IJCS | Volume 31, Nº2, March / April 2018

102 Figure 3 – LITA with presence of collateral circulation. Balzan et al. Atherosclerosis in the internal thoracic artery Int J Cardiovasc Sci. 2018;31(2)97-106 Original Article selected patients. All the studies present a reduced number of patients evaluated, which hinders both the homogeneity of the data and the agreement between the prevalence of the lesions. What is clear is the need to evaluate preoperative LITA in patients candidates for CABG, since in addition to diagnosing lesions that will impair the effectiveness of CABG, it is also possible to identify possible changes that cause consequences for patients , such as lower limb ischemia in cases of IAC acting as collateral circulation, and subclavian steal syndrome in patients with significant subclavian occlusion or stenosis. The presence of chronic aortoiliac occlusive disease is considered an important predictor for the development of anatomical alterations involving LITA. Usually these patients develop collateral perfusions in order to reconstruct the arterial system of the pelvis and lower limbs, avoiding the ischemia of the same. The LITA, together with the superior and inferior epigastric arteries, work as the main parietal collateral pathway in the reconstruction of the external iliac artery, and if this graft is used for myocardial revascularization, the patient may have an acute ischemia of the lower limbs in the post-surgery. 20-25 The presence of this collateral pathway is of such importance that the LITA becomes one of the main arteries responsible for irrigation of the lower limbs, accounting for 38% of the blood flow in the region, and doubling the volume of blood (LITA) every minute. 26 Studies show that the presence of LITA and epigastric as a collateral route to the lower extremities is not an uncommon finding in patients with AOD, and its prevalence is estimated in up to 12% of cases in that AOD was greater than or equal to 75% of the vessel diameter. 25 In our study, one patient presented LITA and epigastric as a collateral route for irrigation to the legs (Figure 3), alteration identified by preoperative selective angiography in patients with coronary artery bypass indication, without the presence of clinical changes which give evidence of the existence of AOD. 26 The identification of LITA as a collateral route occurred through the progression of contrast to lower vessels, upper and lower epigastric arteries (Figure 3), and continuity to the level of the pelvic vessels (Figure 4). We did not investigate alterations that might indicate the presence of AOD in the present study. However, authors such as Kim et al. 25 point out that the presence of weakened femoral pulses in the affected extremity, with decreased amplitude and volume, and alterations in the ankle index doppler probe, less than 0.7, are important indicators of the presence of AOD. After identification of the presence of collateral circulation to the lower limbs by LITA and epigastric lesions, the presence of aortoiliac-atherosclerotic lesions at the site was demonstrated by selective aorto-iliac angiography (Figure 5). Another alteration found in our study was a patient with total occlusion of the subclavian artery, characterized by complete interruption in contrast progression, at the proximal level of the subclavian, evidenced by selective angiography (Figure 6). Such alteration may compromise the results of CABG, where the presence of occlusion is one of the main causes of recurrent angina in the postoperative