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.     

Composite arterial Y graft has less coronary flow reserve than independent grafts

BACKGROUND: It is not known whether a composite Y graft of the left internal thoracic artery can provide sufficient blood flow to the whole left coronary system. The aim of this study was to compare regional myocardial blood flow (MBF) and coronary flow reserve after coronary artery bypass grafting using arterial composite Y graft or independent arterial grafts. METHODS: Positron emission tomography was performed at rest and after dipyridamole infusion using oxygen-15-labeled water 2 weeks after coronary artery bypass grafting. Regional MBF was calculated in seven segments of the left ventricle. Coronary flow reserve was defined as the ratio of MBF after dipyridamole infusion to MBF at rest. In the Y graft group (n = 22), a free arterial graft to obtuse marginal arteries was anastomosed to the proximal side of in situ left internal thoracic artery, which was anastomosed to the left anterior descending artery. In the independent graft group (n = 13), left anterior descending and obtuse marginal arteries were independently revascularized using in situ left internal thoracic artery and a free arterial graft. RESULTS: There was no difference between the groups in MBF at rest. Coronary flow reserve in the Y graft group was lower than that in the independent group in the anterobasal (1.43 +/- 0.07 versus 1.90 +/- 0.13, p = 0.038), apical (1.24 +/- 0.06 versus 1.64 +/- 0.12, p = 0.003), septal (1.34 +/- 0.05 versus 1.75 +/- 0.13, p = 0.023), and lateral regions (1.19 +/- 0.04 versus 1.66 +/- 0.09, p = 0.001). CONCLUSIONS: Although arterial composite Y graft improved MBF at rest, it was not as effective as independent grafts for improving coronary flow reserve soon after coronary artery bypass grafting.     

Lambda graft with the radial artery or free left internal mammary artery anastomosed to the right internal mammary artery: flow dynamics

BACKGROUND: The aim of this study was to evaluate the outcome and flow dynamics of the lambda graft configuration, relative to a second arterial graft. METHODS: From 1998 to 2000, 47 patients (mean age 55.5 +/- 4.7 years) with triple-vessel disease underwent arterial revascularization using the lambda graft. The in situ left internal mammary artery (LIMA) and right internal mammary artery (RIMA) were anastomosed to the left anterior descending (LAD) and obtuse marginal arteries, respectively. In 21 patients (group I) presenting proximal or middle-third LAD or right coronary (RC) arterial stenoses, the lambda graft was constructed by anastomosing the distal LIMA, as a free LIMA graft, to the RC and proximally to the in situ RIMA. In the other 26 patients (group II) presenting with middle-distal third LAD or RC arterial stenoses, the radial artery (RA) was used to construct the lambda graft. All patients underwent transthoracic echo color Doppler before and after an adenosine test at 1 week and 3 months after operation. RESULTS: There were no hospital deaths. Overall, 47 lambda grafts were constructed. There was no difference between baseline and maximal flows and coronary flow reserve (CFR) between groups. CFR at IMA stems increased in both groups within 3 months versus 1 week [(LIMA)CFR = 2 +/- 0.3 vs 2.3 +/- 0.3 (p = 0.002) and (RIMA)CFR = 2.2 +/- 0.4 vs 2.5 +/- 0.3 (p = 0.009) in group I, and (LIMA)CFR = 2.12 +/- 0.33 vs 2.4 +/- 0.35 (p = 0.005) and (RIMA)CFR = 2.17 +/- 0.32 vs 2.52 +/- 0.26 (p = 0.001) in group II]. At 3 months versus 1 week, the (RIMA)diameter(i) (mm) at rest was 1.69 +/- 0.32 versus 1.48 +/- 0.2 (p = 0.015) in group I and 1.66 +/- 0.3 versus 1.47 + 0.2 (p = 0.01) in group II. At 6 +/- 2.4 months, all patients were free of angina. CONCLUSIONS: These data, almost identical for free LIMA and RA to RIMA using the lambda graft, demonstrate that RIMA flow reserve is adequate for multiple coronary anastomoses irrespective of the second arterial graft.     

