H-graft minimally invasive direct coronary artery bypass for coronary artery disease complicated with Leriche syndrome

We present a case of Leriche syndrome, requiring coronary revascularization and both lower extremities. Leriche syndrome shows high aortic occlusion, which has occasionally large collateral pathways from the internal thoracic artery (ITA) to the femoral artery via superior and inferior epigastric arteries. Usual usage of ITA may lead to deterioration of blood supply to lower extremities at surgical coronary revascularization. H-graft minimally invasive direct coronary artery bypass (MIDCAB), which puts arterial graft horizontally between in situ left ITA (LITA) and left anterior descending (LAD) through small incision approach, enables surgical LAD revascularization and keeps blood supply to lower extremities. H-graft MIDCAB contributed to two-stage surgery in a patient with Leriche syndrome complicated with coronary artery disease.     

Growth potential of left internal thoracic artery grafts: analysis of angiographic findings

BACKGROUND: The growth potential of the internal thoracic artery (ITA) is still undetermined, and little is known about the long-term effects of anastomosing it to the coronary artery. METHODS: Fifty-three patients whose left ITA (LITA) had been anastomosed to the left anterior descending (LAD) coronary artery underwent coronary angiography within 1 month of operation and in late follow-up (mean interval: 4.5 +/- 1.5 years). The diameter ratios of LITA to LAD were designated as the matching ratio. RESULTS: In follow-up, the diameter of the LITA increased from 1.83 +/- 0.40 to 2.46 +/- 0.53 mm in the 29 patients with progressive proximal native coronary stenosis. However, late results indicate that the matching ratio did not vary according to the location of the LITA anastomosis on the LAD (proximal portion: 1.13 +/- 0.16, distal portion 1.19 +/- 0.13), and reached an upper limit of about 1.4. CONCLUSIONS: Growth potential of the LITA is limited by the diameter of the coronary artery onto which it is anastomosed. The most effective procedure for enhancing the growth potential of the LITA is to anastomose as proximally as possible onto the LAD.     

Improved distribution of antegrade cardioplegic solution with simultaneous coronary sinus occlusion following acute coronary artery occlusion.

This study was designed to evaluate the distribution of cardioplegic solution infused antegradely with simultaneous coronary sinus occlusion. After 1 hr LAD occlusion, sheep were placed on cardiopulmonary bypass. Hearts were arrested with 300 ml of cold cardioplegia and replenished with two additional doses. In group I (n = 10), antegrade cardioplegia (ACP) was given alone; in group II (n = 9), ACP was given in combination with simultaneous coronary sinus occlusion. Microspheres were infused into the cardioplegic line to determine the antegrade distribution of the solution, while a different microsphere was injected into the anterior interventricular vein to detect the venous backflow of the solution. The data showed that myocardium distal to LAD occlusion in group II received more antegrade (0.17 +/- 0.02 versus 0.06 +/- 0.02 ml/g/min, P less than 0.01, in subendocardium; and 0.15 +/- 0.03 versus 0.09 +/- 0.02 ml/g/min, P = NS, in subepicardium) and retrograde (2181 +/- 455 versus 0 counts/g/min, P less than 0.01, in subendocardium; and 2,146 +/- 527 versus 0 counts/g/min, P less than 0.01, in subepicardium) distribution of cardioplegic solution in comparison to group I. We therefore conclude that simultaneous coronary sinus occlusion significantly improves the distribution of antegrade cardioplegic solution to the regionally occluded myocardium by increasing collateral flow as well as venous backflow.     

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

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

Flow in coronary artery bypass grafts to totally and partially occluded left anterior descending coronary arteries

Flow was determined by electromagnetic flowmeter in vein bypass grafts in 20 patients with a totally occluded left anterior descending (LAD) coronary artery and on 61 patients with a partially occluded LAD. The median flow in LAD grafts was 14.5 ml/min with total LAD occlusion, and 40 ml/min with partial LAD occlusion (p less than 0.001). In cases of total LAD occlusion, the presence of mild or moderate anteroseptal wall dysfunction was associated with more satisfactory flow than was the case with severe anteroseptal wall dysfunction (p less than 0.02). Flows over 25 ml/min were found only when the LAD distal to total occlusion was 1.5 mm or greater. Unsatisfactory flows were consistently found with total LAD occlusion, poor ventricular function, and a distal LAD less than 1.5 mm. Repeat catheterizations to determine an unsatisfactory patency rate under these conditions would be necessary to alter our policy of grafting all suitable vessels beyond a total occlusion.     

