Christian F. Vahl

Reevaluation of Direct True Lumen Cannulation in Surgery for Acute Type A Aortic Dissection

BACKGROUND The optimal mode of arterial cannulation in acute type A aortic dissection is controversial. We retrospectively investigated our experience with direct true lumen cannulation as an alternative to standard cannulation procedures. METHODS From April 2004 to August 2007, 29 patients (20 men, 9 women; mean age of 63.2 +/- 12.6 years) underwent emergency operation for acute type A aortic dissection with direct true lumen cannulation. After venous drainage into the venous reservoir, the ascending aorta was completely transected in the region between the sinotubular junction and innominate artery. After visual and digital identification of the true lumen, the arterial cannula was directly inserted into the true lumen and secured with a ligature. RESULTS Mean aortic cross-clamp time was 77.4 +/- 28.3 minutes, and hypothermic circulatory arrest for the distal anastomosis was 10.4 +/- 11.0 minutes. All patients survived the surgical procedure. No surgical problems were observed by applying this strategy. Mean intensive care unit stay was 4.0 +/- 3.5 days. Postoperative mean ventilation time was 43.3 +/- 41.3 hours. One patient had a prolonged postoperative course and required permanent ventilation. Two patients required temporary hemofiltration. Neurologic disorders occurred in 6 patients: 2 had severe cerebral hypoxia, and 4 had temporary hemiplegia under good regression. All patients were alive at discharge. CONCLUSIONS Direct true lumen cannulation is a promising surgical strategy for emergency operations in type A aortic dissection. It is a simple, quick, and safe method to provide antegrade flow through the true aortic lumen.

Mortality in patients with acute aortic dissection type A: analysis of pre- and intraoperative risk factors from the German Registry for Acute Aortic Dissection Type A (GERAADA)

OBJECTIVES Acute aortic dissection type A (AADA) is an emergency with excessive mortality if surgery is delayed. Knowledge about independent predictors of mortality on surgically treated AADA patients is scarce. Therefore, this study was conducted to identify pre- and intraoperative risk factors for death. METHODS Between July 2006 and June 2010, 2137 surgically treated patients with AADA were enrolled in a multicentre, prospective German Registry for Acute Aortic Dissection type A (GERAADA), presenting perioperative status, operative strategies, postoperative outcomes and AADA-related risk factors for death. Multiple logistic regression analysis was performed to identify the influence of different parameters on 30-day mortality. RESULTS Overall 30-day mortality (16.9%) increased with age [adjusted odds ratio (OR) = 1.121] and among patients who were comatose (adjusted OR = 3.501) or those who underwent cardiopulmonary resuscitation (adjusted OR = 3.751; all P < 0.0001). The higher the number of organs that were malperfused, the risk for death was (adjusted OR for one organ = 1.651, two organs = 2.440, three organs or more = 3.393, P < 0.0001). Mortality increased with longer operating times (total, cardiopulmonary bypass, cardiac ischaemia and circulatory arrest; all P < 0.02). Arterial cannulation site for extracorporeal circulation, operative techniques and arch interventions had no significant impact on 30-day mortality (all P > 0.1). No significant risk factors, but relevant increases in mortality, were determined in patients suffering from hemiparesis pre- and postoperatively (each P < 0.01), and in patients experiencing paraparesis after surgery (P < 0.02). CONCLUSIONS GERAADA could detect significant disease- and surgery-related risk factors for death in AADA, influencing the outcome of surgically treated AADA patients. Comatose and resuscitated patients have the poorest outcome. Cannulation sites and operative techniques did not seem to affect mortality. Short operative times are associated with better outcomes.

Initial Experience in the Treatment of Extensive Iliac Artery Aneurysms With the Nellix Aneurysm Sealing System.

Purpose: To assess the feasibility and effectiveness of the Nellix prosthesis in the treatment of common iliac artery aneurysms. Methods: Between May 2013 and June 2015, 230 patients underwent implantation of the Nellix device at 2 institutions. Fifty of these patients (mean age 76 years; 35 men) were identified as having 60 common iliac artery aneurysms (CIAAs) with a median diameter of 4 cm (range 3.5–7). The majority of patients had aortoiliac aneurysms (5, 70%), 10 (20%) had isolated CIAAs, and 5 (10%) had iliac anastomotic aneurysms after aortoiliac bypass. In 20 patients, the iliac aneurysm was the indication for the intervention; in the other 30 patients, the endovascular iliac repair was an adjunct procedure to endovascular aneurysm sealing (EVAS). An iliac branch device (IBD) was used when feasible to preserve flow to the internal iliac artery. Results: Seventeen (34%) patients underwent elective implantation of the Nellix graft in combination with an IBD, 33 (66%) patients underwent Nellix sealing of the CIAA using 1 (n=5), 2 (n=22), or 3 Nellix grafts (2 bilateral grafts and 1 graft as an extension to the external iliac artery in 6 patients). The technical success rate was 100%, and no graft-related complications were reported postoperatively. No buttock claudication, reinterventions, graft thrombosis, or endoleaks were observed during a mean follow-up of 12 months. Conclusion: Our initial experience demonstrates that Nellix grafts are feasible and safe for the treatment of extensive iliac artery aneurysms. The long-term durability of these grafts should be validated in larger patient cohorts before this promising alternative endovascular technique can gain widespread acceptance.

