How to calculate the main aortic graft-diameter for a chimney-graft

BACKGROUND

The aim of this paper was to present a mathematical model to calculate the required main aortic graft-diameter for parallel chimney-grafts.

METHODS

Geometric approximation model, developed to allow for a standardized calculation of the main aortic graft-diameter determined by the aortic diameter and the diameter of the chimney-graft.

RESULTS

We propose a mathematical formula using circular segments of the aorta and the chimney-graft and provide a table with recommended main aortic graft-diameters for single chimney-grafts of 6 and 8 mm.

CONCLUSION

Geometric approximation can be used to calculate the required main aortic graft-diameter. For parallel running chimney-grafts a significant degree of oversizing is necessary to allow the main aortic body to surround the chimney and to prevent the occurrence of gutters, which may cause type-1 endoleaks.

[Endovascular versus conventional vascular surgery--old-fashioned thinking? Part 2: carotid artery stenosis and peripheral arterial occlusive disease]

Endovascular therapy has widely replaced conventional open vascular surgical reconstruction. For this reason, both techniques were widely considered to be competing approaches. Evidence-based data from randomized prospective trials, meta-analyses and clinical registries, however, demonstrated that both techniques should be used to complement each other. It became increasingly more evident that the use of either procedure depends on the underlying disease and the anatomical conditions, whereby a combination of both (hybrid approach) may be the preferred option in certain situations. This review focuses on the treatment of patients with carotid artery stenosis, intermittent claudication, critical limb ischemia and acute limb ischemia.

[Endovascular versus conventional vascular surgery - old-fashioned thinking? Part 1: interventions on the aorta]

Endovascular therapy has widely replaced conventional open vascular surgical reconstruction. For this reason both techniques were widely considered to be competing approaches. Evidence-based data from randomized prospective trials, meta-analyses and clinical registries, however, demonstrated that both techniques should be used to complement each other. It became increasingly more evident that the use of either procedure depends on the underlying disease and the anatomical conditions, whereby a combination of both (hybrid approach) may be the preferred option in certain situations. This review focuses on the treatment of complicated acute type B aortic dissection, descending thoracic aortic aneurysms, thoracoabdominal aortic aneurysms as well as asymptomatic and ruptured abdominal aortic aneurysms.

Two Decades of Endovascular Repair of Popliteal Artery Aneurysm--A Meta-analysis

OBJECTIVE/BACKGROUND

Over the last two decades endovascular repair (EVR) of popliteal artery aneurysms has emerged as a treatment alternative to conventional open surgical repair (OSR). The aim of this review was to evaluate the safety and efficiency of each repair method, comparing the following outcomes after EVR and OSR: (i) primary patency; (ii) operating time; (iii) length of hospital stay; (iv) peri-operative complications; (v) limb salvage; and (vi) patient survival.

METHODS

The PubMed and Cochrane Central Register of Controlled Trials were searched for publications that compared outcomes after EVR and OSR (last search November 2014). Randomized controlled trials (RCTs), prospective and retrospective observational cohort studies were included. The quality of studies was evaluated using the Newcastle-Ottawa scale and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. Random effect models were employed to estimate odds ratios (ORs), mean differences, and hazard ratios (HRs).

RESULTS

One RCT combined with a prospective cohort study and four retrospective cohort studies with an overall total of 652 cases (236 EVR, 416 OSR) were identified. GRADE quality of evidence was low or very low for all outcomes. After a median follow up of 33 months, patients who received EVR showed equal primary patency rates to patients who received OSR (HR 1.46, 95% confidence interval [CI] 0.92-2.33). Lengths of operation and hospitalization were significantly shorter following EVR; rates of 30 day graft thrombosis (OR 3.16, 95% CI 1.31-7.62) and 30 day re-intervention (OR 2.15, 95% CI 1.02-4.55) were significant higher for patients who received EVR compared with those who received OSR. There was no effect on mortality (OR 2.31, 95% CI 0.37-14.49) or limb loss (OR 0.59, 95% CI 0.16-2.15).

