Jess R. Young

The Utility of Duplex Ultrasound Scanning of the Renal Arteries for Diagnosing Significant Renal Artery Stenosis

Renovascular hypertension may account for 1% to 5% of all cases of hypertension. However, atherosclerotic renal artery stenosis is much more frequently encountered, especially in the elderly patient with evidence of atherosclerosis elsewhere [1]. Arteriography has been the gold standard for detecting renal artery stenosis. Although arteriography allows direct visualization of the renal arteries, it is invasive and expensive and does not adequately assess the functional significance of the renal artery lesion. Because azotemia is not uncommon in patients with atherosclerotic renal artery stenosis [2], it may be advantageous to avoid arteriography as a screening test because of the possibility of causing contrast-induced acute renal failure or atheromatous embolization to the kidneys. Because of these limitations of arteriography, investigators are interested in noninvasive screening for renal artery disease [3, 4]. Many of the noninvasive screening tests (such as intravenous urography, renal scintigraphy, determination of plasma renin activity, and the captopril test) have an unacceptably low sensitivity and specificity. Renal scintigraphy with the administration of captopril is safe and noninvasive and has a reasonable sensitivity and specificity in many circumstances. Captopril renography is not as sensitive in patients with bilateral renal artery stenosis or in patients with stenosis to a solitary functioning kidney [4, 5]. Renal scintigraphy with captopril may also not be as sensitive in patients with substantial azotemia, the subgroup of patients most in need of a safe screening test for renovascular disease. The captopril-stimulated renal flow scan does not provide an anatomical assessment of the degree of stenosis, but it is an excellent test for assessing the functional significance of a stenotic lesion. Magnetic resonance angiography is an attractive noninvasive screening method for assessing the renal arteries [6]. Most segments of the renal artery can be adequately visualized, and it is now possible to view the renal arteries three-dimensionally through post-processing reconstruction [7]. Currently, this technique has two major drawbacks. It is expensive and may overestimate the degree of stenosis. One study of three-dimensional, spiral computed tomographic angiography showed excellent imaging of the mesenteric and renal arteries [8], but the procedure required a large amount of contrast material administered in a bolus, thus limiting the utility of this test in patients with azotemia. Duplex ultrasound scanning of the renal arteries is a noninvasive screening test for the detection of renal artery stenosis. It combines direct visualization of the renal arteries (B-mode imaging) with measurement of various hemodynamic factors in the main renal artery and within the kidney (Doppler), thus providing both an anatomical and a functional assessment [9, 10]. Duplex scanning also allows the measurement of kidney size at the same time that the examination is being done. Unlike other noninvasive screening tests, duplex scanning is not affected by medications that the patient may be taking; the level of renal function; or whether the disease is unilateral or bilateral or affects a solitary functioning kidney. Improvements in image resolution, Doppler technology, and processor software have led to the ability to better scan the visceral circulation [11]. We determined the utility of duplex ultrasound of the renal arteries for identifying patients with renal artery stenosis of 60% or more and for excluding patients with either normal renal arteries or renal artery stenosis of less than 60%. Methods Patients We prospectively entered patients into our study who were being evaluated for possible renal artery stenosis. One hundred and two consecutive patients who had both duplex ultrasound scanning of the renal arteries and renal arteriography were included for analysis. Duplex scanning was done before renal arteriography in 60 (58.8%) patients. Only main renal arteries were analyzed in our study. Only 9 patients had accessory renal arteries on arteriography, which was a smaller number than we expected [5]. The cohort of patients that we studied had a high pretest likelihood of disease. Most patients who were studied had either hypertension that was difficult to control or unexplained azotemia (or both), giving them a pretest likelihood of renovascular disease of 70% [1]. A smaller number of patients was evaluated because of associated peripheral vascular disease or abdominal aortic aneurysm. The pretest likelihood in this group is approximately 40% [1]. The persons who did the duplex ultrasound examinations did not have access to the patients chart or to the results of renal arteriography. All renal arteriograms had at least two views of the renal artery, and the degree of stenosis was estimated by visual examination. Renal arteriograms were both