Sac Pressure Measurements Research Articles

Intra-aneurysm sac pressure measurement using a thin pressure wire during endovascular aneurysm repair.

An endoleak is a typical complication of endovascular aneurysm repair (EVAR). It is characterized by persistent blood flow between a stent graft and the aneurysm sac. Usually, it can be visualized during primary EVAR, but in many cases, this remains impossible. Therefore, other methods of endoleak assessment are urgently needed. The measurement of aneurysm sac pressure (ASP) seems to be a promising direction of research in this area. We aimed to evaluate the safety and efficacy of a new method for invasive pressure measurement inside the abdominal aortic aneurysm (AAA) during EVAR. We also assessed a correlation between pressure values and early angiographic occurrence of an endoleak after the procedure. A total of 20 patients with AAA were included in this experimental prospective study. During EVAR, systolic, diastolic and mean pressure values were recorded both for ASP and aortic pressure (AP) before procedure, after stent graft opening and after final stent graft ballooning. The measurements were successfully obtained in all participants without any complications. There were no significant differences between all ASP and AP before procedure. After the procedure, blood pressure significantly decreased in the aneurysm sac but not in the aorta. Systolic ASP was significantly lower than systolic AP both after stent graft opening (80.4 ±20.9 mm Hg compared to 110.7 ±21.6 mm Hg, p < 0.01) and after its balloon post-dilatation (65.6 ±26.1 mm Hg compared to 107.4 ±22.1 mm Hg, p < 0.001). Diastolic ASP decreased significantly in comparison to diastolic AP only after stent graft ballooning (48.0 ±14.6 mm Hg compared to 56.4 ±13.6 mm Hg, p < 0.05). Our study confirmed that the novel method for the measurement of ASP during EVAR, using a thin pressure wire, is feasible and safe.

Diagnostic imaging methods applied in long-term surveillance after EVAR. Will computed tomography angiography be replaced by other methods?

Endovascular implantation of a stent graft in the abdominal aorta (endovascular aneurysm repair – EVAR) is a widely accepted alternative to open surgery in treatment of abdominal aortic aneurysms. Although EVAR is connected with a significant reduction in the risk of peri- and post-operative complications, it does not eliminate them totally. Long-term surveillance of post-EVAR patients is aimed at early detection of and fast reaction to a group of complications called endovascular leaks. Currently, the gold standard in leak diagnostics is computed tomography angiography (CTA). The other methods are ultrasonography, magnetic resonance (MR) angiography, intra-aneurysm sac pressure measurement, X-ray, and digital subtraction angiography (DSA). Despite many analyses based on long-term research, emphasising the high value and competitiveness of less invasive tests such as US or X-ray compared to CTA, it is still difficult for them to win the trust and acceptance of clinicians. The persisting view is that computed tomography is the test that finally resolves any inaccuracies. Consequently, a patient with a number of concurrent diseases is subject to absurdly high radiation exposure and effects of a radiocontrast agent within a short time. It is therefore logical to acknowledge that the EVAR-related risk is catching up with the open surgery risk, while the endovascular procedure is much more costly. Nevertheless, the status of CTA as the gold standard ultimately seems to be unthreatened. This paper presents a description of the diagnostic imaging tests that make it possible to detect any vascular leaks and to develop strategies for therapeutic processes.

Results of transcaval embolization for sac expansion from type II endoleaks after endovascular aneurysm repair

