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.     

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.     

Real time assessment of myocardial revascularization during coronary artery bypass surgery by means of ultrasonic integrated backscatter.

OBJECTIVE: The recovery of cyclic variation (CV) of ultrasonic integrated backscatter (IB) may provide a more sensitive predictor of the success of myocardial revascularization. This study was designed to elucidate the possibility of real time assessment of coronary artery bypass grafting (CABG) using CV of IB. METHODS: We studied 10 patients (61 +/- 4 years old) with the perfused areas by stenosed or occluded LAD without myocardial infarction. There were six ischemic dysfunctional areas, and four ischemic but non-dysfunctional areas. The CV of IB was measured before and just after extracorporeal circulation (ECC). Wall motion was analyzed by segmental wall thickening during systole at the same time of the IB analysis during CABG and at 3 weeks after CABG. Those 10 areas were completely revascularized. RESULTS: In the non-dysfunctional areas, wall thickening did not change and remained at normal values before and after ECC, and 3 weeks after CABG (31 +/- 3% 29 +/- 3% and 29 +/- 5%, respectively). The magnitude of CV of IB did not also change before and after ECC (8.0 +/- 1.6 dB and 7.8 +/- 1.3 dB). However, in the ischemic dysfunctional areas, while wall thickening did not change before and after ECC (21 +/- 5% and 20 +/- 5%), it increased and reached similar values as the non-dysfunctional regions at 3 weeks after CABG (26 +/- 7%, P < 0.01 vs. before and after ECC values). The magnitude of CV of IB increased even after ECC (3.71 +/- 0.4 dB vs. 7.4 +/- 3.5 dB, P < 0.05), and reached the same level as those in the non-dysfunctional areas. There was a significant relationship between wall thickening at 3 weeks after bypass grafting and magnitude of CV of IB after ECC (r = 0.67, P < 0.05). CONCLUSIONS: Improvement in wall motion was gradually attained after bypass grafting. On the contrary, an increase in the magnitude of CV of IB was obtained immediately after myocardial revascularization. Our data suggest that CV of ultrasonic IB method can provide close real time information regarding the effectiveness of bypass surgery.     

Intraoperative assessment of the physiologic significance of coronary stenosis in humans

Coronary angiography is generally considered the gold standard in assessing the significance of coronary stenosis. The inadequacy of coronary angiography has frequently been demonstrated by intraoperative findings that differ from those projected by the catheterization report. To better assess the physiologic significance of coronary stenosis, we measured intramyocardial pH intraoperatively in 50 myocardial segments supplied by stenotic coronary arteries before and after revascularization in 42 patients undergoing coronary artery bypass grafting. The hemodynamic, electrocardiographic, and pH responses to atrial pacing were recorded intraoperatively before and after revascularization. The coronary angiograms, performed within 3 months before bypass grafting, were reviewed by a single independent observer. Preoperative and postoperative radionuclide ventriculograms were performed and also reviewed by an independent observer. In response to atrial pacing, a fall exceeding 0.02 pH units was considered to represent ischemia and was observed in 28 segments. Patients exhibiting this response comprised Group I. Twenty-two segments demonstrated a fall of less than 0.02 pH units or a rise in pH in response to atrial pacing. Patients having this response comprised Group II. Segments in Group I responded dramatically to revascularization, with the pH during atrial pacing rising from -0.09 +/- 0.01 to -0.02 +/- 0.01 (p less than 0.001). Nine patients demonstrated ischemic S-T changes during atrial pacing, all in Group I. Pre-pacing hemodynamic parameters were similar in both groups. Group I patients, however, demonstrated a significant fall in mean arterial pressure during atrial pacing, from 92.0 +/- 3.0 to 78.4 +/- 3.3 mm Hg (p less than 0.001) whereas Group II patients did not. Twelve segments that angiograms indicated were supplied by critically stenotic vessels (greater than 75%) failed to demonstrate a significant fall in their pH during atrial pacing. In these segments, intraoperative findings and postoperative results corroborated the metabolic findings. Coronary angiography, therefore, was only 45% specific in assessing physiologically significant obstructions. The degree of segmental wall motion abnormalities likewise correlated poorly with the pH changes. Unlike coronary angiography, the response of intramyocardial pH to pacing is an accurate metabolic tool to assess myocardial ischemia in humans.     

