Differences in LIMA Doppler characteristics for different LAD perfusion areas

Objectives: To correlate supraclavicular left internal mammary artery (LIMA) to left anterior descending artery (LAD) area Doppler characteristics with angiographically perfused area. Methods: Sixty patients (50 male, mean age 62±7.3 years) with LIMA to LAD area grafting were prospectively entered in a follow up study. Supraclavicular echo Doppler of the LIMA was studied at the LIMA origin preoperatively, and at 4.8±3.8 months and 1.8±0.9 years postoperatively. The potential area to be revascularized judged from preoperative angiography was called the ‘target’ area. Control angiography (native and LIMA) was done at 1.5±0.9 years. The perfused area % was classified into group I ≤17.0% (n=16), group II >17.0% and <22.50% (n=17), and group III ≥22.50% (n=18) and related to LIMA Doppler characteristics. Multivariate linear regression analyses (MLRA) were performed to assess the relations between Doppler variables and the perfused area, target area and ratio of perfused/target area. Results: At MLRA perfused area was significantly related to the natural logarithm of diastolic peak velocity (DPV) (P=0.013) and diastolic mean velocity (P=0.048) and the ratio only to the degree of LAD stenosis (P=0.004). In hyperaemic response maximal DPV (DPV max) showed significant correlation to the perfused area (P=0.005) as well as to the ratio (P=0.017). When analyzing the additive power of both investigations, only DPV max (P=0.005) correlated significantly to the perfused area and for the ratio only the degree of stenosis of the LAD emerged as significant (P=0.004). Conclusions: At MLRA the diastolic flow pattern at rest and the maximal DPV in hyperaemic response correlated significantly with the LIMA run-off area whereas the last variable is the strongest predictor of the LIMA run-off area.     

Effect of Systemic Vasodilators on Internal Mammary Flow During Coronary Bypass Grafting

Background. The effect of vasodilators on acute flow in the internal mammary (IMA) is unclear. Topical vasodilators show no effect on acute flow when the distal segment of the IMA is resected. The purpose of this study was to evaluate the effect of systemic vasodilators when this segment is resected.

Methods. We studied 60 patients with proximal anterior descending coronary artery lesions in whom the left IMA was harvested for grafting to the left anterior descending coronary artery. The patients were divided into six groups (n = 10), based on which of the following agents were studied: normal saline solution, nitroglycerin, nitroprusside, dobutamine, dopexamine, and amrinone. After harvesting, the IMA was trimmed as proximally as possible (and at least 3 cm proximal to the bifurcation), and free flow was measured before any pharmacologic intervention (flow 1). Systemic infusion of one of the six agents commenced. A mean of 17 ± 3.4 minutes after infusion began, with a comparable cardiac index, a second measurement of IMA flow was taken (flow 2). Hemodynamic measurements for each flow, including blood pressure, heart rate, and cardiac output, were taken.

Results. A significant increase in IMA flow was noted for those patients receiving nitroglycerin (93.5 versus 106.8 mL/min; p = 0.025), and a significant decrease in flow was noted for those receiving nitroprusside (91.0 versus 78.2 mL/min; p = 0.042). The effects remained significant when corrected for cardiac index and compared with the normal saline solution group. No other systemic agents tested significantly affected the IMA flow (dobutamine, 83.8 versus 85.0 mL/min; dopexamine, 101.8 versus 91.4 mL/min; amrinone, 75.4 versus 79 mL/min; normal saline solution, 85.8 versus 84.6 mL/min).

Conclusions. Resection of the distal segment of the IMA and the use of intravenous nitroglycerin optimizes the flow in IMA grafts.     

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.     

Intraoperative and laboratory evaluation of skeletonized versus pedicled internal thoracic artery

Background. The skeletonization of internal thoracic artery is postulated to improve graft length, early blood flow, sternal blood supply, and postoperative respiratory function. Concern exists that skeletonization may injure internal thoracic artery, precluding good results of surgery. Reports on endothelial function of skeletonized internal thoracic artery are lacking.

