Exercise-stimulated arterial transit time in calf muscles measured by dynamic contrast-enhanced magnetic resonance imaging.

The primary goal of this study was to evaluate arterial transit time (ATT) in exercise-stimulated calf muscles as a promising indicator of muscle function. Following plantar flexion, ATT was measured by dynamic contrast-enhanced (DCE) MRI in young and elderly healthy subjects and patients with peripheral artery disease (PAD). In the young healthy subjects, gastrocnemius ATT decreased significantly (P < 0.01) from 4.3 ± 1.5 to 2.4 ± 0.4 sec when exercise load increased from 4 lbs to 16 lbs. For the same load of 4 lbs, gastrocnemius ATT was lower in the elderly healthy subjects (3.2 ± 1.1 sec; P = 0.08) and in the PAD patients (2.4 ± 1.2 sec; P = 0.02) than in the young healthy subjects. While the sensitivity of the exercise-stimulated ATT is diagnostically useful, it poses a challenge for arterial spin labeling (ASL), a noncontrast MRI method for measuring muscle perfusion. As a secondary goal of this study, we assessed the impact of ATT on ASL-measured perfusion with ASL data of multiple post labeling delays (PLDs) acquired from a healthy subject. Perfusion varied substantially with PLD in the activated gastrocnemius, which can be attributed to the ATT variability as verified by a simulation. In conclusion, muscle ATT is sensitive to exercise intensity, and it potentially reflects the functional impact of aging and PAD on calf muscles. For precise measurement of exercise-stimulated muscle perfusion, it is recommended that ATT be considered when quantifying muscle ASL data.

A novel perfused porcine simulator for teaching aortic anastomosis increases resident interest in vascular surgery.

OBJECTIVE: This report describes a novel simulator, euthanized pigs on cardiopulmonary bypass, and validates this simulator with a controlled trial in general surgery residents learning aortic anastomosis. We evaluated this novel simulator with the following hypothesis: our porcine perfused simulator is as good as or better than the standard rubber tubing, low-fidelity models used for vascular anastomotic training. METHODS: Euthanized pigs were placed on cardiopulmonary bypass, creating a perfused, ex vivo model on which to perform surgical procedures. The participants in the study were postgraduate year 2, 3, and 4 general surgery residents. Residents were randomized to practice aortic anastomosis in the pig laboratory (PL) simulator or in a dry laboratory. The PL residents and control residents performed a first vascular anastomosis on the rubber tube model. Anastomosis creation was filmed. The anastomosis and video were stored for later grading. Next, all residents underwent an ungraded, one-on-one training session with the attending vascular surgeon. After the training session, all residents completed a second videotaped rubber tubing anastomosis. The grading scales used were validated by other authors: Global Assessment Score, Final Product Score, and Checklist Scoring Instrument. Survey data describing this experience were collected using a 13-question prelaboratory and 16-question postlaboratory questionnaires consisting of yes/no, multiple selection, and 5-point Likert-type scale questions. RESULTS: All residents had a statistically significant improvement in time to completion and in the Global Assessment Score with tutored practice. The PL residents showed statistically significant improvement in completion time between the first and second videotaped anastomosis; however, there was no statistically significant improvement in the scoring metrics. The control residents showed statistically significant improvement in all three scoring metrics, but no statistically significant difference was found in completion time. The survey data showed a statistically significant shift in considering vascular surgery as a career after the experience in the PL group (P = .05) compared with the control group, who had no change in interest (P = .91). CONCLUSIONS: Our prospective, randomized clinical trial shows that the porcine cardiopulmonary bypass model achieves similar results to a previously validated bench top model while improving general surgery resident interest in vascular surgery as a career.

Outcomes in Critical Limb Ischemia Compared by Distance from Referral Center.

