Tags: Aneurisma | Aneurisma Toracoabdominal

An aneurysm is an abnormal dilation of all layers of the wall of an artery. When the diseased segment extends from the descending thoracic aorta to the abdominal aorta we are talking about THORACOABDOMINAL ANEURYSMA.

DEFINITION

An aneurysm is an abnormal dilation of all layers of the wall of an artery. When the diseased segment extends from the descending thoracic aorta to the abdominal aorta we are talking about THORACOABDOMINAL ANEURYSMA.

The thoracoabdominal aorta is about 40 cm long with a diameter ranging from 23 mm in the proximal and 14 mm at the aortic bifurcation. To consider that the aorta is aneurysmal it should exceed 35 mm in diameter or twice the diameter of the adjacent healthy aorta. Only those that exceed 50 mm in diameter need to be treated.

ETIOLOGY

The etiology of these aneurysms, in order of frequency, is: Average degenerative disease (cystic medial necrosis, myxoid or myxomatous degeneration, senile aorta and Marfan syndrome), aortic dissection, atherosclerosis, aortitis, infection and trauma. All these causes have specific macroscopic or microscopic forms but the end result is progressive dilation of the aorta and the clinical manifestations resulting therefrom.

EPIDEMIOLOGY

Survival at 2 years is 24% -28% and 5 years of 7% -19%. Half of the deaths were caused by thoracoabdominal aneurysm rupture (5 out of 100,000). According to these data, in Spain there are approximately 4,000 people with this type of aneurysm.

Most of these are diffuse and fusiform aneurysms, except for fungal and post-traumatic that are usually saccular. The first occurs in the aortic arch and in the origin of the visceral arteries in the abdominal aorta; the second level is detected at the aortic isthmus immediately below the origin of the left subclavian artery.

CLASSIFICATION

The extent and shape of the aneurysm influences the surgical approach and length and type of prosthetic replacement to be performed. The classification that best fits the morphological findings with surgical decision making is the dividing Crawford thoracoabdominal aneurysms into four groups according to their location:

Type I. - It affects the descending thoracic aorta and upper abdominal aorta (25%).

Type II. - Subsequent to the descending thoracic aorta and almost all abdominal aorta (29%).

Type III. - Subsequent to the distal descending thoracic aorta and almost all abdominal aorta (23%).

Type IV. - It affects the entire abdominal aorta, including the exit of the visceral arteries (23%).

SYMPTOMS

Thoracoabdominal aneurysms can be asymptomatic for years but before rupture, and causing death can occur: chest pain, costal, abdominal or lumbar compression of adjacent structures and erosion of the vertebral bodies, dyspnea, coughing, or pneumonitis distal tracheal or bronchial compression ; hemoptysis by bronchial or pulmonary erosion, dysphagia and/or hematemesis compression and erosion of the esophagus; intermittent or massive gastrointestinal bleeding due to erosion of the duodenum, icterus by compression of the bile duct, hoarseness vagus nerve paralysis secondary to recurrent nerve traction arch level, paraparesis or paraplegia in cases of spinal cord compression or spinal artery thrombosis, although this symptom is more frequent in aortic dissections, in rare situations it has been diagnosed with acute heart failure aortocaval fistulas, and finally distal embolizations are frequent or chronic occlusions of visceral arteries

In our experience the most frequent presentations are asymptomatic, broken or lumbar back pain.

DIAGNOSIS

The diagnosis is usually casual and has scarce clinical manifestation or in the physical examination the grilled rib prevents palpation coast.

The plain chest Rx a widened mediastinum with calcified rims can be detected. The most reliable diagnostic methods are MRI and CT allowing us to detect the location, size, extent and anatomical relationships of thoracoabdominal aneurysms. Its information is scarce regarding associated injuries (20%) in its visceral branches, but it is possible that the appropriate helical CT with 3D reconstruction programs and vascular supply valuable information from these vessels.

Arteriography with injection of contrast at high pressure is used in selected patients to assess the location of the branches of the aorta, but should be particularly cautious in patients with a history of renal failure and that the contrast can make it worse. Before arteriography, patients should be treated with mannitol and serum.

CONCOMITANT DESEASES

Some more of a third of patients with thoracoabdominal aneurysm have another type of aneurysm, especially in ascending aorta and aortic arch. Given the age of patients, it is frequent the presence of cardiorespiratory diseases and kidney failure by 20% of cases, surgical correction of lesions in visceral arteries is needed. Aorto-enteric fistula, aortocaval, cancer or peptic ulcer are less frequent but exceptional.

TREATMENT

The treatment will greatly depend on the diameter of the aneurysm, location, etiology and the clinical manifestations. Below 50 mm in diameter are usually asymptomatic and the risk of rupture is very low and lower than the morbidity of surgical treatment. From 60 mm in diameter of the possibility of aneurysm rupture is the cause of death of the patient is 38% in the next 2 years at the time of diagnosis. Survivals of a 70% and 60% at 2 and 5 years respectively are achieved with surgical treatment and adequately trained and equipped units.

