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Failure to close the side branches of the internal mammary artery can result in ischemia due to coronary steal through a patent mammary artery side branch after coronary artery bypass grafting. The authors present the case of a 56-year-old man with recurrent angina after 6 month surgical myocardial revascularization underwent coronary angiography that showed patent left branch of the internal mammary artery. After demonstration of inducible ischemia, effective percutaneous treatment was performed using coil embolization, improving blood flow and clinical symptoms., (© 2024 Wiley Periodicals LLC.)

Transit-time flow measurement (TTFM) is frequently used to evaluate intraoperative quality control during coronary artery bypass grafting (CABG) and has the ability to assess graft failure intraoperatively. However, perioperative factors affecting TTFM during CABG remain poorly understood. Patients who underwent CABG at a single institution between July 2016 and May 2018 were prospectively evaluated. TTFM and blood viscosity were measured haemodynamically, while mean flow (mL/min), pulsatility index, and diastolic filling were recorded. Arterial blood gas was analysed immediately after left internal mammary artery to left descending artery anastomosis and before sternal closure. Factors associated with TTFM were assessed using multiple linear regression analysis. We evaluated 57 of the 62 patients who underwent CABG during the study period, including 49 who underwent off-pump and 8 who underwent on-pump surgeries. Blood viscosity was not significantly associated with TTFM (p > 0.05). However, TTFM was significantly associated with body mass index, systolic blood pressure, and cardiac index (p < 0.05 each). In conclusion, maintaining the SBP in the perioperative period and maintaining the CI with inotropic support or fluid resuscitation can be important in improving blood flow of graft vessels after surgery.

Background: The left internal thoracic artery (LITA) is the most commonly used arterial bypass conduit in coronary artery bypass graft (CABG) patients and inadequate LITA flow can result in an increase in morbidity and mortality. In this study, we evaluated the effect of excision of the distal spasmodic segment of the LITA on the free flow in CABG patients., Methods: This study consisted of 47 patients who underwent elective CABG performed with or without other cardiac surgery, between July 2015 and December 2015. Excised LITA length was shorter than 15mm in group 1, between 15mm and 30mm in group 2 and longer than 30mm in group 3. Left ITA free flow was measured for 60seconds into a container before and after the distal LITA excision. The inter-measurement differences were calculated for the three groups. Thereafter, the comparison was performed in terms of free flow difference amongst the three groups., Results: The mean difference of LITA free flow was 27.6±22.7ml/minute in group 1, 35.4±26.7ml/minute in group 2, and 52.6±26.1ml/minute in group 3. There were significant differences in terms of free flow difference between the groups (p=0.008). Also, differences were statistically significant in group 1 versus group 3 (p=0.003) and group 2 versus group 3 (p=0.038) in the intergroup comparisons., Conclusions: The distal part of the LITA has more spasmodic potential than other segments. This spasm may result in low flow of LITA grafts. Therefore, an as long as possible excision of the distal LITA segment may be required to avoid the spasmodic effect., (Copyright © 2017 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier B.V. All rights reserved.)

Background: The long-term benefits of a third arterial conduit to the right circulation in triple-vessel disease remain debatable. This retrospective, single-center, propensity-matched study investigates the impact of a third arterial conduit to the right circulation on early and intermediate survival after coronary artery bypass grafting., Methods: Data were retrospectively collected from 2004 to 2014 for all surgical revascularizations for triple-vessel disease with at least 2 arterial conduits to the left circulation and a third arterial or venous conduit to the right circulation. A total of 167 pairs were propensity matched to arterial versus venous third conduit to right circulation. Hazard functions were obtained with Cox multivariate regression and Kaplan-Meier survival curves were compared between the matched cohorts., Results: Extracardiac arteriopathy, logistic euroSCORE, and left main stem disease were significant predictors of adverse survival. A third arterial conduit to the right circulation was not a significant predictor of improved survival in multivariate analysis (HR, 0.72; 95% CI, 0.34-1.55; P = .411). 30-day mortality was 0.6% in both groups. There was no significant difference in early or intermediate survival in the propensity-matched groups (venous vs arterial, 99.2% vs 99.2%; P = 1.000 at 1 year; 85.2% vs 88.8%; P = .248 at 5 years and 69.2% vs 88.8%; P = .297 at 7 years) CONCLUSIONS: The use of a third arterial versus a venous conduit to the right circulation does not improve early or intermediate survival up to 7 years in triple-vessel coronary artery disease in this study. Longer follow-up and larger cohorts may be needed for differences to emerge., (Copyright © 2017 The American Association for Thoracic Surgery. All rights reserved.)

This study aimed to evaluate the feasibility and the mid-term efficacy of an in situ skeletonized right internal mammary artery (IMA) bypass grafting to a left anterior descending artery (LAD), and to determine risk factors for IMA graft failure in a single-center study.From January 2012 to December 2015, 189 patients (173 males, 50.6 ± 6.0 years old) undergoing first isolated coronary artery bypass grafting surgery with the in situ skeletonized right IMA grafting to the LAD were included in this study. Baseline characteristics, peroperative data, and follow-up outcomes were investigated and analyzed.The length of the in situ skeletonized right IMA grafts was 18.6 ± 1.2 cm (17.0-22.0 cm). Intraoperative graft flow of the in situ skeletonized right IMA grafting to LAD was 42 ± 9 mL/minute (18-72 mL/minute) associated with measured pulsatility index of 0.8-4.3. In-hospital mortality was 0.5%. Postoperative morbidity included acute myocardial infarction (0.5%), stroke (0.5%), and deep sternal wound infections (1.1%). The mid-term survival was 97.2% and the incidence of repeat revascularization was 0.6%. The patency rate of the in situ skeletonized right IMA grafting to the LAD was 97.1% by computed tomography angiography examination during the follow-up period of 23.2 ± 9.7 months. Additionally, logistic regression analysis showed that intraoperative graft flow had an independent influence on the risk of the mid-term right IMA graft failure.The strategy of the in situ skeletonized right IMA grafting to the LAD is feasible and effective. Intraoperative graft flow was an independent risk factor for the mid-term right IMA graft failure.