formally interpreted by the person doing the study and reviewed by one of the authors. If a difference of opinion existed between the formal reading and the review, a third investigator evaluated the arteriogram without knowledge of the two previous evaluations and the majority ruled. Those interpreting the arteriograms were blinded to the results of the person doing the study and to the results of the duplex ultrasound. Renal Duplex Scanning Technique All patients were scanned with an Ultramark 9 HDI ultrasound machine (Advanced Technology Laboratories, Bothell, Washington) using a C3 40R transducer. This curved array transducer has a 3.0-MHz imaging probe and a 2.5-MHz pulsed Doppler with a focal zone in the vicinity of the depth of the renal arteries. Patients were studied after a 12-hour fast. Ninety percent of the patients had an adequate examination when studied in the fasting state. If excess bowel gas was present, the patients were studied the following morning or at the next available convenient time for the patient. Patients were studied in the anterior, lateral decubitus, and, at times, the prone position so that all portions of the renal artery from the takeoff of the aorta to where the renal artery enters the kidney were visualized. The hilar approaches were particularly useful in patients with excess bowel gas and in obese persons. The renal arteries were first visualized and identified. The ability to use color duplex imaging may allow the ultrasonographer to directly visualize turbulent blood flow if it is present. Once the renal arteries were correctly identified, the Doppler signature was taken at as close to a 60-degree angle as possible. Under no circumstances was the angle more than 60 degrees. Doppler samples were taken at the origin of the renal artery, the proximal renal artery, the midportion of the renal artery, and the distal renal artery. The renal-aortic ratio was calculated by dividing the peak systolic velocity in the renal artery by the peak systolic velocity in the aorta. The peak systolic velocity is a measure of the maximum velocity of blood flow during systole. Using Doppler principles, as an artery narrows, the velocity of blood flow increases. If the renal-aortic ratio was 3.5 or more, it indicated 60% to 99% stenosis of the renal artery. End-diastolic velocities were also measured in all arterial segments. The end-diastolic velocity is a measure of the velocity of blood flow at the end of diastole. In patients with severe degrees of arterial narrowing, the velocity of diastolic flow may be increased. After studies were done using an anterior approach, the patient was placed in the lateral decubitus or prone position (or both), and renal artery velocities were again sampled. The kidney size was measured at its longest axis. Parenchymal flow samples from the kidney itself were obtained, and the resistive index was calculated by using the formula of the peak systolic velocity minus the end-diastolic velocity divided by the peak systolic velocity. The average time for completion of a renal duplex scan was approximately 1 hour. The most common reasons for technical failure were excess bowel gas and obesity. Identification of accessory renal arteries was sometimes difficult. The criteria used for classifying patients were as follows: 1) A renal-aortic ratio of less than 3.5 and a peak systolic velocity of less than 200 cm/s identified patients with 0% to 59% renal artery stenosis; 2) a renal-aortic ratio of 3.5 or more or a peak systolic velocity of more than 200 cm/s [or both] identified patients with 60% to 99% renal artery stenosis; and 3) occlusion of the renal artery was diagnosed by the absence of a flow signal in the renal artery and by a low-amplitude parenchymal signal. The renal artery duplex scans were done by one of four technicians and were reviewed by one of the attending staff in the vascular laboratory. Technician A did 39 (38%) studies, technician B did 41 (40%) studies, technician C did 12 (12%) studies, and technician D did 10 (10%) studies. The technicians often sought the help of their colleagues for patients who were difficult to study. No difference was noted in the accuracy of the results or in the quality of the studies among the four technicians who participated in our study. Statistical Analysis The sensitivity of ultrasound relative to arteriography was calculated as the proportion of positive arteriograms that were positive by ultrasound. The specificity was calculated as the proportion of negative arteriograms that were negative by ultrasound. The positive predictive value was defined as the proportion of positive ultrasounds that were positive by arteriography, and the negative predictive value was defined as the portion of negative ultrasounds that were negative by arteriography. Comparison of hemodynamic variables between the various levels of stenosis was done using analysis of variance techniques. Values are expressed as mean SD. When the overall difference was significant (P < 0.05), this significance l

