[Endoluminal balloon dilatation of impacted central venous catheter-Case report and literature review]

BACKGROUND

The long-term application of tunneled central venous catheters leads to the development of firm adhesions between the wall of the vein and the catheter, which makes removal of the catheter difficult or impossible. The treatment options in such cases include abandonment of catheter parts or an open surgical approach up to sternotomy. At present, procedural alternatives are available, which include endovascular techniques such as the use of laser energy and endoluminal dilatation.

METHODS

This article describes the successful application of endoluminal dilatation for removal of ingrown central venous catheters in three patients, which had impacted in the superior vena cava and brachiocephalic vein. A 5 Fr (Cordis, Santa Clara, CA, USA) sheath was inserted into one lumen through the severed end of the double lumen catheter. Subsequently, a balloon catheter was inserted into the other lumen to prevent retrograde bleeding or air embolism. Under fluoroscopy a guidewire (0.018, Terumo Medical Corporation, Somerset, New Jersey, USA) was introduced via the sheath to beyond the tip of the hemodialysis catheter into the right atrium. Finally, an angioplasty balloon was inserted (4 × 80 mm) via the guidewire and the complete catheter was sequentially inflated with a pressure of 4 atm. It was then possible to pull out the catheter with no difficulty.

RESULTS

This technique resulted in the removal of the central venous catheters in all three patients, without any relevant complications or resistance.

CONCLUSION

By dissolving adhesions between the catheter and the vein wall, endoluminal balloon dilatation constitutes a reliable and safe technique for the extraction of impacted central venous hemodialysis catheters and may thus help to avoid further invasive surgical procedures.

External Stenting with a New Polyester Mesh Reduces Neointimal Hyperplasia of Vein Grafts in a Sheep Model

Objective

External stents placed around vein grafts have demonstrated effectiveness in reducing neointimal hyperplasia by preventing distension of the thin-walled vein grafts when exposed to arterial pressure. However, the ideal stent material has yet to be defined. The following study investigates the short- and long-term effects of an innovative polyester mesh stent designed with optimized adaptation of circumferential compliance.

Methods

Following in vitro definition of the ideal macro-porous polyester stent material, a total of 12 sheep underwent implantation of bilateral carotid artery vein graft bypasses. In six sheep, the short-term outcome (four weeks of implantation) was investigated by comparing the newly-designed stent to native veins, micro-porous PTFE stent grafts and metallic Biocompound® stents (BCGs). Flow volume and graft diameter were measured prior to explantation. Grafts were evaluated histologically with respect to morphometry and immunoassaying. In the long-term group (6-month implantation time), the polyester stent was compared to native veins.

Results

All stents effectively prevented dilatation of the graft. Perfused vessel diameters of the polyester veins were 8.3±0.6 mm. BCG as well as PTFE veins showed diameter reduction to 7.4±0.7mm (p<0.05) and 7.8±0.4 mm (p<0.05), respectively. Both in the short and long terms, the new polyester stent led to significantly higher reduction of neointimal hyperplasia and luminal encroachment compared to the native vessel. It proved superior to PTFE stenting, while the Biocompound® material failed to prove efficacy.

Conclusions

It was demonstrated that the new macro-porous polyester mesh stent reduced neointimal hyperplasia more effectively than other commercially available stents.

True-positive exercise electrocardiogram/false-negative thallium-201 scintigram: a proposal of a mechanism for the paradox

A 72-year-old man with exertional angina had a strongly positive exercise electrocardiogram (EECG) with a negative thallium-201 myocardial perfusion scintigram (Tl). Arteriography revealed triple-vessel coronary artery disease, for which he underwent aortocoronary bypass grafting. Repeat EECG was negative, and it was again associated with a negative Tl. The false-negative Tl on the first test was felt to be due to a rare phenomenon of homogeneously distributed reversible exercise-induced myocardial ischemia, leading to a uniform radiotracer count density. The even distribution of ischemia would also be expected to render a false-negative EECG, due to electrocardiographic cancellation, and this is frequently the case. However, in the patient presented herein, we propose that the ischemic cardiac apex rendered the EECG strongly positive because its position was not opposed by an ischemic muscular region, and thus an uncancelled ischemic ST-segment vector was generated. This hypothesis is supported by our recent work showing the unique role of the ischemic apex (among all the other myocardial territories) in rendering the EECG positive.