Intraluminal papaverine with pH 3 doubles blood flow in the internal mammary artery

Seventy-five patients undergoing coronary artery bypass grafting were randomized to receive injections of papaverine solution or isotonic saline or no injection into the left internal mammary artery (LIMA) used as graft. Blood flow in the LIMA was measured twice-after dissection of the pedicle and before anastomosis to the coronary artery. Blood flow increased significantly in all three groups, but after papaverine injection it was twice as high as in the control groups, increasing by 285% (from 40 +/- 12 to 154 +/- 32 ml/min, p = < 0.0001). The pH of the papaverine solution was only 3, and we advise that surgeons check and correct pH in the papaverine solutions they use, in order to avoid endothelial damage to the LIMA. Based on these results we can recommend papaverine injection into the arterial graft only if the initial flow is low.     

Off-pump redo coronary artery bypass grafting

BACKGROUND: Conventional redo coronary artery bypass grafting is associated with significant morbidity. The danger of reoperation is mainly in reopening the sternum and in the manipulation of the heart and the old grafts. Therefore, off-pump redo coronary artery bypass grafting with a patient-specific approach in selected cases seems an ideal technique. METHODS: Between October 1995 to September 1999, 50 patients with mean age of 61.8+/-8 years underwent reoperative coronary artery bypass grafting without cardiopulmonary bypass. Isolated left internal mammary artery (LIMA) to left anterior descending artery (LAD) anastomosis was carried out in 25 cases through left anterior minithoracotomy. In 1 patient LIMA was grafted on a previous vein graft to LAD, which was critically stenosed proximally but distal anastomosis was patent. In another case LIMA was grafted to Ramus intermedius branch. Midsternotomy approach was used to carry out LAD and right coronary artery grafting in 21 cases. In 2 patients a posterolateral thoracotomy approach was used to bypass obtuse marginal branches without cardiopulmonary bypass; in these cases proximal anastomosis was performed on the descending aorta. RESULTS: Mortality rate was 4% (2 deaths). Two patients sustained perioperative myocardial infarction. No patient was reexplored for hemorrhage and 38 patients did not require homologous blood transfusion. Sixteen patients underwent check angiogram and all of them were found to have patent redo grafts. Cardiac recovery room stay was 22+/-7 hours and hospital stay 5+/-2 days. CONCLUSIONS: In selected patients, reoperative coronary artery bypass grafting can be performed without cardiopulmonary bypass with a low perioperative morbidity and mortality and satisfactory graft patency.     

Regional myocardial dimensions following coronary artery bypass grafting in patients. Relationship of functional deterioration to graft occlusion.

The direct relationship between graft flow and regional midwall myocardial function has not been documented in patients. Therefore, the present study was designed to quantitate the effects of coronary artery bypass grafting on regional myocardial mechanics distal to a coronary artery obstruction. Twenty-one patients with subtotal or total occlusion of the left anterior descending (LAD) coronary artery underwent coronary artery bypass grafting. Following completion of the aortic and coronary anastomoses, two miniature ultrasonic dimension transducers (2.5 mm. diameter) were positioned within the minor axis of the anterior left ventricular free wall and were allowed complete freedom of movement. The transducers were placed at midwall depth, and areas of clinically apparent myocardial fibrosis were not utilized as sites of implantation. During control, 30 minutes following the termination of cardiopulmonary bypass, regional myocardial dimensions, pulmonary artery diastolic pressure, arterial pressure, and heart rate were recorded with all saphenous vein grafts open and after 30 seconds of single vein graft occlusion. These measurements were repeated during atrial pacing at a rate of 128 +/- 4 beats per minute. Data are mean +/- the standard error of the mean. During control, graft occlusion resulted in a regional decrease in systolic excursion from 1.3 +/- 0.1 to 1.0 +/- 0.2 mm. (p less than 0.01), as well as a decrease in the rate of shortening from 8.7 +/- 0.2 to 6.2 +/- 1.1 mm. per second (p less than 0.05); heart rate, mean arterial pressure, and diastolic pulmonary artery pressure remained unchanged. Graft occlusion with atrial pacing resulted in an exaggerated decrease in both regional systolic excursion, from 1.2 +/- 0.2 to 0.6 +/- 0.2 mm. (p less than 0.01), and rate of shortening, from 9.4 +/- 1.5 to 4.4 +/- 0.2 mm. per second (p less than 0.01). For the group of patients studied, end-diastolic lengths were unchanged with graft occlusion during control and atrial pacing. Moreover, with graft occlusion, isolated patients demonstrated regional dyskinesia as evidenced by holosystolic bulging. These studies in patients have documented for the first time that, despite a constant preload, afterload, and heart rate, regional myocardial function following coronary artery bypass grafting is dependent upon adequate graft flow, especially during stress.     