High incidence of restenosis/reocclusion of stents in the percutaneous treatment of long-segment superficial femoral artery disease after suboptimal angioplasty

PURPOSE To evaluate the efficacy of intravascular stents used to treat long-segment stenoses and occlusions of the superficial femoral artery (SFA) after suboptimal angioplasty. METHODS Fifty-eight limbs in 55 patients who underwent stenting of the SFA were identified from a vascular registry. Indications for stent placement after suboptimal PTA included flow-limiting dissection, residual pressure gradient (>15 mm Hg) or stenosis (>30%), or failure to establish initial patency. Lesion length ranged from 6 to 35 cm (mean, 16.5 cm). Endpoints for primary patency were: restenosis of >50%, reocclusion, or diminution of the postprocedure ankle-brachial index greater than 0.15. RESULTS The mean ankle-brachial index improved from 0.48 +/- 0.19 to 0.71 +/- 0.23 (p = 0.001). Primary patency rates by Kaplan-Meier estimates at 1 month, 6 months, and 1 year were 88%, 47%, and 22%, respectively. Secondary patency rates were 94% at 1 month, 59% at 6 months, and 46% at 1 year. The median time to reaching an endpoint of restenosis or reocclusion was 6 months primarily and 9 months secondarily. Clinical improvement at the time of latest follow-up occurred in 56% of patients (mean, 13.8 months). Periprocedural complications occurred in 24.5% of patients with the first intervention. The only factor that favorably influenced outcome was improvement in clinical category after the procedure (p = 0.001). CONCLUSIONS There was a high incidence of restenosis and reocclusion with long-segment SFA disease that required stents to achieve initial success. Despite close surveillance and reintervention, anatomic patency at 1 year was poor. However, clinical benefit was maintained in the majority of patients. The outcome was similar in the claudication population compared with those who had limb-threatening ischemia. Percutaneous revascularization of long-segment SFA disease requiring stents should be reserved for patients with critical limb ischemia for which no reasonable surgical alternative exists.

Ultrasound-guided compression repair of postcatheterization pseudoaneurysms: Results of treatment in one hundred cases

PURPOSE The purpose of this report is to describe the indications, technique, and results for ultrasound-guided compression repair (UGCR) of postcatheterization pseudoaneurysms at a large medical center in which catheter-based diagnostic and interventional procedures are frequently used. METHODS We reviewed the initial series of 100 consecutive patients who underwent UGCR in our noninvasive vascular laboratory from May 1991 through August 1992. Nearly all (n = 95) of these pseudoaneurysms involved the common femoral artery or its major branches, and each was manually compressed with a 5 MHz linear transducer for 10-minute intervals until the pseudoaneurysm was completely occluded or the procedure was considered to be a failure. RESULTS UCGR was immediately successful in 94 patients, including 30 (86%) of 35 patients who were receiving anticoagulants and 64 (98%) of the 65 who were not (p = 0.019). The average compression time to achieve occlusion was 33 minutes (range 10 to 120 minutes), but was nearly twice as long (51 minutes) for pseudoaneurysms that had been present for more than 14 days. There were no related complications, but recurrent pseudoaneurysms occurred in six (20%) of 30 patients who continued to receive formal anticoagulation, compared with only four (6%) of 64 who did not (p = 0.074). Eight of the 10 recurrences were discovered within 24 hours after primary UGCR, but two others presented at 16 and 35 days, respectively. Eight recurrent lesions were corrected by repeat UGCR, whereas the remaining two required surgical repair. CONCLUSIONS UGCR provides a reliable alternative to surgical treatment for postcatheterization pseudoaneurysms. Adequate follow-up is important, however, especially in patients for whom continued anticoagulation is necessary.

Thrombolysis of peripheral arterial bypass grafts: Surgical thrombectomy compared with thrombolysis ☆ ☆☆: A preliminary report

Twenty-two patients were selected from a group of 33 patients who underwent recombinant human tissue-type plasminogen activator (rt-PA) thrombolysis for thrombosed infrainguinal bypass grafts of the lower extremity and were compared with 38 matched patients who had undergone surgical thrombectomy during the same period. The proportion of persons with diabetes mellitus, smokers, and types of bypass grafts was similar in both groups. More patients in the rt-PA-treated group had hypertension (p = 0.01). To evaluate the different lengths of follow-up, Kaplan-Meier survival analysis was used with a log-rank test to compare the proportion of persons with patent grafts in the two treatment groups. At 30 days, 86% of the rt-PA-treated grafts were still patent compared with 42% of the surgically treated grafts (p = 0.001). When risk factors on the Kaplan-Meier curves were compared, there was no statistical difference with regard to graft patency among the groups. According to simultaneous Cox regression analysis, no risk factor was significantly associated with graft patency. When amputation was evaluated between treatment groups simultaneously with other risk factors in a logistic regression analysis, smoking and age of the graft were marginally significant (p = 0.07), whereas all other factors were clearly not significant. In 91% of the rt-PA-treated patients, a secondary surgical procedure was required to maintain patency of the graft segment. Eighty-nine percent of the surgically treated patients required similar graft revisions. Two patients in the surgical group and one patient in the rt-PA-treated group had major complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrasound-guided compression closure of postcatheterization pseudoaneurysms during concurrent anticoagulation: A review of seventy-seven patients

