Pulsatile wall motion and blood pressure in aneurysms with open and thrombosed endoleaks--comparison of a wall track system and M-mode ultrasound scanning: an in vitro and animal study.

ABSTRACT

OBJECTIVE: Pulsatile wall motion has been suggested as a means by which to evaluate abdominal aortic aneurysms after exclusion from the circulation to determine whether the treatment has been effective. The objective of this study was to investigate the relations between pulsatile wall motion and both the mean and pulse pressures within the aneurysmal sac for both patent and thrombosed endoleaks. Furthermore, we compared the measurements of pulsatile wall motion by means of M-mode ultrasound scanning and a wall track system to determine the most reliable technique. METHODS: First, interobserver and intraobserver variability of M-mode ultrasound scan measurements was determined at different pressure levels in a cow iliac artery placed in an in vitro circulation. M-mode ultrasound scanning and a wall track system were compared in the same model. Second, in an animal experiment, an aneurysm and endoleak model with both patent and thrombosed endoleaks was created. Systemic and aneurysmal mean and pulse pressures were recorded synchronically with pulsatile wall motion by means of M-mode ultrasound scanning and a wall track system. RESULTS: The intraobserver and interobserver variability values for M-mode ultrasound scan measurement in vitro were 0.11 mm (SD = 0.10 mm) and 0.15 mm (SD = 0.13 mm), respectively. In the animal study, a significant difference existed with respect to the level of pulse pressure within the aneurysmal sac between the group with pulsatile wall motion and the group without such motion (P <.0001). The presence of pulsatile wall motion was not correlated with the level of aneurysmal mean pressure. The level of pulsatile wall motion determined by means of M-mode ultrasound scanning correlated well with the level determined by means of the wall track system (r = 0. 74; P =.01). For the level of pulsatile wall motion determined by means of M-mode ultrasound scanning, a significant difference between patent and thrombosed endoleaks existed (P =.04). For detecting endoleaks, the sensitivity and specificity of pulsatile wall motion as determined by means of the wall track system were 52% and 100%, respectively, and the sensitivity and specificity of pulsatile wall motion as determined by means of M-mode ultrasound scanning were 64% and 67%, respectively. For the detection of pulse pressure in the aneurysmal sac, the sensitivity and specificity of pulsatile wall motion as determined by means of the wall track system were 76% and 100%, respectively, and the sensitivity and specificity of pulsatile wall motion as determined by means of M-mode ultrasound scanning were 90% and 71%, respectively. CONCLUSIONS: We found that pulsatile wall motion is correlated with aneurysmal pulse pressure but not with the mean level of pressure inside the aneurysm. Although measurements of pulsatile wall motion are of great theoretic value when groups of patients who have undergone endovascular aneurysm repair are being compared, this method appears to be unreliable in a clinical setting with respect to determining whether the aneurysmal sac is still pressurized in individual patients.