Management of type II endoleaks after endovascular aneurysm repair can be problematic. This study reports our experience with a relatively novel strategy to treat this complication, transcaval coil embolization (TCCE) of the aneurysm sac. We reviewed 29 consecutive patients undergoing TCCE from 2010 to 2013. Demographics, operative details, and outcomes were assessed. Since 2006, 29 TCCEs have been performed at our institution in 26 patients for sac expansion from type II endoleaks. Patients were male (83%) and former or current smokers (88%), with an average age of 78 ± 7.1 years. TCCE was performed a mean of 4.2 ± 4 years after initial endovascular aneurysm repair. Endoleaks resulted in a mean sac growth of 1.2 ± 1 cm in diameter and 37% ± 32% by volume. Forty-six percent had prior procedures (5 translumbar, 3 transarterial, 3 transcaval, 1 aortic cuff, and 1 iliac limb extension). Two patients had no flow identified in the aneurysm sac after puncture was successful, and one was found to have a hygroma rather than arterial flow. An additional two patients had ultimate embolization from sac access between the endograft iliac limb and arterial wall after transcaval puncture failed, for a 90% procedural success (83% for transcaval technical success). Mean fluoroscopy time was 27 ± 13 minutes with 29 ± 21 mL of contrast material used and a median of 10 coils per case. Additional adjuncts included thrombin injection (17%), intravascular ultrasound (14%), sac pressure measurements (28%), and on-table integrated computed tomography (17%). Median length of stay was 1 day (range, 0-5 days). There were no procedural adverse events. Reintervention was required in five cases (three repeated TCCEs, two graft relinings). One-year freedom from reintervention was 95%. At a mean 16.5 months of follow-up, 70% experienced no further endoleak and had stable or decreasing sac diameters. There have been no ruptures during follow-up. In this series, TCCE for treatment of aneurysm enlargement due to type II endoleaks was safe and relatively effective despite prior failed interventions in nearly half of the cases. TCCE is a useful alternative in cases in which the anatomy makes other approaches difficult or impossible.

Utility of Noninvasive Aneurysm Sac Pressure Measurement During and After Endovascular Abdominal Aortic Aneurysm Repair

Purpose The utility of noninvasive pressure sensors in the intra- and postoperative settings is not entirely clear. The objectives of this study were to determine intraoperative pressure criteria in the setting of technically successful endovascular aneurysm repair (EVAR) and to evaluate pressure changes during follow-up. Materials and Methods A total of 55 patients (42 men) underwent attempted noninvasive sensor monitor placement within the aneurysm sac. Pressures were recorded before and after EVAR. Recordings were repeated at 1 day, 2 weeks, 3 months, and 1 year. Clinical data, pressure recordings, and computed tomography were retrospectively assessed. Results Noninvasive pressure sensors were successfully placed in 51 patients. The mean intraoperative decreases in pulse pressure (PP) and PP ratio (PPR) in the setting of technical success were statistically different versus (i) baseline recordings and (ii) pressures obtained in the setting of type I endoleak (74.2% vs 41.5% and 76.2% vs 46.5%, respectively). At follow-up, there were continued decreases in PP and PPR, with a decrease in mean pressure resuming at the 3-month interval. Four of 14 type II endoleaks were treated because of relatively increased pressure with stable or increased aneurysm size. Conclusions An intraoperative decrease in PP and PPR in the range of approximately 70% after EVAR was associated with successful aneurysm exclusion. Noninvasive sensors can provide useful ancillary information in confirming technical success intraoperatively. During follow-up, an increase in sensor pressure recordings may be suggestive of clinically significant endoleak; however, further research is necessary.

Part One: For the Motion. Serial Sac Pressure Measurements can Determine Which Type II Endoleaks can be Treated

Part One: For the Motion. Serial Sac Pressure Measurements can Determine Which Type II Endoleaks can be Treated

Intraoperative Sac Pressure Measurement During Endovascular Abdominal Aortic Aneurysm Repair

