Ultrasound echo-enhancers in the evaluation of endovascular prostheses

Whereas conventional vascular surgical procedures are routinely monitored by ultrasound imaging, endovascular prostheses are usually monitored by radiographical imaging techniques. The aim of this study was to determine the safety, patient acceptance and role of ultrasound echo-enhancers (SHU 508 A) in the evaluation of endovascular devices. Nine patients were studied: six had stents (four in the internal carotid artery and two in the renal artery) and three had endoluminal prostheses (one in the abdominal aorta, one in the subclavian and one in the iliac artery). Endovascular patency and correct placement were studied with contrast angiography and ultrasound examination with and without contrast enhancement. Patients underwent angiography at the end of the endovascular procedure, and ultrasound examinations on the first postoperative day. Ultrasound contrast media (SHU 508 A) was injected through an antecubital vein at a rate of 1 ml/s. A total of 13 injections were given in nine patients. Ultrasonograms were obtained with 7.5 and 3.5 MHz transducers (Acuson 128 XP) and recorded on videotape for off-line visual inspection. Baseline and echo-enhanced sequences were assessed by two independent observers. None of the patients reported side-effects during or after the injection of the ultrasound echo-enhancer. Postoperative angiography showed endovascular patency and correct placement in all patients. The baseline ultrasound examination confirmed endoprosthesis patency in seven of nine patients: none revealed endoprosthesis malplacement. Contrast-enhanced ultrasound examination confirmed endoprosthesis patency. In two cases, the echo-contrast examination revealed persisting flow within the aneurysmal sac: in another patient it showed the incomplete adhesion of the distal portion of the endoprosthesis to the arterial wall. The preliminary findings suggest that ultrasound echo-enhancers are safe to use and induce no side-effects. Echo-enhanced sequences often provide additional information on the technical success of endovascular procedures. They promise to be useful in follow-up studies for assessing the functioning of endoprostheses.