RenoVascular Hypertension in clinical.pptx

rht

1. Imaging in Renovascular Hypertension Moderator Dr Arjun Prakash Assistant Professor Dept of Radiodiagnosis

2. Hypertension : 140/90 mmHg or more.

3. Renovascular hypertension (RVH): Hypertension that occurs secondary to Renovascular compromise is termed Renovascular Hypertension. It constitutes about 0.5%-3%. Why is it essential to detect RVH? Treatment of renal artery stenosis may cure patient’s hypertension. End stage renal disease can be prevented by appropriate intervention. ACEI to be avoided in bilateral renal artery stenosis

4. Pathophysiology

5. Causes of Renovascular hypertension 1) Renal artery stenosis : • Atherosclerosis • Fibromuscular dysplasia • Takayasu’s arteritis • Vasculitis • Dissection • Vasospasm • Coarctation syndrome • Neurofibromatosis • Extrinsic compression • Middle aortic syndrome • Williams syndrome 2) Other causes of RVH • Aneurysm of renal artery • Renal artery embolus • AVF – renal artery • Irradiation • Trauma • Page kidney

6. Atherosclerosis FMD Age After 50yr Young Gender More common in males More common in females Location Proximal 1cm of main renal artery Other sites: at branching points Middle of main renal artery Other sites: Carotids

7. Hypertension is common but RVH is not; Whom to screen for RVH? Accelerated/malignant hypertension in young age (<20yrs). Hypertension uncontrolled by triple drug therapy. Unilateral small kidney discovered with any clinical study. Impairment of renal function after treatment with ACEI . Smokers Patients with peripheral vascular disease

8. Imaging of Renal artery stenosis 1. Localization and number of arteries 2. Characterization of RAS: etiology of stenosis, localization, and poststenotic dilatation 3. Hemodynamics and functional significance of the stenosis 4. Further pathologies or variants that might influence the treatment planning

9. Ultrasound Methodology: Reduce the bowel gas: overnight fasting, examine early in the morning Supine position; at the end of deep inspiration. Low frequency curvi -linear probe : 2.5 – 5.0 MHz : For depiction of abdominal aorta and renal arteries.

10. Anterior approach: main renal arteries Flank approach: intrarenal vessels and main renal artery

11. Gray scale imaging: A normal appearance of the kidneys on ultrasound does not exclude a significant unilateral or bilateral renal artery stenosis. Small decrease in size happens only when stenosis is >60%.

12. Color Doppler Flow Imaging (CDFI): Two approaches are used with Doppler ultrasound. Direct visualization and interrogation of the stenotic segment of the renal artery. Assessment of intrarenal vasculature: Arterial waveform distal to the stenosis within segmental renal vessels

13. Incorrect angle Correct angle

14. Direct Approach Evaluate the entire main renal artery. Spectral traces are obtained from areas of stenosis identified on color Doppler. Aorta is also interrogated and peak systolic velocity should be obtained at the level of renal origins.

15. 19 The Normal Renal Waveform Low resistance waveform. Rapid and steep upstroke during systole. Broad systolic waveform Dicrotic notch. Forward flow thoughout diastole. PSV: 74 - 127 cm/sec

16. Renal Artery : PSV <120cm/sec. Main renal artery RI: ~0.65+/-0.2 Hilar renal artery RI: ~0.54+/-0.2

17. The criteria used to diagnose significant stenosis of a renal artery: An increase in peak systolic velocity: >150-180 cm/sec. Renal artery/aortic ratio (RAR ratio): > 3.5 Turbulent flow in the post stenotic area Visualization of the renal artery without detectable Doppler signal indicates occlusion.

18. Criteria for the classification of RA stenosis by color Doppler US from Zieler and Strandness (Am J Hypertens , 1996).

19. Disadvantages of the direct Doppler method Main renal arteries may not be visualized in upto 42% cases. Accessory renal arteries (present in upto 40% cases) may not be visualized. Branch artery stenosis cannot be diagnosed.