Intraoperative sac pressure was measured during endovascular abdominal aortic aneurysm repair (EVAR) to evaluate the clinical significance of sac pressure measurement. A microcatheter was placed in an aneurysm sac from the contralateral femoral artery, and sac pressure was measured during EVAR procedures in 47 patients. Aortic blood pressure was measured as a control by a catheter from the left brachial artery. The systolic sac pressure index (SPI) was 0.87 +/- 0.10 after main-body deployment, 0.63 +/- 0.12 after leg deployment (P < 0.01), and 0.56 +/- 0.12 after completion of the procedure (P < 0.01). Pulse pressure was 55 +/- 21 mmHg, 23 +/- 15 mmHg (P < 0.01), and 16 +/- 12 mmHg (P < 0.01), respectively. SPI showed no significant differences between the Zenith and Excluder stent grafts (0.56 +/- 0.13 vs. 0.54 +/- 0.10, NS). Type I endoleak was found in seven patients (15%), and the SPI decreased from 0.62 +/- 0.10 to 0.55 +/- 0.10 (P = 0.10) after fixing procedures. Type II endoleak was found in 12 patients (26%) by completion angiography. The SPI showed no difference between type II endoleak positive and negative (0.58 +/- 0.12 vs. 0.55 +/- 0.12, NS). There were no significant differences between the final SPI of abdominal aortic aneurysms in which the diameter decreased in the follow-up and that of abdominal aortic aneurysms in which the diameter did not change (0.53 +/- 0.12 vs. 0.57 +/- 0.12, NS). Sac pressure measurement was useful for instant hemodynamic evaluation of the EVAR procedure, especially in type I endoleaks. However, on the basis of this small study, the SPI cannot be used to reliably predict sac growth or regression.

Abstract No. 214: Usefulness of sac pressure measurements during and after endovascular repair of abdominal aortic aneurysm (EVAR)

Abstract No. 214: Usefulness of sac pressure measurements during and after endovascular repair of abdominal aortic aneurysm (EVAR)

Intra-aneurysm Sac Pressure in Patients with Unchanged AAA Diameter after EVAR

Objective: To study intra-aneurysm sac pressure and subsequent abdominal aortic aneurysm (AAA) diameter changes in patients without endoleaks that remain unchanged in AAA diameter more than 1 year after endovascular aneurysm repair (EVAR). Methods: A total of 23 patients underwent direct intra-aneurysm sac pressure (DISP) measurements 16 months (IQR: 14–35 months) after EVAR. Tip-pressure sensors were used through translumbar AAA puncture. Mean pressure index (MPI) was calculated as the percentage of mean intra-aneurysm pressure relative to the simultaneous mean intra-aortic pressure. Aneurysm expansion or shrinkage was assumed whenever the diameter change was ≥ 5 mm. Values are presented as median and interquartile range. Results: In 18 patients, no fluid was obtained upon AAA puncture (group A). In five patients, fluid was obtained (group B). In group A, follow-up continued for 29 months (IQR: 15–35 months) after DISP; five AAAs shrank, 10 remained unchanged and three expanded (MPIs of 26% (IQR: 18–42%), 28% (IQR: 20–48%) and 63% (IQR: 47–83%) and intra-sac pulse pressures of 3 mmHg (IQR: 0–5 mmHg), 4 mmHg (IQR: 2–8 mm Hg) and 12 mmHg (IQR: 6–20 mmHg), respectively, for the three subgroups). MPI and intra-sac pulse pressures were higher in AAAs that subsequently expanded (P = 0.073 and 0.017, respectively). MPI and pulse pressure correlated with total diameter change (r = 0.49, P = 0.039 and r = 0.39, P = 0.109, respectively). Pulse pressure had a greater influence than MPI on diameter change (R2 = 0.346, P = 0.041, beta standardised coefficient of 0.121 for MPI and 0.502 for pulse pressure). Similar results with stronger, and significant correlation to pulse pressure were obtained when relative diameter changes were used (r = 0.55, P = 0.017). In group B, MPI and AAA pulse pressure were 32% (IQR: 18–37%) and 1 mmHg (IQR: 0–6 mmHg), respectively. After 36 months (IQR: 21–38 months), one AAA shrank, three continued unchanged while one expanded. Conclusions: AAAs without endoleak and unchanged diameter more than 1 year after EVAR will often continue unchanged. Expansion can eventually occur in the absence of intra-sac fluid accumulation and is associated with higher and more pulsatile intra-sac pressure. However, in patients with intra-sac fluid, expansion can occur with low intra-sac pressures.

