Similarity between internal thoracic artery and gastroepiploic artery graft: pharmacological point of view

The pharmacological responses of internal thoracic artery (ITA), gastroepiploic artery (GEA) and saphenous vein (SV) obtained from patients receiving coronary artery bypass grafting (CABG) were assessed by isometric contraction records. The concentration-response curves for ergonovine and serotonin showed the leftward shift in SV compared with ITA and GEA. The 50% effective dose values of SV for ergonovine and serotonin were significantly less than those of ITA and GEA. The concentration-response curves for phenylephrine were similar among three kinds of grafts. There were no significant differences in the 50% effective dose values for phenylephrine among them. The effect of 0.4% papaverine chloride on the free graft flow was assessed in 15 patients receiving CABG with mean body surface area of 1.62 +/- 0.12 M2. The free flow of ITA graft was 71 +/- 32 ml/min before intraluminal papaverine injection, and that increased to 112 +/- 41 ml/min after injection. The free flow of GEA graft was 82 +/- 39 ml/min before injection, and that also increased to 128 +/- 40 ml/min after injection. The patency rates at the mean 2.2 months after grafting were 98% in ITA, 93% in GEA, and 88% in SV. In conclusion, both GEA graft and ITA graft can be expected as an excellent conduit in myocardial revascularization.     

Differences in adaptation to growth of children between internal thoracic artery and saphenous vein coronary bypass grafts

BACKGROUND: It is not known how the internal thoracic artery (ITA) and saphenous vein graft (SVG) adapts to somatic growth of pediatric patients who underwent coronary artery bypass grafting (CABG). METHODS: Twenty-two ITAs and 6 SVGs in 17 patients who underwent at least three postoperative catheterizations with biplanar cineangiography and followed for a minimum of 5 years were evaluated. We evaluated the length, diameter and curvature of the grafts by cineangiographies which were performed at 1 month, 1 year, 5 years and more than 5 years postoperatively. RESULTS: The length of the ITA (1-month: 117+/-31 mm, 1-year: 134+/-32 mm, 5-years: 146+/-28 mm, and >5-years: 155+/-34 mm, p=0.032) and diameter of the ITA (1.4+/-0.4 mm, 2.0+/-0.7 mm, 2.3+/-0.6 mm and 2.6+/-0.6 mm, p<0.0001) significantly increased over time, but neither the length nor diameter of the SVG length: 121+/-33 mm, 119+/-29 mm, 119+/-25 mm and 126+/-1 mm, p=0.9907; diameter: 4.1+/-1.0 mm, 3.9+/-0.7 mm, 4.0+/-0.8 mm and 3.3+/-0.4 mm, p=0.5784) increased. Although the ITA exhibited no change in curvature over time (1 month: 1.15+/-0.07, late: 1.15+/-0.07, p=0.8490), the curvature of the SVG significantly decreased over time (1 month: 1.42+/-0.19 and late: 1.25+/-0.16, p=0.0277). The percent segmental length of ITAs were changed little from early to late after CABG (1 month: proximal: 33.7+/-7.0%, middle: 33.3+/-7.9% and distal: 32.9+/-7.9%, vs late: 34.3+/-7.2%, 33.2+/-7.9% and 32.5+/-7.9%, p=0.937). CONCLUSIONS: ITAs grow in proportion to somatic growth, while SVGs course in a more linear fashion in adapting to patient growth.     

Stress Doppler echocardiography of the internal thoracic artery--a new non-invasive approach for functional assessment after minimally invasive coronary bypass grafting