Background: The objective of this study is to test the effect of permanent right internal mammary artery device closure on coronary collateral function and myocardial ischemia., Methods and Results: This was a prospective, open-label clinical trial in 50 patients with coronary artery disease. The primary study end point was coronary collateral flow index as obtained during a 1-minute proximal right coronary artery (RCA) and left coronary artery balloon occlusion at baseline before and at follow-up examination 6 weeks after distal right internal mammary artery device closure. Collateral flow index is the ratio between simultaneously recorded mean coronary occlusive pressure divided by mean aortic pressure, both subtracted by central venous pressure. Secondary study end points were fractional flow reserve during vessel patency, the quantitative intracoronary ECG ST-segment elevation, and angina pectoris during the same 1-minute coronary occlusion. Collateral flow index in the untreated RCA and left coronary artery changed from 0.071±0.082 at baseline to 0.132±0.117 ( P <0.0001) at follow-up examination and from 0.106±0.092 to 0.081±0.079 ( P =0.29), respectively. RCA fractional flow reserve increased significantly ( P =0.0029) from baseline to follow-up examination, despite deferral of coronary intervention in all patients. There was a decrease in intracoronary ECG ST-elevation during RCA occlusion from baseline to follow-up examination ( P =0.0015); it did not change in the left coronary artery. Angina pectoris during RCA occlusion tended to occur in fewer patients at follow-up versus baseline examination ( P =0.06)., Conclusions: Permanent right internal mammary artery device closure seems to augment extracardiac ipsilateral coronary supply to the effect of reducing ischemia in the dependent myocardial region., Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02475408., (© 2017 The Authors.)

Transit-time flow measurement (TTFM) is a reliable method to check the graft function intraoperatively in coronary surgery. The given parameters are: Mean Graft Flow (MGF); Pulsatility Index (PI) and Insufficiency Ratio (%BF). Some cutoffs of these parameters have been identified as predictors for unfair 1-y clinical outcome: mean graft flow (MGF) less than 20 ml/min and high pulsatility index greater than 5. Other cutoffs have been found as related to postoperative angiography: MGF 15 ml/min or less and pulsatility index at least 3 (sensitivity 94%; specificity 61%); MGF less than 15 ml/min and pulsatility index greater than 3 for left coronary artery or pulsatility index greater than 5 for right coronary artery (sensitivity 96%; specificity 77%); MGF 15 ml/min or less and pulsatility index at least 5.1 left coronary artery (sensitivity 98%; specificity 26%). Hence, with the need to improve the diagnostic accuracy of TTFM, high-resolution epicardic coronary ultrasound module has been added to graft flow evaluation providing 2D ultrasound imaging (either in short-axis or long-axis) and color-flow mapping, allowing an accurate morphological evaluation of body graft and anastomosis. An intraoperative method aimed to verify coronary grafts should be easy to handle, not time consuming, minimally invasive, easily meaningful and relatively cheap; in addition, it should offer objective parameters more than qualitative criteria. We herein report the results of our experience with intraoperative graft verification with TTFM and high-resolution imaging along with a systematic review of the literature in this field with the aim to provide a road map to be followed.

Transit time flow measurement (TTFM) is a quality control tool for intraoperative graft evaluation in coronary artery bypass graft (CABG) surgery. A critical review of the literature available using TTFM in CABG surgery is the focus of this article. The main objectives will be to detail precise parameters for flow evaluation, to show limitations of TTFM and to prove its predictive impact on postoperative graft failure rate. Publications listed in the PubMed database were reviewed, searching for intraoperative graft verification in coronary surgery by TTFM, with postoperative imaging follow-up (FU) modality and with a special focus on publications released after European guidelines from 2010. Nine included publications revealed an overall graft failure rate of ∼12%. Mean graft flow had a positive predictive value in the largest study, and cut-offs, of at least 20 ml/min for internal mammary artery (IMA) grafts, therein partially confirming guidelines, and 30-40 ml/min for saphenous venous grafts (SVGs) were proposed. An explicit correlation between graft flow, patency rate and severity of coronary stenosis, by indicating the fractional flow reserve, was found for IMA grafts. Increased pulsatility index and increased systolic reverse flow probably predict worse outcome and may help identifying competitive flow. Diastolic filling, rarely indicated, could not be confirmed as the predictive marker. No significant correlation of TTFM and graft failure rate for radial and other arterial grafts could be found, partially due to the small number of these types of grafts analysed. Larger target vessels and lower postoperative CK-MB levels may predict better graft patency rates. Low sensitivity for TTFM to reliably detect graft failure is certainly a major issue, as found in randomized analyses. However, methodical limitations and varying threshold values for TTFM render a general consensus difficult. Influence of quantity (vessel territory distribution) and quality (myocardial scar) of the graft perfusion area, on TTFM and FU outcome, was not included by anyone and should be part of future research. TTFM is probably not the tool of choice to detect progressive late graft failure of SVG. Peroperative TTFM values should be correlated with one type of conduit, differentiating between early and late graft failure (by applying a uniform, appropriated definition), to precise and confirm threshold values., (© The Author 2016. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)

Background: The effect of proximal side branches on the patency of the internal thoracic artery (ITA) is controversial. We used echocardiography and Doppler to verify the effect of ligation of branches on the flow and coronary flow reserve (CFR) of the grafted ITA in patients after coronary artery bypass grafting (CABG)., Methods: We prospectively investigated 53 patients with preserved left ventricular ejection fraction (LVEF >50%) who underwent CABG of the ITA. In Group I (25 patients), major branches were ligated during ITA anastomosis to the left anterior descending (LAD) coronary artery, whereas no ligation was performed in Group II (28 patients). Systolic flow (SF), diastolic flow (DF), and total flow (TF = SF + DF) were measured by Doppler echocardiography at the proximal level of the ITA preoperatively, at early postoperative stage, and 6 months after surgery. Dobutamine stress echocardiography (DSE) was performed at 6 months to determine CFR., Results: The ITA flow was predominantly systolic before surgery and diastolic in the postoperative period. We found no differences between the groups in DF. On DSE, SF (19.5±9 mL/min vs 32.7±19 mL/min; P=.003) and TF (79±21 mL/min vs 101±47 mL/min; P=.037) were higher in Group II. There were no differences in CFR (1.9±0.46 vs 2.11±0.56; P=.143)., Conclusion: In patients with preserved LVEF, ligation of major side branches during anastomosis to the LAD does not alter ITA flow or CFR., (© 2016, Wiley Periodicals, Inc.)

