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.     

Coronary artery bypass grafting on the beating heart evaluated with integrated backscatter

BACKGROUND: In beating heart coronary artery bypass grafting (CABG) the effect of ischemic insult during coronary occlusion could not be evaluated immediately. Using transesophageal echocardiography, myocardial performance can be evaluated with analysis of integrated backscatter. METHODS: In 15 beating heart CABGs, cyclic variation (CV) of integrated backscatter of the anterior wall before, during, and after the left internal thoracic artery to left anterior descending (LAD) branch anastomosis was measured with transesophageal echocardiography. The patients were divided into two groups according to collateral vessels status (good collateral group n = 6, poor collateral group n = 9). RESULTS: In all patients, CV increased significantly after revascularization (8.56+/-2.50 to 11.47+/-3.32 dB, p < 0.0001). During LAD occlusion, significant decrease in CV was found in patients who had poor collateral arteries. At 15 minutes of LAD occlusion, CV decreased from the preocclusion value of 7.51+/-2.21 to 3.23+/-4.03 dB (p < 0.01). CONCLUSIONS: Measurement of CV can detect the ischemic insult during coronary occlusion and the effect of revascularization in beating heart CABG.     

Echocardiographic analysis of dysfunctional and normal myocardial segments before and immediately after coronary artery bypass graft surgery.

Echocardiography has revealed evidence of "subnormal" regional contraction patterns that result from myocardial ischemia and are often accompanied by nonadjacent "hyperkinetic" regions. Whether these regions of hyperkinetic wall motion persist unchanged or revert to normal after coronary artery bypass graft (CABG) surgery has not been studied in humans. Using echocardiography, we evaluated both dysfunctional and normal myocardial regions for changes in segmental wall motion and percent of systolic wall thickening that occurred immediately after CABG surgery in 32 patients. Segmental wall motion analysis before CABG surgery in these patients revealed that 170 (66%) of 256 myocardial segments were subnormal, of which 115 (67%) improved and 102 (60%) returned to normal immediately after CABG surgery. Eleven myocardial segments that were hyperkinetic before CABG surgery returned to normal after CABG surgery. Preoperatively, 162 (63%) of 256 myocardial segments had systolic wall thickening less than 30%, which increased from 11.8% +/- 8.9% to 24.3% +/- 14.3% (mean +/- SD) (P less than 0.01) postoperatively. Conversely, a reverse trend was found when systolic wall thickening was greater than 30% before CABG surgery: thickening decreased from 46.2% +/- 13.8% to 33.4% +/- 14.8% after CABG surgery (P less than 0.01). Thus, we conclude that immediately after CABG surgery, there is a recovery of function in some myocardial segments and a reduction in function in others. Furthermore, we conclude that the semiquantitative assessment of percent of systolic wall thickening is a more reliable (consistent) echocardiographic index of myocardial function compared with the qualitative assessment of segmental wall motion immediately after CABG surgery.     

Quantitative assessment of myocardial viability following coronary artery bypass grafting using exercise thallium-201 myocardial single photon emission computed tomography and left ventricular regional wall motion

Using exercise thallium-201 myocardial single photon emission computed tomography (SPECT) and % radial shortening (%RS), 58 patients were evaluated before and after coronary artery bypass grafting (CABG) to quantitatively assess myocardial viability and the effect of CABG. The patient was classified, according to redistribution pattern, as group I with only complete redistribution (20 cases) and group II with including incomplete redistribution (22 cases) and group III with no redistribution (16 cases). 1. Group I was expected complete improvement of ischemic myocardium after CABG but regional left ventricular wall motion was unchanged (sigma i%RS: 142.5 +/- 54.7----138.4 +/- 39.6, sigma a%RS: 201.2 +/- 51.1----238.2 +/- 68.2). 2. Group II was expected to diminish ischemic size after CABG and left ventricular regional wall motion was significantly improved (sigma i%RS: 68.8 +/- 25.9----154.9 +/- 42.6 p less than 0.01, sigma a%RS: 108.4 +/- 62.3----178.9 +/- 77.6, p less than 0.05). 3. Group III was no significant change of ischemic size and left ventricular wall motion after CABG (sigma i%RS: 67.8 +/- 24.1----83.9 +/- 19.2, sigma a%RS: 86.0 +/- 29.0----94.0 +/- 33.9). The present study suggests that quantitative assessment of myocardial viability using exercise thallium-201 myocardial SPECT and %radial shortening was useful method to determine the indication and to assess the effect of CABG.     