BACKGROUND: Little data exist regarding the effect of referral distance on outcomes after revascularization for critical limb ischemia (CLI). We tested the assumption that patients who travel longer distances for revascularization procedures have worse outcomes. METHODS: We identified a retrospective cohort of 300 CLI patients who underwent revascularization between January 1, 2000 and December 31, 2010 at a single academic medical center. Patients were stratified into 2 groups based on distance greater than or less than 100 miles from the referral center. The association between travel distance and outcome measures including length of stay (LOS), postoperative functional status, hospital disposition, patient follow-up, and amputation-free survival (AFS) were evaluated using Cox proportional hazard models controlling for patient comorbidities and type of revascularization procedure. RESULTS: One hundred eighteen (39%) patients travelled >100 miles for CLI revascularization. The 2 groups had similar baseline characteristics. Overall, 211 (70%) patients underwent an open revascularization, 60 (20%) an endovascular, and 29 (10%) a hybrid procedure. Those living >100 miles away less commonly underwent an endovascular procedure (14% vs. 24%, P = 0.05). LOS was similar between near and far groups (7.3 vs. 8.9 days, P = 0.1), as was postoperative functional status (ambulatory 73% vs. 68%, P = 0.34) and discharge to home (68% vs. 74%, P = 0.34). Long-term follow-up (mean 2.07 years) was similar between distance groups (P = 0.6). Five-year AFS (73% vs. 56%, P = 0.02) was superior in the distance >100 group. In the multivariate analysis, distance >100 miles (hazard ratio [HR] 0.6, P = 0.05), preoperative warfarin use (HR 0.5, P = 0.02), and independent ambulatory status (HR 0.5, P = 0.002) were associated with improved AFS. CONCLUSIONS: Patient referral distance did not adversely affect AFS or long-term follow-up after revascularization for CLI. Patients traveling from rural settings for revascularization can expect similar outcomes as patients located near tertiary centers.

α1- and α2-adrenergic responsiveness in human skeletal muscle feed arteries: the role of TRPV ion channels in heat-induced sympatholysis.

The purpose of this study was to determine if heat inhibits α2-adrenergic vasocontraction, similarly to α1-adrenergic contraction, in isolated human skeletal muscle feed arteries (SMFA) and elucidate the role of the temperature-sensitive vanilloid-type transient receptor potential (TRPV) ion channels in this response. Isolated SMFA from 37 subjects were studied using wire myography. α1 [Phenylephrine (PE)]- and α2 [dexmedetomidine (DEX)]-contractions were induced at 37 and 39°C with and without TRPV family and TRPV4-specific inhibition [ruthenium red (RR) and RN-1734, respectively]. Endothelial function [acetylcholine (ACh)] and smooth muscle function [sodium nitroprusside (SNP) and potassium chloride (KCl)] were also assessed under these conditions. Heat and TRPV inhibition was further examined in endothelium-denuded arteries. Contraction data are reported as a percentage of maximal contraction elicited by 100 mM KCl (LTmax). DEX elicited a small and variable contractile response, one-fifth the magnitude of PE, which was not as clearly attenuated when heated from 37 to 39°C (12 ± 4 to 6 ± 2% LTmax; P = 0.18) as were PE-induced contractions (59 ± 5 to 24 ± 4% LTmax; P < 0.05). Both forms of TRPV inhibition restored PE-induced contraction at 39°C (P < 0.05) implicating these channels, particularly the TRPV4 channels, in the heat-induced attenuation of α1-adrenergic vasocontraction. TRPV inhibition significantly blunted ACh relaxation while denudation prevented heat-induced sympatholysis without having an additive effect when combined with TRPV inhibition. In conclusion, physiological increases in temperature elicit a sympatholysis-like inhibition of α1-adrenergic vasocontraction in human SMFA that appears to be mediated by endothelial TRPV4 ion channels.

A design modification to minimize tilting of an inferior vena cava filter does not deliver a clinical benefit.