Minimally invasive surgery for coronary revascularization using the left internal thoracic artery (ITA) has gained increasing interest. For control of graft function the established transcutaneous color-Doppler echocardiography in combination with a stress-test was performed to test the ability of this novel technique. Twenty-one patients having received a single ITA-graft were evaluated early postoperatively at rest and during isometric stress test with a handgrip exercise. Compared to the right internal thoracic artery, the mainly systolic flow is changed to a wide diastolic component when the left ITA is anastomosed to the coronary artery. The peak systolic/peak diastolic velocity ratio changed from 4.5+/-1.9 to 1.4+/-0.47 (P<0.0001). During stress reaction with the isometric handgrip maneuver the grafted ITA showed a significant increase of the mean diastolic flow (29.1+/-13.3 to 44.3+/-14.7 cm/s, P<0.0001) and total blood flow (124.8+/-55.4 ml/min to 176.6+/-71.7 ml/min), which may demonstrate an efficient bypass function. We conclude, that the noninvasive measurement of ITA-graft function with Doppler-ultrasound may be a clinically useful method to assess the functional status after minimally invasive coronary artery bypass grafting. In combination with the hand-grip test it represents a valid new technique with the potential to estimate graft patency.     

A quantitative angiographic study of characteristics of internal thoracic artery grafts in coronary artery bypass surgery

In adult patients with atherosclerotic coronary artery disease and in pediatric patients with Kawasaki heart disease, characteristics of internal thoracic artery grafts (ITA grafts) used for coronary artery bypass grafting (CABG) were quantitatively assessed by postoperative angiography. In 142 adult patients with a ITA graft for the left anterior descending artery (LAD), the diameter ratio between ITA graft and recipient LAD at the point close to the anastomotic site (ITA/LAD diameter ratio) was determined by postoperative angiography. This ratio for the adult patients as a whole was 1.04 +/- 0.34. The multivariate analysis (Quantification I) was performed to assess the effects of the following 12 factors on the ITA/LAD diameter ratio: (1) age at the time of operation, (2) sex, (3) time-duration from the operation to angiography, (4) laterality of the ITA used, (5) presence of an undivided major side branch of the ITA graft, (6) presence of blood flow competition between the ITA graft and other grafts, (7) presence of distal stenosis of the recipient LAD, (8) severity of LAD stenosis after the operation, and (9-12) presence of hyperlipidemia, diabetes mellitus, hypertension, or smoking history. The standardized category scores of 25% LAD stenosis, 50% LAD stenosis, and blood flow competition between the ITA and other grafts were -0.815, -0.359, and -0.306, respectively. Insignificant stenosis of the recipient coronary artery was associated with reduction of the ITA/LAD diameter ratio, and this ratio strongly correlated with the severity of LAD stenosis (partial correlation coefficient: 0.627). However, no other factors significantly influenced on the ITA/LAD diameter ratio. In 15 pediatric patients, the length and diameter of 19 ITA grafts and 5 saphenous vein grafts (SVGs) which remained patent in the early (about one month) and late (14 +/- 4 months) postoperative period were determined. Only in the ITA graft, increases in graft length and diameter associated with patient growth were recognized. In the present study, the physiological characteristics of the ITA graft were demonstrated as a viable conduit with flow adaptability and growth potential.     

Impact of sequential grafting of the internal thoracic or right gastroepiploic arteries on multiple coronary revascularization

OBJECTIVE: The aim of the study is to clarify the efficacy of the sequential anastomotic technique of the arterial conduits for multiple coronary revascularization. BACKGROUND: The internal thoracic artery (ITA) is now widely accepted as a durable conduit for myocardial revascularization. The right gastroepiploic artery (GEA) has been developed as a third in situ arterial graft with an outcome similar to that of the ITA. MATERIAL AND METHOD: One hundred and forty five consecutive patients (116 male, 29 female, mean age 60.4yr) who received sequential grafting of either the ITA or GEA or both were retrospectively analysed. RESULTS: Sequential anastomoses were performed in 121 in situ left ITAs, 36 in situ GEAs and 12 composite right ITAs. No in situ right ITA was anastomosed sequentially. Two to six vessels (mean 3.8) were revascularized for each patient. Of the total 543 bypassed vessels, 432 (79.6%) were reconstructed with the arterial grafts. In 85 patients with quadruple bypass or more, the arterial grafts were able to reconstruct 266 out of 360 (74.0%) target vessels. Seventy one patients (49.0%) were revascularized without venous grafts. The arterial grafts could revascularize 293 out of 310 vessels (94.5%) in the LAD approximately Diagonal region, 83 out of 113 (73.4%) in the distal RCA or Cx region. There were no cardiac events responsible for the arterial grafts in the follow up period. CONCLUSION: In light of our experience, multiple revascularization with in situ arterial sequential grafts is feasible. Aggressive application of this technique provides patients requiring multiple coronary revascularization with favorable long-term results.     

