EXTERNAL AGGRESSION TO THE LIMB AS A PREDICTIVE FACTOR IN THE EVOLUTION OF PATIENTS UNDERGOING ARTERIAL REVASCULARIZATION

PURPOSE: A variety of predictive factors for the evolution of arterial grafts in patients with critical ischemia have been well defined in clinical studies, including diabetes mellitus, dialytic renal insufficiency, smoking, and distal arterial runoff. The goal of this study was to determine whether patients with critical ischemia undergoing arterial reconstruction in which ischemic lesions appeared spontaneously, compared to those in which the ischemic lesion appeared following an external aggression to the limb present different patterns of evolution. METHODS: From February 2002 to January 2004, 100 patients undergoing infra-inguinal arterial reconstruction were followed. They were divided into 2 groups: 1) the spontaneous group (n = 52), comprising individuals presenting with ischemic lesions of spontaneous origin and 2) the external aggression to the limb group (n = 48), comprising individuals for which an external causal mechanism for the appearance of the ischemic lesion was identified. The variables analyzed were limb salvage and graft functioning rates. RESULTS: Patients with spontaneous lesions had rates of limb salvage and graft functioning significantly lower than those for patients with lesions that were secondary to external aggression (42.3% versus 87.5%, respectively for both outcomes; P <.001). CONCLUSIONS: The absence of an external aggression as a contributing factor to a critical ischemic lesion in the lower limb may result in a poorer evolution of both graft function and limb salvage following arterial revascularization. However, this factor is not expected to directly influence the case conduct, since almost half of the patients without evident external aggression had good graft functioning and limb salvage. This prognostic factor should be used just as all others are, i.e., to give patients and doctors a better idea of the possible evolution in such cases.

Revascularization is the procedure of choice for limb salvage in patients with critical ischemia in the lower limbs. 1,2][5] Results of the revascularization surgery have been improving lately, 10% to 32% of these patients do not achieve the expectations for limb salvage, 6,7 hemodynamic improvement at the affected extremity, 8 or survival. 9To improve such results, we must be able to recognize all the factors that could influence on the favorable or unfavorable evolution of the bypasses, i.e., the predictive factors.Through knowledge of these factors, we may be able to prevent or correct what is undesirable and enhance what is desirable.
A variety of predictive factors 10 have been well defined in clinical studies, including diabetes mellitus, 11 dialytic renal insufficiency, 12 smoking, 6 and distal arterial runoff. 1,3ne factor that has not yet been correlated with the post-CLINICS 2005;60(6):451-4 External aggression to the limb as a predictive factor in the evolution of patients Wolosker N et al.   operative evolution of arterial grafts is the presence of external aggression to the limb (EAL).The external aggression could be trauma, infection, or interdigital mycosis that causes an ischemic lesion, thereby decompensating a stable condition of chronic ischemia and turning it into a critical ischemia.
The goal of this study was to ascertain whether patients with critical ischemia undergoing arterial reconstruction in which ischemic lesions appeared spontaneously present an evolution that differs from those in which the lesion appeared through EAL.

METHODS
One hundred patients undergoing arterial reconstruction for critical ischemia over a 2-year period were followed through a prospective, non-randomized, and uncontrolled study.The patients underwent similar treatment, following the same protocol.The study was approved by the Committee of Ethics for Analysis of Research Projects on Human Experimentation, and all subjects gave informed consent.
The patients were divided into 2 groups according to the clinical interview.In the first (spontaneous) group, 52 individuals presented ischemic lesions of spontaneous origin (without trauma, infection, or prior interdigital mycosis).The second (EAL) group consisted of 48 patients with ischemic lesions in whom a non-natural causal mechanism for the appearance of the ischemic lesion was identified.These traumas in the EAL group were: digital trauma in 22 patients, digital infection in 8, and interdigital mycosis in 18.The patients in the spontaneous group did not report any kind of trauma generating the digital lesions.
The average age of patients was 62.8 years; 80.2% were smokers, 50.5% were hypertensive, and 41.6% were diabetic.Baseline characteristics showed no significant differences between the groups as is shown in Table 1.
The indication for surgery was tissue loss (Rutherford III) for all patients.In every case, tissue loss was limited, with lesions of less than 5 cm in diameter or ischemic lesions caused by gangrene confined to the digits.Indication for surgery was confirmed by the presence of an ankle-arm index of less than 0.40 or by no scar formation at the lesion after 4 weeks of appropriate local treatment.
Cultures of the ulcerated lesions were performed, and the appropriate perioperative antibiotic therapy was administered.
All patients underwent preoperative digital arteriography to determine the type of arterial revascularization to be used in each case as well as to evaluate the runoff.The arteriographic pattern is presented in Table 2 and shows that distal obstructions were more frequent in the spontaneous group.
The choice of bypass material and the site of the distal anastomosis was based on the arteriographic pattern and was at the discretion of the surgeon.Above-knee femoralpopliteal procedures were all performed using 8 mm bifurcated Dacron prostheses.In the other cases, the saphenous vein was used.Angioplasties were performed in 2 cases on segmental lesions of less than 3.0 cm in length.
The surgical procedures performed in both groups are listed in Table 3.
Postoperative anticoagulant or antiplatelet therapy was given based on the preference of the surgeon.
Debridement of necrotic tissue was performed either immediately after the arterial reconstructions, or at a later time (some days after the revascularization) according to the indications for each case.
The patients were followed up for 30 days after the operation.At that time, the functioning of the grafts was confirmed by means of color duplex ultrasonography.
The degree of salvage presented by the limb and the functioning of the graft 30 days after the operation were  analyzed for each of the groups.
The distribution of number of open runoff vessels obtained in the arteriographies in both groups was also studied.
The chi-square test was used to analyze the data.The significance level was set at P < .05.