Should the supplemental vein graft be anastomosed upstream or downstream of the internal thoracic artery (ITA) for ITA hypoperfusion?

BACKGROUND: This study was designed to compare internal thoracic artery (ITA) flow in different settings of supplemental vein grafting for ITA hypoperfusion. METHODS: Fourteen dogs each received two coronary bypass grafts to the circumflex artery (CFX), using left ITA and vein grafts, and then the proximal CFX was ligated. The animals were divided into two groups. G-I dogs receiving the vein graft proximally to the ITA graft and G-II receiving the vein distally. ITA flow was evaluated regarding 1) effects of competition from the vein graft, and 2) pharmacological or physiological effects on the ITA's contribution to distal perfusion. Flow is expressed as a mean (ml/min). RESULTS: ITA flow was 44.2+/-5.9 in G-I, and 45.7+/-6.5 in G-II (p=ns), when the vein graft was occluded. With a vein graft open, ITA flow decreased to 7.5+/-1.6 in G-I, and 6.8+/-1.8 in G-II (p=ns), and ITA's contribution to total perfusion requirements was 18% in G-I and 16% in G-II. Adenosine (0.2 mg/min/kg) increased the ITA flow in both groups, 18.4+/-3.2, and 16.3+/-3.8, respectively (p=ns), and ITA's contribution to distal perfusion was increased to 32% in G-I and 27% in G-II. In contrast, phenylephrine (0.003 mg/min/kg) decreased ITA flow and ITA's contribution to distal flow in both groups (6.1+/-1.1, 11% vs 6.2+/-1.4, 11%, p=ns), but increased vein flow significantly. Cardiac pacing (150 bpm) increased the ITA flow and ITA's contribution to distal perfusion equally in both groups (8.4+/-1.5, 16% vs 7.6+/-2.6, 15%, p=ns). CONCLUSIONS: Supplemental vein grafting, whether it is placed distally or proximally, limits ITA flow and ITA's contribution to distal perfusion both in the resting heart and during the increased myocardial oxygen demand.     

Myocardial protective effect of lidocaine during experimental off-pump coronary artery bypass grafting.

Off-pump coronary artery bypass grafting (OPCABG) has recently gained popularity. During OPCABG, patients remain vulnerable to ischemic-reperfusion injury due to a temporary coronary occlusion without any active cardioprotection. Some strategies such as ischemic preconditioning (IP) and an intracoronary shunt have been applied with a view to minimizing the effects of ischemia, but the effects of these strategies remain controversial. This study was carried out to investigate the protective effect of lidocaine against myocardial ischemic-reperfusion injury. Twenty-one pigs were assigned to three groups, each consisting of seven pigs. In the control group, using a left internal thoracic artery (LITA) bypass circuit, the left anterior descending coronary artery (LAD) was occluded for 45 min followed by two hours of reperfusion. In the IP group, five min of occlusion followed by 15 min of reperfusion was performed. In the lidocaine group, 2 mg/kg of lidocaine was administered directly into the LAD just before the LAD occlusion. Infarct size expressed as a percentage of the area at risk was significantly smaller in the lidocaine group (2.7+/-4.2%) than in the control group (79.9+/-6.0%, p<0.001) or the IP group (57.0+/-25.9%, p<0.001). Lidocaine exhibited a potent myocardial protective effect in the present OPCABG model.     