20. Indirect Method Assess segmental arteries (upper, mid and lower poles) Normal waveforms: a steep systolic upstroke with a peak in early systole. RAS: “ tardus-parvas ” waveforms. The early systolic acceleration is the best predictor of RAS and should be measures along the initial portion of the systolic rise and should not include the late compliance peak.

21. Acceleration time: done by placing a calliper at which the gradient begins to rise and finished at the early systolic peak. Normal <0.07 sec Acceleration index Systolic upslope / transducer frequency Normal: 300 cm/sec2

22. RAS: AT: >0.07 sec and AI: <3 m/sec2 The waveform may also demonstrate a decrease in RI and PI. RI >0.8 probably identifies patient with RAS in whom angioplasty or surgery will not improve renal function or blood pressure.

23. Disadvantages of indirect Doppler method These criteria only detect stenosis of greater than 70-80% reliably. Coexisting parenchymal disease may also affect the waveform due to changes in peripheral resistance. The technique also cannot distinguish between high grade stenosis and complete occlusion with collateral flow. Tardus parvus waveform may also be produced by abdominal coarctation .

24. Direct signs Indirect signs Focal colour aliasing AT >0.07sec Colour bruit AI <0.3m/sec2 Turbulence PSV >180cm/sec Renal Aortic Ratio >3.5 Significant stenosis (50-85% diameter reduction) Sever stenosis (>85% diameter reduction)

25. 31 Overview of Renal Artery Study Routine US exam of the Kidneys evaluate size and echotexture , r/o pathology Doppler of Aorta Measure PSV, for RAR calculation Doppler of renal arteries Measure PSV, for RAR calculation Doppler segmental arteries obtain acceleration time & index look for Tardus-Parvus

26. The use of sonographic contrast media like Levovist has been found to enhance the visualization of main renal vessels resulting in higher technical success rates

27. CT Angiography Craniocaudal acquisition Section thickness of 1mm Pitch of 1.5 Intravenous contrast : - Volume ~90-150 ml (300 mg I/ml) - Rate of 3-6 ml/sec - Bolus tracking techniques should be used

28. Images are reconstructed in multiple planes using– MPR, MIP and VRT to assess renal arteries

29. Advantages of CTA over angiography Demonstrate the wall of the aorta unlike angiography which only visualizes the lumen of the vessel. Demonstrates the extent of plaque projecting into the vessel lumen aiding in determining the form of intervention planned such as angioplasty vs primary stent placement. Diagnosis of ostial stenosis—differentiates ostial and truncal stenosis.

30. Advantages of CTA over MR Angiography To assess stent patency : MDCT produced interpretable multiplanar images of the renal artery even with a metallic stent in place. Intrastent diameter was underestimated in most patients as compared to catheter angiography

31. Magnetic Resonance Angiography (MRA)

32. Contrast Enhanced MRA (CE-MRA) Intravenous gadolinium is used in a dose of 0.3mmoles/kg. Entire acquisition is performed during a single breath hold. 3D contrast MRA assess the renal arteries in entirety, including segmental branches and accessory renal arteries

33. TOF MRA TOF MRA is not an useful technique for the evaluation of renal arteries because of the following reasons. 1. It tend to overestimate the degree of stenosis, 2. Loss of signal in slow flow when vessel in oriented in axial plane (in-plane saturation) 3. Require several minutes, causing breathing related degradation or extremely long scan times for signal averaging. 4. Poor visualization of the distal arterial segment where flow is slow.

34. Phase Contrast (PC) MRA Provides quantitative analysis of flow dynamics in RAS. Combining phase contrast with cardiac gating , a 2D velocity map can be obtained, which is termed as “quantitative” or “q” flow. With this flow maps similar to Doppler ultrasound can be generated and analyzed.

35. MRA + 3D PC Contrast enhanced MRA is complemented by 3D-PC acquisition. Areas of hemodynamically significant stenosis are detected by their associated turbulence seen as a signal void on 3D-PC images. The presence of a signal void at or immediately downstream from a stenosis suggests pressure drop across the stenosis. For 3D–PC MRA to be optimally sensitive to turbulent flow echo time should be approximately 8 ms and velocity encoded value (VENC) should be kept at 25-50 cm/sec.

