Distal Internal Thoracic Artery Research Articles

Identifying the optimal monopolar electrocautery output power in pedicular internal thoracic artery harvesting: 20 or 40 watts?

Monopolar electrocautery is an important tool for harvesting the pedicular internal thoracic artery (ITA) in cardiac surgery. The different power outputs of cautery may affect graft integrity and long-term patency. This study aimed to identify the optimal threshold of electrocautery power for ITA harvest. This prospective study included 30 patients who underwent elective coronary artery bypass surgery at the Medipol Mega University Hospital. The ITA was harvested by monopolar electrocautery after a median sternotomy. The output of cautery was adjusted at 20 W in group A and 40 W in group B. Three to 4 cm of a distal ITA sample from each patient was examined under a light microscope by two independent pathologists. The ITA harvest time was longer in group A (21.2 ± 7.5 vs 10.3 ± 8.1 min, p < 0.001) than in group B. ITA free flow was similar in the two groups (43.6 ± 48.7 vs 51.7 ± 45.0 Ml/min, p = 0.762). Mild to moderate injury in the endothelial and sub-endothelial sample was more frequent in the low-cautery group (p = 0.0037). ITA endothelial integrity was found to be better preserved with 40W electrocautery. Moreover, 20W of monopolar electrocautery may not be safe in pedicular ITA harvesting.

Ultrahigh-Resolution Computed Tomography Improves Preoperative Computed Tomography Angiography for Deep Inferior Epigastric Artery Perforator Flap Reconstruction.

The aim of the study was to compare computed tomography (CT) angiography (CTA) imaging of deep inferior epigastric artery perforator (DIEP) using the ultrahigh-resolution CT (UHRCT) and conventional multidetector CT (MDCT). This retrospective study enrolled 20 patients who underwent CTA of DIEP flap with UHRCT and MDCT. Computed tomography values were measured at 4 large vessels (thoracic aorta, abdominal aorta, common iliac artery, and external iliac artery) and 5 peripheral vessels (proximal and distal internal thoracic artery, proximal and distal deep inferior epigastric artery, and DIEP). There were no significant differences in mean CT values of the major vessel between UHRCT and MDCT. Ultrahigh-resolution CT shows higher CT values of the peripheral vessels than MDCT (P < 0.05 for all). The median CT values of the DIEP in UHRCT were approximately 3 times higher than those in MDCT (P < 0.001). Ultrahigh-resolution CT provides higher-quality CTA of DIEP compared with MDCT.

Endothelial Shear Stress of the Saphenous Vein Composite Graft Based on the Internal Thoracic Artery

Endothelial shear stress (ESS) has been suggested as a factor affecting atherosclerosis and remodeling of native vessels and bypass conduits. We compared ESS levels of internal thoracic artery (ITA) and saphenous vein (SV) composite grafts intraoperatively and 1 year after coronary artery bypass grafting (CABG). Intraoperative ESS was calculated by measuring flow volumes and diameters of proximal and distal ITAs and SV conduits in 23 patients who received SV Y-composite grafts based on the in situ left ITA. Early (1.2 ± 0.5 days) and 1-year (12.9 ± 1.1 months) postoperative angiograms were performed in 23 and 15 patients, respectively. An intragraft Doppler-guidewire study for ESS measurement was performed in 6 patients during 1-year angiography. Intraoperative diameters of proximal and distal ITAs and SV conduits were 2.0 ± 0.2 mm, 1.8 ± 0.3 mm, and 3.2 ± 0.4 mm, respectively. ESS levels were significantly different between them (41.0 ± 21.0, 28.4 ± 25.2, and 4.3 ± 3.0 dyne/cm2, respectively). Proximal and distal ITA diameters increased significantly on early angiograms and remained unchanged, but SV diameter increased to 3.7 mm (95% confidence interval, 3.5 to 4.0 mm; p < 0.001) on the early angiogram and decreased to 2.9 mm (95% confidence interval, 2.7 to 3.2 mm; p < 0.001) at 1 year. Significant correlations were found between the initial ESS and proportional changes in conduit diameters during postoperative year 1. SV ESS increased in all 6 patients at 1 year, with no significant differences in ESS levels between the 3 conduits (29.9 ± 7.9, 28.8 ± 7.9, and 21.6 ± 16.3 dyne/cm2, respectively). Initial ESS appears to be associated with proportional changes in conduit diameters in the first year after CABG. ESS values of SV composite grafts were similar to left ITA conduits 1 year after CABG.