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.     

Reduction of systolic and diastolic dysfunction by retrograde coronary sinus perfusion during off-pump coronary surgery

OBJECTIVES: We evaluated the protective effects of retrograde coronary sinus perfusion to offset potential systolic and diastolic dysfunction (myocardial stunning) after temporary regional ischemia needed for off-pump coronary artery bypass grafting. METHODS: Twenty Yorkshire-Duroc pigs (31.8 +/- 3.9 kg) underwent 15 minutes of mid-left anterior descending coronary artery ischemia in the beating heart. In 8 pigs, no protective measures were used. In 12 pigs, an aorta-coronary sinus shunt (with conventional cannulas) allowed retrograde perfusion during temporary ischemia; in 6 of these pigs, no leakage to the right atrium was ensured. Regional endocardial contraction was measured with sonomicrometer crystals. Systolic dysfunction (impaired regional shortening), diastolic dysfunction (contraction extending into early diastole), and coronary sinus nitric oxide and endothelin-1 levels were recorded. RESULTS: Before ischemia, contraction did not extend into the diastolic interval. During ischemia, paradoxic bulging occurred in all hearts except in the occlusive coronary sinus shunt group (16% +/- 6% of baseline, P <.01). Sixty minutes after ischemia, systolic segment shortening recovered 36% +/- 24% without retrograde perfusion versus 56% +/- 20% and 61% +/- 14% with coronary sinus shunting (P <.05). Diastolic dysfunction (as percentage of diastolic time in contraction) was 38% +/- 16% in the nontreated group versus 22% +/- 22% and 9% +/- 9% (P <.05) after shunting and occlusive shunting, respectively. This correlated with a left ventricular end-diastolic pressure increase of 4 mm Hg in the ischemic group versus no change in the retrograde perfusion groups. Nitric oxide decreased 15% without shunting and increased 8% after occlusive coronary sinus shunting (P <.05). CONCLUSIONS: Retrograde coronary sinus perfusion during simulated off-pump coronary revascularization diminishes systolic and diastolic dysfunction. An aortic-coronary sinus shunt is a rapid, recognized approach that can improve myocardial muscle and endothelial safety during off-pump coronary artery bypass grafting.     

Immediate functional benefits after controlled reperfusion during surgical revascularization for acute coronary occlusion.

This study tests the hypothesis that contractile dysfunction that often develops after acute coronary occlusion despite emergency revascularization can be avoided by careful control of the composition of the initial reperfusate and the conditions of the reperfusion. Between January 1987 and May 1989, 31 consecutive patients with acute coronary occlusion (90% resulting from percutaneous transluminal coronary angioplasty failures) were reperfused during emergency myocardial revascularization according to one of two different protocols. In 23 patients the reperfusate was normal blood given at systemic pressure ("uncontrolled reperfusion"); in eight patients the ischemic segment was reperfused during the first 20 minutes with a regional blood cardioplegic solution (substrate-enriched, hyperosmotic, hypocalcemic, alkalotic, diltiazem-containing) at 37 degrees C at a pressure of 50 mm Hg. Thereafter total bypass was prolonged for an additional 30 minutes before extracorporeal circulation was discontinued ("controlled reperfusion"). Assessment of regional contractility (echocardiography, radionuclide ventriculography), electrocardiographic evidence of myocardial infarction, release of creatine kinase and isoenzyme of creatine kinase, and hospital mortality was performed. Regional contractility was quantified with a scoring system from 0 (normokinesis) to 4 (dyskinesis). Data are expressed as mean +/- standard error of the mean. Both groups were well matched for age, sex, and the distribution of the occluded artery. In the controlled-reperfusion group there was a greater prevalence of previous infarctions (63% versus 43%), additional significant stenosis (1.3 +/- 0.2 versus 0.8 +/- 0.2), and cardiogenic shock (38% versus 17%) compared with the uncontrolled-reperfusion group. Furthermore, the interval between coronary occlusion and reperfusion was significantly longer in the controlled-reperfusion group (4.0 +/- 0.5 versus 2.3 +/- 0.3 hr; p less than 0.05). Regional contractility returned to normal in all patients treated by controlled reperfusion (wall motion score = 0.8 +/- 0.3, normokinesis = 0, slight hypokinesis = 1). In contrast, regional contractility remained severely depressed after uncontrolled reperfusion with normal blood (score 2.5 +/- 0.2; p less than 0.05), with only four of 23 patients with a score less than 2 (2 = severe hypokinesis). Postoperatively enzymes and electrocardiographic changes were similar in both groups. One patient died of mitral insufficiency in the controlled-reperfusion group, despite complete recovery of wall motion in the angioplasty-related artery. Conversely, the four of 23 deaths after uncontrolled reperfusion occurred in patients who sustained infarct in the area of the coronary occlusion (mortality 13% versus 17%). In conclusion, these preliminary clinical results indicate that immediate recovery of segmental contractility can be achieved after acute coronary occlusion if the initial reperfusion is controlled.(ABSTRACT TRUNCATED AT 400 WORDS)     

