Papers by Christos V Ioannou
Il Giornale di chirurgia, 2018
Patients with critical limb ischemia are usually compromised, frequently making administration of... more Patients with critical limb ischemia are usually compromised, frequently making administration of general or regional anesthesia problematic. We treated 3 fragile patients presenting contraindications to undertake traditional anesthetic techniques for lower limb revascularization, in whom local anesthesia with conscious sedation was used to complete the operation. An axillo-bifemoral, a unilateral axillo-femoral and a femoro-femoral bypass were performed. Procedure was uneventful in all three cases despite the coexistence of specific surgical challenges (distal anastomosis at the profunda in two cases, redo surgery and scarred groin in the third). Surgical revascularization under local anesthesia may be considered in selected high risk patients.
Cardiovascular and interventional radiology, 2014
Endovascular aneurysm repair (EVAR) is considered to be the treatment of choice for abdominal aor... more Endovascular aneurysm repair (EVAR) is considered to be the treatment of choice for abdominal aortic aneurysms (AAA). Despite the initial technical success, EVAR is amenable to early and late complications, among which the migration of the endograft (EG) with subsequent proximal endoleak (Type Ia) leads to repressurization of the AAA sac, exposure to excessive wall stress, and, hence, to potential rupture. This article discusses the influence that certain geometrical factors, such as neck angulation, iliac bifurcation, EG curvature, neck-to-iliac diameter, and length ratios, as well as iliac limbs configuration can exert on the hemodynamic behavior of the EGs. The information provided could help both clinicians and EG manufacturers towards further development and improvement of EG designs and better operational planning.
Journal of vascular surgery, 2014
Journal of endovascular therapy : an official journal of the International Society of Endovascular Specialists, 2014
Annals of vascular surgery, 2014
Journal of endovascular therapy : an official journal of the International Society of Endovascular Specialists, 2014
Research in Experimental Medicine, 2001
The aim of this experimental study was to investigate the effect of diclofenac sodium and ketopro... more The aim of this experimental study was to investigate the effect of diclofenac sodium and ketoprofen, two non-steroidal anti-inflammatory drugs (NSAIDs) with different excretion pathways, and the role of other enteric factors during simultaneous administration of these drugs on the development of mucosal lesions of the small intestine in canines. Twenty-five animals were divided into three groups. Group I included
Cardiovascular and interventional radiology, 2014
ABSTRACT To the Editor,Massmann and colleagues report on the successful treatment of two juxtaren... more ABSTRACT To the Editor,Massmann and colleagues report on the successful treatment of two juxtarenal aneurysms with the chimney technique using the Ovation abdominal stent graft system (TriVascular, Santa Rosa, CA, USA) [1]. The described two patients had their lowermost renal artery stented with a balloon-expandable (Advanta V12, Atrium Medical Corporation, Hudson, NH) and a self-expandable (Fluency, Bard, Murray Hill, NJ) stent graft, respectively, whereas the small iliac vessels problem was easily encountered with the low-profile introduction system of the Ovation stent graft.As clearly depicted in Fig. 3 of the article, the vertical segment of the balloon-expandable stent graft run parallel to the Ovation’s segment proximal to the first inflatable ring, i.e., the segment where the basis of the suprarenal stent is attached, and thus exerts radial force. However, if one assumes a chimney case where both renal arteries are involved, then the Ovation endograft will be advanced more cephalad to a
Frontiers in Surgery, 2016
Abdominal aortic aneurysms (AAAs) represent a focal dilation of the aorta exceeding 1.5 times its... more Abdominal aortic aneurysms (AAAs) represent a focal dilation of the aorta exceeding 1.5 times its normal diameter. It is reported that 4-8% of men and 0.5-1% of women above 50 years of age bear an AAA. Rupture represents the most disastrous complication of aneurysmal disease that is accompanied by an overall mortality of 80%. Autopsy data have shown that nearly 13% of AAAs with a maximum diameter ≤5 cm were ruptured and 60% of the AAAs >5 cm in diameter never ruptured. It is therefore obvious that the "maximum diameter criterion," as a single parameter that fits all patients, is obsolete. Investigators have begun a search for more reliable rupture risk markers for AAA expansion, such as the level and change of peak wall stress or AAA geometry. Furthermore, it is becoming more and more evident that intraluminal thrombus (ILT), which is present in 75% of all AAAs, affects AAA features and promotes their expansion. Though these hemodynamic properties of AAAs are significant and seem to better describe rupture risk, they are in need of specialized equipment and software and demand time for processing making them difficult in use and unattractive to clinicians in everyday practice. In the search for the addition of other risk factors or user-friendly tools, which may predict AAA expansion and rupture, the use of the asymmetrical ILT deposition index seems appealing since it has been reported to identify AAAs that may have an increased or decreased growth rate.
