Derek P. Nathan

Presentation, complications, and natural history of penetrating atherosclerotic ulcer disease

OBJECTIVES Increased utilization of computed tomography angiography (CTA) has increased the radiologic diagnosis of penetrating atherosclerotic ulcers (PAUs), which are defined as the ulceration of atherosclerotic plaque through the internal elastic lamina into the aortic media. However, the presentation, treatment indications, and natural history of this disease process remain unclear. METHODS The radiology database at a single university hospital was searched retrospectively for the CTA diagnosis of PAU from January 2003 to June 2009. All scans were interpreted by a cardiovascular radiologist. Information on PAU characteristics and need for surgical repair due to PAU disease was collected. PAU stability or progression was assessed by follow-up CTA, if available. Only PAUs in the aortic arch, descending thoracic aorta, and abdominal aorta were included. RESULTS Three hundred eighty-eight PAUs were diagnosed by CTA interpretation. PAU location was in the aortic arch in 27 (6.8%) cases, the descending thoracic aorta in 243 (61.2%) cases, and the abdominal aorta in 118 (29.7%) cases. Two hundred twenty-four (57.7%) PAUs were isolated (without saccular aneurysm or intramural hematoma); 108 (27.8%) PAUs had associated saccular aneurysms; and 56 (14.4%) PAUs had associated intramural hematoma. Rupture was present in 16 (4.1%) cases. Fifty (12.9%) PAUs underwent repair with thoracic endovascular aortic repair (TEVAR) (n = 30), endovascular aneurysm repair (EVAR) (n = 10), or open surgery (n = 10); primary indications for repair were saccular aneurysm (n = 26), rupture (n = 16), and persistent or recurrent symptoms (n = 8). Even if initially treated conservatively with resolution of pain, symptomatic PAU disease was more likely to require repair than asymptomatic PAU disease (36.2% vs 7.8%, P < .001). Follow-up CTA was available for 87 PAUs, 20 (23.0%) of which demonstrated radiographic disease progression at a mean follow-up of 8.4 ± 10.3 months. Symptomatic PAU disease was more likely to progress than asymptomatic disease (42.9% vs 16.7%, P = .029). CONCLUSIONS For PAUs diagnosed on CTA at a single institution, 4.1% were ruptured and 12.9% underwent repair. Close follow-up imaging appears to be indicated for PAUs, particularly in the case of symptomatic disease, which is more likely to require repair and to undergo radiographic progression.

Pathogenesis of Acute Aortic Dissection: A Finite Element Stress Analysis

BACKGROUND Type A and type B aortic dissections typically result from intimal tears above the sinotubular junction and distal to the left subclavian artery (LSA) ostium, respectively. We hypothesized that this pathology results from elevated pressure-induced regional wall stress. METHODS We identified 47 individuals with normal thoracic aortas by electrocardiogram-gated computed tomography angiography. The thoracic aorta was segmented, reconstructed, and triangulated to create a geometric mesh. Finite element analysis using a systolic pressure load of 120 mm Hg was performed to predict regional thoracic aortic wall stress. RESULTS There were local maxima of wall stress above the sinotubular junction in the ascending aorta and distal to the ostia of the supraaortic vessels, including the LSA, in the aortic arch. No local maximum of wall stress was found in the descending thoracic aorta. Comparison of the mean peak wall stress above the sinotubular junction (0.43 ± 0.07 MPa), distal to the LSA (0.21 ± 0.07 MPa), and in the descending thoracic aorta (0.06 ± 0.01 MPa) showed a significant effect for wall stress by aortic region (p < 0.001). CONCLUSIONS In the normal thoracic aorta, there are peaks in wall stress above the sinotubular junction and distal to the LSA ostium. This stress distribution may contribute to the pathogenesis of aortic dissections, given their colocalization. Future investigations to determine the utility of image-derived biomechanical calculations in predicting aortic dissection are warranted, and therapies designed to reduce the pressure load-induced wall stress in the thoracic aorta are rational.