The correlation between flow pattern during cardiopulmonary bypass and patency of the coronary artery bypass grafts

Recently the availability of transit time flow measurement (TTFM) is reported especially in off-pump coronary artery bypass grafting (CABG). But little is known about TTFM findings in on-pump CABG. We examined the correlation between the TTFM flow pattern and the angiography findings in on-pump CABG. The subjects consisted of 52 patients who underwent on-pump CABG and angiography early after operation. In these patients, 55 internal thoracic artery (ITA), 17 gastroepiploic artery (GEA), 13 saphenous vein graft (SVG) and 41 radial artery (RA) were tested with TTFM during cardiopulmonary bypass (CPB). TTFM demonstrated a diastolic filling pattern in 53 ITA, 16 GEA, 13 SVG and 36 RA. The angiography revealed that all these grafts were perfectly patent with the exception of a GEA with a flow competition pattern. TTFM revealed an abnormal flow pattern in 2 ITA (these 2 grafts were revised during CPB and the angiography demonstrated their perfect patency), 1 GEA (to and fro pattern), 0 SVG and 5 RA (the abnormal pattern was due to graft spasm in 3 of 5, and the angiography revealed their perfect patency, however, the angiography detected stenosis in the remaining 2 grafts). The present study found that the TTFM flow pattern during CPB correlated well with the angiography findings. TTFM during CPB was useful to detect graft failure, and grafts were revised safely during CPB.     

ITA versus SVG: a comparison of instantaneous pressure and flow dynamics during competitive flow

Objective: Competitive flow from patent native coronary vessels is implicated in the failure of internal thoracic artery (ITA) grafts, but it is not thought to affect saphenous vein graft (SVG) patency. This study examines instantaneous pressure and flow dynamics in left ITA and SVG grafts in competition with a patent left anterior descending (LAD) artery. Methods: SVG (3.0–4.0 mm) and ITA (1.5–2.0 mm) to proximal LAD (2.5–3.0 mm) coronary bypass was performed in 10 mongrel dogs. Flow and pressure were measured in the occluded (No Competition) and opened (Competition) ITA, SVG and LAD. Results: The ITA and SVG, when each was the sole inflow to the LAD, provided similar flow as the native LAD. During competitive flow, total LAD flow was preserved and flow in the ITA and SVG were reduced (8.20±1.25 and 10.00±1.73 ml/min; P<0.005). SVG diastolic flow was reduced to 11.52±2.17 ml/min (55.5%); P<0.003. Flow in the SVG remained predominantly antegrade. In contrast, ITA diastolic flow was reduced more drastically, to 5.37±1.25 ml/min (80.7%); P<0.0001. When the ITA was the only inflow to the LAD, there was delay in the LAD pressure wave. This delay disappears during competition due to the large, systolic retrograde flow up the ITA. Conclusion: The ITA, compared to the SVG, is a longer and narrower conduit with lower levels of flow during competition. Due to a delay in the pressure wave, the ITA flow is retrograde during early systole. Low levels of flow, with a markedly decreased diastolic phase, and the oscillating pattern in systole (retrograde/antegrade) may be poorly tolerated by the ITA endothelium and lead to graft deterioration.     

Flow dynamic comparison of In-situ internal thoracic and gastroepiploic arterial conduits