Intra-aneurysm Sac Pressure in Patients with Unchanged AAA Diameter after EVAR

To study intra-aneurysm sac pressure and subsequent abdominal aortic aneurysm (AAA) diameter changes in patients without endoleaks that remain unchanged in AAA diameter more than 1 year after endovascular aneurysm repair (EVAR). A total of 23 patients underwent direct intra-aneurysm sac pressure (DISP) measurements 16 months (IQR: 14-35 months) after EVAR. Tip-pressure sensors were used through translumbar AAA puncture. Mean pressure index (MPI) was calculated as the percentage of mean intra-aneurysm pressure relative to the simultaneous mean intra-aortic pressure. Aneurysm expansion or shrinkage was assumed whenever the diameter change was > or =5mm. Values are presented as median and interquartile range. In 18 patients, no fluid was obtained upon AAA puncture (group A). In five patients, fluid was obtained (group B). In group A, follow-up continued for 29 months (IQR: 15-35 months) after DISP; five AAAs shrank, 10 remained unchanged and three expanded (MPIs of 26% (IQR: 18-42%), 28% (IQR: 20-48%) and 63% (IQR: 47-83%) and intra-sac pulse pressures of 3 mmHg (IQR: 0-5 mmHg), 4 mmHg (IQR: 2-8mm Hg) and 12 mmHg (IQR: 6-20 mmHg), respectively, for the three subgroups). MPI and intra-sac pulse pressures were higher in AAAs that subsequently expanded (P=0.073 and 0.017, respectively). MPI and pulse pressure correlated with total diameter change (r=0.49, P=0.039 and r =0.39, P=0.109, respectively). Pulse pressure had a greater influence than MPI on diameter change (R(2)=0.346, P=0.041, beta standardised coefficient of 0.121 for MPI and 0.502 for pulse pressure). Similar results with stronger, and significant correlation to pulse pressure were obtained when relative diameter changes were used (r=0.55, P=0.017). In group B, MPI and AAA pulse pressure were 32% (IQR: 18-37%) and 1 mmHg (IQR: 0-6 mmHg), respectively. After 36 months (IQR: 21-38 months), one AAA shrank, three continued unchanged while one expanded. AAAs without endoleak and unchanged diameter more than 1 year after EVAR will often continue unchanged. Expansion can eventually occur in the absence of intra-sac fluid accumulation and is associated with higher and more pulsatile intra-sac pressure. However, in patients with intra-sac fluid, expansion can occur with low intra-sac pressures.

Aortic aneurysm sac pressure measurements after endovascular repair using an implantable remote sensor: initial experience and short-term follow-up

The purpose of this single-center study was to report our initial experience with an implantable remote pressure sensor for aneurysm sac pressure measurement in patients post-endovascular aneurysm repair (EVAR) including short-term follow-up. A pressure sensor (EndoSure, Atlanta, GA) was implanted in 12 patients treated with different commercially available aortic endografts for EVAR. Pressure was read pre- and post-EVAR in the operating room. One-month follow-up (30 days+/-6 days) was performed including sac pressure readings and IV contrast CT scans. Variables were compared using the paired Student's t test. An intraprocedure type-I endoleak and a type-III endoleak were successfully treated resulting in decreasing sac pressures. In all patients, post-EVAR systolic sac pressure decreased by an average of 33% (P <or= 0.005) compared to pre-EVAR measurements. One-month follow-up demonstrated a 47% decrease in systolic sac pressure (P <or= 0.05). On follow-up CT scans, the average maximum aneurysm diameter pre-EVAR was 6.3+/-1.6 cm and post-EVAR 6.0+/-1.7 cm (P<or=0.05). The diameter of the aneurysm sac was larger only in one patient with a type-III endoleak. Remote sac pressure measurement may provide important information in addition to imaging and may help to reduce the number of follow-up CT scans.

Aneurysm Sac Pressure Measurement with Minimally Invasive Implantable Pressure Sensors: An Alternative to Current Surveillance Regimes after EVAR?