Influence of Elastic and Non-elastic External Dacron Mesh Support on Para-anastomotic Hypercompliance in End-to-End Anastomoses

OBJECTIVE

To quantify the influence of elastic and non-elastic external mesh support on para-anastomotic hypercompliance in end-to-end anastomoses (ex vivo).

MATERIALS

Six end-to-end anastomoses prepared from ovine carotid arteries without mesh support and with external elastic and non-elastic dacron mesh support.

METHODS

Compliance profiles of the anastomised arterial segments were measured successively, in the same anastomotic configuration without mesh support, with external elastic dacron mesh support and with external non-elastic dacron mesh support (randomized order). A pulsatile ex vivo perfusion system using a laser scan micrometer to monitor outer systolic and diastolic diameter was employed.

RESULTS

Median pre-anastomotic and post-anastomotic hypercompliance without external mesh support were 1.45 and 1.19%/100 mmHg, respectively, above reference compliance. Use of the elastic mesh support significantly reduced the median hypercompliance to 0.68%/100 mmHg (pre-anastomotic) and to 0.34%/100 mmHg (post-anastomotic) above reference compliance. The non-elastic mesh support caused approximately the same significantly reduced median hypercompliance to 0.53%/100 mmHg (pre-anastomotic) and 0.43%/100 mmHg (post-anastomotic).

CONCLUSIONS

Both elastic and non-elastic external mesh support significantly reduced pre- and post-anastomotic hypercompliance.

Endotension is Influenced by Wall Compliance in a Latex Aneurysm Model

OBJECTIVES

Even though endovascular aneurysm repair (EVAR) creates a closed chamber except for patent branches, the intra-sac pressure is never zero. This study was designed to investigate whether, and to what extent, aneurysm wall compliance influences intra-sac pressure.

DESIGN

In vitro experimental study.

METHODS

Aneurysm models with six and 12 latex layers were produced, resulting in elastic and stiff circumferential compliance (3.5 +/- 0.5 and 0.9 +/- 0.3%/100 mmHg, respectively). The models with an 18 mm internal neck and maximum aneurysm diameter of 60 mm were inserted into an in vitro circulation system. The systemic mean pressure (SPmean) was varied from 50 to 120 mmHg. After the aneurysm was excluded with a knitted polyethylene graft, aneurysm sac mean pressure (ASPmean) and aneurysm sac pulse pressure (ASPpulse) were measured. Data are presented as mean +/- SD. Statistics were performed using repeated measurements of variance; p<0.05 was considered significant.

RESULTS

In the model EVAR created a closed chamber without endoleak, but with an aneurysm sac pressure related to wall compliance. In the elastic aneurysm model with six latex coats the aneurysm sac mean pressure (ASPmean) and the aneurysm sac pulse pressure (ASPpulse) at all systemic pressures were significantly lower than they were in the stiffer model with 12 latex coats (p<0.05). At a SPmean of 90 mmHg, the ASPmean was 21.0 +/- 0.9 mmHg (six latex coats) and 26.0 +/- 0.2 mmHg (12 latex coats) (p<0.05), the ASPpulse was 5.7 +/- 0.2 mmHg (six latex coats) and 8.8 +/- 0.3 mmHg (12 latex coats) (p<0.05).

CONCLUSIONS

This in vitro model demonstrated that the aneurysm sac mean pressure (ASPmean) and the aneurysm sac pulse pressure (ASPpulse) were significantly influenced by the compliance of the aneurysm wall. These data highlight the need for further studies regarding endotension.