Methods. A prospective assessment of early clinical outcomes of 357 consecutive patients undergoing coronary artery bypass grafting was performed: 287 patients with nonskeletonized and 70 with skeletonized left internal thoracic artery (LITA). The lengths of LITA and of its discarded distal segment, as well as free LITA blood flow, were measured. The dose-effect relationship for relaxation to acetylcholine was studied in the organ bath.

Results. Apart from a higher incidence of breaching the pleura with nonskeletonized LITA the clinical outcomes were comparable. The length of skeletonized LITA was 17.8 ± 1.14 cm versus 20.3 ± 0.52 cm skeletonized (p = 0.11). The length of discarded LITA was shorter in nonskeletonized artery (0.8 ± 0.28 cm versus 2.6 ± 0.49 cm; p = 0.022). The free LITA blood flow was 66.3 ± 7.42 mL/min in nonskeletonized vessel versus 100.3 ± 14.84 mL/min in skeletonized (p = 0.048). The acetylcholine-induced relaxation was similar in both groups (maximal relaxation, 80.7% ± 5.95% in nonskeletonized versus 72.9% ± 9.11% in skeletonized; not significant; negative logarithm of half-maximal effect, 7.43 ± 0.18 versus 7.1 ± 0.10, respectively; p = 0.063).

Conclusions. Skeletonization does not damage the endothelial function of the LITA. Higher free blood flow and available LITA length should encourage the use of skeletonized LITA in clinical practice.     

PET Scan Predicts Recovery of Left Ventricular Function After Coronary Artery Bypass Operation

Background. Viable but hypocontractile myocardium can show functional improvement after revascularization (hibernation). It is sometimes difficult, however, to predict viability and recovery in patients with severe left ventricular function. This study sought to identify possible predictive factors of recovery of cardiac function after revascularization in patients with three-vessel disease.

Methods. Positron emission tomography (fluoro-18-deoxyglucose uptake for metabolism; nitrogen 13–labeled ammonia for flow) and equilibrium-gated nuclear angiography (for the global ejection fraction) were performed in 59 patients with three-vessel disease before and after undergoing coronary artery bypass grafting. The positron emission tomographic data were expressed as match normal (flow and metabolism normal), mismatch (low flow, high metabolism), match viable (moderate decrease in flow and metabolism), and match necrosis (low flow and metabolism).

Results. Stepwise logistic regression analysis showed that only mismatch regions played a significant role in predicting postoperative improvement in function (p = 0.019). There were 1.7 ± 1.5 mismatch regions in 31 patients who showed an improvement in their ejection fraction (0.47 ± 0.14 versus 0.58 ± 0.11; mean ± standard deviation) versus 0.8 ± 1.0 mismatch regions (p = 0.017) in patients who did not show recovery. There was more pronounced functional improvement with increasing numbers of mismatch regions, and patients with at least one mismatch region had a high likelihood of recovery (p < 0.001). In patients with a very low preoperative ejection fraction and two or more mismatch regions, there was early significant recovery (0.27 ± 0.08 versus 0.46 ± 0.06; p = 0.009).

Conclusions. At least one mismatch region must be present for there to be a postoperative functional benefit. When a low left ventricular ejection fraction is associated with mismatch, early recovery is substantial.     

Intraaortic Balloon Counterpulsation Improves Right Ventricular Failure Resulting From Pressure Overload

Background. Right ventricular (RV) dysfunction is common after heart transplantation, and myocardial ischemia is considered to be a significant contributor. We studied whether intraaortic balloon counterpulsation would improve cardiac function using a model of acute RV pressure overload.

Methods. In 10 anesthetized sheep, RV failure was induced using a pulmonary artery constrictor. Baseline measurements included mean systemic blood pressure, RV peak systolic pressure, cardiac index, and RV ejection fraction. Myocardial and organ perfusion were measured using radioactive microspheres.