Baseline flow in coronary bypass grafts

BACKGROUND: The purpose of the study is to estimate the total blood flow in coronary artery bypass grafts. METHODS: In a 3-year period 102 patients having a standardized coronary artery bypass grafting (CABG) with the left internal mammary artery (LIMA) anastomosed to the left anterior descending artery and a sequential vein grafted to the remaining diseased coronary arteries were included in the study, 21 females and 81 males. In females a mean of 3.9 anastomosis (range 2-5) were performed and in males a mean of 4.2 (range 2-6) were performed. Flow in the bypass grafts was measured with the transit-time method before termination of cardiopulmonary bypass. RESULTS: Females: LIMA 31 mL/min, vein graft 74 mL/min (26 mL/min per anastomosis), cumulated flow 105 mL/min. Males: LIMA 31 mL/min, vein graft 93 mL/min (29 mL/min per vein anastomosis), cumulated flow 124 mL/min. CONCLUSION: Conventional CABG may restore half of the normal resting coronary artery blood flow (250 mL/min).     

Dopexamine increases internal mammary artery blood flow following coronary artery bypass grafting.

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.     

Routine use of the left internal mammary artery graft in the elderly

Left internal mammary artery (LIMA) grafts have better long-term patency rates than do saphenous vein grafts and result in improved late survival. The present study was undertaken to assess the results of LIMA grafting in the elderly. From 1980 through 1988, 723 patients 70 years of age or older had isolated coronary artery bypass grafting performed. During the first 5 years, only 11% of the elderly patients received LIMA grafts, whereas 86% having coronary artery bypass grafting since 1985 had LIMA grafts. Since 1986, LIMA use in the elderly has become routine, with 92% of patients receiving internal mammary artery grafts. During the first 5 years, elderly patients had a hospital mortality rate of 9.3%. Since 1985, the hospital mortality rate fell to 5.5%. In addition, the occurrence of major surgical complications was either unchanged or reduced in patients receiving LIMA grafts. Furthermore, late follow-up indicates a significantly improved 4-year survival rate in patients with internal mammary artery grafts compared with those without: 86 +/- 0.02% versus 77 +/- 0.03% (p less than 0.01). Analysis of multiple potential risk factors for early mortality was performed using multiple logistic regression and late survival using the Cox proportional hazards model. Although unmeasured predictor variables may confound retrospective analyses, LIMA grafting appears to be an independent predictor both of improved early and late survival.     

Computer-assisted endoscopic coronary artery bypass anastomoses: a chronic animal study.

BACKGROUND: With traditional instruments, endoscopic coronary artery bypass grafting (ECABG) has not been possible. This study was designed to determine the feasibility of using a robotically-assisted microsurgical system to perform ECABG in a chronic animal model. METHODS: Nine calves were placed on cardiopulmonary bypass after harvesting the left internal mammary artery (LIMA). Subxiphoid endoscopic ports (2 instrument, 1 camera) were placed, and a robotic system was used to perform ECABG between the LIMA and left anterior descending coronary artery. LIMA graft flow (LIMAQ) was measured. Animals were sacrificed at 1 month, and hearts underwent angiographic and histologic analyses. RESULTS: Acute graft patency was 89% (8/9). Two animals died suddenly within the first 48 hours. There was no significant difference in mean acute and chronic (n = 6) LIMAQ (40.9+/-4.7 and 38.5+/-5.0 ml/min, respectively). Survivors had an angiographic patency rate of 100% (6/6), confirmed by histology. CONCLUSIONS: This study shows that ECABG is feasible in a chronic animal model with excellent results.     

Off-pump total arterial myocardial revascularization according to the right Y-graft configuration