Wide sternal retraction may impede internal mammary artery graft flow and reduce myocardial function during off-pump coronary artery bypass grafting: presentation of two cases

The internal mammary artery (IMA) is routinely used for grafting of the left anterior descending coronary artery (LAD), providing good flow to the anterior left ventricle (LV) wall. Impeded IMA-to-LAD flow may result in myocardial ischaemia and haemodynamic deterioration. From a study population, we describe two incidents where myocardial ischaemia was observed during off-pump coronary artery bypass surgery (CABG), with a confirmed reduction in the IMA-to-LAD flow in one patient. In patient no. 1, normal IMA flow was assessed by transit-time flow measurement after a complete IMA-to-LAD anastomosis. The anterior LV wall thickening was monitored continuously by epicardial ultrasonic transducers. Normal wall thickening was confirmed after IMA grafting. During a wide sternal opening for circumflex grafting the anterior wall motion displayed an ischaemic pattern, with reduced systolic and increased post-systolic wall thickening. IMA flow was reduced simultaneously. When easing the sternal opening, IMA flow normalized, as did the motion pattern in the anterior LV wall. In patient no. 2, similar changes in wall thickening occurred during a wide sternal opening after IMA-to-LAD grafting. When easing the retractor, the wall thickening normalized. It is important for the surgeon to be aware of this possible cause of myocardial ischaemia, with a risk of subsequent haemodynamic deterioration. This may not only be of great importance during off-pump CABG, but can also be significant for successful weaning from the cardiopulmonary bypass machine.     

Prolonged ischemic heart disease and coronary artery bypass - relation to contractile reserve.

OBJECTIVE: A major effect of coronary artery bypass grafting (CABG) in patients with ischemic heart disease and impaired left ventricular (LV) contractile function is believed to be an improvement in LV function due to recovery of dysfunctional, but viable myocardium. However, recent studies have indicated a time limit for such a recovery. We therefore investigated the extent of viable myocardium in patients with impaired LV function due to ischemic heart disease after a prolonged strategy of medical treatment and its relation to changes in clinical variables after CABG. METHODS: Forty-five consecutive patients with a mean duration of ischemic heart symptoms of 9 years and LV ejection fraction (EF) <45% referred for CABG were included and LV extent of viable myocardium was measured preoperatively by glucose metabolism--blood flow positron emission tomography imaging and dobutamine stress echocardiography. Symptoms, exercise-capacity and LV function were evaluated before and 7 months after surgery in event-free survivors. RESULTS: LV extent of myocardial viability was <30% in most patients. In event-free survivors, LVEF decreased from 31+/-7 to 26+/-8% 7 months after CABG. The decrease in LVEF was correlated to the LV extent of myocardial metabolism--blood flow reverse mismatch. Most of the patients experienced an improvement in their angina pectoris, heart failure symptoms and exercise capacity after CABG; the overall 3-year survival was 77%. CONCLUSIONS: Patients with chronic ischemic heart disease and impairment of LV function, in whom an initial long-standing conservative treatment has been practiced, benefit from CABG, despite a lack of LV functional reserve.     

Ventricular function after coronary artery bypass grafting: evaluation by magnetic resonance imaging and myocardial strain analysis

OBJECTIVE: Magnetic resonance imaging with radiofrequency tissue tagging permits quantitative assessment of regional systolic myocardial strain. We sought to investigate the utility of this imaging modality to quantitatively determine preoperative impairment and postoperative improvement in ventricular function in patients with ischemic heart disease. METHODS: Magnetic resonance imaging with radiofrequency tissue tagging was performed on 6 patients (average age 60.2 +/- 13.7 years) with coronary artery disease and 32 control subjects with no known heart disease. Patients with coronary artery disease underwent imaging before and 3 months after coronary artery bypass grafting. The ventricle was divided into 6 segments within a midventricular plane. Regional 2-dimensional left ventricular circumferential strain was calculated from tagged magnetic resonance images throughout systole. Circumferential strain results were compared in patients before and after and 3 months after coronary artery bypass grafting and also in control subjects. RESULTS: Before the operation circumferential strain identified 100% (10/10) of all regional wall motion abnormalities seen by preoperative ventriculography. Postoperatively, improvements were demonstrated in 56% (20/36) of the regions, and these improvements agreed with viability testing by single-photon emission computed tomography when available. Additionally, preoperative global circumferential strain for the ischemic group was significantly depressed relative to that in control subjects (0.11 +/- 0.05 vs 0.20 +/- 0.03, P <.001). Global circumferential strain correlated with ejection fraction by ventriculography (r = 0.84, P <.01) and improved after coronary artery bypass grafting (0.14 +/- 0.05 vs 0.11 +/- 0.05, P <.01). CONCLUSIONS: Magnetic resonance imaging with radiofrequency tissue tagging permitted circumferential strain calculation. This technology quantitatively demonstrated improvements in left ventricular wall motion after coronary artery bypass grafting for both individual regions and the entire ventricle. This noninvasive method may prove useful in preoperative evaluation and postoperative serial assessment of left ventricular wall motion.     