Mechanical stimuli are key to understanding disease progression and clinically observed differences in failure rates between arterial and venous grafts following coronary artery bypass graft surgery. We quantify biologically relevant mechanical stimuli, not available from standard imaging, in patient-specific simulations incorporating non-invasive clinical data. We couple CFD with closed-loop circulatory physiology models to quantify biologically relevant indices, including wall shear, oscillatory shear, and wall strain. We account for vessel-specific material properties in simulating vessel wall deformation. Wall shear was significantly lower (p = 0.014*) and atheroprone area significantly higher (p = 0.040*) in venous compared to arterial grafts. Wall strain in venous grafts was significantly lower (p = 0.003*) than in arterial grafts while no significant difference was observed in oscillatory shear index. Simulations demonstrate significant differences in mechanical stimuli acting on venous vs. arterial grafts, in line with clinically observed graft failure rates, offering a promising avenue for stratifying patients at risk for graft failure.

Background: Improvements in myocardial perfusion and thickening were compared in coronary artery bypass grafting patients who received saphenous vein (SV) Y-composite grafts versus those who received right internal thoracic artery ([R]ITA) Y-composite grafts., Methods: Of the 224 patients enrolled in a randomized clinical trial, 116 patients (SV group, n = 65; RITA group, n = 51) in whom myocardial single-photon-emission computed tomography was performed preoperatively, and at 3 months and 1 year postoperatively, were retrospectively studied. A 20-segment model was adopted, and a total of 792 ischemic myocardial segments (SV group, n = 443; RITA group, n = 349) were analyzed. The reversibility score (rest minus stress perfusion value) as an indicator of ischemic myocardium, and Z-values for segmental myocardial thickening, were calculated., Results: Compared with preoperative values, both myocardial perfusion and segmental myocardial thickening had improved significantly at 3 months and 1 year postoperatively (reversibility scores [mean ± SD] were, respectively: 13.5 ± 8.0 vs 5.8 ± 6.2 and 5.1 ± 6.2, P < .001; Z-values were -1.13 ± 1.53 vs -0.62 ± 1.40 and -0.67 ± 1.35, P < .001). Mixed-effect model analyses showed no differences in improvements in myocardial perfusion and segmental myocardial thickening between the 2 groups 1 year after revascularization. Separate analysis demonstrated less improvement of myocardial perfusion in the right coronary artery territory of the RITA group than the SV group, with marginal significance (P = .056)., Conclusions: Improvements in myocardial perfusion and segmental myocardial thickening were similar between the 2 groups at 1 year after revascularization. The SV, versus the right ITA, composite graft may be more beneficial in perfusion improvement of the right coronary artery territory., (Copyright © 2015 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.)

Background: Multiple arterial grafts, in addition to the left internal thoracic artery, improve long-term survival after coronary artery bypass grafting (CABG); yet, the use of this procedure remains low for both the right internal thoracic artery (RITA) and the radial artery (RA). To identify the optimal arterial conduit to deploy for revascularization of diabetic patients, we compared the outcomes for RA and RITA grafts to the circumflex coronary., Methods: From January 1, 1995, to December 31, 2011, 908 consecutive diabetic patients underwent first-time, isolated CABG (99% on-pump), 659 with the RA and 502 with the RITA, respectively, in two affiliated hospitals. Data were prospectively collected, and late mortality was determined from the Social Security Death Index. Propensity matching, based on preoperative and operative variables, identified 202 matched pairs from each group., Results: Long-term survival was similar for matched patients. Mortality, myocardial infarction, reoperation for bleeding, stroke, sepsis, and renal failure were not significantly different between groups. However, deep sternal wound infection (p<0.035) and respiratory failure (p<0.048) favored the RA group, in which the total major adverse events were significantly fewer (p=0.002)., Conclusions: In diabetic patients undergoing multivessel revascularization with either RA or RITA grafts to the circumflex coronary, long-term survival is similar. However, RA patients experienced significantly fewer respiratory or sternal wound adverse events. The RA is the preferred conduit to extend to more diabetic patients the recognized survival benefit of a multiple arterial graft strategy., (Copyright © 2014 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.)

Introduction: It has been proven that blood supply to the heart can include blood from noncoronary collateral circulation. Whether this network can somehow be augmented to provide an alternative therapy for ischemic patients is an intriguing hypothesis with no clear answer yet due to the challenging nature of this research field. In an attempt to enhance noncoronary collateral blood flow, we experimented with left internal thoracic artery ligature and angiogenic growth factors in a canine model., Materials and Methods: Eight dogs weighing between 20 and 29 kg were scheduled for three operations each. Neutron-activated microspheres were used for blood flow measurement throughout the study. The first operation was a left thoracotomy for ameroid constrictor positioning at the proximal segment of the circumflex coronary artery. Three weeks later the left internal thoracic artery was ligatured distally. A micro-pump was positioned in the mediastinum, connected with a small catheter inserted in the proximal segment of the left internal thoracic artery for slow delivery of vascular endothelial growth factor. The protocol called for a coronary angiography 4 weeks later, sacrifice of the animals, and explantation of the heart for microsphere analysis., Results: Four of the dogs failed to tolerate ameroid constrictor positioning by thoracotomy and died after the first operation. The remaining four dogs underwent a second operation to ligate their left internal thoracic arteries and implant micro-pumps with catheters. The implant was a success, but only one dog survived in the postoperative period. When the last dog was voluntarily sacrificed after a third operation, coronary angiography showed no neovascularization, nor did heart slice analysis reveal microspheres., Conclusions: Despite the technical challenge of building research protocols to exactly quantify blood from noncoronary arteries, there are many historical, anatomical, physiopathological, clinical, radiological, and surgical indications suggesting that blood flow from extracardiac structures may play an important role in ischemic heart disease. Our preliminary investigation combining internal thoracic artery occlusion and angiogenic growth factors was unsuccessful for several reasons, the main one being it was too heavy a protocol for the dogs. Despite this, we think that noncoronary collateral blood flow represents an intriguing research field worthy of debate and further study., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Neovascularization such as formation of collateral vessels following total occlusion of native coronary artery is common in coronary artery disease. This is a case report of a very rare connection by newly formed conduit vessels between the left internal mammalian artery and the radial artery establishing bypass, which occurred after failure of bypass grafts.