36. Steady-state Free Precession Magnetic Resonance Angiography 3D –SSFP: intrinsically fast high in signal-to-noise ratio flow compensated in all the three axis. 3D-CE MRA has been proven to be sensitive and effective non-invasive investigation to evaluate renal artery stenosis. Disadvantages: Nephrogenic systemic fibrosis Reduction in spatial resolution secondary to inadequate patient breathholding

37. If SSFP is negative for high grade RAS (> 50%), RAS can be excluded, if SSFP is positive, then further studies (CE-MRI, DSA, CTA) can be done for better delineation of stenosis.

38. Renal angiography Digital subtraction angiography is the gold standard. Not used as screening method, but as a guide for therapeutic transluminal angioplasty.

39. Angiographic evaluation - aortography + bilateral selective renal arteriography. Aortogram : necessary to evaluate the renal artery ostia , identifying accessory renal arteries and avoid mistaking guide wire induced arterial spasm for fixed disease.

40. When intrarenal or branch artery stenosis are suspected selective injections are necessary. Oblique/Lateral view, cranial/caudal angulation or magnification views may be required to optimally delineate stenosis because the origin of renal arteries may overlap on opacified aorta in AP view.

41. Advantages of conventional angiography/DSA High resolution of the technique making it the only modality capable of adequately visualizing branch renal artery stenosis. Pressure gradients can be measured to assess hemodynamic significance Selective renal catheterization may be followed by appropriate intervention in the same sitting.

42. Disadvantages of DSA Expensive and invasive. Risk of iodinated contrast. Angiography only provides intraluminal information; no intramural information is gained about the vessel wall or plaques. At the puncture site: hematoma, pseudoaneurysm or at the level of renal arteries because of selective catheterization, vessel dissection, arterial puncture and cholesterol embolization leading to renal failure. Transient decrease in renal function may occur in upto 5% patients.

43. ACE Inhibitor Scintigraphy Kidney with RVH exhibit impaired function during ACE inhibition. This phenomenon is observed mainly in patients with bilateral RAS or with arterial stenosis in a solitary kidney With unilateral RAS, a unilateral change in renal function induced by ACE inhibition can be revealed with scintigraphy

44. With ACEI there will be disruption of autoregulation (as it dilates the efferent arterioles) which leads to reduction of GFR. ACE inhibitor scintigraphy induces significant changes in the time-activity curves of the affected kidney in comparison with baseline scintigraphy .

45. Pre- requisits for study: Stop anti- hypertensives for 2-5 days Adequate hydration Monitor blood pressure ACEI scintigraphy is performed 1 hour after an oral dose of 25 mg of captopril or 15 minutes after an intravenous dose of 0.04 mg/kg of enalapril maleate.

46. Baseline and ACE inhibitor scintigraphy are performed Radiopharmaceuticals (intravenously) used technetium-99m mercaptoacetyltriglycine (MAG3), iodine-131 orthoiodohippurate (OIH), or Tc-99m diethylenetriaminepentaacetic acid (DTPA). Sequential images and scintigraphic curves are obtained for 30 minutes. Renal uptake is measured at 1–2-minute intervals. Time-activity curves are generated from the renal cortex and pelvis.

47. Post captopril criteria for RVH: (Tc99m -MAG3) Increased asymmetry of split renal function >10% Relative increase in time to peak activity > 2min /40% compared to base line value An increase in residual cortical activity > 15% Change in the renogram curve by >1 grade

48. 63 Patterns of scintigraphic curves Time (min) Activity Grade-0 Grade-1 Grade-3 Grade-4 Grade-5 Grade-2

49. 64 Patterns of scintigraphic curves Grade-0: normal Grade-1: minor abnormalities with t-max > 5min Grade-2: marked delayed excretion rate with preserved washout phase Grade-3: marked delayed excretion rate without preserved washout phase Grade-4: renal failure pattern with measurable kidney uptake Grade-5: renal failure pattern without measurable kidney uptake.