Na(+)/H(+)-exchange inhibition and aprotinin administration: promising tools for myocardial protection during minimally invasive CABG.

OBJECTIVE: Minimally invasive coronary artery bypass grafting (CABG), carried out on the warm beating heart, does not allow conventional myocardial protection. The objective was to investigate the possibility of enhancing tolerance to ischemia during short episodes of coronary artery occlusion, based on a pharmacological approach using a selective Na(+)/H(+)-exchange inhibitor (cariporide) or a serine protease inhibitor (aprotinin). METHODS: Four groups (n=6 in each group) of sheep were subjected to 20 min of normothermic regional ischemia (first lateral branch of the circumflex artery occlusion) followed by 1 h of reperfusion. Regional wall thickening was measured using sonomicrometry, and expressed as the percentage of thickening fraction compared with baseline. Group I was the control with no treatment, group II received cariporide (1 mg/kg administered over 2 min prior to ischemia), group III was treated with aprotinin (2.10(6) kallikrein inactivation units (KIU) load followed by 500.000 KIU/h). Group IV was treated with a combination of cariporide and aprotinin at the same concentrations as in groups II and III, respectively. RESULTS: Wall thickening measurements showed that, compared with control, cariporide was largely able to suppress secondary loss of wall thickening after initial recovery during early reperfusion. Wall thickening in the ischemic/reperfused myocardial area improved from 10+/-31 to 51+/-17% at 1 h of reperfusion (P=0.002). Aprotinin improved wall thickening at the end of 1 h of reperfusion to 70+/-13% (P=0.0001). However, in this group, there was a transient loss of regional contractility similar in amplitude and time course to the one observed in the control group. A combination of cariporide and aprotinin suppressed transient contractile loss and resulted in improved wall thickening at the end of 1 h of reperfusion (65+/-22%, P=0.0002 vs. control). This value was not significantly different from the cariporide (P=0.263) or aprotinin (P=0.704) group. CONCLUSION: These data indicate that both Na(+)/H(+)-exchange inhibition and aprotinin administration are promising tools for cardioprotection during minimally invasive CABG. A combination of both treatments is able to adequately suppress loss of contractility during early reperfusion as a consequence of reperfusion injury, and results in significantly improved wall thickening at the end of 1 h of reperfusion.     

Cardiomyocyte apoptosis and ischemic preconditioning in open heart operations

BACKGROUND: The aim of the present study was to ascertain the percentage of left apical myocardial apoptosis in three-vessel coronary artery bypass grafting patients quantitatively and the impact of ischemic preconditioning. METHODS: Twenty-one patients with three-vessel disease who had elective coronary artery bypass grafting were randomized in a ratio of 2:1 to ischemic preconditioning (n = 14) or a control group (n = 7). The ischemic preconditioning protocol was established by two cycles of ascending aorta occlusion for 2 minutes followed by 3 minutes of reperfusion. Myocardial samples from the apex of the left ventricle were taken using a Tru-Cut needle before aortic cross-clamping and immediately after declamping. The percentage of apoptosis was analyzed by TUNEL methods. Data on hemodynamics and biochemical markers were collected. RESULTS: Low levels of myocardial apoptosis were found before the operation (0.01% +/- 0.00%). During the early reperfusion period, the percentage of myocardial apoptotic cells significantly increased (0.15% +/- 0.05%, p = 0.008). Ischemic preconditioning significantly improved cardiac index and right ventricular ejection fraction recovery after the operation (p = 0.036 and 0.001 respectively, repeated measure) but had no effect on myocardial apoptosis before and after the operation (0.01 +/- 0.00 versus 0.01 +/- 0.00, p = 0.658 and 0.12% +/- 0.04% versus 0.23% +/- 0.14%, p = 0.302). CONCLUSIONS: Cardioplegic myocardial ischemia during open heart operation was associated with induction of cardiomyocyte apoptosis in humans. Attenuation of postoperative cardiac dysfunction by ischemic preconditioning appeared to be independent of apoptosis.     