Effects of ischemic preconditioning and synchronized coronary venous retroperfusion in an off-pump coronary artery bypass grafting model

Off-pump coronary artery bypass grafting (CABG) has become a popular procedure. However, temporary occlusion of the target vessel is sometimes a threat to the patients. Although ischemic preconditioning (IP) has been proposed to reduce myocardial injury, its effects remain controversial. The coronary veins represent an alternate route for delivery of therapeutic agents and arterial blood to the acutely ischemic myocardium. The aim of this study was to investigate the protective effect against myocardial ischemia and reperfusion injury of combined IP and synchronized coronary venous retroperfusion (SCVR) in an off-pump CABG model. Twenty-one pigs were assigned to 3 groups of 7 animals. In the control group, the left anterior descending coronary artery (LAD) was occluded for 45 min followed by 2 h of reperfusion using a left intrathoracic artery (LITA) bypass circuit. In the IP group, LAD occlusion was done for 5 min with 15 min of reperfusion, followed by 45 min of LAD occlusion. In the SCVR group, pretreatment before LAD occlusion was the same as in the IP group. Then, SCVR was commenced just after the start of LAD occlusion for 45 min. The percent systolic shortening of ischemic myocardium (measured by sonomicrometry) after reperfusion via the LITA was significantly (p < 0.001) greater in the SCVR group (14.6 +/- 3.3%) than in the control group (-1.6 +/- 5.6%, 95%CI: -24.3 - -8.1) or the IP group (0.7 +/- 8.0%, 95%CI: -22.0 - -5.8) after 30 min of reperfusion, and this difference persisted throughout the reperfusion period. Infarct size (expressed as a percentage of the area at risk) was significantly (p < 0.001) smaller in the SCVR group (2.4 +/- 2.7%) than in the control group (83.0 +/- 2.3%, 95%CI: -99.0 - -62.4) or the IP group (42.0 +/- 23.0%, 95%CI: -58.0 - -21.3). Combined SCVR and IP had a potent myocardial protective effect in the present off-pump CABG model. This method may be clinically feasible and may be able to prolong a safe coronary occlusion.     

Functional and perfusional assessment with electrocardiograph-gated single photon emission computed tomography after minimally invasive direct coronary artery bypass grafting.

BACKGROUND: Because of limited surgical field, minimally invasive coronary artery bypass grafting (MIDCAB) requires anastomosis to the distal portion of the left anterior descending artery (LAD) of the left internal thoracic artery (LITA) with the heart beating. Though the diameters of these arteries are very small, it is unknown whether blood flow sufficient for the LAD territory is obtained by bypass grafting. METHOD: Eight patients with single-vessel disease of the LAD underwent MIDCAB with the LITA to the LAD and we evaluate the perfusion and function in the LAD territory by quantitative ECG-gated SPECT (QGS) with 99m-technetium sestamibi (MIBI) before and after operation. RESULT: The intraoperatively measured diameters of the LITA and LAD at the site of anastomosis were 1.1+/-0.2 mm and 1.3+/-0.4 mm, respectively. The percentage increases in end-diastolic perfusion, regional ejection fraction and regional wall thickening in the anteroseptal area after MIDCAB were 136.3+/-11.7(p=0.071), 148.4+/-6.6(p=0.007) and 133.0+/-5.6(p=0.029), respectively (paired t-test, mean +/- SD %). Stress-rest MIBI SPECT indicated no ischemia in anteroseptal wall. CONCLUSION: The MIDCAB technique thus appeared to improve perfusion and function in the LAD territory despite bypass to the distal LAD, and ECG-gated MIBI SPECT using QGS software was very useful for evaluating the quality of anastomosis after MIDCAB.     

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

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

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

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

Spontaneous recanalization of postoperative severe graft stenosis. What is the cause and prognosis of the "string sign" in the internal thoracic artery?

A 68-year-old female with unstable angina was treated surgically. She was referred to the surgical ward by cardiologists because of a diagnosis of unstable angina with three vessel disease. On a coronary angiogram (CAG), 90% stenoses were found in the left anterior descending coronary artery (LAD), circumflex (CX), and right coronary artery (RCA). She received elective coronary artery bypass grafting (CABG), in which the left internal thoracic artery (LITA) was anastomosed to the LAD and reversed saphenous vein grafts (SVG) were made to segment 12 of the CX, and segment 4PD of the RCA, respectively. The postoperative course was uneventful, but postoperative early graftgraphy revealed distal narrowing of the LITA graft as the so-called "string sign". However, one year post surgery, the LITA string sign was not found and its patency had markedly improved on the second graftgram. It is reported that the LITA "string sign" might cause late graft occlusion. However, this LITA graft evidently enlarged the size and increased the flow of the artery in proportion to myocardial blood demand. To our knowledge, it has not been reported that an in situ LITA string sign on postoperative early graftgram has disappeared in the late phase. We hypothesize that the LITA string sign might be caused by several different factors such as flow competition, spasm, and/or technical problems. In any event, the LITA string sign does not cause graft occlusion in the late postoperative period in every case.     