CONCLUSION

EVR of popliteal artery aneurysm showed mid-term results comparable to open surgery and appears to be a safe alternative to OSR. However, the existing empirical evidence base is too fragmentary to draw firm conclusions. Further research and the introduction of population based registries will be needed to allow reliable evaluation of EVR.

Transcardiac endograft delivery for endovascular treatment of the ascending aorta: a feasibility study in pigs

PURPOSE

To compare the technical feasibility and hemodynamic alterations during antegrade transcardiac access routes vs conventional transfemoral access (TFA) for endovascular treatment of the ascending aorta in a porcine model.

METHODS

Antegrade transseptal access (TSA), transapical access (TAA), and TFA were used for implantation of custom-made endografts into the ascending aorta under fluoroscopy (6 pigs each). Hemodynamic parameters, myocardial and cerebral blood flow, and carotid artery blood flow were evaluated during baseline (T1), sheath advancement (T2), after sheath retraction (T3), and after endograft deployment (T4).

RESULTS

Endograft deployment was feasible in all animals; all coronary arteries remained patent. Hemodynamic parameters were comparable in all 3 study groups during all measurements. During T2, transient hemodynamic alteration occurred in all groups, with transient severe valve insufficiency in TSA and TAA reflected by the higher pulmonary to mean arterial pressure ratio (p<0.05) as compared with TFA. Values stabilized again at T3 and remained stable until T4. The innominate artery was partially occluded in 4 (TSA), 3 (TAA), and 5 (TFA) animals. There was no deterioration of myocardial or cerebral perfusion during the procedures. Endograft deployment and fluoroscopy times during TAA were shorter than in TSA and TFA.

CONCLUSIONS

TSA, TFA, and TAA to the ascending aorta are feasible for endograft delivery to the ascending aorta in a porcine model. Transient hemodynamic instability in TSA and TAA recovered to near preoperative values. TAA appeared technically easier.

Chronic type B aortic dissection: indications and strategies for treatment

Chronic type B aortic dissection is a distinctive condition that needs individual treatment strategies and different considerations than in therapy of acute or subacute type B aortic dissection. The most common indication for treatment of this complex disease is aneurysmal dilatation of the dissected aortic segment. While open repair of the enlarged dissected aorta remains the best option for good-risk patients and patients with connective tissue disorders in high-volume centers with respective expertise, endovascular management of chronic type B aortic dissection with postdissection aneurysms has significantly gained ground in the past years. But the concept of TEVAR with implantation of a tubular stent-graft into the thoracic aorta to seal the proximal entry tear and reroute the blood flow into the true lumen alone, is not associated with satisfactory results. This is mainly due to the sparse remodeling capacity of the aortic tissue compared to earlier stages of the disease as the aortic wall and the dissection membrane are thickened and more rigid. On the other hand, it is restricted by the most limiting factor for endovascular success in chronic type B aortic dissection: persistent false lumen perfusion. This problem also affects patients with residual dissection after surgical repair of a DeBakey type I aortic dissection or dissection after ascending aortic repair for other pathologies. Hence, it is evident that strategies to achieve endovascular false lumen occlusion are of increasing importance and novel techniques have been introduced to solve the problem of persisting false lumen flow. Thus, the evolution of a large variety of techniques to address the false lumen perfusion issue indicates that complicated chronic type B dissection involves a high diversity in clinical presentation and morphology. A large armamentarium of catheter skills as well as critical individualized treatment strategies are required to address the heterogenous morphological disease pattern for each individual patient. The rapid development in endovascular techniques gives new directions for treatment indications and strategies in chronic aortic dissection and enables new insights into this old disease.