Effects of coronary artery bypass grafting for patients with totally occluded left anterior descending arteries]

Between April, 1987 and March, 1991, 21 patients with totally occluded left anterior descending arteries (TOLAD) underwent coronary artery bypass grafting (CABG) in our institute. All of them were diagnosed as angina pectoris and 15 (71%) of them have had episodes of myocardial infarction. Graftability of TOLAD was 90% (19/21) and two of the TOLADs were not suitable for CABG because severe atherosclerosis of these arteries were observed intraoperatively. There was no operative death. Short term (1-2 months) patency was 64% (7/11) for saphenous vein grafts (SVG) and 100% (8/8) for left internal thoracic artery grafts (LITA). Left ventricular wall motion assessed by left ventriculography showed impaired regional wall motion in 63% segments of the segment #2, #3 and #6 preoperatively. However, the regional wall with impaired motion decreased to 31% after CABG. Thallium-201 scintigraphy showed impaired perfusion in 62% segments of the left anterior wall, apex and interventricular septum preoperatively. However, the regional wall with impaired perfusion decreased to 42% after CABG. Exercises tolerance assessed by treadmill test was improved from 3.8 +/- 0.7 Mets preoperatively to 6.5 +/- 0.7 Mets with patent coronary bypass grafts. These data suggested that CABG can improve the wall motion of the regions perfused by TOLADs and the LIMA is more suitable than the SVG for CABG to TOLAD.     

Clinical study of serum S-100 beta protein as marker of brain injury in cardiovascular surgery

There is no simple and specific marker of brain injury in cardiovascular surgery. S-100 beta protein is a specific protein of the central nervous system. S-100 beta protein detected in spinal fluid and serum is a reflection of brain injury. The aim of this study was to investigate the influence of extracorporeal circulation (ECC) on the brain, with reference to serum S-100 beta protein level and operative factors. Twenty-two patients (12 undergoing coronary artery bypass grafting (CABG), 2 mitral valve replacement, 2 left ventricular aneurysmectomy, 2 grafting of descending thoracic aneurysm, 1 aortic valve replacement (AVR), 1 CABG with AVR, 1 closure of atrial septal defect, 1 aorto-bifemoral and left subclavian artery bypass grafting) without symptomatic neurological complications underwent cardiovascular surgery using ECC. Serum S-100 beta level was measured by enzyme-linked immunosorbent assay before ECC and half an hour after the end of ECC in cardiovascular surgery. Carotid lesions, calcification of the ascending aorta, history of cerebral infarction, and pulsatile or nonpulsatile flow during ECC were evaluated as the operative factors. The correlation of S-100 beta level after ECC with age, duration of ECC and aortic cross clamp time was examined. Serum S-100 beta level was significantly increased after ECC (0.25 +/- 0.48 microgram/l vs. 0.99 +/- 0.64 microgram/l; p < 0.01). Calcification of the ascending aorta was the only significant operative factor that increased S-100 beta level after ECC (calcification 1.35 +/- 0.71 vs. non-calcification 0.68 +/- 0.37 p < 0.01). S-100 beta level after ECC was related to aortic cross clamp time (r = 0.54; p < 0.05, n = 20). It is suggested that brain injury, as reflected by serum S-100 beta protein, is more frequent in cases with calcification of the ascending aorta or a long aortic cross clamp time. It was concluded that serum S-100 beta is a simple potential marker of cerebral injury in cardiovascular surgery with ECC.     

Assessment of coronary artery bypass surgery by exercise thallium imaging.

The purpose of this study was to assess the coronary artery bypass grafting (CABG) in exercise thallium-201 scintigraphy. The study was performed on 18 consecutive patients undergoing elective surgery. We compared the results of the scintigraphic examinations, 1 week before and 1 month postoperatively. Of the 47 bypass grafts, 20 (42. 6%) grafts contributed to the improvement of the ischemic areas and 38% of the bypass grafts did not change the scintigraphic patterns after surgery. Some bypass grafts had been performed on the stenotic arteries that dominated the areas which preoperatively showed normal exercise scintigraphic patterns yet were considered to worsen in the near future. Such grafts main contribution may be to protect and to increase the overall myocardial washout ratio for prevention of an enlargement of ischemic areas.     