50. A normal ACEI scintigram: a low probability (<10%) of RVH. A small, poorly functioning kidney (<30% uptake with a time to maximum activity [ T max ] <2 minutes) that shows no change on the ACE inhibitor scintigram and bilateral symmetric abnormalities such as cortical retention of tubular agents indicate an intermediate probability of RVH. Criteria associated with a high probability of RVH include worsening of the scintigraphic curve, reduction in the relative uptake, prolongation of the renal and parenchymal transit time, and prolongation of T max .

51. Management Drugs : Antihypertensives – ACE inhibitors, Beta blockers, CCBs, AT receptor blockers. -Lifelong, & doesn’t correct the actual disease Surgical correction : Endarterectomy, Aorto-renal bypass - technically difficult - high mortality rate Interventional procedures : a) Percutaneous Transluminal Renal Angioplasty (PTRA). b) Renal artery stents

52. Percutaneous Transluminal Renal Angioplasty (PTRA) and Stenting:

53. Suitable cases : Discrete tight concentric, short segment stenosis located away from ostium and branches of renal arteries. Unsuitable cases : Eccentric, long segment and calcified lesions, occlusion in tortuous vessels, stenosis adjacent to an aneurysm and occlusion or stenosis with a thrombus increase the risk of complications and reduce the likelihood of success.

54. Indications: Percutaneous revascularisation of renal arteries is indicated for Refractory hypertension Preservation of renal function Prevention of ‘flash’ pulmonary edema especially in patients on calcium channel blockers Preservation of renal artery patency.

55. Before PTRA is performed the salvage ability of the procedure must be established. The commonly used criteria are Assess residual function-single kidney GFR by radionuclide studies Kidney size of 8-9 cm Renal biopsy showing preservation of glomeruli and tubule Presence of collateral circulation to intrarenal vessels confirmed by arteriography. Revascularisation is usually not beneficial in patients with severe renal failure (S. creatinine > 4.0 mg/dl).

56. Renal Artery Stenting Angioplasty failure is an absolute indication for stenting. The criteria for angioplasty failure include– Residual stenosis of more than 30% Residual aortorenal pressure gradient of > 20 mmHg Acute occlusive, flow limiting dissection flap and late restenosis Recurrent stenosis > 50%

57. When to do primary stenting? In selected patients in whom the risk of intervention or anatomic considerations make a repeat procedure in the future unlikely. Ostial atherosclerotic RAS.

58. Success in renal revascularization can be judged by Technical success of angioplasty: Residual stenosis is <30% At least 50% enlargement in arterial diameter as compared to pre-angioplasty diameter Pressure gradient of <20 mmHg or reduction in pressure gradient by at least 15 mmHg from the pre-treatment gradient

59. B) Clinical response: - Diastolic blood pressure < 90 mmHg without medication, - Equal or reduced medication required to maintain the diastolic BP <90 mmHg or a 15 mm Hg reduction in BP

60. The results in FMD are uniformly good. Technical success is achieved in 90-100% patients. Hypertension is cured or improved in 98% patients. For atherosclerotic lesions both angiographic and clinical results for nonostial stenosis are superior to those for ostial stenosis (within 2-10 mm of aortic lumen). Lesser success can be expected in patients with bilateral RAS, generalized atherosclerosis, with heavily calcified or segmental artery lesion.

61. CONCLUSION Captopril renography & Doppler are the initial modes of screening but Doppler is highly operator dependent CT angiography requires iv contrast & radiation exposure is another disadvantage In CRF & allergy, MRA is the modality of choice Gadolinum enhanced MRA is becoming an excellent alternative to Conventional Angiography. CTA and MRA have limited role in the evaluation of distal segments However angiography is the confirmatory & can be coupled with the therapeutic purpose.

62. 80 Clinical evaluation of RVH Doppler USG or scintigraphy Positive with H/O Renal failure or Allergy Negative with high clinical suspicion MRA Catheter angiography +/- angioplasty Positive with no H/O Renal failure or Allergy Diagnostic algorithm for patients suspected with RVH