La Radiologia medica, Jan 23, 2016
To investigate if the routine use of an aortic balloon within 15-30Â min after Ovation stent graft... more To investigate if the routine use of an aortic balloon within 15-30Â min after Ovation stent graft ring inflation would resolve any inflow stenosis, which may reach 60Â %, at the level of the sealing rings. Moreover, we estimated the potential hemodynamic compromise in these patients during rest and exercise. Following 3-dimensional reconstruction of AAA models, cross-sectional area of the infrarenal aorta just proximal the sealing mechanism (A aort, R aort, respectively) and internal area at the site of stenosis (A int, R int, respectively) were measured for 83. Forty-nine patients were managed without and 34 with an aortic balloon use. Pressure drop during rest and exercise was estimated. Technical success was 98Â % and there were no perioperative deaths, one type-I endoleak, and 12 (14.5Â %) type-II endoleaks. Median A int and R int were significantly reduced compared to A aort [55Â % reduction, 143 (range 28-380) mm(2) vs 314 (range 177-531) mm(2), P value <0.001] and R aort [42Â %...
Annals of Vascular Surgery, Nov 26, 2014
The Ovation Stent Graft System is a new trimodular endoprosthesis for the treatment of abdominal ... more The Ovation Stent Graft System is a new trimodular endoprosthesis for the treatment of abdominal aortic aneurysms. A long nitinol stent with anchors serves the suprarenal fixation, whereas inflatable rings in the main body achieve sealing. This dissociation precludes the presence of a nitinol skeleton in the endograft, thus, avoiding competing for the same space within the delivery system, enabling the latter to achieve ultra-low profiles. However, the lack of nitinol support may render the endograft&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s docking limb prone to collapse in cases of narrow aortoiliac anatomy. We present a case of challenging contralateral limb catheterization, facilitated effectively through the brachial access. Preparing for the brachial route remains a useful and time-sparing adjunctive measure that guarantees the device&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s safety and effectiveness in challenging anatomies.
Medical & Biological Engineering & Computing, 2014
Abdominal aortic aneurysm wall distensibility can be estimated by measuring pulse pressure and th... more Abdominal aortic aneurysm wall distensibility can be estimated by measuring pulse pressure and the corresponding sac volume change, which can be obtained by measuring wall displacement. This approach, however, may introduce error if the role of thrombus in assisting the wall in bearing the pulse pressure loading is neglected. Our aim was to introduce a methodology for evaluating and potentially correcting this error in estimating distensibility. Electrocardiogram-gated computed tomography images of eleven patients were obtained, and the volume change between diastole and systole was measured. Using finite element procedures, we determined the equivalent pulse pressure loading that should be applied to the wall of a model where thrombus was digitally removed, to yield the same sac volumetric increase caused by applying the luminal pulse pressure to the model with thrombus. The equivalent instead of the measured pulse pressure was used in the distensibility expression. For a relative volumetric thrombus deposition (V ILT) of 50Â %, a 62Â % distensibility underestimation resulted when thrombus role was neglected. A strong linear correlation was observed between distensibility underestimation and V ILT. To assess the potential value of noninvasive wall distensibility measurement in rupture risk stratification, the role of thrombus on wall loading should be further investigated.
La radiologia medica, 2015
Patients were treated under a common protocol, including clinical and imaging follow-up at discha... more Patients were treated under a common protocol, including clinical and imaging follow-up at discharge, 30 days, 6 months, and annually for 5 years. Adverse events, clinical and imaging data and possible re-intervention were recorded. Results The Ovation stent graft was implanted successfully in 36 patients (100 %). None of the patients required conversion to open surgery, and none presented with an aneurysm rupture. Endograft stent fracture or migration was not observed in any case. No type I, III or IV endoleaks were observed; in 12 patients (33.3 %), a type II endoleak was noted, in one case with sac enlargement but not treated due to concomitant comorbidities and the patient's decision. Conclusions The 2-year results of the Ovation Abdominal Stent Graft System demonstrate excellent safety and effectiveness in the treatment of patients with AAAs, particularly in those with challenging anatomical characteristics.