Non-coronary collateral blood flow arrives to the heart from mediastinal, bronchial, and pericardial channels. These enter the heart through the pericardial reflections surrounding the pulmonary and systemic veins, as well as from the vasa vasorum of the aorta and the pulmonary artery leading to and from the myocardium. Before the advent of cardiopulmonary bypass surgery, surgical bilateral ligature of the internal thoracic arteries (ITAs) was performed in patients with ischemic heart disease to increase the perfusion pressure within the channels leading to the heart. Nowadays, the occurrence of natural collaterals between coronary and extracardiac arteries including the ITAs, the potential hemodynamic effects of ITA ligation, the potential of ITAs for developing important collateral branches, and the current availability of angiogenic growth factors could pave the way for the development of a new field in cardiovascular research aimed at developing an alternative strategy of myocardial blood supply by means of the surgical and biological enhancement of non-coronary collateral circulation.

Objective: Vasoconstrictors such as norepinephrine and vasopressin are commonly used to raise the blood pressure during myocardial revascularization. The internal thoracic artery is commonly used for coronary artery grafting because of its long-term patency. However, the internal thoracic artery is a living conduit that responds to vasoactive substances. The objective of this study was to measure change in internal thoracic arterial flow after infusion of norepinephrine or vasopressin., Methods: Forty-one patients undergoing elective off-pump coronary artery bypass grafting participated in this study. After the median sternotomy, the left internal thoracic artery was dissected with a pedicle and grafted to the left anterior descending artery. After all anastomoses were performed and hemodynamic parameters were stable, the grafted internal thoracic arterial blood flow was measured by transit time flowmeter on the distal portion of the graft as a baseline. Norepinephrine or vasopressin was then infused until mean arterial pressure was increased to 20% of baseline. Graft flow and hemodynamic variables were measured when mean arterial pressure reached the intended level., Results: Baseline grafted internal thoracic arterial flows were similar (norepinephrine 57.1 ± 17.7 mL min(-1), vasopressin 66.0 ± 34.3 mL min(-1)). With norepinephrine, flow increased significantly relative to baseline (77.2 ± 31.0 mL min(-1)); with vasopressin, it remained unchanged (68.3 ± 37.0 mL min(-1))., Conclusions: For patients needing vasopressor support after coronary artery bypass grafting, norepinephrine appeared superior to vasopressin because of increased internal thoracic arterial flow., (Copyright © 2011 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.)

Left internal mammary artery (LIMA) bypass conduits undergo gradual longitudinal flow transition from the proximal to distal segments, and the diastolic/systolic (D/S) ratios of the flow indices can diagnose graft patency. However, the influence of graft adaptation on this has not been studied. We examined 46 patients with LIMA graft to the left anterior descending artery using a Doppler-tipped guidewire in the proximal, middle, and distal segments; 34 had patent LIMAs (group A: new LIMAs; <1 month postoperatively; n = 22 and group B: old LIMAs; ≥1 month postoperatively; n = 12), and 12 had new LIMAs with distal stenosis (group C). In diastole, the time-averaged peak velocities, maximum peak velocities, and velocity-time integrals in each segment were significantly greater in group A than in groups B or C; however, in systole, they did not differ significantly among the three groups. The D/S ratios of the indices in all segments in group A were significantly greater than those in groups B or C; however, they did not differ between groups B and C in any of the segments. Graft adaptation of a patent LIMA, itself, affects the longitudinal flow transition pattern. The D/S ratio of the three indices in the patent old LIMAs did not differ from those in the LIMAs with distal stenosis early after surgery. The timing of LIMA flow assessment must be considered during assessment of the graft patency from the flow velocity patterns.

Objectives: Arterial revascularization with the internal thoracic artery (ITA) has shown exceptional long-term results, even though early hypoperfusion can occur and can cause ischemia and contractile dysfunction. Therefore, it is still controversial as to whether the bypass vessel can guarantee the required demand for blood flow during the early postoperative (EPO) phase or whether this is only possible a long time after the operation. This question is important particular in the early postoperative phase to manage afterload and reduce left ventricular oxygen demand. Therefore, stress Doppler echocardiography was performed to assess EPO and late postoperative (LPO) flow capacity after minimal-invasive coronary artery bypass grafting (MIDCAB) in subjects with single vessel disease., Methods: Doppler echocardiography was performed after MIDCAB in 15 patients (mean age 65 years+/-12 standard deviation) in the EPO (15 days) and LPO (266 days) at rest and under stress., Results: The mean diastolic velocity (MDV) as a measure for the coronary perfusion in the bypass-graft was comparable (30.9+/-14.5 EPO to 30.8+/-13.9 cm/s LPO, P>0.05) for both settings (early vs. late). In both tests, the stress reactions by means of handgrip maneuver lead to comparable increases in blood flow: MDV 65.0+/-54.4% (EPO) to 62.5+/-53.7% n.s. (LPO). The flow increase in the bypass graft was just as similar [48.2+/-46.2% (EPO) to 51.1+/-41.6% n.s. (LPO)]., Conclusion: The stress echocardiography revealed for the first time that the ITA-graft after MIDCAB-operation is able to produce the same flow reserve through the EPO phase as well as the LPO phase. Restrictions to a maximum early flow adaptation are not justified. Thus, particularly a patient with severe comorbidities or higher age should be mobilized in the EPO phase to minimize the postoperative complications without risk of myocardial ischemia caused by impaired early blood flow through recent implanted ITA. This method for assessment of ITA blood flow allows for long-time observations and can detect disturbances in perfusion at an early stage.

Flow has been suitably measured by transit-time flow measurement, but measurements in the early period after cardiopulmonary bypass do not reflect expected values because of several factors. We documented that flow measurements during immediate revision of bleeding increased 3 times for the left internal thoracic artery and 2 times for the saphenous vein graft over previous measurements made after cardiopulmonary bypass in a patient who underwent coronary artery bypass surgery.