Increased Ascending Aortic Wall Stress in Patients With Bicuspid Aortic Valves

BACKGROUND Patients with bicuspid aortic valves (BAV) are at increased risk of ascending aortic dilatation, dissection, and rupture. We hypothesized that ascending aortic wall stress may be increased in patients with BAV compared with patients with tricuspid aortic valves (TAV). METHODS Twenty patients with BAV and 20 patients with TAV underwent electrocardiogram-gated computed tomographic angiography. Patients were matched for diameter. The thoracic aorta was segmented, reconstructed, and triangulated to create a mesh. Utilizing a uniform pressure load of 120 mm Hg, and isotropic, incompressible, and linear elastic shell elements, finite element analysis was performed to predict 99th percentile wall stress. RESULTS For patients with BAV and TAV, aortic root diameter was 4.0 ± 0.6 cm and 4.0 ± 0.6 cm (p = 0.724), sinotubular junction diameter was 3.6 ± 0.8 cm and 3.6 ± 0.7 cm (p = 0.736), and maximum ascending aortic diameter was 4.0 ± 0.8 cm and 4.1 ± 0.9 cm (p = 0.849), respectively. The mean 99 th percentile wall stress in the BAV group was greater than in the TAV group (0.54 ± 0.06 MPa vs 0.50 ± 0.09 MPa), though this did not reach statistical significance (p = 0.090). When normalized by radius, the 99 th percentile wall stress was greater in the BAV group (0.31 ± 0.06 MPa/cm vs 0.27 ± 0.03 MPa/cm, p = 0.013). CONCLUSIONS Patients with BAV, regardless of aortic diameter, have increased 99 th percentile wall stress in the ascending aorta. Ascending aortic three-dimensional geometry may account in part for the increased propensity to aortic dilatation, rupture, and dissection in patients with BAV.

Low rehospitalization rate for vascular surgery patients

OBJECTIVES Reducing rehospitalization rates has been proposed to improve care, reduce costs, and as a pay-for-performance criterion. Recent review of Medicare claims data indicates that vascular surgery patients have among the highest rates of 30-day rehospitalization at 23.9%. METHODS We retrospectively examined all live patient discharges (n = 799) from the vascular surgery service at a single university hospital over 12 months. Planned and unplanned 30-day rehospitalizations were distinguished, and predictors of unplanned 30-day rehospitalization were determined. To identify whether patients were readmitted to other hospitals, a prospective study of patient discharges (n = 66) over 1 month was also performed. RESULTS Ninety-five (11.9%) of the 799 patient discharges from the vascular surgery service were rehospitalized within 30 days. Of these, 71 were unplanned; therefore, the unplanned rehospitalization rate was 8.9%. The most common causes of unplanned 30-day rehospitalization were related to wound complications. Diabetes (P = .039) predicted unplanned 30-day rehospitalization by multivariate analysis. Patients with the diagnosis of critical limb ischemia (14.9%) and patients undergoing open lower extremity revascularization (14.6%) had the highest rates of unplanned 30-day rehospitalization. In the prospective portion of this study, no patient was readmitted to any other hospital. CONCLUSIONS Relatively low 30-day rehospitalization was accomplished in vascular surgery patients at a single university hospital. Moreover, planned rehospitalizations accounted for approximately 25% of readmissions in vascular surgery patients. Strategies designed to reduce rehospitalization in diabetics may be warranted.

Predictors of decreased short- and long-term survival following open abdominal aortic aneurysm repair

OBJECTIVES The purpose of this study was to identify predictors of decreased survival after open abdominal aortic aneurysm (AAA) repair at a single university hospital. METHODS Patients undergoing open AAA repair from June 2003 to June 2009 were identified. Primary outcomes were 30-day and 5-year survival. Preoperative, intraoperative, and postoperative variables were assessed for their influence on outcomes using univariate and multivariate analysis, as appropriate. One- and 5-year survival were determined by Kaplan-Meier analysis. RESULTS Four hundred eight patients (289 men; 70.8%) with a mean age of 72.4 ± 8.3 years underwent open AAA repair. Sixty-seven patients (16.4%) underwent nonelective repair. The clamp site was infrarenal in 137 patients (33.6%), suprarenal in 97 patients (23.8%), and supraceliac in 174 patients (42.6%). Thirty-day survival was 95.6%. One- and 5-year survival were 90.0% ± 1.5% and 65.1% ± 3.0%, respectively. Seventy-nine patients (19.4%) had decreased renal function postoperatively compared to preoperatively, 71 patients (17.4%) sustained cardiac complications, and 45 patients (11.0%) sustained pulmonary complications. Patients with chronic obstructive pulmonary disease (91.9% vs 97.2%; P = .004) and chronic renal insufficiency (92.0% vs 98.3%; P = .009) had decreased 30-day survival. Patients with chronic obstructive pulmonary disease (55.8% ± 5.8% vs 67.3% ± 3.6%; P = .013), chronic renal insufficiency (51.2% ± 5.2% vs 72.8% ± 3.7%; P = .043), and cerebrovascular disease (46.8% ± 7.4% vs 67.4% ± 3.4%; P = .003) had decreased 5-year survival. Patients who had decreased postoperative renal function (41.0% ± 7.4% vs 72.2% ± 3.4%; P = .004), and patients who sustained pulmonary complications (45.6% ± 8.8% vs 66.3% ± 3.3%; P = .042) had worse 5-year survival. CONCLUSIONS Open AAA repair can be done with low morbidity and mortality in the era of endovascular aneurysm repair. Careful consideration should be given to preoperative optimization and perioperative care in patients with chronic obstructive pulmonary disease, chronic renal insufficiency, and cerebrovascular disease. Postoperative decrease in renal function and pulmonary complication portend decreased 5-year survival; strategies to ameliorate these factors should be sought.