RESULTS
The rate of graft functioning for the patient group with spontaneous lesions was significantly lower than the rate for patients with lesions that were secondary to EAL (P < .001).Rates for graft functioning in each group after 30 days are shown in Table 4.
The rate of limb salvage for the patient group with spontaneous lesions was significantly lower than the rate for the patients with lesions that were secondary to EAL (P < .001).Rates for limb salvage in each group after 30 days are shown in Table 5.
Twenty patients from the spontaneous group underwent below-knee amputation, and 10 underwent above-knee amputation.Four patients from EAL group underwent below knee-amputation, and 2 underwent above-knee amputation.
The patients in the spontaneous group presented worse runoff than those in the EAL group P <.05.The distribution of number of open runoff vessels obtained in the arteriographies is shown in Table 6.

DISCUSSION
The search for better results in the treatment of patients with critical ischemia has stimulated us to seek predictive factors.One factor that would seem evident is the mechanism of the formation of the ischemic lesions.It appears, however, that this factor has never been studied.Therefore, we decided to perform a prospective evaluation of patients in our service who were undergoing revascularization of lower limbs.
The 2 groups studied were similar in terms of age, preexisting diseases, incidence of a smoking habit, arterial hypertension, diabetes, ankle-arm index, and Rutherford classification of ischemia level.
The great majority of the patients in both groups presented with infections, thus necessitating both preoperative and postoperative antibiotic therapy. 13It is worth emphasizing that we did not observe any specific characteristics in the ischemic lesions that were correlated with the mechanism of lesion formation (i.e., spontaneous or secondary to external aggression).
The objective of defining the predictive factors in patients with critical ischemia is to give an idea of the prognosis for each case, even though such knowledge does not alter the medical conduct, since these are situations of imminent limb loss.The surgical treatment employed in all cases was based on and performed under the same assumption.
When the functioning of the grafts was analyzed after 30 days, it was noted that the patients with spontaneous lesions presented a higher occlusion rate than that of the EAL group (57.7% versus 12.5%).This was due to a worse runoff according to the arteriography (Table 6).
Similarly, the limb salvage rate was greater in the patient group with ischemic lesions secondary to external aggression, than for patients who presented with spontaneous lesions (87.5% vs. 42.3%).This parallelism was probably due to the fact that the patients with spontaneous lesions presented worse runoff.
Spontaneous lesions are a consequence of a more morbid situation in the arterial tree.Blood support in this situation is insufficient to cover the basal metabolism of the tissue, which translates into lesion formation.In contrast, with ischemic lesions secondary to external aggression, there may be greater blood support, and the arterial tree is presumably in better condition.
The conclusion is that patients with critical ischemic lesions of spontaneous origin have worse runoff and a poorer evolution following revascularization procedures than do patients who have ischemic lesions caused by EAL.
Absence of EAL can be considered to be a factor for poorer runoff and poorer evolution of both graft function and limb salvage.However, as with all the other prognostic fac-  tors, this must not directly influence the case conduct, since almost half of the patients without evident external aggression had good graft functioning and limb salvage following the revascularization procedure.This prognostic factor should be used as all others are, i.e., to give patients and doctors a better idea of the possible evolution in such cases.

Table 1 -
Associated risk factors of the study subjects

Table 6 -
Number of open run-off vessels

Table 5 -
Limb salvage following revascularization surgery

Table 4 -
Functioning of the grafts 30 days after revascularization surgery External aggression to the limb as a predictive factor in the evolution of patients Wolosker N et al.