Quantitative gated myocardial perfusion single photon emission computed tomography improves the prediction of regional functional recovery in akinetic areas after coronary bypass surgery: useful tool for evaluation of myocardial viability

Objective

Assessment of myocardial viability in akinetic areas is essential in surgery for ischemic heart disease, including coronary artery bypass grafting and left ventriculoplasty. The aim of this study is to evaluate the utility of quantitative indices of perfusion uptake, wall motion, and wall thickening of each region calculated by quantitative electrocardiogram-gated single photon emission computed tomography (SPECT) for prediction of functional recovery after coronary artery bypass grafting.

Methods

Forty patients scheduled for coronary artery bypass grafting were prospectively included. Electrocardiogram-gated SPECT was performed before and 1 week and 3 months after operation, and coronary angiography was performed before and after operation. The myocardium was divided into 9 segments and myocardial viability, assessed by improvement of the wall motion score using a cine mode display, and evaluated by radionuclide criteria (perfusion uptake, wall motion, wall thickening). Twenty-four segments with moderate hypokinesis and 14 segments with akinesis with patent grafts were assessed.

Results

All segments with moderate hypokinesis except 1 (96%) had improved wall motion scores postoperatively, whereas of 14 segments with akinesis only 7 segments (50%) had improved wall motion scores. The preoperative perfusion uptake in the improved segments was significantly higher than in the nonimproved segments (62.7% ± 15.6% vs 46.4% ± 24.5%, P = .01). There was a significant difference in wall motion between the improved and nonimproved segments (3.8 ± 2.2 mm vs 1.4 ± 1.4 mm, P = .001), and the preoperative wall thickening of the improved segments was significantly higher than in the nonimproved segments (27.2% ± 14.1% vs 8.2% ± 10.3%, P < .0001). The optimal cutoff level of perfusion uptake was 50%, with the highest accuracy of 72%, and the optimal cutoff levels of wall thickening and wall motion were 10% and 1.5 mm, with the highest accuracies of 76% and 85%, respectively.

Conclusion

The regional functional index calculated by electrocardiogram-gated SPECT indicated that wall thickening was well correlated with functional recovery compared with wall motion or perfusion uptake. This suggests that the wall thickening calculated by electrocardiogram-gated SPECT may be more useful to predict functional recovery than regional myocardial perfusion. Or, it could suggest that in addition to perfusion uptake, wall thickening could enhance the objective assessment of myocardial viability.     

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.     

Myocardial protection with Hamburg oxygenated crystalloid cardioplegic solution for multiple coronary bypass and multivalvular replacement

We evaluated myocardial protection with Hamburg oxygenated crystalloid cardioplegic solution in a double study. Part I was a prospective metabolic study, measuring myocardial adenosine triphosphate (ATP) and creatine phosphate (CP) contents before and after ischemia in 30 coronary bypass (CABG) patients. During ischemia, CP levels decreased significantly, whereas ATP did not. After 10 minute of reperfusion, mean ATP contents were 90% of preischemic values and CP levels increased to 85% of preischemic values. Spontaneous myocardial defibrillation was seen in 93.3% of patients. Part II included evaluation of early postischemic myocardial function in 228 patients, 48 with multiple valve replacement (MUVR) and 180 with CABG. Spontaneous myocardial defibrillation was seen in 90.3%. Cardiac index, measured before and 1 and 12 hours after surgery, increased significantly in the postischemic period (from 1.95 +/- 0.9 to 2.5 +/- 0.7 l/min m2 in MUVR, p 0.04; from 2.2 +/- 0.6 to 2.7 +/- 0.7 l/min/m2 in CABG, p 0.01). Myocardial infarction frequency was 3% among CABG patients, and unrelated to the number of distal anastomosis or to aortic cross-clamp time. Early postoperative mortality was 6.2% for MUVR and 0.5% for CABG. Thus, oxygenated cardioplegia with Hamburg solution preserves high-energy phosphate compounds and prevents ischemic injury, with excellent short-term clinical results.     