The absolute indications for surgical treatment are:

-          Rupture

-          Symptoms from compression and erosion of adjacent structures.

-          Diameter greater than 60 mm in patients with Marfan syndrome and over 65 mm in those without IBS.

-          Increased diameter over 1 cm per year.

Contraindications for surgery:

-          Relative, being > 70 years

-          Severe COPD

-          A cancer with scarce survival

PRE SURGERY STUDIES

Possibly the thoracoabdominal aneurysm surgery is the biggest technical challenge and more aggressive surgery of any cardiovascular disease. By age and associated pathologies above mentioned it is essential a careful assessment of risk factors of the patient to select and prepare the pre-surgery process. In general, all of these will be applied to all patients:

• Spirometry.
• Study of renal function.
• Echo-Doppler of supra-aortic trunks.
• Complete cardiac study: ECG, echocardiography / dobutamine versus thallium / dipyridamole and coronary heart though past studies to suspect some degree of coronary ischemia.
• Analytical study: anemia, ions, biochemistry and coagulation.

SURGICAL TREATMENT

The selected patients will be candidates for surgical treatment. The usual technique is replacing the aneurysm by a synthetic tubular prosthesis which is re-implanted in the intercostal and visceral arteries of the patient (Fig.). In the case of not very extensive saccular aneurysms resection aneurysmal sac and closure of the aorta with a synthetic patch can be performed (Fig.).

During surgery and postoperatively most of the technical measures taken will be to prevent the main complications of this intervention: cardiac failure, renal failure, spinal cord ischemia. To achieve minimize these complications, fatal in many cases, it is basic to monitor operations and the performance of anesthesia. All patients will have:

• Continuous ECG.
• Permanent monitoring of bilateral blood pressure.
• Central and peripheral venous lines caliber for rapid infusion of fluids.
• Double-lumen endotracheal tube to collapse the left lung.
• Catheterization for urinary output.
• Swan-Ganz catheter.
• Thermal control.
• Catheter subarachnoid lumbar CSF pressure monitoring.
• A thermal blanket and cellular recoverer will  be used consistently.

In recent times, the use of perioperative transesophageal echocardiography in patients with complex heart disease and measurement of somatosensory evoked potentials for detecting early signs of spinal cord ischemia is extending.

Once monitored, the patient is placed in right lateral position and a brake-thoraco-laparotomy is performed to address and control the entire descending thoracic and abdominal aorta. The level and extent of the incision depends on the type of aneurysm (Crawford classification above). Once in control of the aorta, it is clamped and the prosthetic is replaced. There are different schools advocating different methods to prevent the renal and medullary ischemia during this time. Those who estimate the aortic clamping will not exceed 30 minutes do not usually use any method of protection, if this time should be exceeded some are in favor of partial derivations between left atrium and femoral artery, others are in favor of deep hypothermia and stop circulation or use leads heparinized as Gott shunt, etc. in all cases these techniques depend on the type of aneurysm and technical skill of the surgical team.

RESULTS

In-hospital, mortality is between 6 and 12% in elective surgery, 20-22% in emergency surgery and more than 50% in ruptured aneurysms.

As for the morbidity, it is associated with a third of patients requiring prolonged intubation.

Renal failure is present between 4 and 40% of the cases, depending on the number consulted, but the prognostic factor is the need for dialysis because half of them die.

The spinal cord ischemia is associated with paraparesis or paraplegia occurs between 4 and 27% of those operated while the core protection measures used in recent years seem to us closer to the bottom of the fan.

SUMMARY

Thoracoabdominal aneurysms are potentially very serious disease because of its own evolution toward breaking as associated pathologies which the patient usually has.

From a certain diameter or the occurrence of symptoms today the only treatment is contrasted surgery.

The intervention of these aneurysms requires well-equipped and trained teams and still has substantial morbidity and mortality percentages.

REFERENCES

1 .- Crawford ES, Crawford JL, Safi HJ, et al. : Thoracoabdominal aortic aneurysms: Preoperative and intraoperative factors Determining Immediate and long-term results of operations in 605 patients. J Vasc Surg 3:389, 1986.

2 .- Crawford ES, Swensson LG, Hess KR et al: A prospective randomized study of cerebrospinal fluid drainage to Prevent paraplegiaafter high-risk surgery on the thoracoabdominal aorta. J Vasc Surg 13 (1): 36, 1991

3 .- Swensson LG, Crawford ES, Hess KR et al. : Experience with 1509 patients undergoing thoracoabdominal aortic operations. J Vasc Surg 17:357, 1993.

4 .- Coselli JS. Thoracoabdominal aortic aneurysm. vascular Surgery. Fourth Edition. Robert B. Rutherford. W.B. Saunders Compan: and 1995: 1095-1087.

5 .- Dapunt OE, Galla JD, Sadeghi AM, et al.: The natural history of thoracoabdominal aortic aneurysm. J Thorac Cardiovasc 107:1323, 1994.

Preguntas y Respuestas al Doctor (11)