Outcomes of complex femorodistal sequential autologous vein and biologic prosthesis composite bypass grafts

OBJECTIVE Femorodistal autologous vein bypass proves to be the preferred surgical therapy for long arterial occlusions and provides excellent early and long-term results in critical lower limb ischemia. Whenever vein length was insufficient and two distal outflow arteries were present, a sequential composite bypass configuration was chosen with human umbilical vein (HUV) or ovine collagen prosthesis (Omniflow II; Bio Nova International Pty Ltd, North Melbourne, Australia) as the proximal prosthetic part of the bypass. Single-center experience with this technique regarding limb salvage, graft function, secondary reinterventions, and biodegeneration is presented. METHODS Between January 1998 and January 2009, 122 consecutive sequential composite bypass operations were performed on 116 patients for short-distance claudication (2), chronic critical ischemia (117), or acute ischemia (3) in the absence of sufficient autologous vein length. HUV was used in 90 cases and Omniflow II in 32 cases. Grafts were followed by duplex scan supplemented by angiography in case of recurrent ischemia with prospective documentation of follow-up data in a computerized vascular database. Retrospective analysis of graft patency, limb salvage, and aneurysmal degeneration of the biologic prosthesis was performed. RESULTS Mean follow-up was 59 ± 45.5 months (range, 1-161 months). The 30-day mortality was 4.1%. Early postoperative complete or partial bypass thrombosis developed in 16% (20 cases) and required successful revision in 16 cases. During follow-up, 30 complete and 12 partial bypass occlusions occurred, necessitating selective surgical or interventional revision. Primary, primary assisted, and secondary patency rates and the limb salvage rate were 48%, 62%, 71%, and 87%, respectively, after 5 years and 26%, 46%, 54%, and 77%, respectively, after 10 years for all bypasses. Late biodegeneration of HUV prostheses was detected in four instances. CONCLUSIONS Late graft patency and limb salvage were good. These factors, combined with a tolerable rate of late aneurysmal degeneration, justify the use of biologic vascular conduits and autologous vein for complex femorodistal reconstructions.

Covalent RGD Modification of the Inner Pore Surface of Polycaprolactone Scaffolds

Scaffold production for tissue engineering was demonstrated by means of a hot compression molding technique and subsequent particulate leaching. The utilization of spherical salt particles as the pore-forming agent ensured complete interconnectivity of the porous structure. This method obviated the use of potentially toxic organic solvents. To overcome the inherent non-cell-adhesive properties of the hydrophobic polymer polycaprolactone (PCL) surface activation with a diamine was performed, followed by the covalent immobilization of the adhesion-promoting RGD-peptide. The wet-chemical approach was performed to guarantee modification throughout the entire scaffold structure. The treatment was characterized by means of chemical and physical methods with respect to an exclusive surface modification without altering the bulk properties of the polymer. RGD-modified scaffolds were tested in cell-culture experiments to investigate the initial attachment and the proliferation of three different cell types.

Questionable value of adjuvant arteriovenous fistula in pedal bypass at high risk for early failure.

Results of an adjuvant arteriovenous fistula (AVF) in pedal bypass surgery in the presence of poor status of the recipient artery, severely impaired intraoperative runoff, or revision for early failure and flow restitution were analyzed in a retrospective study. From January 1998 to December 2006, 24 adjuvant AVFs were constructed in autologous vein or composite pedal bypasses with low intraoperative bypass flow, poor status of the pedal artery, or during successful early bypass revision to prevent graft failure. All infrainguinal bypass operations were registered in a computerized database and prospectively followed. Pedal bypasses with adjunctive AVF were reviewed for fistula function, graft patency, limb salvage, and patient survival. Primary and secondary bypass patency rates at 1 year were 59% and 77%, respectively, with an AVF patency of 36%. Four legs were amputated despite a patent bypass with patent AVF on three occasions. The corresponding limb salvage rate was 65% at 1 year. Patient survival was 50% at 3 years. Adjuvant AVF constructed in grafts considered at high risk for early failure in pedal vein graft or composite bypass does not seem to prevent future graft failure. In patent bypasses the fistula has a significant tendency for spontaneous occlusion. It may be considered in the use of prosthetic composite pedal grafts in selected cases.