Current protocols for surveillance after endovascular repair (EVAR) of abdominal aortic aneurysms are mostly based on costly and time-consuming imaging procedures and aim to detect adverse events such as graft migration, endoleaks or aneurysm sac enlargement. These imaging procedures are either associated with radiation exposure to the patients or may be harmful to the patient due to the use of iodine- or gadolinium-containing contrast agents. Furthermore the advantages of EVAR in the short term might be negated by the necessity for endograft surveillance over years. Thus, alternative modalities for follow-up are being investigated. One of these technologies provides pressure information directly from the aneurysm sac. This noninvasive, telemetric pressure sensing was tested in vitro as well as in first clinical trials and was able to identify successful aneurysm exclusion after EVAR. The telemetric pressure sensors showed a promising efficacy and accuracy in detecting type I and type III endoleaks and will help to clarify the clinical relevance of type II endoleaks. This article provides an overview of the in vitro sensors investigated as well as the first clinical trials and the sensors' potential to change the current endograft surveillance regimes.

Endoleaks after endovascular aneurysm repair lead to nonuniform intra-aneurysm sac pressure

This was a study of intra-aneurysm sac pressures in patients who presented with endoleaks after endovascular repair (EVAR) of abdominal aortic aneurysms (AAA). Twenty-five patients (18 men, 7 women) with endoleaks, age (IQR 68 to 80), underwent 31 direct intra-aneurysm sac pressure measurements, DISP at 16 months after EVAR (IQR, 14 to 26 months). Diameter of AAA was 59 mm (IQR, 52 to 67 mm). Six patients underwent DISP twice. Tip-pressure sensors were used through direct translumbar puncture of the AAA except in three patients (transabdominal puncture in 2; endoluminal in 1). Mean pressure index (MPI) was calculated between simultaneously registered intra-aneurysm sac and systemic pressures. Values presented are medians with interquartile range (IQR). Type I endoleaks (n = 1) showed MPI of 93% in the nidus and 62% in the thrombus. Type II endoleaks were associated with lower MPIs in the thrombus (35%; IQR 24% to 38%) when AAAs shrank (n = 4) compared with when the AAAs remained unchanged (n = 11; MPI, 78%; IQR, 47% to 85%) or expanded (n = 6; MPI, 74%; IQR, 58% to 87%; P = .019). The nidus of type II endoleaks (MPI, 79%; IQR, 70% to 90%) had higher pressure than the thrombus (45%, IQR, 34% to 85%; P = .047; n = 7). Successful embolization of type II endoleaks led to AAA shrinkage (n = 3; MPI reduction, 13% to 31%) or diameter stability (n = 3; unchanged MPIs, 37% to 44%). Type III endoleaks (n = 3) had MPIs in the thrombus of 33% to 70%. Endoleaks after EVAR pressurize the AAA sac nonuniformly, with higher, near-systemic, pressure in the endoleak nidus compared with the thrombus. Nevertheless, type II endoleaks in shrinking AAAs have lower intra-sac pressure than expanding or stable aneurysms, and successful endoleak embolization reduces pressure.

Abdominal aortic aneurysm sac shrinkage after endovascular aneurysm repair: Correlation with chronic sac pressure measurement

Abdominal aortic aneurysm sac shrinkage after endovascular aneurysm repair: Correlation with chronic sac pressure measurement

