Biomedical subjects

Mark F Fillinger

Publications and source records attributed to Mark F Fillinger.

24 records · Page 2Linked to original sources

PubMed2002

Isolated dissection of the abdominal aorta: clinical presentation and therapeutic options.

INTRODUCTION: Arterial dissection commonly affects the thoracic aorta and is associated with high morbidity and mortality rates. Although dissection of the abdominal aorta is considered rare, liberal use of diagnostic computed tomographic scan imaging for evaluation of abdominal pain has identified this process with increasing frequency. Because the clinical features and therapeutic options of isolated abdominal aortic dissection are not well characterized, we reviewed our recent experience and provide an algorithm for treatment. PATIENTS AND RESULTS: Since 1996, we have treated 10 patients with abdominal aortic dissection. The mean age was 62 +/- 17 years, and 40% were female. Presentation included abdominal pain in seven patients and lower extremity ischemia in one patient. Dissection was asymptomatic in two of the patients. Hypertension, smoking history, remote trauma, and claudication were noted in four, three, two, and two of the patients, respectively. Three patients had abdominal tenderness, three had a pulsatile mass, and five had a benign abdominal examination. The diagnosis of dissection was made on abdominal computed tomographic scan in eight cases, on arteriogram in one case, and at operation in one case. No patient had an associated thoracic aortic dissection. The dissection flap originated below or at the renal arteries in nine of the cases and at the superior mesenteric artery in one case. Length of the dissection ranged between 21 and 110 mm, and in three patients, the dissection flap extended beyond the aortic bifurcation into the common iliac arteries. In three patients who had an aortogram, evidence of flow limitation was found on the basis of the presence of aortic stenosis or occlusion. Treatment consisted of aortic stent graft deployment in one patient, direct aortic reconstruction in three patients, and observation in the remaining six patients. CONCLUSION: Although the natural history of isolated abdominal aortic dissection has not been well defined, our experience adds to the understanding of this rare process. Because aneurysmal degeneration can occur, close surveillance is indicated if definitive treatment is not used initially. Patients with ischemic symptoms and those with intractable pain need intervention, the nature of which should be based on risk profile and aortoiliac anatomy.

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PubMed2002

In vivo analysis of mechanical wall stress and abdominal aortic aneurysm rupture risk.

OBJECTIVE: The purpose of this study was to calculate abdominal aortic aneurysm (AAA) wall stresses in vivo for ruptured, symptomatic, and electively repaired AAAs with three-dimensional computer modeling techniques, computed tomographic scan data, and blood pressure and to compare wall stress with current clinical indices related to rupture risk. METHODS: CT scans were analyzed for 48 patients with AAAs: 18 AAAs that ruptured (n = 10) or were urgently repaired for symptoms (n = 8) and 30 AAAs large enough to merit elective repair within 12 weeks of the CT scan. Three-dimensional computer models of AAAs were reconstructed from CT scan data. The stress distribution on the AAA as a result of geometry and blood pressure was computationally determined with finite element analysis with a hyperelastic nonlinear model that depicted the mechanical behavior of the AAA wall. RESULTS: Peak wall stress (maximal stress on the AAA surface) was significantly different between groups (ruptured, 47.7 +/- 6 N/cm(2); emergent symptomatic, 47.5 +/- 4 N/cm(2); elective repair, 36.9 +/- 2 N/cm(2); P =.03), with no significant difference in blood pressure (P =.2) or AAA diameter (P =.1). Because of trends toward differences in diameter, comparison was made only with diameter-matched subjects. Even with identical mean diameters, ruptured/symptomatic AAAs had a significantly higher peak wall stress (46.8 +/- 4.5 N/cm(2) versus 38.1 +/- 1.3 N/cm(2); P =.05). Maximal wall stress predicted risk of rupture better than the LaPlace equation (20.7 +/- 5.7 N/cm(2) versus 18.8 +/- 2.9 N/cm(2); P =.2) or other proposed indices of rupture risk. The smallest ruptured AAA was 4.8 cm, but this aneurysm had a stress equivalent to the average electively repaired 6.3-cm AAA. CONCLUSION: Peak wall stresses calculated in vivo for AAAs near the time of rupture were significantly higher than peak stresses for electively repaired AAAs, even when matched for maximal diameter. Calculation of wall stress with computer modeling of three-dimensional AAA geometry appears to assess rupture risk more accurately than AAA diameter or other previously proposed clinical indices. Stress analysis is practical and feasible and may become an important clinical tool for evaluation of AAA rupture risk.