Objective: To assess whether coronary graft flow patterns are affected differently by native coronary competitive flow or by stenosis of the coronary anastomosis., Methods: Nine pigs (65-70 kg) underwent off-pump grafting of the left internal mammary artery to the left anterior descending artery (LAD). Transit-time flow patterns in the mammary grafts were recorded under four different conditions: (1) baseline flow (proximal LAD occluded), (2) full competitive flow, (3) partial competitive flow and (4) after creation of a stenosis in the anastomosis. Competitive flow was achieved by an adjustable occluder on the left anterior descending artery. The mean luminal stenosis of the anastomosis was 75+/-11%, calculated by epicardial ultrasound. Mean flow, systolic and diastolic antegrade and retrograde flow during different flow conditions were calculated as ratios of baseline flow and compared. Different derived flow indexes were calculated and compared in the same manner. Friedman's test and post hoc analyses by Wilcoxon signed-ranks were performed without correction for multiple comparisons., Results: Mean graft flow was more reduced by competitive flow than by a stenotic anastomosis of 75+/-11%. Competitive flow significantly decreased diastolic antegrade flow and both diastolic and systolic maximum peak flows, but increased retrograde flow, compared with baseline and stenosis. Furthermore, competitive flow and stenosis could be distinguished by analysis of several derived indexes. Pulsatility index (maximum-minimum flow/mean flow) and insufficiency percent (retrograde flow as fraction of total flow) was increased significantly more by competitive flow than by stenosis. Diastolic filling percent was significantly reduced at competitive flow compared with stenosis and baseline., Conclusions: The mammary graft flow was significantly reduced by native coronary competitive flow, but marginally decreased by a stenotic anastomosis of 75% mean luminal stenosis. Reduction of graft flow due to competition was particularly evident in diastole. A detailed flow pattern analysis may differentiate between competitive flow and stenosis of the anastomosis.

The left internal mammary artery (LIMA) is the most commonly used arterial graft for coronary artery bypass graft (CABG) surgery, and occluding the LIMA side branches during surgery is important to avoid myocardial ischaemia afterwards. In this study we investigated the incidence of patent LIMA graft side branches in our coronary angiography series, and compared LIMA flow rate changes by means of the thrombolysis in myocardial infarction (TIMI) frame count in patients with and without LIMA graft side branches. Patients with a history of CABG surgery and who were scheduled for coronary angiography in our centre between 1 January and 15 December 2006 were enrolled in the study. We compared LIMA graft TIMI frame counts between patients with and without side branches. The incidence of LIMA graft side branches in our study was 18% (seven patients). Mean TIMI frame count was 27.28 +/- 3.4 in patients with LIMA graft side branches and 15.67 +/- 2.3 in patients without. There was a significant difference between the two groups (p < 0.0001). Patients with LIMA graft side branches were more likely to have anterior ischaemia, determined by myocardial perfusion scintigraphy. We suggest that TIMI frame count may be helpful in evaluating the effect of side branches on LIMA graft flow rate. The increased TIMI frame count of a LIMA graft with side branch is associated with insufficient LIMA flow.

It is widely accepted that in coronary artery surgery, the left internal mammary artery (LIMA) can be used as the single source of blood inflow to multiple coronary grafts as in the T-graft technique. We, herein, present clinical evidence suggesting that in ischemic hypertrophied hearts, single arterial inflow from the LIMA to multiple grafts based on the LIMA may not be sufficient and may not meet myocardial demands, at least during the early perioperative period. This observation was made in two patients in whom a vein graft, previously based on the LIMA, was also connected to the aorta. By providing additional inflow from the aorta, flows to the LAD significantly increased.

Extensive arterial grafting (Art-CABG) in the elderly is still questioned due to the reduced life expectancy and the supposed higher periprocedural risk. Reports further demonstrated accelerated atherosclerosis of arterial grafts in the elderly, with hampered short-term and long-term results. We reviewed our experience of patients undergoing Art-CABG between January 2003 and January 2007, divided into two groups: the elderly (238 patients > or = 70 years; Group A) and the young (195 patients < or = 60 years; Group B). Transit time flowmetric (TTF) maximum and mean flow, pulsatility index (PI), and graft flow reserve (GFR) were compared. Hospital outcome was analyzed. Hospital mortality, need for intra-aortic balloon pump, troponin I, and echocardiographic segmental kinetics were comparable between the two groups (P = not significant [NS]). Stratifying patients for target vessels and type of arterial CABG, no differences in TTF results were recorded between the two groups either on-pump (P = NS) and off-pump (P = NS), both for the two internal mammary arteries (P = NS irrespective of the target vessel) and the radial artery conduits (P = NS irrespective of the target vessel). Although graft flow reserve was significantly recruited in all patients (P < 0.05 in young and elderly, either on-pump and off-pump, irrespective of the arterial conduit and the grafted vessel), GFR of all arterial grafts was comparable between elderly and young patients, either on-pump (P = NS) or off-pump (P = NS). Art-CABG showed similar TTF results in elderly and young patients, regardless of the arterial conduit, target vessel, or surgical technique employed. These functional results supported the reported survival benefit of arterial revascularization in the elderly.

Coronary subclavian steal syndrome refers to decreased or reversed internal mammary artery flow, which causes angina related to severe subclavian steno-occlusive disease in patients with in situ internal mammary-to-coronary artery graft. We report a case, the first in the literature, of a right internal mammary artery-coronary-subclavian unidirectional steal syndrome. Clinical features, pathophysiology, and diagnostic and therapeutic strategies of this unusual adverse event are discussed.

Background: The purpose of this study was to evaluate angiographic results of patients subjected to a technique variation of Vineberg's procedure, as well as their morbidity and mortality in immediate postoperative period, and to analyze the flow of grafted left internal thoracic artery (LITA) at rest and under stress., Methods: Between September 1999 and April 2002 eight patients were operated upon, with implant of the internal thoracic artery (ITA) in the intimal layer of the left ventricle (LV) muscle. After 6 months, they underwent angiographic and Doppler evaluation. According to Doppler study of LITA, the sample was divided in two groups: "Vineberg group," formed by eight patients; and "control group" consisting of 20 patients whose LITA directly revascularize the anterior interventricular artery (AIV). Angiography showed patency of all grafts in both groups. Blood flow and flow velocity in grafts were measured by Doppler echocardiography. T-test for paired and unpaired samples were used for statistical analysis., Results: There were no deaths or complications in immediate postoperative period. Angiography showed 100% patency. The total flow (TF) of Vineberg group was 55% of the flow in the control group. In both groups, the TF increased with the stress., Conclusions: This Vineberg's technique modification can be successfully used in patients who cannot undergo traditional direct revascularization due to its low rates of morbidity and mortality and a high rate of patency, providing a significant blood flow both at rest and under stress.