Invited commentary

After endovascular repair of an aortic aneurysm, the infrarenal aorta continues to demonstrate characteristic changes during follow-up. Even in the successfully excluded aorta, there remains a remodeling process reflected in changes in aortic neck, aneurysm, and iliac artery geometry. With aneurysm sac pressurization these changes are exacerbated and unpredictable, reinforcing the need for long-term surveillance. Until fairly recently, many centers have used static computed tomography (CT) images as their surveillance modality of this dynamic remodeling. Although quite capable of identifying significant endograft migration, contrast-enhanced CT scans are less than perfect in identifying the source of some endoleaks, predicting their physiologic ramifications, and in planning endoleak directed therapies. In the present study, the Baylor group is to be commended for further refining a contrast-enhanced ultrasound protocol for endograft follow-up. They used a continuous infusion technique of an albumin and microsphere suspension-based agent previously used with contrast echocardiography. It proved more accurate than CT imaging in the identification and classification of endoleaks and allowed for longer periods of monitoring compared with ultrasound scans using boluses of contrast. The findings of this 20-patient study certainly suggest further examination of this technique is warranted. This may also prove to be a more cost-effective method of surveillance. Although static (CT) and dynamic (ultrasound) imaging modalities offer extensive detail about endograft integrity, aneurysm geometry, and endoleak identification and classification, they are incapable of predicting the ramifications of these changes. This requires a measure of aneurysm pressurization, of which aneurysm diameter, volume, and endoleak identification are but a surrogate. A noninvasive method of sac pressure measurement has recently been developed that offers the possibility of determining which aneurysms required reintervention based on physiologic parameters.1Ellozy S.H. Carroccio A. Lookstein R.A. Minor M.E. Sheahan C.M. Juta J. et al.First experience in human beings with a permanently implantable intrasac pressure transducer for monitoring endovascular repair of abdominal aortic aneurysms.J Vasc Surg. 2004; 40: 405-412Abstract Full Text Full Text PDF PubMed Scopus (78) Google Scholar As the authors suggest, the perfect surveillance tool after endovascular repair undoubtedly involves an algorithm rather than a single imaging modality. This includes static imaging techniques (plain radiographs, CT, magnetic resonance) to monitor endograft integrity and aneurysm remodeling, dynamic imaging (ultrasound) to accurately identify and classify endoleaks, and physiologic monitoring (intrasac pressure transducer) to determine the need for reintervention. As this surveillance algorithm is elucidated further, it is likely that follow-up regimens will become patient specific, as all aneurysms will not require all surveillance modalities. This continues to be an important and evolving area of endovascular surgery that all vascular surgeons are encouraged to follow closely.

Abdominal aortic aneurysm sac shrinkage after endovascular aneurysm repair: Correlation with chronic sac pressure measurement

Abdominal aortic aneurysm (AAA) sac shrinkage after endovascular aneurysm repair (EVAR) is considered to be evidence of clinical success. Exclusion of the sac from systemic pressure is the likely cause of shrinkage. We report our continuing clinical experience with the use of a permanently implantable, ultrasound-activated remote pressure transducer to measure intrasac pressure and its correlation with changes in sac diameter over time. Over a 22-month period, 21 patients underwent EVAR of an infrarenal AAA with implantation of an ultrasound-activated remote pressure transducer fixed to the outside of the stent-graft and exposed to the excluded aortic sac. Intrasac pressures were measured directly with an intravascular catheter and by the remote sensor at the time of stent-graft deployment. Follow-up sac pressures were measured by remote sensor and compared with systemic arterial pressure at every follow-up visit. Mean follow-up was 11.4 +/- 5.0 months (range, 1 to 26 months). Twenty patients had follow-up of > or =6 months. Mean pressure index (MPI) was calculated as the ratio of mean sac pressure to mean systemic pressure. Pressures could be obtained at all visits in 15 of the 21 patients. Fourteen of these 15 patients had follow-up of at least 6 months. Aneurysm sac shrinkage of >5 mm was seen in seven (50%) of these 14 patients. No aneurysm enlargement was observed in any patient. The MPI was significantly lower in patients with sac shrinkage at 6 months and at final follow-up. Endovascular aneurysm repair results in marked reduction of sac pressure in most patients. Patients with aneurysm shrinkage after EVAR have significantly lower MPI; however, the absence of sac shrinkage does not imply persistent pressurization of the sac. Further clinical follow-up will delineate the role of long-term sac pressure monitoring in surveillance after EVAR.