How to do it: direct true lumen cannulation technique of the ascending aorta in acute aortic dissection type A

In acute aortic dissection type A (AADA), direct true lumen cannulation (DTLC) of the ascending aorta is a fast and safe cannulation site providing antegrade perfusion of the supraaortic and visceral vessels. An Overholt clamp is passed around the ascending aorta to place a Mersilene tape for later securing of the arterial cannula. After draining venous blood into the cardiopulmonary bypass system (CPB), the ascending aorta is transected and the aortic lumen inspected. The true lumen is identified and an arterial cannula inserted directly. Finally, the cannula is secured with the previously placed tape and CPB is initiated. DTLC can be used as arterial cannulation standard technique in operations for AADA.

Tailoring Novel PTFE Surface Properties: Promoting Cell Adhesion and Antifouling Properties via a Wet Chemical Approach

Many biomaterials used for tissue engineering applications lack cell-adhesiveness and, in addition, are prone to nonspecific adsorption of proteins. This is especially important for blood-contacting devices such as vascular grafts and valves where appropriate surface properties should inhibit the initial attachment of platelets and promote endothelial cell colonization. As a consequence, the long-term outcome of the implants would be improved and the need for anticoagulation therapy could be reduced or even abolished. Polytetrafluoroethylene (PTFE), a frequently used polymer for various medical applications, was wet-chemically activated and subsequently modified by grafting the endothelial cell (EC) specific peptide arginine-glutamic acid-aspartic acid-valine (REDV) using a bifunctional polyethylene glycol (PEG)-spacer (known to reduce platelet and nonspecific protein adhesion). Modified and control surfaces were both evaluated in terms of EC adhesion, colonization, and the attachment of platelets. In addition, samples underwent bacterial challenges. The results strongly suggested that PEG-mediated peptide immobilization renders PTFE an excellent substrate for cellular growth while simultaneously endowing the material with antifouling properties.

Cell Adhesive and Antifouling Polyvinyl Chloride Surfaces Via Wet Chemical Modification

Polyvinyl chloride (PVC) is one of the most frequently used polymers for the manufacturing of medical devices. Limitations for its usage are based upon unfavorable surface properties of the polymer including its hydrophobicity and lack of functionalities in order to increase its versatility. To address this issue, wet chemical modification of PVC was performed through surface amination using the bifunctional compound ethylene diamine. The reaction was conducted in order to achieve maximum surface amination while leaving the bulk material unaffected. The initial activation step was characterized by means of various methods including contact angle measurements, colorimetric amine quantification, infrared spectroscopy, and gel permeation chromatography. Depth profiles were obtained by a confocal microscopic method using fluorescence labeling. Exclusive surface modification was thus confirmed. To demonstrate biological applications of the presented technique, two examples were chosen: The covalent immobilization of the cell adhesive Asp-Gly-Asp-Ser-peptide (RGD) onto PVC samples yielded a surface that strongly supported cellular adhesion and proliferation of fibroblasts. In contrast, the decoration of PVC with the hydrophilic polymer polyethylene glycol prevented cellular adhesion to a large extent. The impact of these modifications was demonstrated by cell culture experiments.

A minimally invasive approach for aortobifemoral bypass procedure

Surgical aortobifemoral bypass procedure for aortoiliac occlusive disease remains the gold standard treatment despite rapidly expanding range of indications for endovascular repair. Besides several disadvantages such as dysparaesthesias, hernias, and unpleasant outcome, transperitoneal exposure of the aorta is also associated with operative autonomic nerve injury. In five male patients, infrarenal aorta was exposed through a small (8 cm) supraumbilical midline incision. Incision of the posterior peritoneum above the infrarenal aorta was limited to 3 cm. A 1 cm infraumbilical incision allowed transperitoneal placement of the distal aortic clamp outside of the operative field. Four centimeters transverse incisions were made over the femoral bifurcations and implantation of the aortobifemoral graft followed. Extubation was performed after an operating time of 200 to 150 minutes with 30 to 20 minutes aortic clamping time. Nonopioids or nonsteroidal anti-inflammatory drugs were intermittently administered during 12 hours of intermediate care unit monitoring. Oral alimentation started 6 hours and complete mobilization at 48 hours postoperatively. Hospital discharge followed on the fourth to tenth postoperative day. This minimally invasive technique allows a precise and controlled open performance of all vascular anastomoses minimizing intraoperative and postoperative complications and significantly decreasing patient discomfort related to standard abdominal surgery.