Objective: We tried to experimentally clarify the flow dynamic differences under flow competitive conditions between the internal thoracic artery (ITA) and gastroepiploic artery (GEA) as in-situ arterial bypass conduits. Methods: The ITA and the GEA were anastomosed close together to the left anterior descending artery (LAD) in 8 pigs. Flow characteristics of the ITA and the GEA were analyzed using a transit time flow meter under the following flow competitive conditions; condition A: the ITA, GEA and LAD were left open, condition B: either of the ITA or GEA were clamped and the LAD was left open, condition C: the ITA and GEA were open but the proximal LAD was clamped, condition D: either of the ITA or GEA were clamped and the proximal LAD was also clamped. Results: The flow volume of the ITA was significantly (p<0.001) greater than that of the GEA in condition A (27±11 ml/min vs. ?4±9 ml/min), B (26±17 ml/min vs. ?1±14 ml/min) and C (38±14 ml/min vs. 0±4 ml/min), but did not differ (p=0.685) in condition D (29±6 ml/min vs. 31±14 ml/min). Retrograde flow in systole and antegrade flow in diastole was seen in the GEA in condition A, B and C. Conclusion: Under flow competitive conditions, flow of the GEA was inferior to that of the ITA. These data suggested that the GEA is more sensitive to competitive flow than the ITA. This may be due to anatomical differences between these in-situ bypass conduits.     

Flow dynamic comparison of In-situ internal thoracic and gastroepiploic arterial conduits

Objective: We tried to experimentally clarify the flow dynamic differences under flow competitive conditions between the internal thoracic artery (ITA) and gastroepiploic artery (GEA) as in-situ arterial bypass conduits. Methods: The ITA and the GEA were anastomosed close together to the left anterior descending artery (LAD) in 8 pigs. Flow characteristics of the ITA and the GEA were analyzed using a transit time flow meter under the following flow competitive conditions; condition A: the ITA, GEA and LAD were left open, condition B: either of the ITA or GEA were clamped and the LAD was left open, condition C: the ITA and GEA were open but the proximal LAD was clamped, condition D: either of the ITA or GEA were clamped and the proximal LAD was also clamped. Results: The flow volume of the ITA was significantly (p<0.001) greater than that of the GEA in condition A (27±11 ml/min vs. −4±9 ml/min), B (26±17 ml/min vs. −1±14 ml/min) and C (38±14 ml/min vs. 0±4 ml/min), but did not differ (p=0.685) in condition D (29±6 ml/min vs. 31±14 ml/min). Retrograde flow in systole and antegrade flow in diastole was seen in the GEA in condition A, B and C. Conclusion: Under flow competitive conditions, flow of the GEA was inferior to that of the ITA. These data suggested that the GEA is more sensitive to competitive flow than the ITA. This may be due to anatomical differences between these in-situ bypass conduits.     

Fractional flow reserve of pedicled internal thoracic artery and saphenous vein grafts 6 months after bypass surgery.

BACKGROUND: Although the internal thoracic artery was proven superior to saphenous vein graft in long-term patency, it is thought to be a more resistive conduit than the vein graft. Moreover, patency studies comparing both left and right internal thoracic arteries have provided results favoring the former. Fractional flow reserve is an established functional index of coronary blood flow. METHODS: To compare the fractional flow reserve between both internal thoracic arteries and saphenous vein grafts, 43 bypass grafts were studied 6 months after revascularization. Intra-graft pressures were measured during cardiac catheterization using a pressure-wire advanced to the first distal anastomosis of 12 left internal thoracic arteries (ITAs), 10 right ITAs and of 21 vein grafts. Pressure gradients between the aorta and the graft were measured at baseline and during a maximal hyperemia. RESULTS: At baseline, pressure gradient was recorded in the left ITA (2.9+/-2.2 mmHg), in the right ITA (1.2+/-1.2 mmHg) and in the vein graft (0.4+/-0.7 mmHg). During maximal hyperemia, pressure gradient increased to 9.6+/-3.2 mmHg in left ITA, to 4.5+/-2.0 mmHg in the right ITA (p<0.001 vs left ITA) and to 3.3+/-2.7 mmHg in vein (p<0.001 vs left ITA; NS vs right ITA). Fractional flow reserve was 0.90+/-0.04 in left ITA, 0.95+/-0.03 in right ITA (p<0.01 vs left ITA) and 0.96+/-0.03 in vein (p<0.001 vs left ITA). CONCLUSION: Internal thoracic arteries and saphenous vein grafts allow myocardial revascularization with minimal resistance to maximal blood flow. The resistance appears significantly higher in left ITA compared to both the right ITA and venous grafts.     

