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.     

Passive external cardiac constraint improves segmental left ventricular wall motion and reduces akinetic area in patients with non-ischemic dilated cardiomyopathy.

OBJECTIVE: To verify changes in left ventricular (LV) volumes and regional myocardial wall motion after implantation of a textile cardiac support device (CSD) for passive external constraint in non-ischemic dilated cardiomyopathy. METHODS: In nine male patients participating in a non-randomized clinical trial LV volumes were determined and the segmental LV wall motion was studied by contrast-enhanced electron-beam CT in a sectionwise manner at three ventricular levels (base, middle and apex of ventricle) before and 32+/-6 months after CSD implantation. In 16 myocardial segments ejection fraction and wall thickening were measured semiautomatically after drawing the myocardial contours. The wall motion score index was calculated based on semiquantitative visual grading in each segment. RESULTS: The global LV volumes decreased significantly from 304.3 +/- 90.9 to 231.5 +/- 103.9 ml at end-diastole and from 239.7 +/- 83.7 to 164.0 +/- 97.7 at end-systole (P<0.05). Overall ejection fraction increased from 14.8 +/- 8.2 to 25.7 +/- 17.1% (P<0.05). A segment-by-segment analysis demonstrated a significant increase of regional ejection fraction in the basal myocardium as well as in the mid-inferior, mid-inferolateral, and mid-anterolateral myocardium. Overall wall thickening increased from 16.4 +/- 13.3 to 24.2 +/- 18.1% (P<0.05), but without significant differences in a segment-by-segment comparison. The mean wall motion score index improved from 2.70 +/- 0.26 to 2.20 +/- 0.71 (P<0.05), with an increased wall motion in eight (89%) patients. A section-by-section analysis demonstrated significantly improved wall motion in the inferior and lateral segments at each ventricular level. Postoperatively, the number of akinetic and markedly hypokinetic segments decreased significantly (P<0.05) from 56 (39%) to 26 (18%) and from 76 (53%) to 56 (37%), respectively. CONCLUSION: CSD implantation improves segmental wall motion, predominantly in the inferior and lateral myocardium, and reduces the number of akinetic and hypokinetic segments.     

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.     

Noninvasive assessment of left ventricular function prior to and 6 months after renal transplantation

BACKGROUND: The purpose of this study was to evaluate the effect of a successful kidney transplantation on left ventricular functional parameters that can be measured with gated-single photon emission computed tomography (gated-SPECT) myocardial perfusion scintigraphy in patients with end-stage renal disease. MATERIALS AND METHODS: Thirty-two consecutive patients (22 male) who had undergone a successful kidney transplantation in whom gated-SPECT myocardial perfusion scintigraphy was performed prior to and 6 months after surgery were included. Functional parameters, such as left ventricular ejection fraction (LVEF), wall motion, and wall thickening, were calculated with quantitative gated-SPECT. RESULTS: The mean LVEF improved significantly (P<.001) from 52% (SD+/-11) before to 63% (SD+/-10) after renal transplantation. This was attributable to a significant improvement in the end-systolic volume (P=.028). Wall motion and wall thickening improved in almost all myocardial segments. We found a significant correlation between the levels of urea and creatinine and the LVEF. However, correlations between an increase in the LVEF and the improvement in urea (P=.30) and creatinine (P=.26) levels were not significant, which is probably related to the number of patients studied. CONCLUSION: The systolic left ventricular dysfunction in terms of LVEF, wall motion, and wall thickening improves significantly 6 months after kidney transplantation in patients with end-stage kidney disease. Long-term follow-up is required to establish the prognostic value of these findings.     

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.     

Is there a long-term predictive value of intraoperative low-dose dobutamine echocardiography in patients who have coronary artery bypass graft surgery with cardiopulmonary bypass?