The physiologic and histologic properties of the distal internal thoracic artery and its subdivisions

We compared the flow rates, reactivity, and morphology of the distal internal thoracic artery and its branches, the superior epigastric and musculophrenic arteries, to test their applicability as possible conduits in coronary artery bypass grafting surgeries. Skeletonized internal thoracic artery and subdivisions of patients undergoing coronary artery bypass grafting were studied intraoperatively (n = 100) for flow and length measurements and in vitro in organ baths (n = 58) for active response to norepinephrine. Quantitative microscopic analysis of the muscle density and degree of intimal hyperplasia was performed. Results were analyzed according to age, gender, risk factors, and medications. Internal thoracic artery subdivisions contributed an average extra length of 2 cm. Free flow rates were 129 ± 45 mL/min, 114 ± 41 mL/min, and 93 ± 36 mL/min in the internal thoracic artery, superior epigastric artery, and musculophrenic artery, respectively. Sternum and internal thoracic artery length and free flow rates were significantly lower in women. The subdivisions were significantly more reactive to norepinephrine than the distal internal thoracic artery (P ∼ .005), although sensitivity to norepinephrine was similar. Patients treated with beta-blockers had significantly decreased reactivity (P = .009). Microscopic analysis suggests similar muscle content in the internal thoracic artery and subdivisions. Eccentric (28%) and concentric (62%) intimal hyperplasia were observed in 90% of specimens, with no evidence for atherosclerotic plaques. There was no significant difference in the degree of intimal hyperplasia between the distal internal thoracic artery and its subdivisions, and there was no correlation to risk factors. Our results confirm the previous studies on the higher contractility in internal thoracic artery subdivisions, suggesting caution in the use of the bifurcation for revascularization. However, the extra length, sufficient flow, and favorable histologic properties suggest that the bifurcation may be appropriate for coronary revascularization in selected cases.

“Choke” vessels between vascular territories of the abdominal wall: Literature review and rare case of Leriche's syndrome

We undertook a review of the anatomical changes of "choke" vessels between the internal thoracic artery (ITA) and deep inferior epigastric artery (DIEA), as highlighted by a case of aortoiliac occlusive disease (Leriche's syndrome), and discuss the physiological concepts observed with regard to surgical delay procedures within the abdominal wall performed prior to abdominal cutaneous free flaps and coronary artery bypass grafting. Computed tomographic angiography (CTA) was undertaken on a patient with a rare case of Leriche's syndrome and a literature review of over 200 references on the anatomy, physiology and clinical uses of choke vessels in the abdominal wall was undertaken. The CTA demonstrated that in patients with Leriche's syndrome, there is a marked dilatation of all ITA-DIEA pathways and increased flow through choke vessels. If these changes can be surgically replicated in the form of a delay procedure for patients seeking to undergo autologous breast construction, this could improve the outcomes of abdominal cutaneous free flaps and coronary artery bypass grafting. We accordingly propose three surgical methods for augmenting blood flow to the abdominal wall: a) ligation of the DIEA; b) ligation of the distal ITA; and c) creation of an arterio-venous fistulae in the DIEA. Our review of the literature confirmed the viability of these propositions. The dilatation of choke vessels in response to increased haemodynamic stress may thus be utilised to enhance blood supply to tissues prior to transfer and can be achieved through simple and minimally invasive methods.

Quality of Internal Thoracic Artery Grafts After Mediastinal Irradiation

With the increase of patients of advanced age requiring coronary artery bypass grafting (CABG), the number of those with previous mastectomy and irradiation of the chest increases proportionally. The question of whether mediastinal irradiation leads to relevant internal thoracic artery (ITA) graft damage remains unclear. The aim of the present study was to proof the quality of ITAs and to evaluate the early clinical outcome after using one or both ITAs in this specific population. One hundred twenty-five patients (group A) with previous mastectomy or Hodgkin/non-Hodgkin disease and mediastinal irradiation operated on between January 1993 and September 2006 underwent CABG (n = 88) or CABG plus valve replacement (n = 37). Sixty-two patients received bilateral, 43 received unilateral ITAs, and 20 patients received veins. Postoperative complications and mortality were analyzed and compared with a propensity score pair-matched control group of 125 patients receiving CABG or CABG plus valve replacement within the same period (group B). A histomorphologic investigation was performed in 133 irradiated distal ITA segments and compared with a control group of 133 nonirradiated ITAs. Thirty-day mortality revealed 3.2% in group A versus 5.6% in group B. Sternal instabilities were more frequent in group A (3.2%) than in group B (0%). Mediastinitis occurred in 1.6% (group A) versus 1.6% (group B). Histomorphologic investigations did not identify any severe irradiation induced fibrosis or damage of ITA grafts. From the histologic point of view, there is no need for restrictions in use of ITA conduits after mediastinal irradiation. Compared with a control group, cardiac surgery was associated with a slightly enhanced incidence of sternal instabilities.