Shortest route for in situ left thoracic artery to left anterior descending coronary artery

For coronary artery bypass grafting, the internal thoracic artery (ITA) graft carries a greater long-term patency and a decreased need for reoperation when compared with the saphenous vein graft. However, the number and length of ITAs limit their use. In an effort to extend the use of the ITA and to improve patency, we evaluated the shorter course from the left ITA (LITA) origin to the left anterior descending coronary artery (LAD). We compared the distance using the conventional route over the lung (20 patients) with that using the newly-devised route medial to the lung and through the pericardial incision (20 patients). The distance using the route medial to the lung and through the pericardial incision was 12.6 +/- 1.4 cm (mean +/- SD), which was shorter compared with 15.1 +/- 1.1 cm of the route over the lung (p less than 0.01). And also the route medial to the lung and through the pericardial incision could avoid the danger of strectching or kinking by the inflated left lung. From these results, we concluded that the use of the route medial to the lung and through the pericardial incision was better method of extending the use of the in situ LITA to LAD.     

Thoracic epidural anesthesia reduces myocardial infarct size after coronary artery occlusion in dogs

The effect of thoracic epidural anesthesia (TEA) with lidocaine on regional myocardial blood flow (RMBF), hemodynamic performance, and myocardial infarct size after coronary artery occlusion was assessed in 21 dogs. In seven dogs, the left anterior descending coronary artery (LAD) was temporarily occluded twice: once before TEA (control) and once during TEA. Systemic hemodynamic parameters, RMBF (using radionuclide-labeled microspheres), and epicardial electrocardiographic maps (15 sites) were obtained before and 15 min after each temporary LAD occlusion. Compared with the ischemic period before TEA, the following were decreased during ischemia with TEA: heart rate, ST segment elevation, cardiac index, the peak first time derivative of left ventricular (LV) pressure, LV tension-time index, the rate-pressure product, and LV stroke-work index. Ischemic zone endocardial RMBF was increased from a control value of 26 +/- 6% to 36 +/- 6% of normal during TEA (P less than 0.05). An additional 14 dogs randomly received either TEA (1% lidocaine, 10 ml/hr) or epidural saline plus 1% lidocaine (10 ml/hr, intramuscularly), beginning 1 hr after LAD occlusion. After 6 hr, the heart was removed and the left ventricle was sectioned parallel to the atrioventricular groove. The infarcts (tetrazolium-stained) were 46% smaller with TEA than with saline, 15.4 +/- 1.8% vs 28.7 +/- 2.3% of the left ventricle (P less than 0.05). Thus TEA reduced hemodynamic correlates of myocardial O2 consumption, improved regional (ischemic zone) endocardial perfusion, and reduced the extent of myocardial infarction.     

Epicardial coronary artery Doppler: validation in the animal model

The aim of the study was to validate a newly-designed epicardial coronary artery Doppler probe and test its detection of changes in coronary blood flow velocity. Left anterior descending (LAD) coronary blood flow and flow velocity were evaluated in four pigs with a pericoronary transit time flow (TTF) probe and a newly-designed epicardial Doppler micro-probe. Four consecutive measurements were taken for each of the following conditions: basal, partial stenosis, occlusion, and reperfusion of the LAD. Mean TTF value (ml/min) was 23.2+/-6.6 in basal condition, 16.2+/-5.7 after partial LAD stenosis, 0.1+/-0.3 during LAD occlusion, and 67.4+/-23.3 at reperfusion (P<0.001). Similar patterns were recorded in terms of Doppler velocity (cm/s) with values of 4.0+/-1.9 in basal condition, 3.5+/-2.3 after partial LAD stenosis, 0.5+/-1.4 during LAD occlusion, and 11.1+/-5.5 at reperfusion (P<0.001). No significant differences in both TTF and Doppler velocity were detected between basal condition and partial LAD stenosis (P=ns). Epicardial coronary arterial Doppler represents a valuable tool to detect coronary arterial flow velocity in basal condition. Although changes in flow velocity are easily recorded after coronary occlusion and reperfusion, modifications after partial coronary stenosis are not clearly defined.     