Validation of the disease-specific quality of life Wuerzburg Wound Score in patients with chronic leg ulcer

Background: Aim of the study was to validate a newly developed disease-specific quality of life questionnaire (Wuerzburg Wound Score, WWS) in patients with chronic arterial or venous leg ulcers. Patients and methods: In this prospective study 115 patients with vascular disease associated leg ulcer (54 arterial ulcer, 61 venous ulcer) were studied (mean age 66 ± 11 years, 51 % male). All patients completed the WWS at baseline, and after four and 12 weeks. To assess construct validity additionally all patients completed the generic QoL-questionnaires Short Form-36 (SF-36) and Nottingham Health Profile (NHP). Construct validity and responsiveness of the WWS were tested. Results: WWS showed acceptable construct validity versus SF-36 (r = 0.5 - 0.78; P < 0.001) and NHP (r = 0.36 - 0.68; P < 0.001). Responsiveness of the WWS was superior to SF-36 (P < 0.05) and NHP (P = 0.01). Generic as well as disease-specific QoL were more impaired in patients with arterial ulcer. Conclusions: The WWS is a valid measure of disease-specific QoL in patients with leg ulcers and it is more sensitive than the generic instruments in detecting changes of wound healing over time. Further assessment of the psychometric properties of the WWS with larger patient samples is required before the test can be recommended for use in clinical practice.

TEVAR for chronic aortic dissection - is covering the primary entry tear enough?

Treatment-strategies for type B aortic dissection (TBAD) are rapidly developing towards endovascular treatment strategies. While TEVAR for acute TBAD shows favourable results, TEVAR in chronic TBAD following the same interventional strategies as in acute TBAD by covering the proximal entry-tear alone has shown unsatisfactory results with one third of the patients developing further false-lumen growth and mortality of 36% at 3 years. This review article describes endovascular strategies and adjunctive techniques to prevent distal false-lumen back-flow in patients with chronic TBAD, as covering the proximal entry tear has proven insufficient.

Spinal cord ischemia in open and endovascular thoracoabdominal aortic aneurysm repair: new concepts

For more than half a century ischemic spinal cord injury (SCI) and consecutively permanent paraplegia remained the most devastating complication after open and endovascular thoracoabdominal aortic aneurysm (TAAA) repair. Various neuroprotective strategies (e.g., motor-/somatosensory evoked potential monitoring and cerebrospinal fluid drainage) used as adjuncts have lowered the SCI; maybe most importantly, the modern collateral network (CN) has begun to replace the classic understanding of spinal cord blood supply implying several consequences. Reliable non-invasive tools to monitor cord perfusion to detect imminent spinal cord malperfusion, ischemia and forthcoming neurologic injury (particularly early postoperatively) is not available, neither is a reliable strategy to prevent ischemic injury during distal circulatory arrest and after segmental artery occlusion. Currently, two promising new concepts--potentially advancing spinal protection in open and endovascular TAAA repair--address these issues: 1) non-invasive real-time monitoring of the paraspinous CN-oxygenation via near-infrared spectroscopy (NIRS) as an alternative to the demanding direct neuromonitoring; and 2) preconditioning of the CN as minimally invasive, endovascular "first stage" to increase the resilience of spinal cord perfusion prior to definite aortic repair. This article illustrates both concepts discussing: 1) the clinical application of thoracic and lumbar collateral NIRS monitoring to indirectly detect spinal cord hypoperfusion; and 2) minimally invasive selective segmental artery coil-embolization (MISACE) for (arteriogenic) preconditioning of the CN prior to extensive open or endovascular staged TAAA repair.

Acute aortic syndromes: definition, prognosis and treatment options

Acute aortic syndromes (AAS) are life-threatening vascular conditions of the thoracic aorta presenting with acute pain as the leading symptom in most cases. The incidence is approximately 3-5/100,000 in western countries with increase during the past decades. Clinical suspicion for AAS requires immediate confirmation with advanced imaging modalities. Initial management of AAS addresses avoidance of progression by immediate medical therapy to reduce aortic shear stress. Proximal symptomatic lesions with involvement of the ascending aorta are surgically treated in the acute setting, whereas acute uncomplicated distal dissection should be treated by medical therapy in the acute period, followed by surveillance and repeated imaging studies. Acute complicated distal dissection requires urgent invasive treatment and thoracic endovascular aortic repair has become the treatment modality of choice because of favorable outcomes compared to open surgical repair. Intramural hematoma, penetrating aortic ulcers, and traumatic aortic injuries of the descending aorta harbor specific challenges compared to aortic dissection and treatment strategies are not as uniformly defined as in aortic dissection. Moreover these lesions have a different prognosis. Once the acute period of aortic syndrome has been survived, a lifelong medical treatment and close surveillance with repeated imaging studies is essential to detect impending complications which might need invasive treatment within the short-, mid- or long-term.