OBJECTIVES: The aims of this study were as follows: 1) to evaluate the early outcome of the off-pump total arterial myocardial revascularization according to the right y-graft (lambda-graft) configuration and 2) to compare baseline flow and maximum flow between patients undergoing on-pump and off-pump right y-graft (RYG) construction. METHODS: Between December 1998 and January 2001, 47 patients (Group I) and 20 patients (Group II) with three vessel disease underwent on-pump and off-pump coronary artery bypass graft (CABG) respectively according to the RYG configuration. The mean age was 55.5 +/- 4.7 years and 55 +/- 6.4 years in Groups I and II, respectively. The RYG was constructed employing both internal mammary arteries (IMAs) only, in 21 and 8 patients in Groups I and II, respectively, presenting proximal-middle third stenosis of the left anterior descending artery (LAD) and right coronary artery (RCA). The modified RYG configuration employing both IMAs and radial artery (RA) was performed in 26 and 12 patients in Groups I and II, respectively, presenting middle-distal third stenosis of the LAD and distal stenosis of the RCA or posterior descending artery stenosis. Postoperatively all patients underwent transthoracic echo color-Doppler (TTECD) contrast enhanced (by Levovist) before and after adenosine provocative testat one week and three months after operation. RESULTS: There were no hospital deaths. The mean mechanical ventilation was significantly different in Group I versus Group II patients, 18 +/- 4.4 hours versus 13 +/- 5.7 hours, respectively (p = 0.041). The mean intensive care unit stay was 1.5 +/- 0.6 days in Group I and 1 +/- 0.4 days in Group II (p = 0.033). There were no differences between Groups I and II regarding the IMA diameter, mean velocity, and mean flow. At follow-up time, 6 +/- 2.4 months after the surgical procedure, all patients were alive and free of angina. The coronary flow reserve (CFR) at LIMA main stem was significantly higher at three months when compared to the values at one week after the surgical procedure within the same group, (LIMA)CFR (three months) = 2.37 +/- 0.6 versus (LIMA)CFR (one week) = 2.07 +/- 0.4 (p = 0.005) in Group I and (LIMA)CFR (three months) = 2.4 +/- 0.4 versus (LIMA)CFR (one week) = 2.06 +/- 0.3 (p = 0.004) in Group II. Similarly, the CFR at RIMA main stem were significantly higher at three months when compared to the values at one week after the surgical procedure: (RIMA)CFR (three months) = 2.47 +/- 0.7 versus (RIMA)CFR (one week) = 2.1 +/- 0.5 (p = 0.004) in Group I and (RIMA)CFR (three months) = 2.48 +/- 0.5 versus (RIMA)CFR (one week) = 2.08 +/- 0.4 (p = 0.008) in Group II. CONCLUSION: The flow dynamic data, almost identical between patients undergoing off-pump and on-pump total arterial myocardial revascularization (TAMR) according to the RYG configuration, demonstrate that this technique can be applied with excellent results without the employment of cardiopulmonary bypass in selected coronary artery disease patients.     

Changes in left anterior descending coronary artery flow profiles after coronary artery bypass grafting examined by means of transthoracic Doppler echocardiography

OBJECTIVE: We sought to investigate the changes of velocity profiles in the left anterior descending coronary artery after coronary artery bypass grafting using transthoracic Doppler echocardiography. METHODS: Forty-five patients who received a bypass graft to the left anterior descending coronary artery were studied. Before coronary artery bypass grafting, Doppler velocity profiles of the distal left anterior descending coronary artery were recorded with transthoracic Doppler echocardiography. Peak systolic velocity, mean systolic velocity, peak diastolic velocity, mean diastolic velocity, total velocity time integral, systolic velocity time integral, and diastolic velocity time integral were measured. Three weeks after coronary artery bypass grafting, left anterior descending coronary artery antegrade flow in the distal portion of the anastomosis was obtained by using the same method. Coronary angiography was performed before and 3 weeks after coronary artery bypass grafting. RESULTS: The overall success rate of measuring the left anterior descending coronary artery flow was 60.0% preoperatively and 80.0% postoperatively. In 25 patients, in whom all parameters were obtained both before and after coronary artery bypass grafting, the following increased significantly after coronary artery bypass grafting: peak systolic velocity (14.86 +/- 7.50 vs 25.07 +/- 17.02 cm/s, P =.0045), mean systolic velocity (9.86 +/- 5.42 vs 18.03 +/- 12.94 cm/s, P =.0026), peak diastolic velocity (24.26 +/- 12.54 vs 48.28 +/- 31.66 cm/s, P =.0021), mean diastolic velocity (14.94 +/- 6.65 vs 30.36 +/- 20.71 cm/s, P =.0022), diastolic velocity time integral (7.22 +/- 2.88 vs 15.55 +/- 10.39 cm, P =.0009), total velocity time integral (10.50 +/- 4.48 vs 19.27 +/- 12.63 cm, P =.0034), and diastolic-to-systolic velocity time integral ratio (3.09 +/- 1.53 vs 4.97 +/- 2.75, P =.0044). Angiography showed graft patency and no significant change in left anterior descending coronary artery stenosis in all patients. CONCLUSIONS: Transthoracic Doppler echocardiography showed a significant increase in some parameters in left anterior descending coronary artery flow after coronary artery bypass grafting. Measurement of left anterior descending coronary artery flow by means of transthoracic Doppler echocardiography might be a noninvasive method to evaluate the effect of bypass grafting on the left anterior descending coronary artery.     