Direct intra-aneurysm sac pressure measurement using tip-pressure sensors: In vivo and in vitro evaluation

Direct intra-aneurysm sac pressure measurement with percutaneous translumbar puncture is a new method for follow-up after endovascular aneurysm repair. The purpose of this study was to evaluate a tip-pressure sensor system for intra-aneurysm pressure measurement in an in vitro aneurysm model and in vivo in patients by studying intraobserver variability. We used 0.014-inch guide wire-mounted tip-pressure sensors. For the in vitro aneurysm model, saccular aneurysms filled with thrombus were inserted in a left-heart-driven aneurysm model. Pressure was measured simultaneously with guide wire pressure sensors in the lumen of the model and within the aneurysm thrombus. In vivo, intraobserver variability was evaluated with double percutaneous translumbar puncture of the abdominal aortic aneurysm (AAA) with pressure measurement in 15 patients (14 men, 1 woman; median age, 75 years [63-80 years]; median AAA diameter, 55 mm [47-80 mm]) at a median of 32 months (2-100 months) after endovascular aneurysm repair. Mean pressure index was calculated as the percentage of mean intraaneurysm pressure relative to simultaneous mean systemic pressure. In vitro, the difference in pressure between the tip-sensor measurements and the pressure output of the aneurysm model was 2 mm Hg (1-4 mm Hg) when the output varied between 150/50 and 200/100 mm Hg (n = 90). Mean pressure in the lumen of the model and within the aneurysm thrombus differed by 1 mm Hg (-5-15 mm Hg (n = 10). In vivo, intraobserver variability of mean pressure index (Bland-Altman plot) was 0% (-7%-17%; n = 15%). Direct intra-aneurysm sac pressure measurement with tip-pressure sensors mounted on 0.014-inch guide wires is a reliable and reproducible technique for measuring intra-AAA pressure both in vitro and in vivo.

Type II endoleak in porcine model of abdominal aortic aneurysm

Clinical relevance We set out to show that aortic aneurysm sac pressurization caused by lumbar arterial flow in the setting of type II endoleak can be reproduced in an in vivo porcine model of endovascular aortic aneurysm repair. Indeed, in this model the aneurysm sac pulse pressure was a sensitive indicator of type II endoleak, correlating well with findings at computed tomography, and lumbar artery ligation eliminated the endoleak, as demonstrated on computed tomography scans and sac pressure measurement. Therefore we believe this in vivo large animal model can be instrumental in the study of many aspects of the physiologic features of type II endoleak.

Intra-aneurysm sac pressure measurements after endovascular aneurysm repair: differences between shrinking, unchanged, and expanding aneurysms with and without endoleaks

Objective Our objective was to study intra-aneurysm pressure after endovascular aneurysm repair (EVAR) in shrinking, unchanged, and expanding abdominal aortic aneurysms (AAAs) with and without endoleaks. Methods Direct intra-aneurysm sac pressure measurement (DISP) by percutaneous translumbar puncture of the AAA under fluoroscopic guidance was performed 46 times during the follow-up of 37 patients (30 men; median age, 73 years [range, 58-82 years]; AAA diameter: median, 60 mm [range, 48-84 mm]). Three patients were included in two different groups because DISP was performed more than once with different indications. Tip-pressure sensors mounted on 0.014-inch guidewires were used for simultaneous measurement of systemic and AAA sac pressures. Mean pressure index (MPI) was calculated as the percentage of mean intra-aneurysm pressure relative to the simultaneous mean intra-aortic pressure. Results Median MPI was 19% in shrinking (11 patients), 30% in unchanged (10 patients), and 59% in expanding (9 patients) aneurysms without endoleaks. Pulse pressure was also higher in expanding (10 mm Hg) compared with shrinking (2 mm Hg; P < .0001) AAAs. Four of the nine patients with expanding AAAs underwent five repeated DISPs later in the follow-up, and MPIs were consistently elevated. Seven of the 10 patients with unchanged AAAs without endoleaks underwent further computed tomography follow-up after DISP; 2 expanded (MPI, 47%-63%), 4 shrank (MPI, 21%-30%), and 1 remained unchanged (MPI, 14%). Type II endoleaks (6 patients, 7 DISPs) were associated with wide range of MPI (22%-92%). Successful endoleak embolization (n = 4) resulted in pressure reduction. Conclusions Intra-aneurysm sac pressure measurement is an important adjunctive for EVAR evaluation, possibly allowing early detection of failures. High pressure is associated with AAA expansion and low pressure with shrinkage. Type II endoleaks can be responsible for AAA pressurization, and successful embolization appears to result in pressure reduction.