Assessment of blood flow of the internal thoracic artery in patients with aortic stenosis

The number of patients undergoing combined aortic valve replacement (AVR) for aortic stenosis (AS) and coronary artery bypass grafting (CABG) has been increasing. In CABG, the internal thoracic artery (ITA) is the preferred conduit for its long-term patency. Although Doppler studies on ITA have been widely used, flow characteristics of the vessel in patients with AS have not been reported. To evaluate blood flow pattern of the ITA in AS, duplex scanning was performed in 10 patients before and after AVR. Peak systolic velocity was measured, and blood flow was calculated from mean velocity and cross-sectional area. The mean diameters of the vessels were approximately 1.8 mm on both sides. AVR caused an increase in systolic velocities from 61.2 cm/sec to 85.5 cm/sec in right ITA and from 58.4 cm/sec to 84.7 cm/sec in left ITA. The flow volumes increased from 32.2 ml/min to 46.7 ml/min in right and increased from 31.6 ml/min to 46.3 ml/min in left after AVR. In simultaneous AVR for AS and CABG, suitability of the ITA should be assessed before its use, and concomitant AVR may be quite important to provide adequate flow of the ITA as a conduit.     

Effects of skeletonization on intraoperative flow and anastomosis diameter of internal thoracic arteries in coronary artery bypass grafting

BACKGROUND: We examined the hypothesis that complete skeletonization of an internal thoracic artery (ITA) results in increased diameter of the graft for anastomosis and therefore improves graft flow in coronary artery bypass grafting. METHODS: We studied 65 consecutive patients who underwent coronary artery bypass grafting, in which the left ITA was anastomosed to the left anterior descending artery. The first 20 consecutive ITA were harvested as a pedicle (group P) and later 45 consecutive ITAs were harvested as an ultrasonically skeletonized graft (group S). Intraoperative ITA graft mean flows were obtained with a transit-time flowmeter. Three diameters of the ITA graft were measured quantitatively in postoperative angiograms performed 14 +/- 5 days after the coronary artery bypass grafting; D1, at the origin from the subclavian artery; D2, at the level of the second intercostal space; and D3, just proximal to the anastomosis. RESULTS: Intraoperative mean flow was significantly greater in group S than in group P (S: 42.6 +/- 29.1 mL/min versus P: 26.4 +/- 16.1 mL/min, p = 0.03). Although the diameters D1 and D2 were not significantly different between groups, D3 was significantly larger in group S than in group p (S: 1.77 +/- 0.28 mm versus P: 1.57 +/- 0.17 mm, p = 0.02). CONCLUSIONS: Compared with pedicle harvesting, complete skeletonization of ITA may make it possible to anastomose an ITA with a larger diameter in coronary artery bypass grafting, which leads to increased graft flow by decreasing vascular resistance.     

Human gastroepiploic artery has greater chymase activity than the internal thoracic artery

Objective: Recent reports have demonstrated that long-term patency of the gastroepiploic artery (GEA) in coronary artery bypass grafting (CABG) is less satisfactory compared with the internal thoracic artery (ITA). However, the reason has not been fully elucidated. Angiotensin II is known to play an important role in the development of intimal hyperplasia, we hypothesized that the GEA is different from the ITA with respect to angiotensin II-forming ability. Accordingly, we measured activities of angiotensin II-forming enzymes, angiotensin-converting enzyme (ACE) and chymase, in human GEA and ITA. Methods: Remnant of the GEAs and ITAs were obtained from 24 patients who underwent CABG in which both conduits were used simultaneously. Activities of ACE and chymase were measured by using the extract form the GEA or ITA. Sections of the GEA or ITA were immunohistochemically stained with anti-human chymase antibody. Results: The ACE activity of the GEA (0.28 ± 0.16 mU/mg protein) was greater than that of the ITA (0.18 ± 0.11, p < 0.001). The chymase activity of the GEA (11.11 ± 7.15 mU/mg protein) was also greater than that in the ITA (7.13 ± 4.89, p < 0.001). The density of chymase-positive cells in the GEA (3.8 ± 4.2 cells/mm²) was greater than that in the ITA (1.1 ± 1.2, p < 0.01). Conclusion: Activities of both ACE and chymase were significantly greater in the GEA compared with the ITA. The GEA may be different from the ITA with respect to potential ability of angiotensin II-formation.     