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PubMed2002

Prediction of early graft failure with intraoperative completion duplex ultrasound scan.

PURPOSE: The purpose of this study was to determine intraoperative hemodynamic parameters that predict early failure of infragenicular vein grafts with intraoperative completion duplex ultrasound scan. METHODS: We reviewed the results of intraoperative duplex scans that were selectively performed after completion of 45 tibial/pedal vein bypass grafts at high risk for failure. Bypass was performed for rest pain (39%) or tissue loss (61%), and 60% of the cases were disadvantaged because of compromised vein quality or poor arterial outflow. A 10-MHz low-profile transducer was used to scan the entire graft at bypass completion. All grafts were determined to be technically adequate (absence of retained valves, arteriovenous fistulas, or localized velocity increases and the presence of bypass-dependent distal pulses). Peak systolic velocity (PSV) and end diastolic velocity (EDV) were also measured at each anastomosis, in the outflow artery and in the proximal and distal portions of each graft. Resistive indices (RI) were calculated at each measurement point (PSV-EDV/PSV). Statistical analysis was performed with unpaired t test, chi(2) test, and multivariate analyses. RESULTS: Twenty infragenicular vein bypass grafts (44%) thrombosed within 12 months. Intraoperative hemodynamic parameters were significantly different between grafts that remained patent or thrombosed. EDV was lower (5 +/- 1 cm/s versus 13 +/- 3 cm/s; P =.02) and RI was higher (0.90 versus 0.81; P <.01) in the proximal portions of grafts that thrombosed within 12 months. Distal EDV was also lower (6 +/- 1 cm/s versus 15 +/- 2 cm/s; P <.01) and distal RI was higher (0.89 versus 0.78; P <.01) in grafts that thrombosed. With multivariate analysis, only low distal EDV was predictive of early graft failure (P <.05). Distal bypass EDV of less than 8 cm/s predicated early graft thrombosis with 76% sensitivity and 75% specificity (positive predictive value, 71%; negative predictive value, 78%). Absence of diastolic flow (EDV of 0 cm/s) predicted early graft failure with 100% specificity and 100% positive predictive value. CONCLUSION: In this initial experience, low EDV measured with intraoperative duplex scan was associated with early thrombosis of tibial level vein grafts. When such values are observed, measures should be taken to improve graft hemodynamic parameters. Prospective study of infragenicular vein bypass grafts may better define hemodynamic parameters predictive of early graft thrombosis.

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PubMed2002

Internal iliac occlusion without coil embolization during endovascular abdominal aortic aneurysm repair.

