]   Fig. 1. —Drawings show MR phase-contrast waveform patterns. Patterns I-VI show healthy sharp systolic upstroke and are considered normal. Variations in diastolic flow are assumed to represent differences in compliance. Patterns VII-X, including separate category (pattern X) that we define as having no observable systolic phase, are considered abnormal. (Modified and reprinted with permission from [16])

View larger version (123K): [in a new window]   Fig. 2A. —61-year-old man with hypertension and questionable abdominal bruit. MR phase-contrast measurements taken from right (A) and left (B) renal hila at baseline (without angiotensin-converting enzyme inhibitor) show mean velocity values (centimeters per second) within region of interest placed over renal arteries, measured at multiple points during one heart cycle (744 msec). Plots are superimposed on selected phase-contrast image on which region of interest (short arrows) is shown. Velocity waveform for left renal artery is inverted because flow direction is encoded as left to right. Both waveforms show pattern II-type curves with normal sharp systolic upstroke and early systolic peak (long arrows).

View larger version (123K): [in a new window]   Fig. 2B. —61-year-old man with hypertension and questionable abdominal bruit. MR phase-contrast measurements taken from right (A) and left (B) renal hila at baseline (without angiotensin-converting enzyme inhibitor) show mean velocity values (centimeters per second) within region of interest placed over renal arteries, measured at multiple points during one heart cycle (744 msec). Plots are superimposed on selected phase-contrast image on which region of interest (short arrows) is shown. Velocity waveform for left renal artery is inverted because flow direction is encoded as left to right. Both waveforms show pattern II-type curves with normal sharp systolic upstroke and early systolic peak (long arrows).

View larger version (96K): [in a new window]   Fig. 2C. —61-year-old man with hypertension and questionable abdominal bruit. Maximum-intensity-projection reconstruction of three-dimensional breath-hold single-dose gadolinium-enhanced MR angiogram reveals normal single renal artery to each kidney.

View larger version (111K): [in a new window]   Fig. 3A. —59-year-old woman with peripheral vascular disease and retinopathy who developed sudden worsening of hypertension refractory to medication. MR phase-contrast measurements taken from right (A) and left (B) renal hila at baseline (without angiotensin-converting enzyme inhibitor) show normal right waveform but abnormal left waveform. Velocity waveform for left renal artery is inverted because flow direction is encoded as left to right.

View larger version (102K): [in a new window]   Fig. 3B. —59-year-old woman with peripheral vascular disease and retinopathy who developed sudden worsening of hypertension refractory to medication. MR phase-contrast measurements taken from right (A) and left (B) renal hila at baseline (without angiotensin-converting enzyme inhibitor) show normal right waveform but abnormal left waveform. Velocity waveform for left renal artery is inverted because flow direction is encoded as left to right.

View larger version (91K): [in a new window]   Fig. 3C. —59-year-old woman with peripheral vascular disease and retinopathy who developed sudden worsening of hypertension refractory to medication. Maximum-intensity-projection reconstruction of three-dimensional breath-hold single-dose gadolinium-enhanced MR angiogram reveals normal single renal artery to right kidney and significant proximal stenosis (>60%) on left (arrow).

View larger version (163K): [in a new window]   Fig. 3D. —59-year-old woman with peripheral vascular disease and retinopathy who developed sudden worsening of hypertension refractory to medication. Conventional angiogram of selective injection of left renal artery confirms renal artery stenosis (arrow) that was successfully treated with angioplasty.

View larger version (107K): [in a new window]   Fig. 4A. —77-year-old woman with late-onset hypertension. MR phase-contrast measurement at right renal hilum taken before administration of enalaprilat. Both baseline and angiotensin-converting enzyme inhibitor-enhanced (not shown) renal artery velocity waveforms show normal systolic upstroke and acceleration index.

View larger version (134K): [in a new window]   Fig. 4B. —77-year-old woman with late-onset hypertension. Maximum-intensity-projection reconstruction of three-dimensional breath-hold single-dose gadolinium-enhanced MR angiogram reveals right renal artery stenosis (60%) at ostium (arrow).

View larger version (118K): [in a new window]   Fig. 4C. —77-year-old woman with late-onset hypertension. Conventional angiogram by selective injection depicts less narrowing at ostium than shown on MR angiogram. Dense calcifications were observed on unenhanced angiograms. On basis of angiographic findings, patient did not undergo interventional therapy. This patient had false-positive MR angiography finding, but true-negative velocity waveform analysis.

View larger version (135K): [in a new window]   Fig. 5A. —53-year-old woman with history of peripheral vascular disease and hypertension refractory to medication. MR phase-contrast velocity waveform from left renal hilum after administration of angiotensin-converting enzyme inhibitor was graded as abnormal.

View larger version (91K): [in a new window]   Fig. 5B. —53-year-old woman with history of peripheral vascular disease and hypertension refractory to medication. Maximum-intensity-projection reconstruction of MR angiograms depicts left renal artery stenosis (arrow), which was estimated to be equal to or greater than 60% from source images (not shown).

View larger version (113K): [in a new window]   Fig. 5C. —53-year-old woman with history of peripheral vascular disease and hypertension refractory to medication. Conventional angiogram with selective injection of left renal artery shows only tortuous vessel with no pressure gradient measured across proximal renal artery. This study is false-positive MR examination, likely resulting from dephasing caused by turbulent flow through tortuous vessel.

View larger version (119K): [in a new window]   Fig. 6A. —82-year-old woman with sudden onset of hypertension refractory to medication. MR phase-contrast measurements at right renal hilum taken before (not shown) and after administration of angiotensin-converting enzyme inhibitor show normal systolic upstroke. Image findings were classified as normal by both investigators independently and by consensus.

View larger version (120K): [in a new window]   Fig. 6B. —82-year-old woman with sudden onset of hypertension refractory to medication. Maximum-intensity-projection reconstruction of three-dimensional breath-hold single-dose gadolinium-enhanced MR angiogram shows bilateral ostial renal artery stenosis (arrows). On basis of source images (not shown), narrowing of right renal artery (60%) was greater than that of left renal artery (<60%).

View larger version (113K): [in a new window]   Fig. 6C. —82-year-old woman with sudden onset of hypertension refractory to medication. After MR angiography, second phase-contrast measurement was performed distal to right renal artery stenosis using similar parameters with encoding velocity of 150 cm/sec. Elevated systolic velocity of 257 cm/sec (with phase unwrapping to correct for velocity aliasing) suggests significant proximal stenosis.

View larger version (119K): [in a new window]   Fig. 6D. —82-year-old woman with sudden onset of hypertension refractory to medication. Conventional contrast-enhanced angiogram confirms substantial right renal artery stenosis (arrow). Patient underwent concurrent right renal artery angioplasty with subsequent improvement in hypertension.

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