Mid-term results of combined transmyocardial laser revascularization and coronary artery bypass

BACKGROUND: Transmyocardial laser revascularization is increasingly used to treat intractable angina in the absence of graftable vessels; however, its role in combination with coronary artery bypass grafting remains undefined. The aim of this pilot study was to investigate the outcome of the combination therapy at mid-term follow-up. METHODS: Patients (n = 20) who had elective coronary artery bypass with one or more nongraftable coronary arteries were prospectively randomized to have either coronary artery bypass grafting alone or combination coronary artery bypass grafting plus transmyocardial laser revascularization with a holmium:YAG (yttrium-aluminum-garnet) laser to nongraftable areas. All patients had an exercise tolerance test preoperatively and at 6, 18, and 36 months follow-up. Stress echocardiography was performed on 17 patients at 18 months postoperatively, and regional wall motion score index was calculated in lased and nonlased nonrevascularizable myocardium of the left ventricle at rest and with dobutamine stress. RESULTS: Both groups of patients were similar in preoperative demographics and operative data. There was no perioperative death. There was no difference between the two groups in angina scoring at 6, 18, and 36 months follow-up. Exercise tolerance improved by a mean of 46.8 +/- 20.0 seconds in the coronary artery bypass grafting group versus 199.2 +/- 66.5 seconds per patient in the coronary artery bypass grafting plus transmyocardial laser revascularization group (p = 1.8 x10(-6)) at 6 months; this benefit was maintained at 18 months (157 +/- 46.3 versus 61 +/- 39.2 seconds; p = 4 x10(-4)) but was lost at 36 months (57.2. +/- 42.1 versus 68.1 +/- 46.7 seconds; p = 0.70). The mean values for wall motion score index in the lased and nonlased regions at each stage of dobutamine stress at 18 months after surgery were not statistically significant. CONCLUSIONS: The combination of coronary artery bypass and transmyocardial laser revascularization improved exercise tolerance in patients in whom complete revascularization could not be achieved by bypass grafting alone in the short term, but this benefit was lost by 36 months postoperatively. The transient improvement in exercise tolerance cannot be explained by changes in contractility in the lased areas.     

The effects of coronary revascularization on left ventricular function in ischemic heart disease