PURPOSE: When abdominal aortic aneurysms and common iliac artery (CIA) aneurysms undergo concomitant endovascular repair, endograft limb extension into the external iliac artery is often necessary. Usually, the internal iliac artery (IIA) is coil embolized in such a case to prevent endoleak. It has been our practice to coil embolize the IIA only in cases where there is not adequate stent graft seal in the CIA immediately proximal to the IIA origin (effectively sealing the entire IIA origin). In this study, we evaluated the outcomes of this approach. METHODS: We retrospectively reviewed 204 consecutive endovascular abdominal aortic aneurysm repairs at Dartmouth-Hitchcock Medical Center from 1996 to 2001. Computed tomographic angiography with three-dimensional reconstruction was the primary preoperative imaging modality, and the decision to cover the IIA without concomitant coil embolization was based before surgery on the presence of adequate graft oversizing (> or =10% to 15%) in the most distal 5 mm of CIA and 15 mm of proximal external iliac artery, respectively. RESULTS: The IIA was occluded 33 times in 31 patients. In 22 cases (67%), the IIA was covered without coil embolization (COVER group). The remaining 11 patients (33%) with inadequate graft oversizing in the CIA underwent IIA coil embolization (COIL group). The follow-up periods for the COVER and COIL groups were 19 +/- 2 months and 10 +/- 3 months, respectively. All operations in both groups were technically successful without evidence of endoleak at completion angiography. No endoleaks, graft migrations, or aneurysm enlargements were associated with the covered or coiled IIAs during the follow-up period. No clinical sequelae were seen in the COVER group, with the exception of buttock claudication in six patients (27%) that resolved completely in five patients. In the COIL group, five patients (45%) had buttock claudication. In addition, one case of buttock necrosis and one case of ischemic neuropathy occurred in the COIL group. CONCLUSION: Covering the IIA without coiling effectively excluded the CIA aneurysm in every case and was associated with a low incidence rate of complications compared with coil embolization. With detailed preoperative imaging and patient selection, IIA coil embolization may not be necessary in as many as two thirds of patients who need IIA occlusion.

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PubMed2002

Life expectancy after endovascular versus open abdominal aortic aneurysm repair: results of a decision analysis model on the basis of data from EUROSTAR.

BACKGROUND/OBJECTIVES: Although endovascular abdominal aortic aneurysm (AAA) repair (ENDO) has decreased operative morbidity risks compared with open AAA repair (OPEN), risks of rupture and reintervention are higher after ENDO. We used decision analysis to examine the effect of these competing risks on quality-adjusted life expectancy (QALE) after ENDO and OPEN. METHODS: We used a Markov decision-analysis model to simulate hypothetic cohorts of patients undergoing ENDO or OPEN. Patients moved through a multistate transition model according to probabilities derived from the literature, the EUROSTAR database (for ENDO) and Medicare claims data (for OPEN). Our primary outcome measure was QALE after surgery. We used sensitivity analysis to determine which factors most influenced this outcome. RESULTS: In the base-case analysis of 70-year-old men, life expectancy after ENDO was 7.09 quality-adjusted life years compared with 7.03 quality-adjusted life years for OPEN, a difference of 3 weeks. Sensitivity analysis showed that at less than age 64 years, OPEN results in greater QALE. However, the difference in QALE was small (<3 months) across the entire range of ages studied (60 to 85 years). The optimal strategy was sensitive to changes in ENDO and OPEN operative mortality rate, rupture rate after ENDO, late conversion to OPEN rate, ENDO revision rate, and OPEN reoperation rate. However, the difference between OPEN and ENDO strategies was small across the plausible range of most of these variables. CONCLUSION: For most patients who are candidates for AAA repair, ENDO and OPEN result in similar QALE. Decision analysis suggests that OPEN may be preferred for younger patients with low operative risk and ENDO may be preferred for older patients with higher operative risk. However, given the similarity in overall outcome, patient preference should be weighed heavily in decision making.

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PubMedDate not supplied

The engineering of endovascular stent technology: a review.

The evolution of minimally invasive endovascular technology has initiated a significant paradigm shift in the treatment of vascular disease. A fundamental understanding of the science and engineering behind the technology of endovascular stents is a key to their appropriate implementation in practice. Furthermore, the rapid influx of new devices into the field requires practitioners to make their decisions on a foundation of the relative strengths and weaknesses of the various products. Although the principles of their use are not complex, the device design can have a profound effect on the device's functionality. Shape, thickness, coating, material selection, and imaging are just a few of the factors to consider in stent design. Subtle differences may have profound results. This review is designed to provide the reader with an overview of fundamental concepts that will aide the assessment of new technology.

Biocompatible Materials↗