Clinica Vascular Zurbano, Varices, Tratamientos Laser, Masaje Linfatico, Cirugia Vascular, Tratamiento del Linfedema, Tratamiento Aneurisma

Tags: Tratamientos

The two main lines that have been developed more in the medicine in the second half of this century to achieve diagnostic pursuing safer and less traumatic treatments. The arterial disease is possibly one of the most benefited from these advances in the last 25 years; the so-called endovascular treatments have been developed.

They are called endovascular treatments to those that act on vascular disease from inside the vessel itself. Currently comprise a large group of actions such as  angioplasties, stent placement, intra-arterial fibrinolysis, the embolization and more recent stent implantation for treatment of aneurysms.

 

Currently the treatment of choice for preventing rupture of aneurysms is surgical repair by interposition of prosthesis. This technique is associated with low levels of mortality (between 1'4% and 6.5%) in elective surgery and about 50% for ruptured aneurysms.

 

During the decade of the 80s they were successfully tested in various animal models the ability to treat these aneurysms by endovascular means. The first infrarenal aortic aneurysm treated by endovascular means in a human was performed by Juan Parodi in 1990 in Buenos Aires in a patient with very high surgical risk. Since then this technique has been developed and spread widely and, so far, there are more than 7000 patients with thoracic aortic aneurysms and infrarenal that have been treated by this method worldwide. The aim of endovascular treatment is to prevent growth and rupture of the aneurysm. The technique involves implanting a prosthesis via endovascular aneurysmal to exclude blood flow and strengthen the wall of the aorta in the neck. This system should only be done if we have a few vessels in which the wall of the neck is not ectatic, with an adequate length and of good quality (free of thrombus and calcifications).

 

WITH THIS PERSPECTIVE, CAN WE CONSIDER THAT ENDOVASCULAR TREATMENT IS THE END POINT FOR TREATMENT OF AORTIC ANEURYSMS?

 

To answer this question we must assess, what do we know about aneurysms? And what are stents? How are the endoprosthesis implanted? What % present complications? And will they evolve at medium or long term?

 

 

 

ANEURYSMS AND MORPHOLOGY

 

Aneurysms are bulges in all layers of the wall of the aorta. Its walls are usually lined by abundant thrombotic material and often there are aneurysmal involvements of one or both common iliac arteries. For its morphological presentation it is divided into five groups:

A. - It is an infrarenal aneurysm that has a good neck below the origin of the renal arteries and above the origin of the common iliac arteries.

B. - Similar to Group A, but without neck above the aortic bifurcation.

C. - In this case we find a good neck from renal arteries to aneurismal but this affects the rest of the infrarenal aorta and both common iliac, respecting the iliac bifurcation.

 

 

D.- As in group C, but with involvement of the origin of external and internal iliac.

 

 

 

Regardless of these 5 groups, referring to the shape of the aneurysm, we must take into account the readiness of the healthy aorta and iliac arteries with special attention to the angles they present. These angles may contraindicate the implantation of an endoprosthesis.

 

 

ENDOPROSTHESIS

 

Until 1992, endoprosthesis were constructed manually by each surgeon and basically consisted of a stent (metal mesh that could be relaxed to a certain diameter) sutured to a synthetic prosthesis and compressed inside a long tube and semiflexible (introducer) that allowed taking and releasing the stent in the aneurysm sack excluding it. The construction process was quite cumbersome and accidents during the implementation quite common. Since 1992 the industry began to develop different models that were pursuing the following characteristics:

 

• Self-expanding stent with high radial force to the fixed to the aneurysmal neck.
• Prosthetic material thin and strong.
• Sheaths of smaller caliber and greater flexibility.
• Ease of implementation.

 

 

At the moment the type of stent that seems most popular for achieving these objectives are composed of nitinol (alloy of nickel and titanium) and in super elastic form or thermal memory (spreading by contact with the blood) are the most used. These stents are placed in different positions according to the commercial model available, so we will find some that are located only at the ends of the graft or the length of the same or that are sewn into the inside or outside of it.