Results. After pulmonary artery constriction, there was an increase in RV peak systolic pressure (32 ± 2 to 60 ± 3 mm Hg; p < 0.01) and a decrease in mean systemic blood pressure (68 ± 4 to 49 ± 2 mm Hg; p < 0.01), RV ejection fraction (0.51 ± 0.04 to 0.16 ± 0.02; p < 0.01), and cardiac index (2.48 ± 0.04 to 1.02 ± 0.11; p < 0.01). Blood flow to the RV did not change significantly, but there was a significant reduction in blood flow to the left ventricle. The initiation of intraaortic balloon counterpulsation (1:1) using a 40-mL intraaortic balloon inserted through the left femoral artery resulted in an increase in mean systemic blood pressure (49 ± 2 to 61 ± 3 mm Hg; p < 0.01), cardiac index (1.02 ± 0.11 to 1.45 ± 0.14; p < 0.05), RV ejection fraction (0.16 ± 0.02 to 0.23 ± 0.02; p < 0.01), and blood flow to the left ventricle.

Conclusions. In a model of right heart failure, the institution of intraaortic balloon counterpulsation caused a significant improvement in cardiac function. Although RV ischemia was not demonstrated, the augmentation of left coronary artery blood flow by intraaortic balloon counterpulsation and subsequent improvement in left ventricular function suggest that left ventricular ischemia contributes to RV dysfunction, presumably through a ventricular interdependence mechanism. Therefore, study of the safety and efficacy of intraaortic balloon counterpulsation in the management of patients with acute right heart dysfunction is warranted.     

体外循环与非体外循环冠状动脉旁路移植术患者桥血流的对比研究

目的比较非体外循环和体外循环下冠状动脉旁路移植术(CABG)的左乳内动脉(LIMA)和大隐静脉(SV)桥血流的变化。方法将547例行CABG患者分为非体外循(OPCAB)组(403例)和体外循环(CCABG)组(144例)。常规用LIMA与左前降支(LAD)吻合,其余靶血管使用SV吻合。于全部吻合口吻合完毕血流动力学稳定情况下,用即时血流测量仪(TTFM)直接测量并记录桥血流各项参数。结果搏动指数(PI值)、无效血流率及舒张期峰流量,LIMA桥OPCAB组分别为2.7±1.8,(2.2±4.3)%,(46.8±2.7)m l/m in,CCABG组分别为2.8±2.0,(3.4±3.1)%,(52.8±3.7)m l/m in;SV桥,OPCAB组分别为2.8±0.1,(1.8±0.3)%,(85.8±3.2)m l/m in,CCABG组分别为2.6±0.2,(1.3±0.2)%,(93.9±5.6)m l/m in,两组比较差异均无统计学意义(P均>0.05);平均流量及收缩期峰流量,CCABG组[SV桥(62.9±3.9)与(106.9±7.3)m l/m in,LIMA桥(32.5±23.5)与(41.6±4.4)m l/m in]均大于OPCAB组[SV桥(47.2±1.7)与(58.0±2.7)m l/m in,LIMA桥(26.5±19.9)与(27.0±1.6)m l/m in],差异有统计学意义(t=6.61,6.77,5.16,5.96,P均<0.01);CCABG组血管阻力LIMA桥与SV桥分别为(3.6±0.3)与(1.6±0.2)mm Hg.m l-1.m in-1,小于OPCAB组的(4.7±0.2)与(2.7±0.1)mm Hg.m l-1.m in-1,两者比较差异有统计学意义(t=4.32,P均<0.01)。结论CCABG组与OPCAB组对比,桥血管的通畅率无显著性差别。     

Long-term results of bilateral internal thoracic artery grafting

Background. Little is known about the long-term results of the uniform group of patients who had bilateral internal thoracic artery (ITA) grafting with the method of left ITA-to-left anterior descending coronary artery and right ITA-to-circumflex artery.