Although it is well established that coronary revascularization can reverse exercise-induced ischemic dysfunction, the effects on resting ventricular performance are controversial. From a group of 183 patients receiving surgical therapy for ischemic heart disease, 166 underwent bypass graft arteriography at an average of 7 to 14 days postoperatively. In 149 patients, satisfactory preoperative and postoperative biplane left ventriculograms were obtained. Regional wall motion was assessed by the 100 segment method of Sheehan and Dodge, and a perioperative change in shortening greater than 2 standard deviations of normal variability over 20 or more adjacent segments was considered significant. Ninety-five patients had stable or progressive angina, 88 had medically refractory unstable angina, 155 were in New York Heart Association Class IV, and 37 had a preoperative left ventricular ejection fraction of less than 0.4. Myocardial integrity was preserved with crystalloid cardioplegia and topical hypothermia. Seven hundred ninety-eight bypass grafts were performed (522 vein grafts and 276 mammary artery grafts), and 13 patients had concomitant left ventricular aneurysmectomy. Hospital mortality was 2.2%. The overall early graft patency rate was 95.9% (93.7% for vein grafts and 100% for mammary arteries). Only one patient had a decrement in regional wall motion, and 51 (37%) had significant postoperative improvement (27 in the unstable angina group and 24 in the stable angina group); in the patients with improved regional wall motion, ejection fraction increased by an average of 0.18 (p less than 0.01). Ejection fraction also improved after aneurysmectomy, and the increment seemed to result from both a reduction in end-diastolic volume and improved regional wall motion. Thus, reversible ischemic myocardial dysfunction appears to be common in the general population of patients undergoing coronary artery bypass grafting; 40% of patients with unstable angina and 34% of those with stable angina can be expected to have improved regional wall motion after successful revascularization. Finally, ventricular aneurysm resection significantly enhances left ventricular performance as assessed by ventriculographic ejection fraction.     

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.     

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.     

Myocardial lactate metabolism in relation to preoperative regional wall motion and to early functional recovery after coronary revascularization

OBJECTIVE: To evaluate myocardial lactate metabolism as a marker of functional status after surgical coronary revascularization. DESIGN: Single-center, prospective, cohort study. SETTING: Tertiary care teaching hospital. PARTICIPANTS: Fifty patients with stable angina, ejection fraction >0.40, undergoing coronary artery bypass surgery for multiple-vessel disease. MEASUREMENTS AND MAIN RESULTS: Before (T1) and 30 minutes (T2) after coronary artery bypass grafting, the authors simultaneously sampled blood from artery and coronary sinus to determine myocardial lactate dynamics and performed transesophageal echocardiography (TEE) to assess segmental wall motion. Wall motion score index (WMSI) was calculated with an online/offline comparison. At T2, WMSI improved from 1.40 +/- 0.31 to 1.17 +/- 0.23 (p = 0.0001). Preoperatively, 2 patterns of lactate balance were found: 39 patients were lactate extractors (17% +/- 10%) and 11 were lactate producers (-11% +/- 11%). At T2, lactate metabolism was shifted towards a pattern opposite to the baseline: delta lactate extraction was -8% +/- 16% in extractors at T1 versus 7% +/- 9% in producers at T1 (p = 0.003). Changes in WMSI were not correlated with changes in lactate utilization. No single preoperative variable predicted postoperative WMSI or its changes from baseline. Cardiopulmonary bypass (CPB) time was the only significant predictor of postoperative lactate extraction by multivariate regression (r = -0.46, p = 0.001): at T2, patients in the highest CPB time quartile showed frank lactate production (-6% +/- 13%) when compared with those in the lowest quartile (15% +/- 11%, p = 0.005). However, postoperative WMSI was similar in different CPB time groups. CONCLUSIONS: Myocardial lactate metabolism pattern is not associated with functional status before and early after successful coronary revascularization. CPB time was the only significant predictor of postoperative lactate extraction. Measurement of lactate does not appear to be a valuable tool to assess the coupling of myocardial regional function and metabolism in the setting of coronary artery surgery and mild-to-moderate functional impairment.     

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.     

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

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

Segmental wall motion abnormalities during telerobotic totally endoscopic coronary artery bypass grafting