Noninvasive assessment of right gastroepiploic artery graft patency using transcutaneous color Doppler echocardiography

BACKGROUND: Because the right gastroepiploic artery graft (GEA), when routed antegastrically, is situated just behind the abdominal wall, we investigated the possibility of evaluating graft patency and flow characteristics using transabdominal color Doppler echocardiography. METHODS: The right GEA graft was evaluated in 71 patients who underwent complete arterial revascularization, 4 months (range, 2 to 17 months) postoperatively. Selective angiography of the right GEA was performed in the patients in whom the graft could not be visualized using color Doppler echocardiography. RESULTS: Flow in the right GEA graft was detected in 65 (91.5%) of 71 patients using color Doppler echocardiography. In all visualized right GEAs, a biphasic flow pattern was observed, with higher peak velocity during systole. Mean (+/- standard deviation) peak systolic velocity was 76+/-16 cm/s. Mean (+/- standard deviation) velocity was 41+/-14 cm/s. Selective angiography of the right GEA in 5 patients in whom the graft could not be visualized using echocardiography showed four patent and functional grafts and one graft that was open but not functional ("slender sign"). One patient died before angiography could be performed. The sensitivity of noninvasive ultrasound assessment of the patency of the right GEA graft was 94% (65 of 69 patients). In this group of patients, an overall right GEA graft patency rate of 97% (69 of 71 patients) was found at mean follow-up of 4 months (range, 2 to 17 months). CONCLUSIONS: The right GEA graft is an adequate coronary artery graft with a good short-term patency rate, and transcutaneous color Doppler echocardiography is a useful tool for evaluating its patency and flow characteristics. Selective angiography of the right GEA can be avoided in most cases and is indicated only when the graft cannot be detected using Doppler echocardiography.     

Does competitive flow reduce internal thoracic artery graft patency?

BACKGROUND: In coronary arteries with moderate stenosis, competitive flow may lead to internal thoracic artery (ITA) graft occlusion. The goals of this study were to determine if competitive flow reduces ITA patency, and if there is a degree of coronary stenosis below which ITAs should not be used. METHODS: From 1972 to 1999, 50,278 patients underwent primary coronary artery bypass grafting (CABG). Of these, 2,002 had at least one ITA graft and postoperative angiography before coronary reintervention; 2,999 angiograms of 2,121 ITAs were made. Time-related ITA occlusion was modeled using longitudinal analysis to identify its risk factors while accounting for lack of independence introduced by repeated angiography and multiple ITA anastomoses per patient. Proximal coronary stenosis (maximum preoperative stenosis between ITA anastomosis and aorta) was the surrogate for competitive flow. RESULTS: Unadjusted ITA patency was 93%, 89%, 90%, and 92% at 1, 5, 10, and 15 years after CABG. Risk factors associated with ITA occlusion were lesser degree of proximal coronary stenosis (p < 0.0001); longer time from CABG in grafts to non-left anterior descending coronary arteries (p < 0.0001); female sex (p = 0.0003); later date of CABG (p = 0.01); right ITA (p < 0.0001); and smoking (p < 0.0001). In all arteries, as preoperative proximal coronary stenosis decreased, ITA patency declined; however, at no degree of stenosis was there a sharp decline. CONCLUSIONS: Internal thoracic artery patency decreases as coronary competitive flow increases. However, the nature of this relationship indicates ITAs should not be abandoned at moderate grades of stenosis.     