Homografts and extra-anatomical reconstructions for infected vascular grafts

Managing graft infections is a challenge in vascular surgery. The incidence of vascular graft infections varies between 2% and 6%. The number of patients treated by means of implantation of artificial prostheses is constantly growing. The treatment of vascular graft infections remains controversial. This article discusses in-situ repair and the role of extra-anatomic routes. Homografts present the lowest rate of reinfection with acceptable rates of degradation and aneurysm formation. Silvergrafts and synthetic grafts coated with antimicrobials show similar early and late mortality rates, but higher reinfection rates. The outcome extra-anatomic bypass surgery seems to be improved in actual series compared with historical results but their disadvantages (limited patency, higher rate of amputations as well as high rates of reintervention combined with higher early mortality) are obvious.

Acute ischemia and bypass occlusion: current options

AIM

Acute limb ischemia (ALI) and bypass occlusion are vascular emergencies and require immediate decisions and therapy. There are a lot of options, and the vascular therapist should be able to provide multiple alternatives. In this article we give on overview over the actual therapeutic options and present the data of a retrospective analysis of bypass occlusions.

METHODS

Therapeutic options of ALI are discussed according to the current literature. For the retrospective study, patients with acute or subacute occlusion of below knee alloplastic bypass were included. Endpoints of the study were secondary patency and limb salvage rate. A prognostic index was calculated to estimate the specific risk.

RESULTS

We analyzed 262 bypass occlusions; 161 patients were male. The majority of patients (N.=249) presented with threatened limb at readmission. After one year, 2/3 of the bypasses showed a reocclusion. Introducing the therapy with bypass thrombolysis enhanced the prognosis significantly. Of the factors examined, cardiac and renal insufficiency had a significant poor influence, whereas therapy with Coumadin enhanced the prognosis in terms of patency. The prognostic index was calculated using the factors identified as relevant in the multivariate analysis.

DISCUSSION

Despite all new technical tools, ALI and bypass occlusion is still associated with a significant risk for limb loss and mortality. Endovascular procedures are excellent options. The prognostic index may be a helpful tool in estimating the patency or risk of limb loss.

Association of multiple biomarkers and classical risk factors with early carotid atherosclerosis: results from the Gutenberg Health Study

BACKGROUND

In the Gutenberg Health Study, a random sample of the population was scanned with vascular ultrasound for early atherosclerosis. A continuous classical risk marker model (waist circumference, HbA1c, LDL/HDL ratio, pack years and pulse pressure) was compared to a model of modern biomarkers (C-reactive protein, troponin I, N-terminal pro B-type natriuretic peptide, copeptin, mid-regional pro-adrenomedullin, and asymmetric dimethylarginine) with regard to the ability of ruling out abnormal intima-media thickness (IMT), respectively, carotid plaques.

METHODS

Data of the first consecutive 5,000 participants (aged 35-74 years; 2,540 men, 2,460 women) were analyzed. IMT was measured at both common carotid arteries using an edge detection system. Plaques were defined as protrusion of ≥1.5 mm in common, internal and external carotid artery.

RESULTS

For classical risk factors, in comparison to a model of six modern biomarkers, regarding the variable (a) IMT>0.85 mm negative and positive predictive value (NPV and PPV) were 0.98 and 0.16 for both the classical risk factor model and the biomarker model. The second variable (b) presence of plaque could be ruled out with an NPV of 0.84 and identified with a PPV of 0.61 for classical risk factors, and 0.84 and 0.58 for biomarkers, respectively. Values were calculated using logistic regression analysis.

CONCLUSION

Classical risk factors allow ruling out pathologic IMT and presence of carotid plaques in a population of primary prevention in a reliable way. Modern biomarkers performed almost equally well but did not provide further information.

[Screening of carotid arteries before surgery: when does preoperative duplex ultrasound make sense?]