In addition to single-lung ventilation (SLV), intrathoracic CO2 insufflation is mandatory for adequate exposure during totally endoscopic coronary artery bypass grafting. With transesophageal echocardiography, we investigated biventricular myocardial wall motion in 25 patients with isolated disease of the left anterior descending coronary artery who underwent totally endoscopic coronary artery bypass grafting with the "Da Vinci" robotic surgical system. At distinct time points during the operation, a cine loop of both ventricles was registered from a transgastric mid-short-axis view. Myocardial wall motion analysis was performed according to an established segmentation model of the left ventricle and to an established five-point scale for wall motion (1, normal; 5, dyskinesia). Significant alterations from preoperative baseline wall motion were visible in the septal, inferior, and anterior segments of the left ventricle at some time during the prebypass period, combined with a markedly decreased PaO2 under SLV and increased intrathoracic pressure. The same findings applied to the right ventricle; however, wall motion abnormalities were more pronounced here. After myocardial revascularization, weaning from cardiopulmonary bypass, CO2 deflation, and return to double-lung ventilation, myocardial wall motion recovered to baseline values. Clinically significant hemodynamic instability did not occur. The data suggest that robot-assisted coronary artery bypass grafting leads to significant prebypass alterations of biventricular segmental wall motion. On the basis of our data, it cannot be definitively stated whether the observed results were due to reduced oxygenation during SLV and thus "real" myocardial ischemia, intrathoracic CO2 insufflation with positive pressure leading to mechanical compromise of the heart, absolute or relative hypovolemia, or a combination of these factors. However, in this cohort, which consisted of patients with single-vessel disease and good ventricular function, these changes were of limited clinical relevance. IMPLICATIONS: Segmental myocardial wall motion was evaluated with transesophageal echocardiography during robot-assisted totally endoscopic coronary artery bypass grafting. Significant biventricular segmental wall motion abnormalities occurred before cardiopulmonary bypass under single-lung ventilation and carbon dioxide insufflation. The changes in myocardial wall motion were of limited clinical relevance.     

On-line assessment of regional ventricular wall motion by transesophageal echocardiography with color kinesis during minimally invasive coronary artery bypass grafting

OBJECTIVE: Our objective was to determine the changes in regional ventricular wall motion during minimally invasive direct coronary artery bypass grafting by color kinesis using transesophageal echocardiography. METHODS: Minimally invasive coronary artery bypass grafting was performed in 34 patients, during which transesophageal echocardiography was used. Thirteen patients had isolated disease of the left anterior descending artery. Regional ventricular wall motion was analyzed by color kinesis with the SONOS 2500 transesophageal echocardiograph (Hewlett-Packard Co, Andover, Mass). On-line assessment of regional wall motion was continued during the operation. RESULTS: Wall motion abnormalities during ischemia were present in 4 cases, left ventricular mid-anterior hypokinesis in 3 cases, and left ventricular apical-lateral hypokinesis in 1 case. In all cases, wall motion was maintained after bypass. In patients with total coronary occlusion, changes in wall motion did not occur during anastomosis. CONCLUSIONS: Color kinesis allowed us to evaluate the change in regional ventricular wall motion induced by myocardial ischemia during minimally invasive coronary artery bypass grafting both objectively and quantitatively.     

Effects of coronary artery bypass grafting on global and regional myocardial function. An intraoperative echocardiographic assessment.

The immediate effect of coronary artery bypass grafting on global and regional myocardial function was studied by means of epicardial two-dimensional echocardiography during operations in 20 patients. Echocardiograms were recorded before cardiopulmonary bypass and 5 and 30 minutes after bypass. Global left ventricular function was expressed as percent short-axis area change and regional function as percent fractional area change. Segments were classified according to their baseline function as normal (percent fractional area change greater than 40%), moderately hypokinetic (percent fractional area change 21% to 40%), or severely dysfunctional (percent fractional area change less than 20%). Percent short-axis area change was significantly reduced immediately after cardiopulmonary bypass (from 42.0% +/- 4.6% to 34.9% +/- 3.0%, p less than 0.05) but had returned to baseline 30 minutes after bypass (42.6% +/- 4.0%). Similarly, function of normal and moderately hypokinetic segments decreased significantly immediately after cardiopulmonary bypass (normal segments: percent fractional area change 56% +/- 0.9% before bypass to 42.3% +/- 1.5% after bypass, p less than 0.0001; moderately hypokinetic segments: 31.0% +/- 0.9% to 25.1% +/- 1.4%, p less than 0.002). Both normal and moderately hypokinetic areas regained baseline function by 30 minutes after bypass (normal segments: 53.4% +/- 1.6%; moderately hypokinetic segments: 35.4% +/- 2.0%). In contrast, severely dysfunctional segments were found to be significantly improved immediately after bypass (14.7% +/- 0.9% before bypass to 27.7% +/- 2.1% after bypass, p less than 0.0001). This improvement was maintained 30 minutes after bypass (22.8% +/- 1.5%, p less than 0.001). We conclude that coronary revascularization exhibits an immediate beneficial effect on chronically underperfused myocardium having severely depressed baseline function. However, in normal and moderately hypokinetic areas, the depressant effects of global ischemia and reperfusion prevail in the immediate postbypass period, leading to a global depression of cardiac function.     