Intraoperative and Histochemical Comparison of the Skeletonized and Pedicled Internal Thoracic Artery

Skeletonization of the internal thoracic artery (ITA) has advantages, but the variation of ITA preparation may be traumatic for the arterial wall. We sought to compare intraoperative results and endothelial nitric oxide synthase (e-NOS) expression on the vessel wall after left ITA harvesting with skeletonization and the conventional technique. A prospective evaluation of 84 consecutive patients undergoing coronary artery bypass grafting was performed: 40 patients with skeletonized and 44 patients with pedicled left ITA. The lengths of ITA and free ITA blood flow were measured. Distal ITA segments were analyzed histopathologically and stained by antibodies against e-NOS. In the skeletonized group, the length of the ITA were significantly longer than in the pedicled group (15.7 +/- 0.4 cm versus 19.0 +/- 0.6 cm; P = .001). Also, the free-flow capacity of the ITA was significantly higher than in the pedicled group (62.4 +/- 4.8 mL/min versus 88.6 +/- 6.9 mL/min; P = .001). e-NOS expressions on endothelial cells were similar between the groups. Dense e-NOS immunostaining was observed in vaso vasorum of the adventitia in the pedicled group. However, there was not any e-NOS immunostaining in vaso vasorum of the adventitia in the skeletonized group. Although skeletonization of the ITA is a more technically demanding procedure, it provides some advantages such as increased available graft length and reduced sternal devascularization. This technique did not have any detrimental effects on the endothelial cell lining and e-NOS expressions on the endothelial layer. To reach a definitive judgment for using skeletonized ITA, we need information about the long-term angiographic patency rates.

Novel proximal and distal anastomotic devices for coronary artery bypass surgery

THE CURRENT LITERATURE describes many varied experimental and clinical applications of minimally invasive techniques to enhance outcomes after coronary artery bypass grafting (CABG). Many techniques facilitating anastomotic procedures are described, but long-term data supporting improved patency rates, efficiency of surgical technique, and outcomes are limited. The growing need for minimally invasive procedures and means of reducing the complexity of endoscopic suturing will be the impetus that drives the development and implementation of such anastomotic devices. Applications of simultaneous suturing, stapling, clipping, stenting, and sealing devices have provided insight toward the development of clinically acceptable procedures to facilitate positive outcomes in minimally invasive CABG surgery. Proximal anastomotic devices not only decrease operative time but also allow the surgeon to avoid using a partial occlusion clamp on the ascending aorta during CABG.1 Successful reports of an aortic anastomotic device (AAD) for sutureless anastomosis to the proximal aorta of saphenous vein grafts without aortic manipulation2,3 may provide the technologic basis to pursue distal anastomotic devices in coronary surgery. However, applying such techniques to create distal anastomoses may prove more difficult and require development of unique technologies; robotic assistance toward totally endoscopic CABG makes these goals more challenging. The ideal distal anastomotic device would have applicability to all potential conduits with interchangeable proximal/distal order and a safe bailout in the case of device malfunction.4 The ability to decrease operative time, create superb anastomoses without technical imperfection, and improve long-term patency rates lends excitement to the developing frontier of distal anastomotic devices in minimally invasive CABG surgery. The objective of this review is to compare the existing devices and provide a basis for continued development of novel anastomotic devices. The anesthetic implications will be considered.

Histomorphological studies of the distal internal thoracic artery which support its use for coronary artery bypass grafting

The use of the internal thoracic artery (ITA) for myocardial revascularization in coronary artery disease increased because of its relative immunity to atherosclerotic obstruction. This study investigated the distal part of the vessel, the region of anastomosis by means of histology to focus the visualization of this region of interest. The histological examination of arterial segments showed minor intimal thickening in 48 out of 100 patients. Twelve patients demonstrated a severe intimal thickening, the residual patients were without any changes. In 52% the elastic type dominated in the distal part. Hybrid and muscular patterns were found in 22 and 26%, respectively. The media could be classified into three different types: muscular, hybrid and elastic type. There was no correlation concerning the different histological type and the incidence of intimal thickening. No evidence whatsoever of atherosclerotic lesion was encountered in any of the investigated vessels. There is no limitation in the use of the distal part of the ITA for coronary artery revascularization.