Carotid artery stenosis is a marker for generalized atherosclerosis with high cerebrovascular and cardiovascular morbidity and mortality rates. There is an estimated increase in prevalence of moderate stenosis for older age and male sex. Asymptomatic carotid artery stenosis is a risk factor for perioperative neurological events during general surgery. Planning of effective preoperative screening of populations at risk for asymptomatic carotid artery stenosis is best evaluated for cardiac surgery. General screening is not recommended; however, preoperative screening for asymptomatic carotid artery stenosis should be performed in high-risk patients with options for surgical or interventional treatment. These are patients with clinical signs of peripheral arterial disease and patients over 65 years old with at least one of the risk factors coronary artery disease, smoking and hypercholesterinemia. Preoperative screening in patients with carotid bruits may also be useful. Preoperative carotid artery screening may be beneficial in detecting occult carotid artery stenosis and thereby reducing perioperative neurological events.

How to calculate the main aortic graft-diameter for a chimney-graft

Aim: The aim of this paper was to present a mathematical model to calculate the required main aortic graft-diameter for parallel chimney-grafts. Methods: Geometric approximation model, developed to allow for a standardized calculation of the main aortic graft-diameter determined by the aortic diameter and the diameter of the chimney-graft. Results: We propose a mathematical formula using circular segments of the aorta and the chimney-graft and provide a table with recommended main aortic graft-diameters for single chimney-grafts of 6 and 8 mm. Conclusion: Geometric approximation can be used to calculate the required main aortic graft-diameter. For parallel running chimney-grafts a significant degree of oversizing is necessary to allow the main aortic body to surround the chimney and to prevent the occurrence of gutters, which may cause type-1 endoleaks.

Alloplastic bypass material below the knee: actual rationale

AIM

The greater saphenous vein is considered as material of first choice for a below-knee bypass. A high number of below knee synthetic, polytetrafluoroethylene or knitted polyester, bypass grafts in the institution of the senior author formed the basis to analyze factors for outcome of below-knee synthetic grafts.

METHODS

A total of 533 patients (327 men, 206 women; age: 71.2 ± 10.3 years), who had their first below knee bypass, were followed-up for up-to 9 (4.1 ± 2.6) years. Survival, primary and secondary patency, and limb salvage were compared between vein bypasses and synthetic grafts by Kaplan Meier analysis. Within the group of 377 patients with synthetic grafts comorbidities, previous interventions, indications, graft diameter, and technical aspects were related to outcome including univariate (log-rank) and multivariate (Cox Proportional Hazard Ratio) statistics.

RESULTS

The greater saphenous vein was superior to synthetic graft in primary and secondary patency as well as limb salvage (5 year limb salvage 73.3% vs. 56.7%, P=0.001). In patients with a synthetic bypass, relevant preoperative factors for higher patency rates were hypertension, coronary heart disease and no previous endovascular intervention. Patency and limb salvage was significantly improved for anastomoses not to a single crural vessel. Adding a St. Mary's Boot as cuff technique did not improve the results. In multivariate analysis, independent factors for higher primary patency were no previous endovascular intervention, low severity of peripheral arterial occlusive disease, coronary heart disease and age above 65. Additionally, femoropopliteal and tibioperoneal anastomoses were related to better limb salvage.

CONCLUSION

The greater saphenous vein reveals the best results for below-knee bypass grafts. However, if a vein is not available, synthetic grafts appear to be an valuable alternative especially in patients with no previous radiologic intervention, coronary heart disease, and age over 65.

Risk-adjusted strategies in the prevention of early arterial thrombosis following lower extremity arterial reconstruction: a comparison of unfractionated versus low molecular weight heparin

AIM

In vascular surgery postoperative thrombosis prophylaxis must sufficiently prevent arterial thrombosis. This cohort study examines different therapeutic approaches of unfractionated heparin (UFH) or low molecular weight heparin (LMWH) after vascular reconstruction.