In patients with coronary artery disease, chronic regional left ventricular systolic dysfunction at rest may be caused by hibernating or by infarcted myocardium. Intraoperative low-dose dobutamine (LDD) echocardiography reliably predicts the immediate recovery of regional myocardial function after coronary artery bypass graft (CABG) surgery. We sought to determine whether intraoperative LDD echocardiography would also predict recovery of regional function after 1 yr. Twenty-five patients with coronary artery disease who underwent CABG surgery with intraoperative LDD echocardiography were evaluated 1 yr later with a follow-up transthoracic echocardiogram. The covariates of left ventricular ejection fraction, old myocardial infarction, and diabetes mellitus were considered in an analysis of regional wall motion (RWM). A 16-segment model and a 1-5-point scoring system were used to evaluate 350 myocardial segments. Multiple logistic regression analysis was performed to determine whether response to intraoperative LDD echocardiography (5 microg. kg(-1). min(-1)) predicted changes in regional function at 1 yr. A segment was defined as stunned if the RWM score obtained during LDD infusion deteriorated after cardiopulmonary bypass but recovered in the 1-yr follow-up echocardiogram. A response to intraoperative LDD predicted changes in regional function at 1 yr. The overall odds of improvement in regional function were 2.22 times greater (95% confidence interval = 1.29, 3.82; P = 0.0039) with a positive response to intraoperative LDD. The positive predictive value of intraoperative LDD echocardiography for improvement in myocardial function was 0.81 and the negative predictive value was 0.34. The predictive values did not vary with the examined covariates. Of segments with unexpected deterioration of RWM immediately after cardiopulmonary bypass, 87% recovered at the time of the 1-yr follow-up echocardiogram. Contractile reserve demonstrated by intraoperative LDD echocardiography predicts regional function at 1 yr; however, the test cannot predict which segment will not recover. Most of unexpected regional ventricular systolic dysfunction immediately after CABG surgery can be attributed to myocardial stunning. IMPLICATIONS: In patients undergoing coronary artery bypass graft surgery, intraoperative low-dose dobutamine echocardiography has only limited value for the prediction of regional myocardial function at 1 yr. Small-dose dobutamine echocardiography predicts regional myocardial function at 1 yr when baseline regional wall motion abnormalities improve with dobutamine; however, the test cannot be used to predict which segment will not recover at 1 yr.     

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.     

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.     

Emergency coronary artery bypass grafting in patients with severe pump failure complicating acute myocardial infarction]

Thirty patients with severe pump failure (Killip's degree III or more) complicating acute myocardial infarction (MI) underwent emergency coronary bypass grafting (CABG). Average age was 66 years old and CABG was performed 2.6 days after the onset of MI. The patients were divided into two groups according to the mechanisms that can bring about severe pump failure: 19 patients had large MI alone (G-I). The other 11 patients had severe ischemia occurring either at areas distant from the site of coronary occlusion or in the previous area at risk (G-II). To estimate the ventricular wall motion quantitatively, the left ventricular wall was divided into 17 segments. Each segment was graded on a four-point scale: akinesis, 3; severe hypokinesis, 2; hypokinesis, 1; normal 0. Wall motion score was estimated by summing the number of asynergic segments score. In G-I, Cardiac index (CI (l/min/m2)) increased from 2.03 +/- 0.91 to 2.68 +/- 0.73 and pulmonary wedge pressure (PCWP (mmHg)) decreased from 28 +/- 5 to 15 +/- 5, 72 hours after the surgery (p < 0.01). In G-II, CI increased from 2.17 +/- 0.78 to 3.17 +/- 1.01 and PCWP decreased from 29 +/- 6 to 13 +/- 5 after the surgery (p < 0.01). There was no difference in preoperative and postoperative hemodynamics between two groups. The wall motion score at the risk area did not change postoperatively (from 16 +/- 7 to 17 +/- 9 in G-I, from 15 +/- 8 to 11 +/- 5 in G-II).(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

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.     

Deterioration of regional wall motion immediately after coronary artery bypass graft surgery is associated with long-term major adverse cardiac events

BACKGROUND: Patients undergoing coronary artery bypass graft (CABG) surgery frequently develop wall motion abnormalities diagnosed by intraoperative transesophageal echocardiography. However, the relation between deterioration in wall motion and postoperative morbidity or mortality is unclear. Therefore, the authors hypothesized that deterioration in intraoperative left ventricular regional wall motion immediately after CABG surgery is associated with a higher risk of adverse cardiac events. METHODS: With institutional review board approval, data were gathered from 1,412 CABG surgery patients. Echocardiographic wall motion score (WMS) was derived using a 16-segment model. Outcomes data were gathered for up to 2 yr after surgery. The primary outcome, major adverse cardiac event, was a composite index of myocardial infarction, need for subsequent coronary revascularization, or all-cause mortality during the follow-up period. RESULTS: Two hundred twenty-one patients (16%) had 254 primary outcome events during follow-up. Postbypass WMS did not change in 812 patients (58%), deteriorated in 219 patients (16%), and improved in 368 patients (26%). Kaplan-Meier analysis showed that patients with deterioration in WMS after CABG experienced significantly lower major adverse cardiac event-free survival than patients with either no change or improvement in WMS (P = 0.004). Cox proportional hazards regression modeling revealed a significant association between deterioration in WMS and the composite adverse outcome (hazard ratio, 1.47 [1.06-2.03]; P = 0.02). CONCLUSIONS: The authors confirmed their hypothesis that deterioration in wall motion detected by intraoperative echocardiography after CABG surgery is associated with increased risk of long-term adverse cardiac morbidity. Worsening wall motion after CABG surgery should be considered a prognostic indicator of adverse cardiovascular outcome.     