Benefits of off-pump bypass on neurologic and clinical morbidity: a prospective randomized trial

BACKGROUND: Neurologic and clinical morbidity after coronary artery bypass grafting (CABG) can be significant. By avoiding cardiopulmonary bypass, off-pump CABG (OPCAB) may reduce morbidity. METHODS: Sixty patients (30 CABG and 30 OPCAB) were prospectively randomized. Neurocognitive testing was performed before the operation and 2 weeks and 1 year after the operation. Neurologic testing to detect stroke and (99m)Tc-HMPAO whole-brain single photon emission computed tomography scanning to assess cerebral perfusion were performed before the operation and 3 days afterward. Bilateral middle cerebral artery transcranial Doppler scanning was performed intraoperatively to detect cerebral microemboli. All examiners were blinded to treatment group. Clinical morbidity and costs were compared. RESULTS: Coronary artery bypass grafting was associated with more cerebral microemboli (575 +/- 278.5 CABG versus 16.0 +/- 19.5 OPCAB (median +/- semiinterquartile range) and significantly reduced cerebral perfusion after the operation to the bilateral occipital, cerebellar, precunei, thalami, and left temporal lobes (p < or = 0.01). Cerebral perfusion with OPCAB was unchanged. Compared with base line, OPCAB patients performed better on the Rey Auditory Verbal Learning Test (total and recognition scores) at both 2 weeks and at 1 year (p < or = 0.05), whereas CABG performance was statistically unchanged for all cognitive measures. Patients who underwent CABG had more chest tube drainage (1389 +/- 1256 mL CABG versus 789 +/- 586 mL OPCAB, p = 0.02) and required more blood (3.9 +/- 5.8 U CABG versus 1.2 +/- 2.2 U OPCAB, p = 0.02), fresh frozen plasma (3.0 +/- 6.0 U CABG versus 0.5 +/- 2.2 U OPCAB, p = 0.03), and hours of postoperative use of dopamine (16.3 +/- 21.2 hours CABG versus 7.3 +/- 9.7 hours OPCAB, p = 0.04). These differences culminated in higher costs for CABG ($23,053 +/- $5,320 CABG versus $17,780 +/- $4,390 OPCAB, p < 0.0001). One stroke occurred with CABG, compared with none with OPCAB (p = NS). One OPCAB patient died because of a pulmonary embolus (p = NS). CONCLUSIONS: Compared with CABG, OPCAB may reduce neurologic and clinical morbidity as well as cost.     

Echocardiographic demonstration of improved myocardial function early after coronary artery bypass graft surgery

The time course of recovery of left ventricular (LV) function after coronary artery bypass grafting (CABG) surgery is largely unknown. We aimed to test the hypothesis that LV function improves shortly after CABG by using echocardiography to elucidate myocardial contractility before and after CABG, and to determine the segmental distribution of viable myocardium. We prospectively studied 42 patients undergoing elective isolated CABG. No selection was done regarding preoperative LV ejection fraction. All patients underwent serial transthoracic two-dimensional echocardiography preoperatively, and at two to four days and six to seven weeks postoperatively. Regional wall motion was evaluated at each examination, and wall motion score index (WMSI) was calculated to assess recovery of contractile function. WMSI improved by surgery (P=0.005), stepwise from preoperatively to two to four days postoperatively (P=0.05) and borderline significantly between the two postoperative examinations (P=0.06). One hundred and one (15%) of 670 segments had abnormal contraction preoperatively; of which 69 were hypokinetic and 32 were akinetic. At six to seven weeks postoperatively a normalization of function was found in 35 (51%) hypokinetic and four (13%) akinetic segments. Our data suggest that CABG improves myocardial contractility within the first days postoperatively. Echocardiographic determination of wall motion is a useful tool to observe LV function.     

Increased incidence of acute ascending aortic dissection with off-pump aortocoronary bypass surgery?

BACKGROUND: An apparent increase in the incidence of acute ascending aortic dissection following off-pump coronary artery bypass grafting (OPCAB) led us to assess retrospectively the rate and circumstances of this complication in our institution on a consecutive series of patients undergoing aortocoronary bypass performed with and without extracorporeal circulation (ECC). METHODS: A retrospective analysis of acute ascending aortic dissections complicating coronary artery bypass grafting surgery in 3,031 patients in our institution since April 1, 1995, was performed using the database of the Montreal Heart Institute. RESULTS: There was a greater frequency of hypertension in the OPCAB group. Iatrogenic acute aortic dissection occurred in 3 patients among 308 operated on without ECC (0.97%) and 1 patient among 2,723 operated on under ECC (0.04%). This difference was statistically significant (p < 0.00001). CONCLUSIONS: The risk of aortic dissection may be increased in OPCAB. Careful manipulation of the aorta with a single side-clamping and a control of the arterial pressure should be used to minimize aortic trauma. High-risk patients should undergo CABG without side-clamping of the aorta or CABG with ECC to prevent this redoubtable complication of myocardial revascularization.     