OBJECTIVE: In July 2007, our group began to use a modified conical inferior vena cava filter with additional stabilizing struts designed to reduce tilting of retrievable filters. We analyzed our experience with this modified filter (Cook Medical, Bloomington, Ind) from July 1, 2007 to December 31, 2008 and compared it to our experience with the standard filter (Günther Tulip, Cook Medical, Bloomington, Ind) from January 1, 2006 through December 31, 2008 to determine if adoption of the modified filter reduced tilting and delivered a discernible clinical benefit. METHODS: The primary outcome measure was tilt angle after deployment. Secondary outcomes were change in tilt angle between deployment and retrieval (self-centering) and retrieval failure due to inability to engage the filter hook. Measurements were retrospectively determined using the anteroposterior venogram at the time of placement and removal. Tilt angle was defined by the center line of the filter relative to the center line of the inferior vena cava (IVC). Statistical significance was assumed for P ≤ .05. RESULTS: During the study period, a total of 302 IVC filters were placed. Retrieval was attempted for 85 of 194 (44%) standard filters and 52 of 108 (48%) modified filters. The overall difference in tilt angle (degrees) between the standard (median [interquartile range] = 5 [3, 8]) and modified (5 [3, 8]) filters at the time of placement was not statistically significant (P = .44). Modified filters deployed through a femoral route (8 [4, 11]) had significantly greater tilt angles than modified filters deployed using jugular access (4 [2, 6]; P < .0001). At the time of retrieval, evidence of self-centering was observed more often with modified (32 of 52 [62%]) than standard (36 of 85 [42%]) filters (P = .03). Overall, there were only four failures to retrieve the filter due to excess tilting (standard, 3 of 85 [4%], modified, 1 of 52 [2%]; P = .59). CONCLUSION: Overall, tilt angle at insertion did not differ between the modified and standard filters, although more modified filters displayed self-centering. There was no difference between the groups in retrieval failure due to excess tilting. Despite its greater tendency to self-center, we did not recognize a measurable clinical advantage of the modified filter.

A ruptured pancreaticoduodenal artery aneurysm repaired by combined endovascular and open techniques.

Aneurysms of the pancreaticoduodenal arteries (PDA) are rare, accounting for <2% of all visceral aneurysms. An association with celiac artery stenosis has been reported. Many present with rupture, and a high mortality can be expected. Treatment is therefore challenging. Arterial ligation, anuerysmectomy, or bypass has been the mainstay of treatment. We recently treated a patient (who had no celiac axis) with a ruptured PDA aneurysm with combined open and endovascular techniques. A 46-year-old man was transferred to our hospital with a 1-day history of abdominal pain and syncope. On admission, an abdominal and pelvis computerized tomographic (CT) scan identified a large mesenteric hematoma, a 1.9 cm PDA aneurysm, and an occluded celiac axis. Mesenteric angiography revealed no active aneurysm leak and a stenotic superior mesenteric artery (SMA) origin. All hepatic blood flow originated from the stenotic SMA via markedly enlarged PDA collaterals. The patient was brought to the operating room, where absence of the celiac axis was confirmed. An aorto-to-proper hepatic and SMA bypass was performed using a bifurcated polyester graft. The next day, the patient was brought to the angiography suite, where the PDA aneurysm was coiled. Postprocedure CT scans confirmed thrombosis of the aneurysm. Ruptured mesenteric artery aneurysms are a challenging problem for the vascular surgeon. PDA aneurysms are rare and often occur in an unfavorable location. There appears to be an association with anatomic anomalies of the mesenteric circulation. Prompt invasive and noninvasive diagnostic studies aid in the definitive management of this often fatal problem. Combined endovascular and open techniques can be used for successful treatment.

Meeting AHA/ACC secondary prevention goals in a vascular surgery practice: an opportunity we cannot afford to miss.