Clinical evaluation of pressure-controlled intermittent coronary sinus occlusion: randomized trial during coronary artery surgery

Pressure-controlled intermittent coronary sinus occlusion (PICSO) was evaluated in a randomized trial in 30 patients undergoing bypass surgery. PICSO was applied for one hour during early reperfusion. Myocardial function was determined from short-axis cross-sectional views of intraoperative two-dimensional echocardiography. Changes of sectional and segmental wall motion during extracorporeal circulation were analyzed. Although sectional wall motion did not change significantly, hypokinetic segments were preserved better in PICSO-treated patients than in controls (-1.3 +/- 2.4 versus -9.1 +/- 2.6 delta% fractional area change; p less than 0.04). Although not significant, the same trend was found for normal and severely hypokinetic segments. Cumulative enzyme release was related to coronary sinus occluded pressure (r = 0.94; p less than 0.006), indicating washout of metabolites during PICSO. Three months after operation, functional classification was similarly favorable in both groups. Long-term effects of PICSO cannot be predicted because PICSO was applied only during early reperfusion. We conclude that PICSO is a safe procedure and that its short-term beneficial effects on myocardial function suggest a preservation of myocardial viability.     

Abnormalities in myocardial segmental wall motion during lumbar epidural anesthesia

The effect of lumbar epidural anesthesia on myocardial wall motion was compared in two groups of patients using precordial two-dimensional echocardiography (2DE). All patients were scheduled to undergo lower abdominal or peripheral surgery. Group 1 included five healthy ASA PS 1 subjects and group 2 included 10 patients with coronary artery disease (CAD). In all patients 12.5 ml of 2% lidocaine HCl was injected into the lumbar epidural space, and systolic and diastolic blood pressures, and heart rate were continuously monitored. 2DE evaluation was performed before and at 10, 20, 30, and 60 min (T10-T60) after epidural lidocaine injection. The left ventricular wall was divided into 16 segments for parasternal long-axis, short-axis and apical four-chamber views. The wall motion of each segment was graded on a scale from 1 (dyskinesia) to 6 (hyperkinesia), with 5 representing normal motion. A decrease in segmental wall motion greater than or equal to 2 grades was considered indicative of ischemia. Plasma lidocaine and catecholamine levels were measured before and 10, 20, and 60 min after epidural lidocaine injection. Peak plasma lidocaine levels in groups 1 and 2 were 2.79 +/- 1.06 micrograms/ml (mean +/- SD) and 2.58 +/- 1.48 micrograms/ml at 10 min, respectively (NS). Plasma epinephrine and norepinephrine levels were unchanged from baseline. Systolic pressures decreased significantly in group 2 from T10 to T60. Diastolic pressure decreased significantly in the same group from T20 to T60, and in group 1 only at T10. Mean arterial pressure decreased significantly in both groups at T30, without change in heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in regional myocardial function after coronary artery bypass graft surgery are predicted by intraoperative low-dose dobutamine echocardiography

BACKGROUND: Left ventricular dysfunction is often reversed after coronary artery bypass graft (CABG) surgery; however, this change is not easily predicted. The authors hypothesized that functional changes after a low dose of dobutamine (5 microgram. kg-1. min-1) intraoperatively would predict functional changes when complete revascularization was achieved. METHODS: The authors analyzed 560 segments in 40 patients scheduled for elective CABG surgery for regional wall motion (1-5 scoring system) at four stages: baseline (after induction and intubation), with administration of low-dose dobutamine before cardiopulmonary bypass, after separation from cardiopulmonary bypass (early), and after administration of protamine (late). Two independent observers scored the myocardial regions according to a 16-segment model in multiple imaging planes. For each segment, the response to dobutamine was dichotomized as improved or not improved from baseline and analyzed with logistic regression. The influence of covariates (ejection fraction, myocardial infarction, diabetes mellitus, and beta blockers) was also determined with logistic regression models. P < 0.05 was considered significant. RESULTS: Changes in myocardial function after low-dose dobutamine were highly predictive for early (P < 0.0001) and late (P < 0.0001) changes in myocardial function from baseline regional scores. The overall odds ratio for early and late improvement increased by 20.7 and 34.6, respectively, when improvement was observed after low-dose dobutamine was administered. The overall positive predictive value of improved regional wall motion after CABG did not vary with left ventricular ejection fraction, a history of myocardial infarction, or beta blocker use, and it varied little with diabetic status (range, 0.86-0.96) if regional wall motion improved with low-dose dobutamine before CABG. The overall negative predictive value was 0.70; however, the range varied with diabetic status (i.e., lowest in diabetic patients and highest in nondiabetic patients). CONCLUSION: Intraoperative low-dose dobutamine is a reliable method to predict myocardial functional reserve and to determine functional recovery expected after coronary revascularization.     