Evaluation of aortocoronary bypass operation using a He-Ne laser flowmeter--comparison between internal mammary artery grafts and saphenous vein grafts

It was very difficult to measure myocardial blood flow in clinical cases. Recently, a He-Ne laser doppler flowmeter was developed, and we made it possible to measure the pre-and post-operative myocardial blood flow in cases of coronary artery bypass grafting (CABG). We applied a laser flowmeter to 30 cases of bypass grafting to the left anterior descending coronary artery (18 cases with IMAG and 12 cases with SVG). The preoperative myocardial blood flow at the right ventricular anterior wall was 77 +/- 15 ml/min/100 gr, and the postoperative flow at the same point was 81 +/- 12 ml/min/100 gr. There was no significant change between the pre-operative value and the postoperative one. Myocardial blood flow at the left ventricular anterior wall in SVG group significantly increased from the preoperative value of 58 +/- 11 ml/min/100 gr to the postoperative value of 86 +/- 9 ml/min/100 gr (p less than 0.001). In IMAG group, myocardial blood flow at the left ventricular anterior wall similarly increased from 73 +/- 14 ml/min/100 gr to 83 +/- 15 ml/min/100 gr (p less than 0.01). The postoperative value of IMAG group was almost equal to the value of SVG group. The increased rate of myocardial blood flow at the left ventricular anterior wall was 52 +/- 32% in SVG group and 18 +/- 12% in IMAG group. These rates were obviously distinguished from the increased rate at the right ventricular anterior wall.(ABSTRACT TRUNCATED AT 250 WORDS)     

Is cardiopulmonary bypass a reason for aspirin resistance after coronary artery bypass grafting?

OBJECTIVE: 'Off-pump' coronary artery bypass grafting (OPCAB) is an alternative to conventional coronary artery bypass grafting (CABG) using cardiopulmonary bypass (CPB). While midterm results after OPCAB have become available, systematic studies of changes in platelet function after OPCAB are still missing. Since we have previously shown that oral aspirin treatment (100mg) does not achieve sufficient platelet inhibition in the majority of patients operated on with CPB, we hypothesized that bypass surgery without CPB (off-pump coronary artery bypass, OPCAB) causes less impairment of platelet inhibition by aspirin. The aim of this study was to investigate platelet function and the antiplatelet effect of aspirin after off-pump coronary artery bypass grafting in comparison with conventional on-pump surgery. METHODS: We compared platelet function (in vitro aggregation and thromboxane formation) before and at days 1 and 5 after coronary artery bypass grafting, performed with (n=15) or without (n=14) CPB. Oral aspirin treatment (100mg/d) was started at day 1 after surgery. RESULTS: After a 5 day oral treatment with aspirin, platelet aggregation was inhibited significantly in OPCAB-patients to 55.7+/-16.3% of control before surgery (P<0.05), whereas aggregation remained unchanged after CPB (105.8+/-26.9% of control before surgery; P>0.05). Since aspirin primarily inhibits platelet thromboxane formation, thromoboxane was determined after in vitro aggregation. According to platelet aggregation, thromboxane formation was only inhibited significantly after OPCAB (29.2+/-13.0% of control before surgery, P<0.05), but not after CPB (74.5+/-21.4% of control before surgery, P>0.05). This resistance to aspirin after CPB may be caused by an increased release of new platelets which are competent to form thromboxane, since the number of platelets decreased from 237+/-11x10(3)/microl before CPB to 174+/-13x10(3)/microl at day 1 after surgery and increased significantly the following days reaching 303+/-17x10(3)/microl at day 5. Platelet counts of patients operated on without CPB showed no significant changes (236+/-16x10(3)/microl before OPCAB, 220+/-16x10(3)/microl at day 1 and 266+/-31x10(3)/microl at day 5 after surgery). CONCLUSIONS: The antiplatelet effect of aspirin is largely impaired after CPB, but not after CABG without CPB. Hence, increased platelet turnover after CPB seems to contribute to aspirin resistance, since an increased number of platelets might be competent to form thromboxane within the dosing intervals.