OBJECTIVE: In an effort to reduce cardiovascular mortality, patients with atherosclerotic arterial disease should undergo risk factor modification according to the American Heart Association/American College of Cardiology (AHA/ACC) Secondary Prevention Guidelines (hereafter, Guideline). We assessed compliance with the Guideline in a group of patients seen in a vascular surgery practice. METHODS: We evaluated 200 consecutive patients with lower-extremity occlusive disease, cerebrovascular disease, or abdominal aortic aneurysm seen by a university-based vascular surgery practice. The subjects were patients who had been seen previously in our clinic (ESTABLISHED) and new referrals (NEW). Data pertinent to each of the nine AHA/ACC Guideline goals were collected from patient interviews, medication histories, and laboratory records. Compliance with each of the Guideline goals was evaluated. Differences in compliance between ESTABLISHED and NEW patient groups were also compared. We also recorded whether a patient had a previous endovascular or open surgical vascular intervention (EVENT or NO EVENT). Differences in compliance between the EVENT and NO EVENT groups were compared. RESULTS: Most patients did not achieve the secondary prevention goals recommended in the Guideline. Patients who had a prior vascular intervention (EVENT) were significantly more likely to achieve goals for low-density lipoprotein level (43% vs 23%), and for statin (71% vs 39%), beta-blocker (46% vs 27%), angiotensin-converting enzyme inhibitor (53% vs. 35%), and antiplatelet agent (85% vs. 68%) use (P < .05). ESTABLISHED patients were significantly more likely than NEW patients to have a prior EVENT (87% vs 47%, P < .0005). ESTABLISHED patients were significantly more likely than NEW patients to achieve goals for low-density lipoprotein level, beta-blocker, and statin use; however, these differences were likely due to the higher proportion of EVENT patients in the ESTABLISHED group. CONCLUSION: Compliance with the Guideline is suboptimal in patients with atherosclerotic arterial disease. Secondary prevention goals were more often achieved in the EVENT patient group, suggesting that a vascular intervention may lead to increased patient and physician awareness and compliance with the Guideline. A targeted effort towards risk factor modification in patients with atherosclerotic arterial disease could improve compliance with the Guideline and reduce cardiovascular mortality.

Pneumococcal aortitis: a difficult preoperative diagnosis.

Primary infections of the aorta are rare. We recently treated a patient who was given a diagnosis of noninfectious aortitis after an extensive work-up, but after clinical deterioration, was found to have a pneumococcal mycotic aneurysm at the time of surgery. The difficulty in distinguishing microbial aortitis from noninfectious chronic periaortitis is discussed as well as the need for frequent surveillance imaging of the aorta if immunosuppression is used to treat the latter entity. The infected aortoiliac segment was ultimately repaired with autologous femoral veins.

Computed tomographic scanning without oral contrast solution for blunt bowel and mesenteric injuries in abdominal trauma.

BACKGROUND: Computed tomographic (CT) scanning using intravenous and oral contrast material has traditionally been advocated for the evaluation of intra-abdominal injury, including blunt bowel and mesenteric injuries (BBMIs). The necessity of oral contrast in detecting these injuries has recently been called into question. The purpose of this study was to determine the sensitivity and specificity of CT scanning without oral contrast for BBMIs. METHODS: We prospectively enrolled 500 consecutive blunt trauma patients who received CT imaging and interpretation (CT-Read1) of the abdomen from July 2000 to November 2001. All patients were imaged without oral contrast, but with intravenous contrast. CT images were reviewed within 24 hours of admission by a research radiologist (CT-Read2) blinded to CT-Read1. For study purposes, true BBMI was determined to be present if either laparotomy or autopsy identified bowel or mesenteric injury, or both CT-Read2 and the hospital discharge summary described bowel or mesenteric injury. Three-month telephone follow-up was also completed. RESULTS: CT-Read1 detected 19 of 20 bowel and mesenteric injuries. CT-Read1 missed one duodenal perforation. There were two patients with false-positive interpretations of CT-Read1 for bowel injury. The sensitivity and specificity of CT imaging for the detection of BBMIs were 95.0% and 99.6%, respectively. CONCLUSION: CT imaging of the abdomen without oral contrast for detection of BBMIs compares favorably with CT imaging using oral contrast.