Effect of pyruvate on regional ventricular function in normal and stunned myocardium.

The prolonged ventricular dysfunction following brief periods of coronary artery occlusion that does not produce irreversible damage has been termed the "stunned" myocardium. Although ventricular function returns to preischemic values by 1 to 7 days after reperfusion is established, inotropic therapy may be necessary to enhance contractility in the stunned heart. The purpose of this study was to determine the effect of pyruvate on ventricular function in normal and stunned myocardium. Eight chloralose/urethane anesthetized dogs were instrumented with ultrasonic crystals to measure systolic wall thickening in the left anterior descending artery (LAD) and left circumflex artery perfused regions of the left ventricle. Pyruvate (1 ml/min of 150 mM sodium pyruvate, pH 7.4) was infused directly into the LAD prior to and 30 minutes after a 10 minute LAD occlusion. Prior to LAD occlusion, LAD pyruvate infusion increased systolic wall thickening in the LAD-perfused region from 16.2% +/- 4.3% to 23.4% +/- 5.1% (p less than 0.05). Thirty minutes after LAD occlusion, regional wall thickening was depressed (3.3% +/- 2.6%; p less than 0.05), which is indicative of stunned myocardium. Subsequent LAD pyruvate infusion increased wall thickening in the stunned myocardium to 12.7% +/- 2.5%. The improvement of regional ventricular function was maintained only during the pyruvate infusion, as function returned to prepyruvate levels within 20 minutes after cessation of pyruvate infusion. These data indicate that pyruvate exerts a positive inotropic effect in normal and stunned myocardium. If pyruvate, a key intermediate in energy-producing pathways, exerts its inotropic effect through an enhancement of the energy state of the heart, it may have advantages over traditional inotropic agents in the treatment of postischemic contractile dysfunction.     

术中多巴酚丁胺负荷经食道超声心动图预测冠状动脉旁路移植术后心肌存活的评价

目的 评价术中多巴酚丁胺负荷经食道超声心动图(DSE)预测冠状动脉旁路移植术后心肌存活情况.方法 择期拟行冠状动脉旁路移植术病人24例,性别不限,年龄50～75岁,体重55～90 kg,NYHA分级Ⅱ或Ⅲ级,左室射血分数30%～55%.麻醉诱导后,采用食道超声按16节段法,观察左室节段室壁运动情况,行半定量评分.静脉输注多巴酚丁胺,初始速率5μg·kg~(-1)min~(-1),然后以1μg·kg~(-1)min~(-1)的速率递增,每一速率持续输注3 min.将舒张末室壁厚度>0.5 cm的节段、室壁运动异常评分较给药前降低≥1分的心肌定义为存活心肌.计算DSE预测心肌运动恢复的敏感度、特异度、准确率、阳性预测率和阴性预测率.结果 DSE预测心肌存活率(36.3%)低于术后心肌运动改善率(43.2%)(P<0.05).DSE预测心肌存活的敏感度、特异度、准确率、阳性预测率和阴性预测率分别为75.3%、92.7%、85.3%、88.4%和83.5%.结论 术中DSE可有效地预测冠状动脉旁路移植术后存活心肌及功能恢复.     

Deterioration of Regional Wall Motion Immediately after Coronary Artery Bypass Graft Surgery Is Associated with Long-term Major Adverse Cardiac Events

Background: Patients undergoing coronary artery bypass graft (CABG) surgery frequently develop wall motion abnormalities diagnosed by intraoperative transesophageal echocardiography. However, the relation between deterioration in wall motion and postoperative morbidity or mortality is unclear. Therefore, the authors hypothesized that deterioration in intraoperative left ventricular regional wall motion immediately after CABG surgery is associated with a higher risk of adverse cardiac events.

Methods: With institutional review board approval, data were gathered from 1,412 CABG surgery patients. Echocardiographic wall motion score (WMS) was derived using a 16-segment model. Outcomes data were gathered for up to 2 yr after surgery. The primary outcome, major adverse cardiac event, was a composite index of myocardial infarction, need for subsequent coronary revascularization, or all-cause mortality during the follow-up period.