Assessment of left mammary artery grafts (LIMA) to left anterior descending artery (LAD) after off-pump coronary artery bypass grafting by color Doppler.

BACKGROUND: Off-pump coronary artery bypass grafting (OPCAB) on a beating heart with a LIMA graft to the LAD is established for patients with one vessel disease. The aim of the study was to assess the LIMA patency noninvasive by transcutaneous duplex ultrasound. METHODS: 25 patients (16 male, 9 female, mean age 58+/-13 yr) with LIMA grafts to LAD by OPCAB procedures were studied 7-20 days after surgery. Doppler velocity parameters were measured by use of a 7 MHz transducer placed in left intercostal space. The conventional coronary angiographies performed showed the LIMA graft patent. RESULTS: In all cases a typical biphasic pattern of blood flow was recorded with forward flow in both systole and diastole respectively. Under basal conditions the mean peak velocities in systole were 0.36 m/s and the mean peak velocities in diastole were 0.27 m/s with a mean systolic/diastolic ratio of 1.33. CONCLUSION: Transcutaneous Doppler ultrasound is useful in the detection of the LIMA graft flow. This non-invasive technique may find applications for routine postoperative follow-up of patients with LIMA grafts.     

Right Y-graft, a new surgical technique using mammary arteries for total myocardial revascularization

BACKGROUND: We report a new technique that consists of a right Y-graft using only skeletonized internal mammary arteries (IMA) for total arterial myocardial revascularization. METHODS: This technique consists of anastomosing the in situ left IMA (LIMA) and right IMA (RIMA) to the left anterior descending and obtuse marginal artery, via the transverse sinus, respectively. The distal free LIMA was anastomosed to the right coronary artery and afterwards in a Y fashion to the RIMA stem. Eleven patients with triple-vessel disease underwent coronary artery bypass grafting using this technique. Postoperatively and at follow-up all patients underwent color Doppler contrast-enhanced transthoracic echocardiography (TTE) before and after an adenosine provocation test. RESULTS: Overall, 33 IMA-coronary anastomoses were made and 11 right Y-grafts were constructed. At 1 week after operation color Doppler contrast-enhanced TTE before and after the adenosine provocation test, respectively, showed an increase in LIMA stem diameter of 0.31 mm and in mean flow 62 mL/min. Coronary flow reserve (CFR) was 2+/-0.3. The increase in RIMA stem diameter was 0.2 mm and in mean flow was 121.7 mL/min. Coronary flow reserve was 2.5+/-0.4. Only 1 patient demonstrated an anomalous Doppler pattern, suggesting a partial Y-graft closure. CONCLUSIONS: Such a technique permits total myocardial revascularization using only mammary arteries and left ventricular perfusion from both IMAs simultaneously. The color Doppler contrast-enhanced TTE is a rapid, accurate, and noninvasive test allowing a good assessment of IMA patency.     

The effect of isosorbide dinitrate spray on patients receiving coronary artery bypass grafting

The effect of isosorbide dinitrate (ISDN) spray on hemodynamics and coronary artery diameter was studied in 10 patients with ischemic heart disease. Significant decrease in systolic blood pressure and systolic and diastolic pulmonary artery pressure was recognized at 2 minutes after spray. But there were no significant changes in heart rate and diastolic blood pressure. The diameter of the right coronary artery was 2.6 +/- 0.3 mm before ISDN, which significantly increased to 3.5 +/- 0.4 mm after ISDN. Then, the effect of ISDN on saphenous vein (SV) graft and internal thoracic artery (ITA) graft in 5 patients receiving coronary artery bypass grafting was assessed. The diameter of ITA was 1.7 +/- 0.2 mm before ISDN, and that was 2.0 +/- 0.2 mm after ISDN. The increase was recognized in all patients. The diameter of SV was 4.0 +/- 0.3 mm before ISDN, and that was 4.0 +/- 0.3 mm after ISDN. The diameter of the left anterior descending artery was 1.9 +/- 0.2 mm before ISDN, and that was 2.4 +/- 0.4 mm after ISDN. It was concluded that ISDN spray had a vasodilation effect on ITA graft as well as coronary artery. ISDN spray was expected to be useful for the solution of graft spasm and rapid abortion of anginal attacks even after coronary surgery.     

