Computed tomography assessment of abdominal aortic aneurysm morphology after endograft exclusion

AbstractObjectives: Assessment of the long-term function of endografts to exclude abdominal aortic aneurysm (AAA) includes determination of aneurysm dimensions and morphologic changes that occur after implantation. This study reports the dimensional analysis of patients treated with AneuRx bifurcated endoprostheses with postintervention, 1-year (n = 51), 2-year (n = 28), and 3-year (n = 10) postimplantation contrast computed tomography data. Methods: Maximal diameter (D) and cross-sectional area (CSA) of the AAA were measured from axial computed tomography images. Total volume, AAA thrombus volume (AAA volume minus the volume of the device and luminal blood flow), diameter of the aorta at the level of the renal arteries and within the device, distance from the renal arteries to the device, length of the device limbs, and the angle of the proximal neck were also determined at the same follow-up intervals after deployment with computed tomography angiograms reconstructed in an interactive environment. Results: Fifty-one of 98 consecutively treated patients with the AneuRx bifurcated prosthesis (29 “stiff” and 22 “flexible” body devices) had complete data from the postprocedure and follow-up computed tomography studies available for analysis. Max D, CSA, total volume of the AAA, and AAA thrombus volume decreased sequentially from year to year compared with the postimplantation values. D and CSA decreased or were unchanged in all except four patients, two who had unrestricted enlargement of the aneurysm with eventual rupture and one who had surgical conversion for continued expansion despite four diagnostic angiograms and attempted embolizations. Total volume of the AAA increased in 11 of 51 patients at 1 year, eight of whom had endoleaks at some interval during the follow-up. Thrombus volume increased more than 5% in four of these patients, including the two with eventual rupture and the one conversion. Patients with endoleaks who had spontaneous thrombosis or were successfully treated either remained at the same volume or had decreased volume on subsequent examinations. D at the renal arteries increased an average of 0.9 mm during the first year, with a concomitant increase of 2.8 mm within the proximal end of the device related to the self-expanding nature of the Nitinol suprastructure. Subsequent enlargement of the proximal neck continued at a slow rate in some cases but never exceeded the diameter of the endoluminal device. The distance from the renal arteries to the device increased by an average of 3 mm over the first year, with the greatest increases occurring in patients with a “stiff” body device and those with rapid regression (>10% total volume) in 1 year. As regression of the AAA occurred, the angle of the proximal neck varied from -5° to +25° from the original alignment. Limb length varied from -8 mm to +10 mm, with no consistent pattern for the change, that is, ipsilateral or contralateral limb. Conclusion: Significant variation in the quantitation of aneurysm size occurs depending on the technique of computed tomography assessment used. In most patients diameter assessment is adequate, although volumetric analysis appears to be very helpful in certain patients who do not show aneurysm regression, or in whom the diameter increases or where endoleaks persist. Three-dimensional reconstruction and volumetric analysis are also useful to assess the mechanism by which the endovascular device accommodates to morphology changes and to determine criteria for reintervention. (J Vasc Surg 2001;33:S1-10.

Clinical results of argon laser tissue fusion

Tissue fusion by laser energy is an intriguing arxi very promising new application for laser technology. In coniparison to using high laser energy to ablate tissue as in the aricplasty application, laser tissue fusion is possible in any soft tissue by deliverir appropriate lc levels of energy to the cppose tissue surfaces. This technology is particularly appealing for vascular applications in inakir sutureless blood vessel anastornosis and for securir the endpOints of erxarterect:amies ani dissection planes. Although there have been limitel evaluations of this technology the preliminary experimental ar1 clinical data is very promisir for continu development arid application