Angiographic Follow-up of Internal Thoracic Artery for Free Bypass Grafting

Background. The use of free internal thoracic artery (ITA) grafts in patients with smaller body surface areas has been questioned because of technical difficulties and inadequate graft flow.Methods. To evaluate postoperative changes in the diameter of free ITA grafts, we performed coronary angiography immediately after coronary artery bypass grafting and then again at a mean of 42 ± 6 months later. In 20 consecutively treated patients, 21 free ITAs were used as bypass conduits. Two ITA grafts that were patent at the time of the first angiography had closed at the second angiography. Postoperative changes in ITA graft diameter were measured in the 19 patent ITA grafts.Results. At the first angiography, the mean diameters of the proximal, middle, and distal ITA grafts were 2.28 ± 0.45 mm, 2.34 ± 0.39 mm, and 2.12 ± 0.38 mm, respectively. At the second angiography, the mean diameters of the proximal, middle, and distal ITA grafts were 2.85 ± 0.50 mm, 2.89 ± 0.53 mm, and 2.72 ± 0.53 mm, respectively. All segments of the ITA grafts had dilated significantly between the first and second angiographic evaluations (p < 0.01). The percentage change in graft diameter was greater when the initial ITA diameter was less than 2.3 mm (32.0% ± 28.0%) than when it was 2.3 mm or more (18.8% ± 11.3%) (p < 0.05).Conclusions. The postoperative increase in free ITA graft diameter depends on coronary blood flow requirements.

Skeletonized and pedicled internal thoracic artery grafts: Effect on free flow during bypass

The skeletonization technique of the internal thoracic artery (ITA) is used as a dissection technique for myocardial revascularization procedures. This study compared free flow between skeletonized ITA grafts and ITA pedicled grafts. The ITA pedicled grafts were sprayed and wrapped in sponges soaked in dilute papaverine solution in 14 patients and prepared with intraluminal papaverine injection in 18 patients. For 23 other patients, the ITA was skeletonized. We measured the first free flow from the distal ITA early after the start of cardiopulmonary bypass and the second free flow just before the ITA was grafted to the left anterior descending artery. The first flow was greater in the skeletonized ITAs than in the ITA pedicled grafts with topical application of papaverine alone (38.9 +/- 15.8 versus 18.0 +/- 6.8 mL/min; p < 0.001). For the second flow, the pedicle grafts with intraluminal papaverine injection and the skeletonized ITAs showed greater flow rate than the pedicled grafts with topical application of papaverine (67.4 +/- 25.5 and 59.7 +/- 22.5 versus 38.1 +/- 13.1 mL/min; p < 0.005 and p < 0.05, respectively), but there was no significant difference between the former two groups (p = 0.53). Skeletonization of the ITA is as efficient a strategy to increase the flow as intraluminal papaverine injection for the ITA pedicled graft. When the ITA is harvested in a skeletonized fashion, arterial spasm and reduced early flow can be avoided, even without intraluminal injection of papaverine.

Port-access coronary artery bypass grafting: A proposed surgical method

Minimally invasive surgical methods have been developed to provide patients the benefits of open operations with decreased pain and suffering. We have developed a system that allows the performance of cardiopulmonary bypass and myocardial protection with cardioplegic arrest without sternotomy or thoracotomy. In a canine model, we successfully used this system to anastomose the internal thoracic artery to the left anterior descending coronary artery in nine of 10 animals. The left internal thoracic artery was dissected from the chest wall, and the pericardium was opened with the use of thoracoscopic techniques and single lung ventilation. The heart was arrested with a cold blood cardioplegic solution delivered through the central lumen of a balloon occlusion catheter (Endoaortic Clamp; Heartport, Inc., Redwood City, Calif.) in the ascending aorta, and cardiopulmonary bypass was maintained with femorofemoral bypass. An operating microscope modified to allow introduction of the 3.5× magnification objective into the chest was positioned through a 10 mm port over the site of the anastomosis. The anastomosis was performed with modified surgical instruments introduced through additional 5 mm ports. In the cadaver model (n = 7) the internal thoracic artery was harvested and the pericardium opened by means of similar techniques. A precise arteriotomy was made with microvascular thoracoscopic instruments under the modified microscope on four cadavers. In three other cadavers we assessed the exposure provided by a small anterior incision (4 to 6 cm) over the fourth intercostal space. This anterior port can assist in dissection of the distal internal thoracic artery and provides direct access to the left anterior descending, circumflex, and posterior descending arteries. We have demonstrated the potential feasibility of grafting the internal thoracic artery to coronary arteries with the heart arrested and protected, without a major thoracotomy or sternotomy. (J T HORAC C ARDIOVASC S URG 1996;111:567-73)