METHODS

Four hundred seventy-five patients entered the study between 2005 and 2008. Our clinical routine made a differentiation between low-risk patients (N.=375) and patients with peripheral bypass, which were grouped as high-risk (N.=148). We changed our postoperative anticoagulation management after 24 months in the low-risk and after each 16 months in the high-risk group. The anticoagulation of low-risk patients consisted of either two applications of 7.500 IU UFH subcutaneously (N.=158) or one daily application of 40 mg LMWH each up to discharge (N.=169). High-risk patients received either 25.000 IU UFH i.v. over 24 hours and 4 days (N.=48), 2-times (N.=51) or one-time weight-adjusted LMWH (N.=49) up to discharge (1 mg/kg body weight). Minor complications (bleedings) were differentiated from major early graft occlusion during the postoperative course. Further follow-up was not done for this study.

RESULTS

Low risk: under LMWH, complications could be significantly reduced (P=0.001). Under LMWH significantly fewer occlusion complications occurred (P=0.01) and operation-induced hemorrhages were less frequently observed (P=0.05), this was significant in the complete low-risk group. High-risk: the one-time weight-adjusted LMWH group similarly exhibited many occlusions, like the unfractionated group (NS). The two-time LMWH treatment was significantly superior to the one-time application with respect to occlusion followed by amputations (P=0.03). Minor complications could be minimized overall by administration of LMWH and its dose reduction (NS).

CONCLUSION

The differentiation between patients with high and low risk seems reasonable. An improvement could be achieved by differentiated LMWH application. Synthetic specific antifactor Xa substances (fondaparinux) or other medications could lead in future to other changes in the management of vascular surgery patients and should be further evaluated.

Intraoperative quality control in vascular surgery

Since graft patency is the predominant predictor of long-term survival after vascular surgery, intraoperative graft patency control is of major importance for improving quality assurance. Intraoperative quality control is of major importance to obtain good short- and longterm results and to eliminate the need for reoperation. Currently there is no standardized approach and intraoperative quality control is not performed routinely by most surgeons. The most commonly used intraoperative assessment techniques include arteriography, duplex ultrasonography, angioscopy and transit-time flow measurement (TTFM). Fluorescent angiography (FA) using the dye indocyanine green (ICG) is a novel noninvasive technology for intraoperative visualization and documentation of vessels, bypass grafts, and perfusion with an infrared sensitive imaging device, so far validated for quality control in coronary bypass surgery. FA and TTFM are methods for quantitative assessment of blood flow measurement, which are currently exclusively used as intraoperative quality control in cardiac bypass surgery. Up to now, there are no experiences published for peripheral vascular reconstructions. However, transposition and implementation of these techniques seem to be valuable and useful. Therefore further studies for intraoperative quality control in vascular surgery are necessary.

Perioperative management and "Fast-Track" therapy in vascular medicine

Perioperative risk in vascular medicine is particularly high due to the increased prevalence of cardiovascular comorbidity. Therefore, it is of the utmost importance that during periprocedural management the patient remains in good general condition and that the patient is mobilized as soon as possible. Along with implementation of minimally-invasive techniques and endovascular procedures, networking and cooperation between the surgeon, anesthesiologist, physiotherapist and the nursing team can lead to an optimization of perioperative mobilization. The Fast-Track concept represents uncharted territory in the field of vascular surgery and it can provide advantages, particularly in relation to multimorbidity in the field of vascular medicine. The Fast-Track concept was introduced by Danish surgeon Henrik Kehlet and was originally intended to be implemented in general surgery. When compared to conventional management, this method offers better medical results, lower costs and other advantages for the patient: besides a better perioperative condition a reduction of postoperative complications and reduction of overall in-hospital stay was achieved. Therefore, the next logical step was to introduce and adapt this concept to other fields of operative medicine. This paper represents a systematic review on the actual experience of the fast-track concept in vascular surgery.

[Disappearing borders between the disciplines vascular surgery and interventional radiology from the perspective of vascular surgeons]

Demographic development leads to an exponential increase of cardiovascular illness. Additionally, technical development of conservative and invasive treatment modalities adds to an increase of specified therapy. Both items lead to increased specialization and a new orientation of vascular specialties. This concept implies that specific contents are referred and contained to the partner specialties. Angiology, vascular surgery and radiology are primary partners in this concept, however, in the following article the focus lies on vascular surgery and radiology.