Epicardial colour-Doppler scanning of coronary artery stenoses and graft anastomoses

OBJECTIVE: Epicardial ultrasound scanning was applied during coronary surgery to assess coronary artery stenoses and quality of distal graft anastomoses, with special emphasis to the left anterior descending artery (LAD). DESIGN: Twenty-three patients with coronary artery disease (M:F 19:4, mean age 65.0 +/- 9.5 years) had coronary artery bypass grafting (CABG) on cardiopulmonary bypass. Intraoperative scanning of coronary artery stenoses and graft anastomoses was performed with a new 10 MHz linear array Vingmed transducer connected to a GE Vingmed System FiVe echocardiography unit. Coronary stenoses detected by ultrasound were compared with preoperative angiograms. Intraoperatively, coronary graft flow was assessed with a Medi-Stim transit-time flowmeter. RESULTS: Twenty LADs were investigated. In 17 LADs (85%) stenoses were clearly identified. In three LADs (15%) stenoses were not identified because LADs were deeply intramyocardial or the stenosis was very proximal. There was a significant correlation between LAD stenoses detected by ultrasound and angiogram (R = 0.7; p < 0.01). Mean number of grafts was 3.8 +/- 0.9. Of 26 LAD anastomoses assessed, good images were obtained in 22 cases (84.4%); the mean LAD diameter measured 1 cm below the anastomosis was 1.6 +/- 0.2 mm. In two LADs images were rated fair and in two LADs images were poor because of intramyocardial LAD. No technical error of the anastomoses was detected. All grafts had good flows as ascertained by flow measurements. CONCLUSION: Epicardial ultrasound scanning with the new 10 MHz transducer allowed satisfactory imaging of coronary stenoses and graft anastomoses. Factors limiting the quality of imaging are proximal lesions, intramyocardial vessel, vessel tortuosity, and extensive calcifications. Epicardial ultrasound scanning with updated technology should become a further advancement to graft assessment during off-pump coronary surgery.     

Influence of milrinone on internal mammary artery grafts]

To evaluate the effects of milrinone on blood flow in the left internal mammary artery (LIMA) grafts and hemodynamic variables, we conducted a prospective randomized study. Twenty-four patients undergoing coronary artery bypass grafting were randomized to receive milrinone treatment (Milrinone; n = 12) or no milrinone treatment (Control; n = 12). Milrinone was given after induction of anesthesia at a speed of 0.5 microgram/kg/min for 24 hours. After start of cardiopulmonary bypass (CPB), CPB perfusion flow was adjusted to 2.4 l/m2 and LIMA blood flow was measured. Blood samples for determination of plasma cAMP levels were collected and hemodynamic measurements were also assessed perioperatively. LIMA blood flow was significantly greater in Milrinone than that in Control (40 +/- 4 vs 29 +/- 4 ml/min/m2, p < 0.05). Plasma levels of cAMP were significantly (p < 0.05) greater in Milrinone than those in Control at tha start of CPB (18 +/- 1 vs 13 +/- 1 pmol/ml) and at the end of CPB (24 +/- 2 vs 17 +/- 2 pmol/ml). Systemic vascular resistance was significantly (p < 0.05) lower and cardiac index was significantly (p < 0.05) greater in Milrinone than those in Control postoperatively. With its positive inotropic and systemic vasodilator activities, milrinone may have direct vasodilator effect on LIMA.     

Coronary flow reserve early and late after minimally invasive coronary artery bypass grafting in patients with totally occluded left anterior descending coronary artery.