PURPOSE Data from our institution and elsewhere have demonstrated that ultrasound-guided compression closure (UGCC) is an effective method of treating postcatheterization pseudoaneurysms. Whereas patients receiving anticoagulation do not have as high a success rate as those not receiving anticoagulants, there have been no large series evaluating the factors associated with success or failure in patients receiving anticoagulation. The purpose of this study is to determine whether uninterrupted anticoagulation interferes with successful UGCC of pseudoaneurysms and to identify factors associated with success or failure. METHODS From May 1991 to September 1994, 238 cases of attempted UGCC of pseudoaneurysms were performed in our vascular laboratory. Only patients who received uninterrupted heparin, warfarin, or both at the time of pseudoaneurysm compression were eligible for inclusion into the study. Seventy-seven patients were identified who met the study criteria. RESULTS Successful pseudoaneurysm compression was obtained in 56 (73%) patients, whereas 21 (27%) patients had a failed UGCC. In the successfully treated group, seven (12.5%) required between two to three compression attempts to induce sustained thrombosis. There was no statistical difference in age, sex, sheath size, days after procedure, location of pseudoaneurysm, or number of chambers in the pseudoaneurysm between those patients who had a successful repair and those who did not. If the pseudoaneurysm was less than 4 cm in diameter, 51 of 65 patients (78%) had a successful repair compared with 5 of 12 patients (42%) with a pseudoaneurysm of 4 cm or greater (p = 0.013). There was no statistical difference between success and failure in patients receiving warfarin alone (3.73 mean international normalized ratio, 72% success rate), heparin alone (mean activated partial thromboplastin time of 63 seconds, 92% success rate), or heparin and warfarin (mean activated partial thromboplastin time of 70 seconds, mean international normalized ratio of 4, success rate of 67%). No arterial or venous thrombosis occurred during pseudoaneurysm compression. CONCLUSION Successful UGCC of pseudoaneurysms occurred in a large percentage of patients receiving full-dose, uninterrupted anticoagulation. The only factor influencing success was the size of the pseudoaneurysm.

Local thrombolysis in the treatment of thrombosed arteries, bypass grafts, and arteriovenous fistulas

We reviewed the results, systemic effects, and complications associated with the selective infusion of low-dose streptokinase in 151 patients. Successful thrombus lysis was achieved in 78% of atherosclerotic thrombotic occlusions less than 30 days old, in 81% of post-procedural occlusions less than 14 days old, and in 87% of patients with thrombosed arteriovenous fistulas no more than 4 days old. During the first 12 hours of treatment 81% to 84% of patients had greater than 50% decrease in plasma fibrinogen levels and 100% showed the same decline after 24 hours of treatment. The thrombin time was prolonged to at least 1 1/2 times the control thrombin time in 33% to 42% of patients measured at 4 hours of therapy and in 93% to 97% of patients measured at 24 hours of treatment. Fifteen patients (9.9%) had major complications. Eleven of these had hemorrhagic complications, two had significant distal emboli, one had a thrombosed brachial artery, and one had a false aneurysm at the catheter entry site. We have found that selective low-dose streptokinase is effective in the treatment of acute and chronic thrombotic occlusions and is a useful adjuvant to vascular reconstruction or percutaneous transluminal angioplasty. Although the local infusion dose is substantially lower than the usual systemic dose, a systemic lytic effect was seen in all patients. Hemorrhagic complications occurred despite customary precautions.