Aneurysm sac pressure measurements after endovascular repair of abdominal aortic aneurysms

Objectives: The goal of endovascular grafting of abdominal aortic aneurysms (AAAs) is to exclude the aneurysm sac from systemic pressure and thereby decrease the risk of rupture. Unlike conventional open surgery, branch vessels in the sac (eg, lumbar artery and inferior mesenteric artery [IMA]) are not ligated and can potentially transmit pressure. The purpose of our investigation was to evaluate the feasibility of various interventional techniques for measuring pressure within the aneurysm sac in patients who had undergone endovascular repair of AAAs. Methods: Sac pressure measurements were performed in 21 patients who had undergone stent graft repair of AAAs. Seventeen of 21 patients had endoleaks demonstrated on 30-day computed tomographic (CT) scans. Access to the aneurysm sac in these patients was through direct translumbar sac puncture (5 patients), through a patent IMA accessed via the superior mesenteric artery (SMA) (9 patients), or by direct cannulation around attachment sites (3 patients). Four patients had perioperative pressure measurements obtained through catheters positioned along side of the endovascular graft at the time of its deployment. Two of these catheters were left in position for 30 hours during which time CT and conventional angiography were performed. Pressures were determined with standard arterial-line pressure transduction techniques and compared with systemic pressure in each patient. Results: Elevated sac pressure was found in all patients. The sac pressure in patients with endoleaks was found to be systemic (15 patients) or near systemic (2 patients) and all had pulsatile waveforms. Elevated sac pressures were also found in patients without CT or angiographic evidence of endoleak (2 patients). Injection of the sacs in two of these patients revealed a patent lumbar artery and an IMA. Conclusions: It is possible to measure pressures from within the aneurysm sac in patients with stent grafts with a variety of techniques. Patients may continue to have pressurized AAA sacs despite endovascular AAA repair. Endoleaks transmit pulsatile pressure into the aneurysm sac regardless of the type. It is possible to have systemic sac pressures without evidence of endoleaks on CT or angiography. (J Vasc Surg 2001;33:32-41.)

Quality Control during Endovascular Aneurysm Repair: Monitoring Aneurysmal Sac Pressure and Superficial Femoral Artery Flow Velocity

Purpose: To use intraoperative aneurysmal sac pressure measurement and flow monitoring of the superficial femoral artery (SFA) to ensure complete exclusion of the aneurysm from the circulation. Methods: A 5F catheter was positioned in the aneurysmal sac of 15 consecutive patients undergoing endovascular aortomonoiliac aneurysm repair between February and September 1997. The catheter was connected to an external pressure transducer allowing pressure monitoring throughout the operation and for 24 hours postprocedurally. Flow velocity was monitored in the contralateral SFA by insonation with a 2-MHz Doppler ultrasound probe. Results: No technical defect was observed in the deployment of 10 endografts, which demonstrated marked reduction in sac pressure and good flow in the lower limb. The mean aneurysm pressure dropped from 123 to 57 mmHg after graft insertion. In 5 cases, monitoring detected problems during the endograft procedure. In 3, incomplete stent deployment was detected by a failure of sac pressure to fall following stent inflation and by the presence of flow in the contralateral femoral artery. In the other 2 cases, a distal endoleak was detected by direct injection of contrast into the sac. Conclusions: Measuring aneurysm pressure in combination with SFA Doppler flow monitoring can detect complications of endovascular aneurysm repair.