Methods. Late follow-up study was performed in the first consecutive 203 patients (mean age, 62.6 ± 9.1 years) who underwent isolated coronary artery bypass grafting with the left ITA anastomosed to the left anterior descending coronary artery and the right ITA to major branches of the circumflex artery. The patients were grouped according to the patency of ITA grafts demonstrated by early postoperative angiography (Both patent (BP) group, 168 patients: both ITAs showed complete patency; Not patent (NP) group, 23 patients: at least one ITA was dysfunctional).

Results. Actuarial 7-year survival in all patients was 89.3% ± 3.1%. The cumulative probability of event-free survival for cardiac death, myocardial infarction, intervention, and angina at 7 years was 96.6% ± 1.8%, 98.0% ± 1.5%, 86.7% ± 3.2%, and 90.7% ± 2.9%, respectively. NP group had more myocardial infarction and angina than the BP group, but was not statistically significant. Because of failed grafts at the early angiography, intervention was performed more frequently in NP group (p < 0.01).

Conclusions. Our results of actuarial 7-year survival and the cumulative probability of event-free survival were at least comparable to the results of other similar studies using bilateral ITA. The freedom from angina appeared to be better than in the previous study. Overall our study supports the continued use of this method of ITA grafting.     

Postoperative Changes in Duplex Ultrasound Velocity Characteristics in the Nonmobilized Right Internal Mammary Artery in Patients with Left Internal Mammary Artery Bypass Grafting

The internal mammary artery (IMA) is the conduit of choice in coronary revascularization because of its long-term patency. We analyzed the effect of left internal mammary artery (LIMA) harvesting on sternal perfusion. Diameters and velocity parameters of the nonmobilized right internal mammary artery (RIMA) were noninvasively analyzed with duplex ultrasound in 41 patients with LIMA myocardial revascularization pre- (2.6 ± 5 days) and postoperatively (4.9 ± 3.9 months). Data of 41 patients were analyzed; 38 patients underwent all examinations with adequate supraclavicular signals. The proximal RIMA diameter and all velocity parameters increased significantly at follow-up (3.1 ± 0.6 vs. 3.2 ± 0.5 mm, p = 0.03; diastolic peak velocity [DPV] 15 ± 7 vs. 27 ± 9 cm/sec, p < 0.0001; systolic peak velocity [SPV] 90 ± 24 vs. 105 ± 29 cm/sec, p < 0.02). This was more pronounced for the diastolic parameters and for all parameters in the proximal part of the RIMA than in the distal part (DPV 11.9 ± 10.1 vs. 9.5 ± 10.2 cm/sec, p = NS; SPV 14.9 ± 33.9 vs. 7.4 ± 26.0 cm/sec, p = NS). With longer time intervals of follow-up the increase in all diastolic velocity parameters became less pronounced. As demonstrated in the RIMA velocity parameters, patients with skeletonized LIMA grafts (n = 4) had significantly more flow, suggesting hyperemic flow, than patients with pedicled LIMA grafts (n = 34). Only in diastolic velocity integral (DVI) and systolic/diastolic velocity ratio (SDVRA) were there significant differences between diabetics (n = 9) and nondiabetics (n = 29) and only in DVI between female, (n = 8) and male (n = 30) patients. This study indicates that duplex ultrasound is a useful tool for noninvasive RIMA follow-up in LIMA myocardial revascularization.Presented at the Twenty-fifth World Congress of the International Society for Cardiovascular Surgery, Cancun, Mexico, September 9-13, 2001.     

Risk Factors and Solutions for the Development of Neurobehavioral Changes After Coronary Artery Bypass Grafting

Background. As operative mortality for coronary artery bypass grafting has decreased, greater attention has focused on neurobehavioral complications of coronary artery bypass grafting and cardiopulmonary bypass.