Internal thoracic artery malperfusion: fast decision for an additional vein graft has impact on patient outcome

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.     

Effects of isoflurane and halothane on coronary vascular resistance and collateral myocardial blood flow: their capacity to induce coronary steal

Some coronary vasodilators, paradoxically, may endanger patients with coronary artery disease by causing "coronary steal." To determine the capacity of isoflurane and halothane to cause coronary steal, the authors studied their effects on coronary vascular resistance (CVR), diastolic coronary artery pressure, and collateral myocardial blood flow. Using ameroid constrictors, chronic occlusions of the left anterior descending (LAD) coronary artery were created in ten dogs. Six to eight weeks after implantation, the dogs were anesthetized with fentanyl and pentobarbital, and a stenosis was created on the circumflex (Cx) coronary artery. Isoflurane and halothane were each administered in doses of 0.5 and 1.5 MAC. Diastolic aortic pressure was held constant. Using small catheters in the circumflex and LAD coronary arteries, the authors measured diastolic coronary artery pressures. Collateral myocardial blood flow was measured by the microsphere method. In this model, halothane and isoflurane minimally affect CVR. The maximum change in CVR, which was found during 1.5 MAC isoflurane, was -8% (not significant). Diastolic coronary pressures distal to the Cx stenosis (54.5 +/- 11.5 mmHg) and distal to the LAD occlusion (44.5 +/- 5.2 mmHg) did not change significantly with either isoflurane or halothane. Transmural collateral blood flow distal to the LAD occlusion (0.51 +/- 0.11 cc.g-1.min-1) was unaltered by either drug. There was no evidence of coronary steal. Epicardial ECG S-T segments showed no evidence of ischemia. The finding of minimal direct effects of halothane and isoflurane on CVR, diastolic coronary pressure, and collateral myocardial blood flow suggest that, under the conditions of this study, neither agent, when used as an adjuvant to high-dose narcotic anesthesia, is likely to cause myocardial ischemia by a coronary "steal" mechanism.     

Acute effect of cerivastatin on cardiac regional ischemia in a rat model mimicking off-pump coronary surgery

BACKGROUND: Although the off-pump technique is becoming widely used in coronary bypass surgery, there has been no experimental rat heart model of regional reversible ischemia. The aims of this study were to investigate the optimal duration of coronary occlusion for making reversible ischemia and to examine whether cerivastatin increases myocardial tolerance against prolonged coronary occlusion. METHODS: Study 1--Male Sprague-Dawley rats (350 to 450 g) underwent temporary occlusion of either left anterior descending artery (LAD; for 3, 5, 7.5, 10, 12.5, 15, or 20 min) or circumflex artery (CX; for 5, 10, or 15 min). Study 2--Rats were divided into two groups, control and cerivastatin groups, which had 0.1 mg/kg cerivastatin intravenously after anesthesia. LAD was occluded for 10, 15, or 20 minutes. In the both studies, hearts were stained to determine the area at risk (AR) and infarcted (IF) area 24 hours after reperfusion. RESULTS: In LAD occlusion, IF/AR increased in a time dependent manner: 4.5 +/- 3.2%, 9.7 +/- 5.2%, 17.2 +/- 3.0%, 16.8 +/- 2.7%, 23.9 +/- 9.5% (p < 0.01 vs. 3 min), 62.4 +/- 2.9% (p < 0.0001), and 63.4 +/- 2.9% (p < 0.0001) at 3, 5, 7.5, 10, 12.5, 15, and 20 min, respectively. Also in CX, IF/AR increased with time: 14.3 +/- 2.3%, 25.9 +/- 2.1%, and 40.9 +/- 6.2% (p < 0.001 vs. 5 min) at 5, 10, and 15 min, respectively. Cerivastatin significantly reduced IF/AR at 15 minutes (43.7 +/- 6.2%) and at 20 minutes (44.6 +/- 5.3%) compared to control (62.4 +/- 2.9% and 60.6 +/- 2.5%, respectively, p < 0.05). CONCLUSION: Cerivastatin increased myocardial tolerance after prolonged coronary occlusion over 10 minutes, which was considered to be the upper limit for creating a regional reversible ischemia in rats.     