Annals of Vascular Surgery, 2012
Vascular and Endovascular Surgery, 2012
Ankle-brachial index (ABI) is a basic diagnostic tool of peripheral arterial disease (PAD) and an... more Ankle-brachial index (ABI) is a basic diagnostic tool of peripheral arterial disease (PAD) and an indicator of its severity. 1 Its estimation is also of paramount importance in assigning diagnosis of lower extremity wounds and in estimating the necessity for prompt revascularisation. 2-4 An ABI <0.9 indicates PAD both in symptomatic and asymptomatic patients and is associated with elevated risk of future cardiovascular events. 1,5,6 According to the TransAtlantic Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II), ABI should be evaluated in all patients experiencing walking disabilities, those between 50 and 69 years old carrying known risk factors for cardiovascular disease, as well as in patients older than 70 years regardless of existence of cardiovascular risk factors or with Framingham risk score 10% to 20%. 1 In general, ABI has high specificity and sensitivity, 7 provided that it is evaluated by well-trained health professionals. 8 However, there is evidence that training of medical students and doctors during their early residency is rather limited, leading to unreliable and false measurements. 9-11 Additionally, poor measurement technique and limited knowledge result in false assessment and misinterpretation of ABI, 10 which may be coupled with notable discrepancy between doctors of different medical specialties in measured values for variable levels of PAD severity. 12 Hence, better training of medical students and junior doctors in the assessment of ABI is required. In the medical school of Democritus University of Thrace, Vascular Surgery is a mandatory course for students. We have previously shown the effectiveness of systematic methodical training in the use of a pocket Doppler apparatus. 13 The aim of this study was to evaluate whether undergraduate training can lead to reliable ABI results. To the best of our knowledge, this is the first study examining ABI training in medical students.
American Journal of Case Reports, 2013
Advanced age and comorbidities in the setting of acute type A aortic dissection It is important t... more Advanced age and comorbidities in the setting of acute type A aortic dissection It is important to consider whether it is acceptable to leave uncorrected substantive comorbidities in the setting of emergency surgery, or if treating them at the cost of deferred or denied surgery is more appropriate. Mehta and associates have shown that the risk of mortality from surgery for acute type A aortic dissection is 45% for patients 80 to 84 years of age and 50% for those 85 or older. 8) These are formidable levels of operative risk that
Annals of Vascular Surgery, 2012
Annals of Vascular Surgery, 2006
Our purpose was to identify and quantify hemodynamic factors contributing to the generation, prol... more Our purpose was to identify and quantify hemodynamic factors contributing to the generation, proliferation, and rupturing of abdominal aorta aneurysms (AAAs) using a computational investigation of steady laminar and turbulent flow in AAA models. Steady laminar and turbulent flows were computed using the incompressible Navier-Stokes equations. Flow fields in symmetric shapes of different extents and degrees of expansion are presented first. Two representative cases of asymmetric AAAs are considered next: an aneurysm with an elliptic cross section and an aneurysm with preferential expansion in one direction. For symmetric aneurysms, parametric studies are presented. For asymmetric aneurysms, flow fields are computed only for high flow rates representative of systolic flow. For all cases, a recirculating flow region was found in the expanded part of the AAA. Recirculation is accompanied by a minor increase in pressure but a significant increase in wall shear stress. For cases where turbulent flow was considered, it was found that the recirculation zone diminishes but the computed wall shear stress reaches levels higher than laminar flow. The levels of wall shear stress reached in turbulent flow may cause lesions of the aneurysmal wall. The minor variation of pressure within the aneurysms with smooth expansions indicates that the structural properties of the arterial wall tissue may play a significant role for the generation and subsequent proliferation of the aneurysm. However, the high values of the wall shear stress in AAAs appear to be an important hemodynamic factor that may contribute to wall degeneration and eventual rupturing. The recirculating flow in AAAs may explain the generation of intraluminal thrombi. Furthermore, the asymmetry and complexity of the flow in asymmetric AAAs may explain the frequently observed asymmetric thrombi distribution.
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Papers by Christos V Ioannou