Results: Two hundred twenty-one patients (16%) had 254 primary outcome events during follow-up. Postbypass WMS did not change in 812 patients (58%), deteriorated in 219 patients (16%), and improved in 368 patients (26%). Kaplan-Meier analysis showed that patients with deterioration in WMS after CABG experienced significantly lower major adverse cardiac event-free survival than patients with either no change or improvement in WMS (P = 0.004). Cox proportional hazards regression modeling revealed a significant association between deterioration in WMS and the composite adverse outcome (hazard ratio, 1.47 [1.06-2.03]; P = 0.02).     

Near-infrared spectroscopy for noninvasive evaluation of chest wall ischemia immediately after left internal thoracic artery harvesting

OBJECTIVE: The conclusions remain controversial about whether the sternal blood flow is preserved or diminished after internal thoracic artery (ITA) harvesting for coronary artery bypass grafting (CABG), especially in diabetic patients. We investigated the blood supply of the chest wall noninvasively using near-infrared spectroscopy (NIRS) immediately after CABG. METHODS: The study group comprised 30 patients who underwent CABG using a skeletonized left ITA through median sternotomy. As a control group, three nondiabetic patients undergoing valve surgery through median sternotomy were also included. On arrival of the patient in the intensive care unit immediately after surgery, two reflectance sensors were placed on the bilateral parasternal regions at the fourth intercostal space to record regional oxygen saturation (rSO(2)) and hemoglobin index (HbI) continuously approximately for 17 h. RESULTS: The differences in right and left values (R-L rSO(2) and R-L HbI) were significantly greater in the diabetic patients than in the nondiabetic patients (3.74% +/- 2.47% vs. 1.98% +/- 1.67 %, p = 0.036; and 0.28 +/- 0.19 vs. 0.13 +/- 0.13, p = 0.020). The R-L HbI was significantly greater in the on-pump patients than in the off-pump patients, although there was no significant difference in R-L rSO(2). Both R-L rSO(2) and R-L HbI were similar among the control, nondiabetic, and off-pump patients. CONCLUSION: The technique of NIRS enables noninvasive, continuous monitoring of chest wall perfusion immediately after ITA harvesting. Our study using NIRS showed a decrease in blood flow and oxygen metabolism of the hemisternum after LITA harvest in diabetic CABG patients.     

Does intraoperative evaluation of left ventricular contractile reserve predict myocardial viability? A clinical study using dobutamine stress echocardiography in patients undergoing coronary artery bypass graft surgery

To determine the contractile reserve of the left ventricle during reperfusion as a predictor of myocardial viability in patients undergoing coronary artery bypass graft surgery, we measured the response of left ventricular regional wall motion and thickening by using dobutamine stress echocardiography (DSE) after myocardial revascularization. All patients were monitored with radial and pulmonary arterial catheters, transesophageal echocardiography, standard five-lead clinical electrocardiography, and three-channel Holter electrocardiography. Immediately after separation from cardiopulmonary bypass, dobutamine was administered IV starting at 5 microg. kg(-1). min(-1), with increases in rate every 3 min to 10, 20, 30, and 40 microg. kg(-1). min(-1). Within 1 wk after surgery, resting and redistribution thallium-201 myocardial perfusion imaging (thallium studies) was performed to assess the relationship between the intraoperative contractile response and myocardial viability. One-hundred patients completed DSE up to 10 microg. kg(-1). min(-1), and 85 patients received the larger escalating doses of the DSE. Seventy-two patients had postoperative thallium studies. At the completion of the small-dose dobutamine infusion, 689 (97.7%) of 705 segments had a normal response (improvement), and 16 segments (2.3%) had a positive response (deterioration). During large-dose dobutamine infusion, 577 (95.8%) of 602 segments had a normal response, and 25 segments (4.2%) had a positive response. Myocardial segments that had a positive response during large-dose DSE (48%) were more likely to be considered as nonviable on postoperative thallium studies compared with segments that had a normal response (14.7%) (P < 0.00001). By using thallium studies as the reference standard, the sensitivity of DSE was low (31% and 48% for small- and large-dose DSE, respectively) in predicting nonviable myocardium. However, the specificity was higher (86% and 85% for small- and large-dose DSE, respectively). In a separate analysis of patients who developed new regional wall motion abnormalities (RWMA) in the early intraoperative reperfusion period, 15 (75%) of 20 abnormally contracting myocardial segments had normal postoperative thallium studies. Our results demonstrate that a normal response to DSE is highly specific for viable myocardium; however, a positive response to DSE has low sensitivity in predicting nonviable myocardium. The majority of new postbypass regional wall motion abnormalities appear to be related to stunned myocardium.