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.

Objectives: The purpose of this study was to evaluate which Doppler-derived flow index best predicts new distal left anterior descending coronary artery (LAD) stenosis in patients with left internal mammary artery (LIMA) graft., Background: The LIMA flow measurement has been proposed to assess graft function, but it may be misleading in case of new distal LAD stenosis and/or competitive flow from native LAD. Distal LAD coronary flow reserve (CFR: hyperemic/baseline peak flow velocity ratio) may be more appropriate., Methods: The LIMA and distal LAD flow was measured by transthoracic Doppler echocardiography in 96 patients undergoing diagnostic/therapeutic coronary angiography, 7 +/- 4 years after cardiac bypass surgery. The LIMA flow indexes (systolic-to-diastolic peak velocity ratio [SDPVr] >1, diastolic time velocity integral fraction [DTVIf] <0.5, and CFR <2) and LAD CFR <2 were used to predict > or =70% new LAD stenosis., Results: The LAD CFR <2 predicted new LAD stenosis, found in 21 of 77 patients without competitive flow from native LAD, with significantly higher diagnostic accuracy (98%) than LIMA flow indexes (SDPVr >1 = 61%, DTVIf <0.5 = 69%, and CFR <2 = 72%). The LIMA flow indexes were abnormal in 17 of 19 patients with competitive graft flow, but only 5 had graft restriction, and none had significant LAD stenosis. In a multivariate model of new distal LAD stenosis prediction, competitive flow from native LAD reduced the predictive role of LIMA but not of LAD CFR., Conclusions: In patients without competitive flow from native LAD, LAD CFR is more accurate for the detection of LAD stenosis than LIMA CFR. In patients with competitive graft flow, abnormal LIMA flow patterns and blunted LIMA CFR do not reflect downstream LAD flow as LAD CFR does.

Background: Internal thoracic artery (ITA) malperfusion has been described as a potentially devastating and lethal complication of coronary artery bypass grafting (CABG). It is our practice to perform an additional vein graft to the distal left anterior descending (LAD) artery in such cases., Methods: From August 1999 to July 2002, 2877 CABG procedures were performed at our institution. In 65 patients (2.3%) ITA malperfusion was observed. All of them were treated with an additional vein graft to the distal LAD. All patient data were screened for the time interval between the occurrence of ITA malperfusion and the decision to perform an additional vein graft., Results: Of 65 patients with ITA malperfusion, 54 patients (83%) survived (group 1), 11 patients (17%) died (group 2). There was no difference in preoperative risk status between the groups. Cross clamp time was 88 +/- 4 minutes in group 1 and 104 +/- 11 minutes in group 2 (p = 0.04). Intraoperative ITA flow to LAD was 6 +/- 1 mL/min in group 1 and 10 +/- 5 mL/min in group 2 (p = 0.2). Time between release of cross clamp and second period of cross clamping was 50 +/- 5 minutes in group 1 and 75 +/- 11 minute group 2 (p = 0.02). Time between termination of cardiopulmonary bypass (CPB) and second period of cross clamping was 23 +/- 3 minutes in group 1 and 46 +/- 7 minutes in group 2 (p = 0.003). Vein graft flow to distal LAD was 54 +/- 4 mL/min in group 1 and 52 +/- 12 mL/min in group 2 (p = 0.5). Maximum postoperative troponin I was 35 +/- 11 ng/mL in group 1 and 136 +/- 32 in group 2 (p = 0.003)., Conclusions: Survivors of ITA malperfusion had shorter cross clamp times and less myocardial damage as evidenced by lower postoperative troponin I levels. Time intervals between first and second cross clamp and between termination of CPB and second cross clamp were lower in survivors, thus indicating that a fast decision for an additional vein graft may influence postoperative patient outcome.

From October 2000 through April 2001, we prospectively evaluated the flow characteristics of the left internal thoracic artery (LITA) graft in a homogenous group of 44 men with isolated severe proximal left anterior descending coronary artery stenosis who underwent elective coronary artery bypass grafting with cardiopulmonary bypass. We performed transthoracic color Doppler ultrasonography preoperatively and repeated this examination in each patient between the 5th and 7th postoperative days, obtaining cross-sectional area, total flow volume, diastolic velocity, systolic velocity, mean velocity, pulsatility index, and resistance index. These results were compared with those of the intraoperative free-bleeding technique. Good-quality Doppler images of the LITA were easily obtained with a combined supraclavicular-parasternal approach. After surgery, systolic flow velocity, pulsatility index, and resistance index decreased significantly, but diastolic flow velocity and mean flow velocity increased significantly. The intraoperative flow volume obtained by the free-bleeding technique (32.42 +/- 12.33 mL/min) was significantly less than both pre- and postoperative ultrasonographic values (42.22 +/- 10.77 mL/min and 45.36 +/- 19.52 mL/min, respectively). No significant difference was found when changes in LITA values were compared between patients with (n=19) and without (n=25) normal anterior wall motion. We conclude that color Doppler ultrasonography is a reliable noninvasive technique for preoperative evaluation of the LITA as a graft and for postoperative long-term follow-up of graft function. However the intraoperative free-bleeding technique is not reliable for flow-volume measurement due to anesthesia-related hemodynamic changes and vasospasm. Color Doppler can prevent useless LITA harvesting and decrease the need for postoperative LITA angiography.

In some patients, myocardial ischemia after coronary artery bypass graft surgery has been attributed to a coronary steal phenomenon through a thoracic side branch originating from the left internal mammary artery (LIMA), even in the absence of subclavian or LIMA stenosis. To demonstrate that coronary flow through the LIMA is unchanged by occlusion of a LIMA side branch, we examined LIMA coronary flow velocity measurements (0.014" Doppler flow wire) in three patients at rest, during adenosine hyperemia, and again during hyperemia induced by left arm exercise before and again after the balloon occlusion of the thoracic side branch. For the three patients, no significant changes in resting or hyperemic flow were noted due to side-branch occlusion. Before side-branch occlusion, pharmacologic intra-arterial (adenosine) coronary flow reserve (hyperemic-to-basal flow velocity ratio) was 2.6, 1.5, and 3.2 and exercise flow reserve was 2.1, 1.3, and 1.2, respectively. After side-branch occlusion, pharmacologic coronary flow reserve was 2.5, 1.8, and 2.7 with exercise flow reserve of 1.8, 1.1, and 1.3, respectively. Under most ordinary circumstances, thoracic side-branch steal does not exist and that side-branch occlusion does not alter LIMA flow at rest or during pharmacologic or exercise-induced hyperemia. These data further suggest that a demonstration of the physiologic value of side-branch occlusion should precede surgical or percutaneous interruption of the thoracic artery in such patients., (Copyright 2004 Wiley-Liss, Inc.)