Methods. To assess risk factors and to evaluate changes in surgical technique, between 1991 and 1994 we evaluated 395 patients undergoing coronary artery bypass grafting with an 11-part neurobehavioral battery administered preoperatively and at 1 and 6 weeks postoperatively. Patients were instrumented with 5-MHz focused continuous-wave carotid Doppler transducers intraoperatively to estimate cerebral microembolism as an instantaneous perturbation of the velocity signal. Microembolism data were quantitated and compared with surgical technical maneuvers during operation and with neurobehavioral deficit (≥20% decline from preoperative performance on two or more neurobehavioral tests) postoperatively. These data and patient demographics were statistically analyzed (χ², t test) and the results at 2 years (1991 and 1992; group A) were used to influence surgical technique in 1993 and 1994 (group B).

Results. Significantly associated with new neurobehavioral deficits were increasing patient age (p < 0.05), more than 100 emboli per case (p < 0.04), and palpable aortic plaque (p < 0.02). Group B patients had a significant decline in the neurobehavioral event rate (group A, 69%, ; versus group B, 60%, ; p < 0.05) of postoperative neurobehavioral deficits at 1 week and at 1 month (group A, 29%, ; versus group B, 18%, ; p < 0.01). The stroke rate was less than 2% in both groups (p = not significant). Modifications of surgical technique used in group B patients included increased use of single cross-clamp technique, increased venting of the left ventricle, and application of transesophageal and epiaortic ultrasound scanning to locate and avoid trauma to aortic atherosclerotic plaques.

Conclusions. Neurobehavioral changes after coronary artery bypass grafting are common and associated with cerebral microembolization. Surgical technical maneuvers designed to reduce emboli production may improve neurobehavioral outcome.     

Different behavior of sequential versus single left internal mammary artery to left anterior descending area grafts(1)

To study echo Doppler characteristics of sequential versus single left internal mammary artery (LIMA) to left anterior descending (LAD) area grafts transthoracic echo Doppler at the LIMA origin and angiography were performed pre- and postoperatively.In 17 patients single LIMA to LAD (group I) and in 45 patients sequential LIMA to LAD area (group II) bypass grafting was performed. All patients show an early postoperative shift towards diastolic coronary Doppler velocity spectra. Only group II shows a further significant late increase in diastolic, velocity time integral and some systolic echo Doppler parameters at rest. Diastolic peak and diastolic as well as total mean and velocity time integral maximal values are significantly higher in group II in late postoperative hyperemic response. Preoperative and late control angiography showed no significant differences in overall grading of native LAD stenosis between both groups. The large coronary reserve in LIMA sequential grafts may contribute to an improved long-term patency.     

Reversibility of Cardiac Dysfunction After Valve Replacement in Elderly Patients With Severe Aortic Stenosis

Background. The role of aortic valve replacement for aortic stenosis has not been fully defined in terms of the postoperative reversibility of cardiac dysfunction and pulmonary hypertension in elderly patients.

Methods. Cardiac function, assessed by radioisotope ventriculography and catheterization data, was evaluated before and after operation, and their results were compared between preoperative and postoperative data in each group of younger patients (<69 years, group I, n = 29) and elderly patients (≥70 years, group II, n = 21).

Results. One month postoperatively the peak ejection rate determined by radioisotope ventriculography improved significantly in comparison with the preoperative value in elderly patients (preoperatively, 228 ± 38 versus postoperatively, 319 ± 116% end-diastolic volume per second, p < 0.05), although their preoperative peak ejection rate was severely depressed. The postoperative peak filling rate of the elderly group was not completely reversible to almost normal value, whereas that of the younger group was completely reversible. Early diastolic peak filling rate (one-third peak filling rate) was not reversible in both two groups. Pulmonary hypertension in the elderly patients was reversible to postoperative almost normal pulmonary artery pressure despite the severity of aortic stenosis (systolic pulmonary artery pressure preoperatively, 37 ± 16 mm Hg versus postoperatively, 25 ± 5 mm Hg, p < 0.02; diastolic pulmonary artery pressure preoperatively, 15 ± 6 mm Hg versus postoperatively, 10 ± 4 mm Hg, p < 0.05).