Thoracic Endografting Reduces Morbidity and Remodels the Thoracic Aorta in DeBakey III Aneurysms

BACKGROUND The efficacy of endovascular treatment of aneurysms secondary to chronic DeBakey type III aortic dissection (CD3) remains controversial. The objective of this study was to compare outcomes from open and endovascular treatment of CD3 aneurysms, and to determine the efficacy of thoracic endovascular aortic repair (TEVAR) in remodeling the chronically dissected thoracoabdominal aorta. METHODS From 2005 to 2012, 58 patients underwent open aortic replacement (open) and 31 patients underwent endovascular therapy (TEVAR) for the treatment of CD3 aneurysms. The TEVAR patients were divided into CD3a (n = 12) or CD3b (n = 19) subgroups based upon the DeBakey classification of aortic dissection. Total aortic, true and false lumen diameters were measured at different anatomic locations. True lumen and false lumen indices were calculated to evaluate the impact of TEVAR on remodeling. RESULTS In the open group, operative mortality was 10.3% and the incidence of pulmonary failure, renal failure, and paraplegia was 13.8%, 10.3%, and 12.1%, respectively. There were no operative mortalities in TEVAR patients, and no cases of pulmonary failure, renal failure, or paraplegia. Endovascular therapy stabilized aneurysm size and remodeled the thoracic aorta in 87% of patients. The TEVAR significantly expanded the true lumen and reduced the false lumen within the stent graft in CD3a and CD3b patients (p < 0.001). Thoracic false lumen thrombosis was achieved in 100% of CD3a and in 68% of CD3b patients. CONCLUSIONS In these early results, TEVAR reduces operative morbidity and mortality compared with open aortic replacement in the treatment of CD3 aneurysms. The TEVAR is effective in remodeling the chronically dissected thoracic aorta. Abdominal false lumen patency is maintained in patients with thoracoabdominal dissection-related aneurysms.

Delayed complications of inferior vena cava filters: case report and literature review.

Inferior vena cava (IVC) filters are frequently placed to prevent pulmonary embolism in patients in whom anticoagulation is contraindicated or ineffective. Delayed erosion of the filter into adjacent vital structures is a rare complication. We report 3 complications of IVC filters managed with both surgical and endovascular therapies. A review of the available literature addresses incidence of delayed IVC filter complications, the approach to these problems, and the role of retrievable IVC filters.

Predictors of early and late mortality following open extent IV thoracoabdominal aortic aneurysm repair in a large contemporary single-center experience.

OBJECTIVE The primary purpose of this study was to examine outcomes following open repair of extent IV thoracoabdominal aortic aneurysms (TAAAs) at a single university hospital. As a secondary aim, comparison was made to patients who underwent open abdominal aortic aneurysm (AAA) repair with supraceliac clamping but without left renal artery bypass to assess the effect of left renal artery bypass on outcomes. METHODS Patients undergoing open extent IV TAAA repair from 1998 to 2008 were identified (n = 108). Primary outcomes were 30-day and long-term survival. Secondary outcomes were major complication, renal failure, and postoperative change in renal function. A second analysis was performed, comparing patients undergoing extent IV TAAA repair with patients undergoing AAA repair with supraceliac clamping but without left renal artery bypass (n = 50). RESULTS Eighty-three men (76.9%) and 25 women (23.1%), with a mean age of 72.9 years, underwent open extent IV TAAA repair. Nine patients (8.3%) were ruptured. Mean aneurysm maximal diameter was 6.5 ± 1.3 cm. Supraceliac and left renal ischemic times were 22.9 ± 9.3 and 40.6 ± 16.2 minutes, respectively. Six patients (5.6%) died at 30 days. The only predictor of 30-day mortality was decreased preoperative estimated glomerular filtration rate (eGFR) (P = .044 by multivariate analysis; and P = .011 by univariate analysis). One-year and 5-year survival rates were 87% and 50%, respectively. Patients with a history of cerebrovascular disease (P = .001) and postoperative renal insufficiency (P = .034) had increased long-term mortality by log-rank test. Twenty-five (25.3%) patients sustained a postoperative decrease in renal function, while 19 (19.2%) patients had an improvement in renal function. There was no difference in 30-day mortality (5.6% vs 6.0%; P = 1.000), 5-year survival (50% vs 48%; P = .886), major complications (37.0% vs 38.0%; P = 1.000), renal failure (6.1% vs 0%; P = .215), or postoperative change in renal function, in patients undergoing extent IV TAAA repair vs AAA repair with supraceliac clamping but without left renal artery bypass. CONCLUSIONS Open extent IV TAAA repair can be performed with low morbidity and mortality rates. The performance of left renal artery bypass does not appear to contribute to the morbidity and mortality of extent IV TAAA repair. While decreased preoperative eGFR appears to increase the risk of 30-day mortality, a history of cerebrovascular disease and postoperative renal insufficiency appear to increase the risk of long-term mortality. Finally, open extent IV TAAA repair not uncommonly improves renal function.