BACKGROUND: The impairment of flow reserve of the left anterior descending coronary artery in the early postoperative period in patients receiving a left internal thoracic artery graft has been related to the effects of cardiopulmonary bypass. Indeed, the late improvement in flow has been attributed to a late increase in left internal thoracic artery diameter. METHODS: We evaluated 12 patients who underwent minimally invasive direct coronary artery bypass surgery with the internal thoracic artery used to graft an occluded left anterior descending artery without extracorporeal circulation. Early and 6 months after the operation, patients underwent a second angiogram of the left internal thoracic artery graft and assessment of coronary flow reserve by use of an intracoronary 0.014-inch Doppler guide wire. RESULTS: At the late study, coronary flow reserve had increased compared with the early postoperative data from 1.8 +/- 0.4 (standard deviation) to 2.5 +/- 0.6 (P =.002) because of a significant decrease in baseline averaged peak velocity (32.4 +/- 6.2 vs 21.3 +/- 6.4 cm/s, P =.002), whereas the hyperemic values were similar (51 +/- 6 vs 53.7 +/- 21.9 cm/s, P =.6). The diameters of the thoracic artery (2.1 +/- 0.3 vs 2.2 +/- 0.3 mm, P =. 7) and the left anterior descending coronary artery (1.8 +/- 0.1 vs 1.8 +/- 0.2 mm, P =.5), as well as myocardial oxygen consumption (106 +/- 14 vs 101 +/- 16 mm Hg. beats/min. 10(-2), P =.5), were unchanged. CONCLUSIONS: Our findings suggest that the late improvement in coronary flow reserve is independent of the diameter of the graft and probably reflects an early distal coronary vessel dysfunction, which normalizes with time.     

Effects of coronary revascularization on regional wall motion. An intraoperative two-dimensional echocardiographic study

Although coronary artery bypass grafting effectively reduces the symptoms of myocardial ischemia, its immediate effect on regional wall motion dysfunction is not well defined. This intraoperative study was undertaken to determine whether bypass grafting improves regional wall motion in areas of preoperative ischemic dysfunction. In 17 patients undergoing coronary bypass, short-axis echocardiograms were obtained with the chest open 30 minutes before and after cardiopulmonary bypass. Regional wall motion was calculated quantitatively as the percent increase in segmental wall thickness during systole, with 40% thickening or less defined as indicating ischemic dysfunction. Qualitatively, it was evaluated by visual changes in endocardial wall motion according to a graded score (0 = normal to 4 = dyskinesia). Of the 136 segments studied, 44 (32%) had evidence of ischemic dysfunction before coronary bypass. When regional wall motion was analyzed in all 136 segments after coronary bypass, there was no significant change in either quantitative indices (62% +/- 7% before grafting versus 58% +/- 6% after grafting) or qualitative indices (0.19 +/- 0.06 versus 0.17 +/- 0.06). However, in those segments with ischemic dysfunction before grafting, there was a significant increase in quantitative indices of regional wall motion after grafting (24% +/- 2% versus 50% +/- 5%; p less than 0.02). By contrast, qualitative indices continued to show no significant improvement (1.3 +/- 0.1 versus 1.05 +/- 0.2). We conclude that coronary artery bypass grafting significantly improves areas of ischemic regional wall dysfunction. These changes can be difficult to detect with visual qualitative methods and are best analyzed by techniques assessing changes in segmental wall thickness.     

Angiographic assessment of sequential and individual coronary artery bypass grafting

OBJECTIVE: In trying to answer the question about the controversial use of sequential grafts, we determined the mid-term angiographic outcome of patients in whom coronary artery bypass was performed with different types of vein grafts. METHODS: A total of 1034 coronary anastomoses on 724 saphenous vein grafts (SVGs) (apart from 497 left internal mammarian artery (LIMA) anastomoses) were assessed in 509 patients in an average of 55.4 +/- 17.6 months after coronary artery bypass grafting. RESULTS: The patency rates of sequential conduits were markedly higher than those of individual ones (86.6% vs 69.6%, p = 0.0001). Also, the anastomoses on the sequential conduits had better patency rates (80.6% vs 69.6%, p = 0.0001). This difference was even more pronounced in coronary arteries of poor quality/small (< 1.5 mm) diameter (68.9% vs 51.6%) for the sequential and individual grafts, respectively (p = 0.03). Also, the patency of the entire sequential conduit was lower when most distally located anastomosis was of poor runoff (45.2%). CONCLUSIONS: The patency of a sequential vein conduit is generally superior than that of an individual one, especially for poor runoff coronary vessels, provided that the most distally located anastomosis is performed on a good coronary artery in terms of quality and diameter. Using a minimal length of SVG is another advantage. However, failure of a single sequential conduit jeopardizes all of the anastomoses along that graft segment. Besides, being technically more demanding, technical expertise in performing a sequential anastomosis is probably among the important predictors of patency.