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.     

Off-pump coronary artery bypass grafting provides complete revascularization with reduced myocardial injury,transfusion requirements,and length of stay: a prospective randomized comparison of two hundred unselected patients undergoing off-pump versus conventional coronary artery bypass grafting

OBJECTIVE: Retrospective comparisons of selected patients undergoing off-pump versus conventional on-pump coronary artery bypass grafting have yielded inconsistent results and raised concerns about completeness of revascularization in off-pump coronary artery bypass grafting. METHODS: Two hundred unselected patients referred for elective primary coronary artery bypass grafting were randomly assigned to undergo off-pump coronary artery bypass grafting with an Octopus tissue stabilizer (Medtronic, Inc, Minneapolis, Minn) or conventional coronary artery bypass grafting with cardiopulmonary bypass by a single surgeon. Revascularization intent determined before random assignment was compared with the revascularization performed. All management followed strict, unbiased, criteria-driven protocols. Patients and nonoperative care providers were blinded to surgical group. RESULTS: Baseline characteristics were similar. The number of grafts performed per patient (mean +/- SD 3.39 +/- 1.04 for off-pump coronary artery bypass grafting, 3.40 +/- 1.08 for conventional coronary artery bypass grafting) and the index of completeness of revascularization (number of grafts performed/number of grafts intended, 1.00 +/- 0.18 for off-pump coronary artery bypass grafting, 1.01 +/- 0.09 for conventional coronary artery bypass grafting) were similar. Likewise, the index of completeness of revascularization was similar between groups for the lateral wall. Combined hospital and 30-day mortalities and stroke rates were similar. Postoperative myocardial serum enzyme measures were significantly lower after off-pump coronary artery bypass grafting, suggesting less myocardial injury. Adjusted postoperative thromboelastogram indices, fibrinogen, international normalized ratio, and platelet levels all showed significantly less coagulopathy after off-pump coronary artery bypass grafting. Patients undergoing off-pump coronary artery bypass grafting received fewer units of blood, were more likely to avoid transfusion altogether, and had a higher hematocrit at discharge. Cardiopulmonary bypass was an independent predictor of transfusion (odds ratio 2.42, P =.0073) by multivariate analysis. More patients undergoing off-pump coronary artery bypass grafting were extubated in the operating room and within 4 hours. Postoperative length of stay (in days) was shorter for off-pump coronary artery bypass grafting (5.1 +/- 6.5 for off-pump coronary artery bypass grafting, 6.1 +/- 8.2 for conventional coronary artery bypass grafting, P =.005 by Wilcoxon test). One patient (in the conventional coronary artery bypass grafting group) required angioplasty for graft closure within 30 days. CONCLUSIONS: When compared with conventional coronary artery bypass grafting with cardiopulmonary bypass, off-pump coronary artery bypass grafting achieved similar completeness of revascularization, similar in-hospital and 30-day outcomes, shorter length of stay, reduced transfusion requirement, and less myocardial injury.     

Acute effects of aortocoronary bypass surgery on left ventricular function and regional myocardial mechanics: a clinical study.

The acute effects of myocardial revascularization on overall left ventricular performance and on myocardial segmental wall motion were assessed intraoperatively in 22 patients who had unstable (11 patients) or stable angina pectoris (11 patients). Segmental contraction patterns were evaluated using an ultrasonic transit-time method. In 9 patients with unstable angina pectoris, notable improvement in segmental wall motion was observed as the short-term response to coronary bypass grafting. Hypokinetic patterns were rendered normal after revascularization. Despite marked changes in segmental myocardial function, overall left ventricular performance was not altered notably. In contrast, reperfusion did not lead to acute effects on either segmental wall motion or total left ventricular function in patients with stable angina pectoris. The results indicate that aortocoronary bypass grafting may improve segmental wall motion in patients with unstable angina.