Clinical results, graft patency and flow reserve capacity of multiple coronary artery bypass with bilateral or sequential internal thoracic artery grafts

Multiple coronary artery bypass grafting (CABG) was performed utilizing the internal thoracic arteries (ITA) in 87 patients ranging in age from 3 to 76 years. Bilateral ITAs were used in 67, sequential grafting was performed in 16, and the combination of both techniques was applied in 4 patients. Twelve patients had coronary arterial obstructions due to Kawasaki disease (mean age 9.7 +/- 3.3 years) and the remaining 75 patients had atherosclerotic coronary artery disease (mean age 53 +/- 10 years). Triple vessel disease and left main trunk disease occupied 85% of the patients. The number of grafts was 2 to 5 per patient with an average of 3.2 +/- 0.7 per patient. In bilateral ITA grafting, the combination of the RITA to LAD and LITA to LCX was most frequently used, and in sequential grafting, the LITA-diagonal artery-LAD was the most common use. There were no early or late mortalities in the present series. The patency rates for the RITA and LITA were 93% and 96%, respectively, and those of sequential grafting were 100% in both the proximal and distal anastomoses. The clinical outcome of multiple CABG with ITAs was quite satisfactory, and the bilateral ITAs could be used in the very wide range of patient's age from 3 to 76 years. In addition, blood flow reserve provided by bilateral ITAs was equivalent to that of the SVG alone or SVG plus ITA on the basis of the result of coronary sinus flow (CSF) measurements during exercise, and thus complete revascularization of the left ventricle could be accomplished by multiple CABG with ITAs.     

Free flow capacity of skeletonized versus pedicled internal thoracic artery grafts in coronary artery bypass grafts.

OBJECTIVE: The internal thoracic artery (ITA) is the ideal conduit for coronary artery bypass grafting (CABG). The skeletonization technique of this arterial conduit has been proposed to reduce chest wall trauma, increase graft length and facilitate construction of sequential anastomoses. Nevertheless, some surgeons decline this technique because of potentially increased trauma to the ITA with impairment of flow. In this investigation we compared the free flow of skeletonized with that of pedicled ITA grafts. METHODS: Two surgeons operated on 80 consecutive patients with coronary artery disease for elective CABG. In group I (n = 40), the left ITA was dissected using the skeletonization technique. In group II (n = 40), it was harvested as a pedicled graft. In 23 patients of group I both ITA's were dissected in skeletonized fashion for complete arterial revascularization. Diluted papaverine was instilled into the lumen of the ITA after distal transection of the vessel in both groups. Free flow of the ITA was registered before and 15 min after intraluminal application of diluted papaverine. Mean arterial pressure was maintained at 70 mmHg. RESULTS: Before the application of papaverine, free flow of skeletonized and pedicled ITA grafts was identical between the two groups. After treatment with papaverine maximum free flow was significantly higher in the skeletonized ITA's (group I 197.2 (+/-66.6) ml/min; group II 147.1 (+/-70.5) ml/min; P < 0.05). There was no significant difference between free flow after dilatation of the left and right ITA in group I (left 197.2 (+/-66.6) ml/min; right 198.9 (+/-61.8) ml/min). CONCLUSIONS: Preparation of the ITA with the skeletonization technique results in significantly, higher free flow capacity than in pedicled grafts. This may increase the safety of arterial revascularization by reducing the risk of ITA hypoperfusion syndrome.     

Revascularization with bilateral internal thoracic artery grafts in patients with left main coronary stenosis.

Left main occlusive disease (LMD) is a potentially fatal lesion which is optimally treated with surgical revascularization. Although the internal thoracic artery (ITA) is recognized as having superior long term patency, there has been concern regarding possible flow limitation. Because of this concern, there may be reluctance to use only this conduit in patients with LMD in whom high graft flows are desirable. From 1985 to 1990, 45 patients (38 males, 7 females) with LMD ranging in age from 37 to 75 years (mean 55.9 +/- 8.7) underwent revascularization using bilateral ITA grafts placed to the left anterior descending and circumflex arteries. The right ITA was used as a free graft in 19 of 45 (42%) patients and the left ITA was used as a free graft in 3 of 35 (7%). No saphenous vein grafts were placed to the left coronary system in any patient. Over half of these patients (24 patients, 53%) also had occlusive disease in the right coronary artery. A saphenous vein graft was placed to the right coronary artery in 22 of 45 (49%) patients. Ventricular function in this patient subset was good (mean LV score 7.1 +/- 2.1). Intra-operative ITA graft flows were 49.7 +/- 29.1 ml/min for grafts to the left anterior descending and 45.5 +/- 31.7 ml/min for circumflex grafts. There were no perioperative deaths. Morbidity included myocardial infarction, stroke and reoperation for bleeding in 1 patient each (2.2%). Low cardiac output occurred in 2 patients (4.4%). No patient had a mediastinal wound infection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of flow competition on internal thoracic artery graft: postoperative velocimetric and angiographic study