Conclusions. Both cardiac dysfunction, reflected by reduction of peak ejection rate, and pulmonary hypertension in elderly patients with severe aortic stenosis were reversed, reaching almost normal values 1 month after operation.     

Leukocyte Depletion of Blood Cardioplegia Attenuates Reperfusion Injury

Background. Leukocytes are associated with myocardial injury during reperfusion after ischemia. Short periods of leukocyte depletion during reperfusion result in persistent attenuation of postischemic myocardial dysfunction.

Methods. Leukocyte depletion was examined in a canine model of regional myocardial ischemia and reperfusion. The extracorporeal circuit and cardioplegia circuits underwent leukocyte depletion by mechanical filtration. Animals were instrumented for baseline global function before 90-minute occlusion of the left anterior descending coronary artery. Global function during ischemia and at 5, 30, 60, and 90 minutes after a 60-minute cardioplegic arrest using continuous blood cardioplegia was assessed in leukocyte-depleted (n = 9) and control (n = 10) groups.

Results. No significant difference between groups was seen for systemic leukocyte counts, global function, or water content. Endothelial function was significantly protected as assessed by response to both calcium ionophore (endothelial-dependent, receptor-independent relaxation: leukocyte-depleted, 72% ± 19% of endothelin-induced constriction versus control, 46% ± 14%; p < 0.05) and acetylcholine (endothelial-dependent, receptor-dependent relaxation: leukocyte-depleted, 83% ± 11% versus control, 44% ± 15%; p < 0.05).

Conclusions. Leukocyte-mediated endothelial reperfusion injury can be attenuated by leukocyte depletion during reperfusion.     

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

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

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

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

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

Cardiopulmonary bypass affects cognitive brain function after coronary artery bypass grafting

Background. The causes for cognitive impairment after coronary artery bypass grafting (CABG) have long been a topic for debate.

Methods. We prospectively followed 308 consecutive, unselected survivors of CABG at our institution. In addition to determination of clinical measurements, cognitive brain function was measured objectively by P300 auditory-evoked potentials before CABG, at 7-day and at 4-month follow-up. Standard psychometric tests (Trail Making Test A, Mini Mental State Examination) were also performed.

Results. At 7-day follow-up cognitive P300 auditory-evoked potentials were significantly impaired compared with preoperative levels (peak latencies: 376 ± 40 ms versus 366 ± 37 ms, p = 0.0001). P300 measurements were almost normalized at 4-month follow-up (peak latencies: 369 ± 33 ms, p = NS versus preoperative). Standard psychometric tests failed to detect this subclinical cognitive impairment. Multiple regression analysis revealed that use of cardiopulmonary bypass was the only independent predictor of impaired cognitive brain function at 7-day (p < 0.0001) and 4-month follow-up (p = 0.0008). The presence of diabetes mellitus (p = 0.0135) or concomitant repair of significant carotid artery stenosis (p = 0.0049) was predictive of late improvement of cognitive brain function at 4-month follow-up.

Conclusions. Objective cognitive P300 auditory-evoked potential measurements demonstrate that the use of cardiopulmonary bypass is the only predictor of short- and long-term cognitive brain dysfunction after CABG. Interestingly, the presence of diabetes mellitus and concomitant repair of a significant carotid artery stenosis were predictive for long-term cognitive benefit.     

Improved clinical outcomes in patients undergoing coronary artery bypass grafting with coronary endarterectomy

Background. Coronary artery bypass grafting (CABG) with coronary endarterectomy (CE) has been associated with increased morbidity and mortality. We sought to evaluate the impact of recent advances in operative and perioperative management on outcomes after CE.

Methods. One hundred fifty-one consecutive patients undergoing first-time CABG with CE between 1991 and 1997 were compared with a concurrent group of 757 patients undergoing CABG without CE (Control).