Potential of intraluminal ultrasound for angioplasty guidance

The manifestation of atherosclerotic lesions in arteries can vary from asymptomatic thickening in the vessel wall to complete occlusion. Experimental studies on non-human primates and on human subjects indicate that atherosclerotic lesions may progress without a reduction in luminal diameter because of dilatation of the arterial wall . Although angiography has been considered the "gold standard" for visualization of the arterial tree ar1 detection of luminal narrowing, it does not demonstrate arterial wall thickening or morphology. Moreover, the measurement of luminal diameter of the sane lesion can vary considerably depending on the plane of projection of the x-ray beam. This is attributed to the eccentric nature of the residual lumen in an atherosclerotic vessel . Extraluminal B-mode real time imaging has the feasibility of demonstrating arterial lumen and arterial wall thickness. However, it is still in some instances limited by inadequate resolution and image quality. Intraluminal ultrasound using a phased array or rotating transducer gives better definition of the vessel wall and luminal diameter as it is not limited by the tissue interposed between the vessel and the probe in transcutaneous devices. This paper demonstrates further experience with intravascular ultrasound as a diagnostic tool using B-mode real time imaging

Continuous Piezoelectric Pulse-Sensor Monitoring of Peripheral Vascular Reconstructions

Postoperative assessment of vascular surgical reconstructive procedures is most commonly performed by means of Doppler flowmetry or manual pulse palpation. Because these techniques are intermittent and can be subjective, the authors have investigated the application of a piezoelectric pulse sensor in monitoring distal pulses continuously in patients undergoing limb revascularization. By placing a piezoelectric sensor on the skin overlying an artery, systolic displacement of the underlying vessel wall and tissue is converted into a graphically displayed real-time waveform. Hardcopies of the waveforms (n = 90) were obtained at hourly postoperative intervals from a total of 10 patients undergoing vascular surgery for occlusive disease. In all cases, continuous monitoring confirmed ongoing patency of the reconstructions, despite impalpable distal pulses in 60% of the patients. The amplitudes of the waveforms increased (mean = 18%, range = 6% to 33%) during the first eight postoperative hours. Because of the small size and sensitivity of the sensor, this technique was especially useful in patients with foot lesions requiring occlusive dressings, or where sequential stenoses prevented accurate assessment of postoperative circulation by manual palpation or Doppler examination. The authors conclude that continuous postoperative piezoelectric pulse monitoring allows accurate, continuous assessment of limb revascularization and alleviates the subjective, time-consuming observations by physicians and ancillary personnel

In-vivo intravascular ultrasound in human ileo-femoral vessels

This study evaluates the ability of intravascular ultrasound (IUS) to image normal and mildly diseased human ileo-femoral vessels during angioplasty or vascular bypass procedures. Five Fr. and 8Fr. rotating A scan IUS catheters were used to obtain 43 images in 4 superficial femoral arteries, and 5 iliac arteries in 8 vascular surgery patients. Luminal cross sectional (LCS) areas measured by IUS were compared to LCS areas calculated by uniplanar angiography (ANGIO) at the same location in the vessel. The correlation between the areas (IUS vs ANGIO) for all images was significant (n = 43, r = 0.90, P<0.05). Mean LCS area calculated from ANGIO (33.7 +/- 21 mm ) was greater than LCS area measured by IUS (30.6 +/- 19.5 mm ) with n = 43; P = 0.02. In addition to providing accurate luminal determinations, IUS images displayed transmural morphology, the location of the atherosclerotic lesions and the thickness of the vessel wall. We conclude that IUS imaging provides accurate, novel information regarding human vessel wall anatomy and luminal dimensions. This technology may play a significant role in future diagnostic and interventional therapies

Intravascular Ultrasonography

Intravascular ultrasonography is developing rapidly as a method for defining the transmural anatomy of vascular structures, with diagnostic and therapeutic applications. The ultrasound technology not only has unique diagnostic capabilities by defining the distribution and character of lesions, but also provides accurate control information regarding efficacy of angioplasty methods. An exciting recent development is the three-dimensional reconstruction of two-dimensional images which permits global examination of luminal and transmural vessel morphology. This technology may enable improved guidance of intraluminal devices to enhance lesion removal without damaging adjacent normal wall structure and appropriate device selection by differentiating specific plaque characteristics