OBJECTIVES: To assess the effects of competitive blood flow on internal thoracic artery grafts, we investigated postoperative flow velocity characteristics and angiographic findings of the grafts with various grades of native coronary artery stenosis. METHODS: Fifty patients who had an internal thoracic artery graft to the left anterior descending artery underwent intravascular Doppler graft velocimetry during postoperative angiography. Patients were divided into 3 groups according to the grade of native coronary stenosis: group H (28 patients), 80% stenosis or greater; group M (16 patients), 60% to 79% stenosis; and group L (6 patients), 40% to 59% stenosis. Phasic flow velocity of the grafts was measured with an intravascular Doppler ultrasound-tipped guide wire during angiography. Graft flow volume was calculated from the diameter and the average peak velocity. RESULTS: Average peak velocity (group H, 27.1 +/- 8.6 cm/s; group M, 16.9 +/- 3.9 cm/s; group L, 7.2 +/- 3.7 cm/s), distal graft diameter (group H, 2.27 +/- 0.23 mm; group M, 2. 00 +/- 0.28 mm; group L, 1.07 +/- 0.27 mm), and calculated graft flow volume (group H, 33.1 +/- 12.0 mL/min; group M, 16.2 +/- 5.8 mL/min; group L, 2.3 +/- 2.0 mL/min) significantly differed among the 3 groups. Graft flow in diastole and systole also differed among the 3 groups. CONCLUSIONS: Competitive blood flow reduces internal thoracic artery graft flow and diameter according to the grade of the native coronary artery stenosis. These data suggest that grafting the internal thoracic artery to the coronary artery with stenosis of a low grade can cause graft atrophy and failure.     

Noninvasive assessment of coronary flow reserve in the right gastroepiploic artery graft

Background. To investigate the functional capacity of the right gastroepiploic artery graft (GEA) and its ability to adapt to provide adequate flow at peak myocardial demand, we investigated the feasibility of determining coronary flow reserve (CFR) provided by this vessel using transabdominal color Doppler echocardiography and the correlation between this noninvasive determination of flow reserve and nuclear stress scintigraphy.

Methods. In 40 selected patients, who underwent complete arterial myocardial revascularization using the GEA and the internal thoracic arteries (ITAs), CFR of the GEA was measured at maximum coronary hyperemia induced by intravenous adenosine infusion, 7 months (range 3 to 20) after surgery. In the same period, in 31 of this group of patients, exercise thallium scintigraphy was performed.

Results. We succeeded in measuring CFR in 37 of 40 patients with values ranging from 1.1 to 3.6 with an average of 2.1 ± 0.7. During adenosine infusion, mean velocity in the GEA significantly increased from 48 ± 20 to 89 ± 41 cm/sec (p < 0.001), mean arterial blood pressure significantly decreased from 96 ± 11 to 87 ± 11 mm Hg (p < 0.001), and heart rate significantly increased from 74 ± 11 to 87 ± 15 beats/min (p < 0.001). In 8 of these 37 patients, the nuclear exercise test was positive (compatible with reversible ischemia in the distribution area of the GEA). Average CFR in these 8 patients with positive nuclear stress test was 1.46 ± 0.28 versus 2.27 ± 0.70 in those patients with a negative test (p < 0.001).

Conclusions. Noninvasive determination of CFR of GEAs is feasible, using transabdominal Doppler echocardiography. The present study shows that coronary vasodilator reserve and autoregulation is maintained in myocardium supplied by the GEA and that the CFR has a significant correlation with the results of noninvasive nuclear exercise testing. Therefore, noninvasive determination of CFR by transabdominal Doppler echocardiography might be a valuable contribution to functional assessment of GEAs.