A case of 47-year-old man with occlusion of the subclavian artery occurring few months after CABG with the left internal mammary artery grafting is presented. The patient developed a subclavian-coronary steal syndrome with retrograde blood flow from the coronary circulation to the subclavian artery through the left internal mammary artery. Clinical presentation consisted of vertigo and recurrence of chest pain. The increasing frequency of this syndrome and the preoperative preventive methods such as pressure gradient measurement between the left and right upper limb are discussed.

Objective: To compare the blood flow of left internal mammary artery (LIMA) anastomosed to left anterior descending artery (LAD) with variable degree of stenosis in off pump coronary artery bypass grafting (OPCAB)., Methods: From 2000.9 to 2002.12, 167 cases (from a total of 209 OPCAB) were involved in this study. According to the degree of stenosis of LAD, all the cases were divided into group A (< 75%), group B (75% approximately 95%) and group C (> 95%). Blood flow of LIMA, routinely anatomized to LAD was immediately measured after anastomosis with transit-time flowmeter (TTFM) and several parameters were recorded., Results: The mean blood pressure at measurement was not significantly different (P = 0.08). Mean blood flow of group A (11.1 +/- 1.2) ml/min, B (16.3 +/- 1.6) ml/min and C (28.3 +/- 3.2) ml/min and diastolic flow of group A (26.3 +/- 2.8) ml/min, group B (34.8 +/- 3.2) ml/min and group C (55.1 +/- 5.3) ml/min, were significantly different between every two groups (P < 0.01) and the latter was bigger than the former. Systolic blood flow among group A (5.3 +/- 0.7) ml/min, group B (4.3 +/- 1.4) ml/min and group C (4.6 +/- 1.3) ml/min were not different (P = 0.91). Pulsatility index (PI) of group C (2.75 +/- 0.14) was significantly smaller than that of group A (4.36 +/- 0.47) and group B (3.72 +/- 0.31) (P < 0.01), but PI between groups A and B was of no significant difference (P = 0.12)., Conclusion: Mean and diastolic blood flow of LIMA were closely related to the degree of stenosis of LAD. The higher the degree, the bigger the blood flow, and the smaller the value of PI. However, systolic blood flow was not influenced by the degree of lesion.

Objective: Vasoactive agents and inotropes influence conduit-coronary blood flow following coronary artery bypass grafting (CABG). It was hypothesized that dopexamine hydrochloride, a dopamine A-1 (DA-1) and beta(2) agonist would increase conduit-coronary blood flow. A prospective randomized double blind clinical trial was carried out to test this hypothesis. DA-1 receptors have previously been localized to human left ventricle., Methods: Twenty-six American Society of Anaesthesiology class 2-3 elective coronary artery bypass graft patients who did not require inotropic support on separation from cardiopulmonary bypass (CPB) were studied. According to a randomized allocation patients received either dopexamine (1 microg/kg per min) or placebo (saline) by intravenous infusion for 15 min. Immediately prior to and at 5,10 and 15 min of infusion, blood flow through the internal mammary and vein grafts (Transit time flow probes, Transonic Ltd.), heart rate, cardiac index, mean arterial pressure and pulmonary haemodynamics were noted. The data were analysed using multivariate analysis of variance., Results: Low-dose dopexamine (1 microg/kg per min) caused a significant increase in mammary graft blood flow compared to placebo at 15 min of infusion (P=0.028, dopexamine group left internal mammary artery (LIMA) flow of 43.3+/-14.2 ml/min, placebo group LIMA flow at 26.1+/-16.3 ml/min). Dopexamine recipients demonstrated a non-significant trend to increased saphenous vein graft flow (P=0.059). Increased heart rate was the only haemodynamic change induced by dopexamine (P=0.004, dopexamine group at 85.2+/-9.6 beats/min and placebo group at 71.1+/-7.6 beats/min after 15 min of infusion)., Conclusion: This study demonstrates that administration of dopexamine (1 microg/kg per min) was associated with a significant increase in internal mammary artery graft blood flow with mild increase in heart rate being the only haemodynamic change. Low-dose dopexamine may improve graft flow in the early post CABG period with minimal haemodynamic changes.

Background: Partial harvesting of the left internal mammary artery (LIMA) is a widespread technique used during minimally invasive coronary operations performed through a left anterior small thoracotomy. The influence of persisting LIMA branches was investigated to evaluate their effect on the blood flow of the left anterior descending artery., Methods: Thirty patients, 15 with totally (group A) and 15 with partially (group B) harvested LIMAs, were evaluated. All the patients underwent postoperative angiography, during which a flow map of the LIMA was performed. The average peak velocity and the diastolic-to-systolic peak velocity ratio were recorded. The LIMA graft flow pattern was recorded in the proximal and distal thirds of the artery. Intramammary adenosine (12 to 14 microg) was injected and the average peak velocities before and after injection were calculated., Results: The average peak velocity was similar in both groups in the proximal and distal thirds of the LIMA (25 +/- 7 and 26 +/- 5 cm/sec, respectively, in group A versus 27 +/- 5 and 25 +/- 5 cm/sec, respectively in group B; p = NS). The diastolic-to-systolic peak velocity ratio was similar proximally (0.78 +/- 0.3 in group A versus 0.69 +/- 0.3 cm/s in group B; p = NS), but not distally (1.72 +/- 0.1 in group A versus 0.97 +/- 0.3 in group B; p < 0.0005). The LIMA graft flow reserve was similar both proximally and distally (2.6 +/- 0.6 and 2.5 +/- 0.3 cm/s, respectively, in group A versus 2.6 +/- 0.5 and 2.6 +/- 0.3 cm/s, respectively, in group B; p = NS)., Conclusions: The persistence of LIMA branches does not influence the blood flow of the left anterior descending artery after acute adenosine-induced myocardial hyperemia. If a left anterior small thoracotomy is used in left anterior descending artery direct revascularization, complete LIMA harvesting is not mandatory and depends on the personal preference of the surgeon.