Results. Age, gender, left ventricular ejection fraction, percent nonelective were similar in both groups. Compared with control, the CE group had a higher incidence of hypertension (80% versus 71%, p = 0.02), diabetes (42% versus 32%, p = 0.01), prior myocardial infarction (MI) (68% versus 59%, p = 0.05), peripheral vascular disease (36% versus 16%, p < 0.001), renal failure (15% versus 4%, p < 0.001), and three-vessel coronary disease (81% versus 70%, p = 0.007), resulting in higher Society of Thoracic Surgeons database predicted mortality (4.9 ± 5.9% versus 3.9 ± 4.6%, p = 0.05). Despite the higher risk profile of the CE group, hospital mortality (CE 2.0%, Control 1.2%) and the incidence of major complications such as cerebrovascular accident (CVA) (0.7% versus 1.5%), major respiratory complications (8% versus 5%), and postoperative MI (3% versus 1.4%) were similar between the groups (all p = NS). In a multiple logistic regression analysis, prolonged cardiopulmonary bypass time was an independent predictor of postoperative MI (odds ratio 1.2, CI 1.05 to 1.39, p < 0.01) and the use of heparin-bonded cardiopulmonary bypass circuits of reduced MI rate (odds ratio 0.25, CI 0.08 to 0.76, p < 0.01). Mean follow-up for 94% of patients was 30 ± 19 months (range 1 to 83 months). Five-year survival after CE was 70 ± 5%, with 96% of patients in Canadian Cardiovascular Society class I/II.

Conclusions. In a contemporary series of carefully selected patients, mortality and major complications after CE are now similar to CABG without CE. CE itself is not an independent predictor of postoperative MI. Functional class of hospital survivors is excellent.     

Ischemic preconditioning reduces neutrophil accumulation and myocardial apoptosis

Background. This study tested the hypothesis that ischemic preconditioning (IP) inhibits myocardial apoptosis after a short period of ischemia and reperfusion.

Methods. In 9 anesthetized dogs, the left anterior descending (LAD) coronary artery was occluded for 30 min and reperfused for 3 h (control), while in 9 others, LAD occlusion was preceded by 5 min of occlusion and 5 min of reperfusion (IP). DNA from frozen myocardial tissue samples was extracted, and apoptosis were identified as “ladders” by agarose gel electrophoresis or confirmed histologically using the terminal transferase UTP nick end-labeling (TUNEL) assay. Neutrophil accumulation was detected by measuring cardiac myeloperoxidase activity.

Results. Thirty minutes of LAD occlusion caused a significant decrease in blood flow (colored microspheres), which was comparable between groups. In the control group, DNA ladders occurred in the area at risk (AAR) in six out nine experiments. In contrast, DNA laddering in the AAR was not observed in any of the IP group. AAR in the control group showed a greater percentage of apoptotic cells than IP (6.7 ± 0.9% vs 1.2 ± 0.2%; p < 0.01). Cardiac myeloperoxidase activity (U/g tissue) was significantly reduced from 0.07 ± 0.004 in control to 0.04 ± 0.01 in IP group (p < 0.05).

Conclusions. We conclude that ischemic preconditioning attenuates apoptosis and neutrophil accumulation in the AAR in a model of nonlethal acute ischemia and reperfusion.     

Release of S100B during coronary artery bypass grafting is reduced by off-pump surgery

Background. S100B, a plasma marker of brain injury, was compared after coronary artery bypass grafting with and without cardiopulmonary bypass (CPB).

Methods. Fourteen patients with off-pump operations and 18 patients with CPB were compared. Seven patients in the off-pump group underwent a minithoracotomy and received only an arterial graft, whereas 7 patients underwent sternotomy and received both an arterial and one or two vein grafts. S100B was measured in arterial plasma using an immunoassay with enhanced sensitivity.