Effects of the site of distal anastomosis on the branch flow of coronary arteries in an A-C bypass grafting

Hemodynamics of coronary branch with retrograde blood flow of the host artery was examined in seven mongrel dogs, when the distal side of the graft was anastomosed at distal site to branching point in A-C bypass grafting. A Y-shaped tube was interposed to reconstruct coronary blood flow between the right carotid artery and the left anterior descending coronary artery (LAD), its one arm of Y was connected to proximal site of the branching point of the first diagonal artery (proximal anastomosis), and the other arm was connected to distal site of the branching point (distal anastomosis). After the LAD was ligated just distal to the bifurcation from the left main coronary artery, each arm was clamped in turn, and blood flow of the first diagonal branch was evaluated. Heart rate, left ventricular pressure and cardiac output (cardiac function), and blood pressure, flow and resistance of the interposed tube (bypass function) were not changed significantly in each arm clamped. The diagonal branch flow decreased from 11.2 +/- 2.7 ml/min (mean +/- S.D.) in proximal anastomosis to 10.3 +/- 3.1 ml/min in distal anastomosis with significant difference (P less than 0.05). The diagonal branch/bypass graft flow ratio decreased from 0.422 +/- 0.159 in proximal anastomosis to 0.395 +/- 0.160 in distal anastomosis with significant difference (p less than 0.05). The blood flow in systolic phase of the diagonal branch tended to increase in distal anastomosis as compared with proximal anastomosis. However, diastolic flow of the branch significantly decreased from 8.3 +/- 2.1 ml/min in proximal anastomosis to 7.1 +/- 2.2 ml/min in distal anastomosis (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Arterial conduit shear stress following bypass grafting for intermediate coronary artery stenosis: a comparative study with saphenous vein grafts.

OBJECTIVES: Graft failure has been reported when the arterial conduit, such as the internal thoracic artery (ITA) or the right gastroepiploic artery (GEA), is grafted to a lower grade coronary artery stenosis. The shear stress as a significant factor affecting graft patency was compared between the arterial conduit and the saphenous vein graft (SVG) after surgery. METHODS: In 101 patients, 40 ITAs, 27 GEAs and 34 SVGs were examined using a Doppler-tipped guide wire during postoperative angiography. The graft flow volume and shear stress were calculated from velocity and diameter data. The study grafts were classified according to the grade of native coronary artery stenosis: group L had more than 50 up to 75% stenosis, and group H had more than 75% stenosis. Group H consisted of 25 ITAs, 17 GEAs and 21 SVGs, while group L consisted of 15 ITAs, 10 GEAs and 13 SVGs. RESULTS: In group H, graft flow volume did not significantly differ among the ITA (34+/-11 ml/min), GEA (36+/-16 ml/min) and SVG (41+/-15 ml/min), and graft shear stress significantly (ITA vs. GEA P<0.0001; GEA vs. SVG P<0.01) differed among the ITA (16.0+/-4.8dyn/cm(2)), GEA (9.1+/-3.2dyn/cm(2)) and SVG (4.8+/-1.6dyn/cm(2)). In group L, flow volume was lower (P<0.001) in the ITA (18+/-6 ml/min) and GEA (13+/-8 ml/min) than in the SVG (35+/-16 ml/min), and shear stress was significantly (P<0.001) greater in the ITA (13.7+/-4.9dyn/cm(2)) than the GEA (5.6+/-2.0dyn/cm(2)) or SVG (4.6+/-2.0dyn/cm(2)). CONCLUSIONS: These data suggest that shear stress of the ITA is superior and maintained despite the flow volume being reduced by flow competition. Lower shear stress of the GEA for intermediate stenosis may be associated with the development of conduit failure.