The incidence of deep venous thrombosis in patients undergoing abdominal aortic aneurysm resection

PURPOSE Fifty consecutive patients undergoing abdominal aortic aneurysm resection were studied prospectively for the presence of deep venous thrombosis (DVT) after surgery. METHODS Bilateral venography was performed 5 days after surgery in all patients. There were 42 men and 8 women, with a mean age of 70 years (range 60 to 83 years). No patients received DVT prophylaxis before surgery. RESULTS Nine (18%) of 50 patients had a venogram positive for acute DVT. Nine (21%) of 42 men and none of eight women had DVT. Six patients had DVT in the left leg and three patients in the right leg. No patients had symptoms to suggest DVT. Seven (78%) of the nine patients with DVT had thrombi in the calf veins and two patients (22%) had thrombi in the more proximal venous segments, representing 14% and 4% of the entire series, respectively. No clinically evident pulmonary emboli were observed. CONCLUSIONS Eighteen percent of 50 consecutive patients undergoing abdominal aortic aneurysm resection had DVT. Because of this high incidence, a study should be undertaken to determine whether DVT prophylaxis can lower the incidence of DVT after abdominal aortic aneurysm resection.

Coronary artery disease in patients with aortic aneurysm: a classification of 302 coronary angiograms and results of surgical management

In an attempt to reduce early and late mortality caused by myocardial infarction in patients with aortic aneurysms, coronary arteriography and, when indicated, myocardial revascularization were performed prior to elective aortic reconstruction in 302 patients with infrarenal (289) or thoracoabdominal (13) aortic aneurysms. Severe correctable coronary artery disease (CAD) was identified in 31% of the entire series, whereas severe inoperable CAD was seen in another 5%. Severe, correctable CAD was documented in 42% of patients suspected to have CAD by standard clinical criteria and in 19% of those in whom CAD was not suspected. The overall mortality for 89 cardiac and 227 infrarenal aortic surgical procedures was 4,4%. Fatal complications after infrarenal aneurysm resection occurred in only one (1.6%) of 61 patients who had had preliminary myocardial revascularization.

Peripheral artery and bypass graft thrombolysis with recombinant human tissue-type plasminogen activator

Recombinant tissue-type plasminogen activator (t-PA) is a DNA-synthesized thrombolytic agent recently approved for clinical trials. We present the results of t-PA infusions in 18 patients with thrombosed peripheral arteries (12 patients) and peripheral bypass grafts (six patients). The duration of occlusion ranged from 1 to 21 days (mean, 6.8 days). Infusions of t-PA were done by way of an intra-arterial approach at a dose of 0.1 mg/kg/hr. All patients demonstrated thrombus lysis angiographically. Fifteen of 18 (83%) had clinical as well as angiographic improvement. Secondary procedures to maintain patency of the arterial segment were required in seven patients. No complications occurred that were related to the t-PA infusion. No significant prolongation of the prothrombin, thrombin, or activated partial thromboplastin times occurred. At the end of t-PA infusion, the mean circulating fibrinogen level was 59% of the starting value. The therapeutic use of t-PA is still in its preliminary stages and the efficacy and safety of this promising agent need to be further established. From our early experience with t-PA, it appears to be safe as well as effective.

Late results of Coronary Bypass in Patients Presenting with Lower Extremity Ischemia: the Cleveland Clinic Study

Cardiac catheterization was performed in a prospective series of 1000 patients under consideration for elective peripheral vascular reconstruction from 1978-1982. Of these, 381 (mean age 62) presented primarily because of lower extremity ischemia. Severe, surgically correctable coronary artery disease (CAD) was documented in 79 (21%) of the leg group, and 68 (18%) received myocardial revascularization, with three fatal complications (4.4%). In this subset, 39 patients have had uneventful aortoiliac, femoropopliteal or distal extremity procedures, compared to an operative mortality of 23% for 13 others with uncorrected or inoperable CAD (p = 0.015). A total of 286 patients have undergone 407 peripheral vascular operations with eight early deaths (2.8%). An additional 114 patients (30%) died during the late follow-up interval, including 48 (13%) with cardiac events. Both the cumulative 5-year survival (72%) and cardiac mortality (16%) after coronary bypass are superior to comparable figures (21% and 56%, respectively) among 36 other patients with severe, uncorrected or inoperable CAD (p = 0.0001). Five-year survival appears to be improved by myocardial revascularization in men (p = 0.0027), hypertensives (p = 0.0001), nondiabetics (p = 0.0002) and those over 60 years of age (p = 0.0072).