Compliance in Anastomoses With and Without Vein Cuff Interposition

OBJECTIVE

to compare anastomotic compliance in end-to-side anastomoses with and without vein cuff interposition. Materials polytetrafluoroethylene graft to bovine carotid artery without (standard) and with vein interposition (Linton-patch and Miller-cuff).

METHODS

zonewise compliance measurement of end-to-side anastomoses in an in-vitro circulation system. The zone most distal to the suture-line served as reference compliance.

RESULTS

directly distal to the suture-line the compliance of the Linton-patch (5.6+/-1.6%/100 mmHg) and Miller-cuff anastomosis (5.2+/-1.1%/100 mmHg) more closely approached reference compliance (standard: 5.0+/-1.2, Linton-patch: 4.5+/-1.5, Miller-cuff: 4.9+/-1.0%/100 mmHg) than that of the standard anastomosis (7.9+/-3.0%/100 mmHg). The maximal compliance values of the Linton-patch (9.5+/-2.3%/100 mmHg) and Miller-cuff anastomoses (9.8+/-2.7%/100 mmHg) were significantly higher than that of the standard end-to-side anastomosis (7.9+/-3.0%/100 mmHg). However, maximal compliance was shifted from the zone directly distal to the suture line in the standard end-to-side anastomosis, to the vein cuff interposition in the Linton-patch and Miller-cuff anastomoses.

CONCLUSION

the shift in maximal compliance to the wider portion of the anastomosis in the Miller-cuff and Linton-patch anastomoses may obviate reocclusion.

Does vascular stapling improve compliance of vascular anastomoses?

Elastic properties of vessel walls are altered by vascular anastomoses. Such alterations may lead to neointimal hyperplasia, which is a common cause of reocclusion following vascular surgery. The severity of paraanastomotic hypercompliant zones and anastomotic compliance drop depend on suturing material and on elastic properties of the anastomotic vessel segments. This study compares paraanastomotic hypercompliance and anastomotic compliance drop when using a new vascular closure system (VCS) and a conventional, continuous suture line in the preparation of end-to-end anastomoses. Compliance of artery-artery, vein-artery, and polytetrafluoroethylene-artery anastomoses was measured in an artificial circulation system at mean pressures of 60, 90, and 120 mm Hg, comparing conventional suturing and the VCS. When using the VCS for vein-artery anastomoses, significantly less postanastomotic hypercompliance was achieved at mean pressures of 60 mm Hg (14.2 +/-3.8% above remote postanastomotic area), compared to suture (55.1 +/-14.8%, p<0.05). At 90 mm Hg, respective values were 11.0 +/-2.3% for VCS and 54.7 +/-10.1% for suture, p<0.01. At 120 mm Hg, in polytetrafluoroethylene-artery anastomoses, the anastomotic compliance drop was significantly less when using the continuous suture line (93.9 +/-1.1% below remote postanastomotic compliance), compared to VCS (97.2 +/-0.2%, p<0.05). Compared to conventional suturing, use of the VCS reduced postanastomotic hypercompliance in vein-artery anastomoses.

Transient left posterior hemiblock during myocardial ischemia-eliciting exercise treadmill testing: a report of a case and a critical analysis of the literature

We describe a 75-year-old male patient with two-vessel coronary artery disease, who developed transient left posterior hemiblock (LPH) while undergoing an exercise treadmill test (ETT). The intraventricular conduction abnormality initially had the features of alternating LPH, which evolved to stable LPH prior to dissipating, and it occurred at the first minute of recovery. The exercise electrocardiogram and the associated thallium-201 myocardial perfusion scintigraphy (Tl) revealed severe reversible myocardial ischemia. This rare occurrence is discussed in the context of the observed coronary lesions, the distribution of the radionuclide-detected ischemia, and the previous experience from the literature. An insight regarding the low prevalence of transient LPH is afforded, since the described case derives from a series of 2,160 consecutive patients who underwent ETT in conjunction with Tl. Finally, a comment is provided on the complexities of deciphering the specific pathophysiologic mechanism(s) of transient LPH, occurring during ETT.