Breath-hold velocity-encoded cine MR (VENC-MR) imaging is a feasible method for measuring phasic blood flow velocity in small vessels that move during respiration. The purposes of the current study are to compare breathhold VENC-MR measurements of flow velocities in the internal mammary arteries (IMA) with nonbreath-hold measurements and to characterize the systolic and diastolic flow velocity curves in a cardiac cycle in native IMA and IMA grafts. Flow velocity in 30 native IMA and 8 IMA grafts were evaluated with a breath-hold VENC-MR sequence with K-space segmentation and view-sharing reconstruction (TR/TE = 16/9 msec, VENC = 100 cm/s). In 10 native IMA, nonbreath-hold VENC-MR images were acquired as well for comparison. Breath-hold VENC-MR imaging showed significantly higher systolic and diastolic peak velocities in native IMA (43.1 cm/second +/- 15.0 and 10.0 cm/second +/- 4.8), in comparison to those of nonbreath-hold VENC-MR imaging (27.6 cm/second +/- 10.2 and 7.3 cm/second +/- 3.9, P < .05). The diastolic/systolic peak velocity ratio in the IMA grafts (.88 +/- .41) was significantly higher than that in native IMA (.24 +/- .08, P < .01). Interobserver variability in the flow velocity measurement was less than 4%. Breath-hold VENC-MR imaging demonstrated higher peak flow velocity in the IMA than nonbreath-hold VENC-MR imaging. This technique is a rapid and effective method for the noninvasive assessment of blood flow velocity in IMA grafts.

A patient who had undergone myocardial revascularization with a saphenous vein graft to the left anterior descending artery and a left internal thoracic (mammary) artery graft to the 1st diagonal branch presented with an unusual form of subclavian steal syndrome. Occlusion of both the left subclavian and the left anterior descending arteries caused retrograde flow through the internal thoracic artery to the distal subclavian artery; the blood flow was supplied by the vein graft via the distal left anterior descending artery and diagonal branch.

Isometric contraction of small group of muscles is believed to increase heart rate and contractility and arterial pressure without significant changes in systemic arterial resistance. Such a manoeuvre has been employed in this work to study dynamic changes induced in blood flow into coronary bed, in subjects in which an anastomosis of the internal mammary artery to anterior descending coronary artery was performed. Ten patients with no clinical signs of myocardial ischaemia at rest and during exercise, were requested to perform an endurance left handgrip manoeuvre, at 50% of maximal voluntary contraction. Doppler blood velocity curve in the anastomosed mammary artery; non-invasive blood pressure curve at a finger of the right hand by Finapres; the electrocardiogram, were recorded. A significative increase in heart rate and mean and diastolic blood pressure was found. Blood flow significantly increased, approximately in the same percentage as double product was increased. A calculated index of coronary resistance did not show significant changes. In this group of patients, the handgrip manoeuvre may display the ability of the cardiac pump to match its metabolic needs due to increased pressure load, by employing the same developed pressure load as an adequate coronary perfusion pressure. It is suggested to employ this simple test in the routine monitoring of patients with internal mammary artery bypass grafts.

Transcutaneous doppler ultrasound was used to examine internal-mammary-artery (IMA) blood-flow in 26 patients with IMA coronary bypass grafts. The ungrafted right IMA could be seen in all of 19 patients, the grafted left IMA in 16 of 26, and the grafted right IMA in 3 of 7. The velocity profile recorded from the proximal part of the grafted IMA is distinct from that of an ungrafted artery, with a systolic peak which reflects graft capacitance in the face of high intramyocardial resistance, and a diastolic peak which represents graft conductance when intramyocardial resistance is low. Total graft blood-flow can be estimated from the mean velocity and the measured vessel diameter; resting flows ranged from 22 to 79 ml/min. In recently grafted patients, resting graft blood-flow correlated with myocardial "run-off" estimated from preoperative arteriograms; graft blood-flow increased appropriately with exercise. This simple, non-invasive technique to measure IMA graft blood-flow may find applications for routine postoperative follow-up of patients with IMA grafts and for studies on the physiology and pharmacology of coronary artery blood-flow.

Internal mammary artery (IMA) flow patterns were analyzed in a dog model without interference with the coronary artery bed (n = 6, mean bodyweight: 21 +/- 4 kg) during the following conditions: a) baseline values and steady state: b) acute hypovolemia (withdrawal of 20% of circulating volume over 90 s): c) retransfusion (same volume over 90 s): d) progressive hypovolemia (withdrawal of the same volume over 240 s): e) bolus of nitrates (500 micrograms/kg over 60 s).

Of 336 isolated coronary artery bypass procedures performed over an 11 month period, one internal mammary artery (IMA) was used in 81% of cases. In 41 patients, two IMAs were used for grafting three or more arterial segments in single or sequential fashion. Repeat coronary arteriography was performed in 26 of these patients 7 to 10 days after bypass surgery. The left IMA in situ was used either singly or sequentially to graft the left anterior descending (LAD) and diagonal arteries and all branches of the circumflex system. The right IMA was used to graft the LAD, diagonal, mid marginal, right, and posterior descending branch of the right coronary artery. Blood flow to a grafted arterial segment occurred primarily through the IMA in situ in 61% of segments bypassed but was equally distributed through the IMA graft and native circulation in 35%. This was in contradistinction to the free IMA and saphenous vein graft, in which the majority of flow was via the graft in 86% and 94% of grafted segments, respectively. For those instances in which major flow was via the IMA graft in situ, the mean diameter reduction of the proximally grafted arterial segment was 83% vs 63% for those segments in which flow was equally shared between native coronary and IMA graft (p less than .05). There was a trend, although not statistically significant, for increasing flow to occur via the native circulation if the first anastomosis in a sequential IMA graft in situ was performed to a larger artery than the distally grafted segment. This was especially true when there was low-grade stenosis in the proximally grafted arterial segment.(ABSTRACT TRUNCATED AT 250 WORDS)