 

Different materials have been used to build the most widespread graft but are made of polyester fabric and in PTFE in lesser extent.

 

Currently two major types of prostheses are used for these procedures:

• The stent-prosthesis: in them fixing the prosthesis to the proximal and distal collars are made through a wire mesh (stent).
• Covered stents: the metal framework of the prosthesis is not limited to the extremities of the prosthesis, but covers its entire length so as to avoid the path plication in the prosthesis and subsequent migration.
• Both the stent and full armor can be metal or alloy of nickel and titanium shape memory retaining (Nitinol). Its expansion can be spontaneous or need of an inflatable balloon.

 

Three types of stents are the most used:

• The straight aorto-aortic tube: it maintains the same diameter throughout its length and its use is now limited to the segment of thoracic aorta or iliac or femoral arteries.
• The bifurcated prosthesis: the broadest range of infrarenal aortic aneurysms with or without iliac involvement. They are usually modular prosthesis, typically consisting of a segment of the aorta and iliac branches and another to complete the contralateral iliac.
• The conical prosthesis: prosthesis is a straight line which fits the largest diameter of aortic neck and the smaller diameter is adapted to the iliac artery, in this way a Aoto-iliac bypass  is implanted unilaterally. In these cases devices to occlude the contralateral iliac is necessary and they sometimes are associated with by-pass femoro-femoral surgery.

 

 

 

TECHNICAL IMPLEMENTATION

 

Currently, and pending new developments as they prepare the basic form of implantation of stents is as follows:

 

1. Patient under general anesthesia, spinal or even local
2. Dissection of femoral artery and the contralateral percutaneous approach or dissection of both femoral arteries.
3. Introduction of these guidelines through femoral approach.
4. Angiographic study to locate the boundaries of stent implantation.
5. Implantation of the body and one arm of the stent.
6. Through the contralateral approach implementation of the other branch of the graft.
7. Angiographic control to verify proper stent placement and no leakage of contrast into the aneurysmal sack.
8. Closure of the femoral approach.

 

RESULTS AND COMPLICATIONS

 

Given that the first prosthesis was introduced just 20 years ago we still do not have long-term results, what does bring out all the studies is the need for a learning curve and that the initial prosthesis, craft construction, have more number of complications that current industrial design.

Early mortality ranges from 0 to 12.5% of patients, especially in relation to patient risk factors and the surgeon's learning curve.

The rate of conversion to open surgery is the worst series of 15%.

Perioperative complications between 5 and 30% and usually are associated with local complications in the surgical approach, but when an aneurysm ruptures during the procedure, the mortality is nearly 100%.

Leakage is defined as the persistence of circulating flow inside the aneurysm sac and is a sign of poor prognosis in preventing late rupture. If you have a bad indication (prosthesis anatomically adapted to the profile of the patient), or a defect of implantation and are usually identified in the study preoperative -Aand B- and may be corrected immediately with endovascular procedures or open conversion . In some cases early leaks are due to reflux of collateral arteries in the aneurysm sac-D- (a. inferior mesenteric or lumbar) and most of them are thrombosed spontaneously in the weeks following stent implantation. Leaks are discovered late, but initial checks were normal, due to opening of collateral, loss of cooptation at the necks, to displacement of segments of the stent or the material breaks by "fatigue" mechanical-C-. This type of leakage should be treated in all cases either by endovascular procedures or open surgery.

 

 

SUMMARY

 

Endoprosthesis represent a major advance in the treatment of aortic aneurysms because they increase the range of patients who may benefit from treatment of aneurysms with lower surgical aggression, shorter hospital stay and lower initial morbidity but, conversely, not a decrease mortality, require increased monitoring of evolution, further complications occur late and the cost of the endoprosthesis is substantially higher than those that are implanted surgically.

 

Recent studies comparing large series of open surgical treatment of aneurysms of the aorta (Medicare) and endovascular treatments (Eurostar) is found that the major technical benefits of the latter are mainly: older patients (> 75 years), those with risk factors multiple partners (heart disease, respiratory disease, diabetes, severe obesity, ...) and those that present a hostile abdomen (multiple abdominal operations).