Peak Wall Stress Predicts Expansion Rate in Descending Thoracic Aortic Aneurysms

BACKGROUND Aortic diseases, including aortic aneurysms, are the 12th leading cause of death in the United States. The incidence of descending thoracic aortic aneurysms is estimated at 10.4 per 100,000 patient-years. Growing evidence suggests that stress measurements derived from structural analysis of aortic geometries predict clinical outcomes better than diameter alone. METHODS Twenty-five patients undergoing clinical and radiologic surveillance for thoracic aortic aneurysms were retrospectively identified. Custom MATLAB algorithms were employed to extract aortic wall and intraluminal thrombus geometry from computed tomography angiography scans. The resulting reconstructions were loaded with 120 mm Hg of pressure using finite element analysis. Relationships among peak wall stress, aneurysm growth, and clinical outcome were examined. RESULTS The average patient age was 71.6 ± 10.0 years, and average follow-up time was 17.5 ± 9 months (range, 6 to 43). The mean initial aneurysm diameter was 47.8 ± 8.0 mm, and the final diameter was 52.1 ± 10.0 mm. Mean aneurysm growth rate was 2.9 ± 2.4 mm per year. A stronger correlation (r = 0.894) was found between peak wall stress and aneurysm growth rate than between maximal aortic diameter and growth rate (r = 0.531). Aneurysms undergoing surgical intervention had higher peak wall stresses than aneurysms undergoing continued surveillance (300 ± 75 kPa versus 229 ± 47 kPa, p = 0.01). CONCLUSIONS Computational peak wall stress in thoracic aortic aneurysms was found to be strongly correlated with aneurysm expansion rate. Aneurysms requiring surgical intervention had significantly higher peak wall stresses. Peak wall stress may better predict clinical outcome than maximal aneurysmal diameter, and therefore may guide clinical decision-making.

A modern experience with saccular aortic aneurysms

OBJECTIVE Repair of saccular aortic aneurysms (SAAs) is frequently recommended based on a perceived predisposition to rupture, despite little evidence that these aneurysms have a more malignant natural history than fusiform aortic aneurysms. METHODS The radiology database at a single university hospital was searched for the computed tomographic (CT) diagnosis of SAA between 2003 and 2011. Patient characteristics and clinical course, including the need for surgical intervention, were recorded. SAA evolution was assessed by follow-up CT, where available. Multivariate analysis was used to examine potential predictors of aneurysm growth rate. RESULTS Three hundred twenty-two saccular aortic aneurysms were identified in 284 patients. There were 153 (53.7%) men and 131 women with a mean age of 73.5±10.0 years. SAAs were located in the ascending aorta in two (0.6%) cases, the aortic arch in 23 (7.1%), the descending thoracic aorta in 219 (68.1%), and the abdominal aorta in 78 (24.2%). One hundred thirteen (39.8%) patients underwent surgical repair of SAA. Sixty-two patients (54.9%) underwent thoracic endovascular aortic repair, 22 underwent endovascular aneurysm repair (19.5%), and 29 (25.6%) required open surgery. The average maximum diameter of SAA was 5.0±1.6 cm. In repaired aneurysms, the mean diameter was 5.4±1.4 cm; in unrepaired aneurysms, it was 4.4±1.1 cm (P<.001). Eleven patients (3.9%) had ruptured SAAs on initial scan. Of the initial 284 patients, 50 patients (with 54 SAA) had CT follow-up after at least 3 months (23.2±19.0 months). Fifteen patients (30.0%) ultimately underwent surgical intervention. Aneurysm growth rate was 2.8±2.9 mm/yr, and was only weakly related to initial aortic diameter (R2=.19 by linear regression, P=.09 by multivariate regression). Decreased calcium burden (P=.03) and increased patient age (P=.05) predicted increased aneurysm growth by multivariate analysis. CONCLUSIONS While SAA were not found to have a higher growth rate than their fusiform counterparts, both clinical and radiologic follow-up is necessary, as a significant number ultimately require surgical intervention. Further clinical research is necessary to determine the optimal management of SAA.