Results. S100B before the operation was 0.03 μg/L. At wound closure, S100B in patients of the off-pump and CPB groups reached a maximum level of 0.22 ± 0.07 and 2.4 ± 1.5 μg/L, respectively (p < 0.001). No strokes occurred. Patients without CPB receiving arterial and vein grafts released slightly more S100B (p < 0.05) than patients with only arterial grafting. In patients undergoing CPB, S100B increased slightly before aortic cannulation (p < 0.001), to the same level as the maximum reached for the non-CPB group.

Conclusions. Coronary artery bypass grafting with CPB caused a 10-fold greater increase in S100B than off-pump grafting. S100B release after off-pump sternotomy with vein grafting was slightly greater than in arterial grafting through a minithoracotomy.     

Port-Access Bilateral Internal Mammary Artery Grafting for Left Main Coronary Artery Disease: Canine Feasibility Study

A bstract Background : To extend the applications of minimal access cardiac surgery, an endovascular cardiopulmonary bypass (CPB) system that allows cardioplegia delivery and cardiac venting was used to perform bilateral internal mammary artery (IMA) bypass grafting in six dogs. Methods : The left IMA (LIMA) was taken down thoracoscopically from three left lateral chest ports, followed by the right IMA (RIMA) from the right side. One left-sided port was extended medially 5 cm with or without rib resection, to expose the pericardium. Both IMAs were divided and exteriorized through the left anterior mediastinotomy. Flow and pedicle length were satisfactory in all cases. Femoral-femoral bypass was used and the heart arrested with antegrade delivery of cardioplegic solution via the central lumen of a balloon catheter inflated to occlude the ascending aorta. All anastomoses were made through the mediastinotomy under direct vision. In five studies the RIMA was attached to the left anterior descending artery (LAD) and the LIMA to the circumflex, and in one study the RIMA was tunneled through the transverse sinus to the circumflex and the LIMA was anastomosed to the LAD. All animals were weaned from CPB in sinus rhythm without inotropes. CPB duration was 108 ± 27 minutes (mean ± SD) and the clamp duration was 54 ± 10 minutes. Results : Preoperative and postoperative cardiac outputs were 2.9 ± 0.71/min and 2.4 ± 0.31/min, respectively (p = NS), and corresponding pulmonary artery occlusion pressures were 6 ± 3 mmHg and 7 ± 2 mmHg, respectively (p = NS). All 12 grafts were demonstrated to be fully patent. Postmortem examination revealed well aligned pedicles and correctly grafted target vessels. Conclusion : This canine model demonstrates the potential for a less invasive approach to the surgical management of left main coronary artery disease in humans.     

Effect of Low-Dose Positive Inotropic Drugs on Human Internal Mammary Artery Flow

Background. Dobutamine (a β-receptor agonist), enoximone (a type III selective phosphodiesterase inhibitor), and epinephrine (an - and β-mimetic) frequently are used in the perioperative management of patients undergoing coronary artery bypass grafting.

Methods. We performed a double-blind clinical study to compare the effects on internal mammary artery free flow of low doses of these three positive inotropic drugs. Thirty patients in whom the left internal mammary artery was used for coronary artery bypass grafting were randomized into three groups. Internal mammary artery free flow and hemodynamic measurements were evaluated before and 10 minutes after the intravenous infusion of dobutamine (3 μg · kg⁻¹ · min⁻¹), enoximone (200 μg/kg), or epinephrine (0.05 μg · kg⁻¹ · min⁻¹).

Results. A significant increase in free flow occurred only in the dobutamine group (33 ± 7.5 and 42.2 ± 7.9 mL/min before and after drug infusion, respectively; p = 0.013). Comparison of the increase in flow between the groups, however, showed no difference. These drugs, at doses designed to produce a positive inotropic effect, caused little increase in the free flow of the internal mammary artery.

Conclusions. The use of dobutamine, enoximone, and epinephrine as low-dose positive inotropic treatments in the perioperative and postoperative periods of coronary artery bypass grafting should depend on their positive inotropic effects rather than their vasodilative effects on the arterial grafts.