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.     

Surgical ventricular restoration based on evaluation of myocardial viability with delayed-enhanced magnetic resonance imaging

OBJECTIVE: We examined whether the determination of myocardial viability by preoperative delayed-enhanced magnetic resonance imaging (DE-MRI) would be useful for planning surgical ventricular restoration (SVR). METHODS: Eight consecutive patients with poor cardiac function (ejection fraction < 30%) due to ischemic cardiomyopathy underwent surgical treatment based on findings of preoperative cine-MRI and DE-MRI. Our surgical strategy consisted of (1) complete revascularization on viable segments; (2) SVR in a patient with extensive nonviable segments; and (3) mitral valve plasty in a patient with a more than moderate degree of mitral regurgitation. Based on the MRI assessments, four of the patients (group A) underwent isolated coronary bypass surgery, and the other four (group B) underwent SVR and mitral valve plasty concomitantly with coronary bypass surgery. Perioperative changes in ventricular function were quantitatively assessed in each group. RESULTS: The mean end-diastolic volume index was reduced from 115 +/- 29 ml/m2 to 95 +/- 14ml/m2 in group A and from 163 +/- 35ml/m2 to 125 +/- 28ml/m2 in group B. The mean end-systolic volume index was reduced from 91 +/- 25ml/m2 to 68 +/- 16ml/m2 in group A and from 135 +/- 36ml/m2 to 98 +/- 28 ml/m2 in group B. The mean ejection fraction increased from 20% +/- 6% to 28% +/- 9% in group A and from 17% +/- 6% to 22% +/- 5% in group B. The mean New York Heart Association (NYHA) functional class was reduced from 3.0 +/- 0.8 to 1.8 +/- 0.6 in group A and from 3.5 +/- 0.5 to 2.2 +/- 0.2 in group B. CONCLUSION: DE-MRI was highly effective in helping to select which patients and which areas of the left ventricle are indicated for SVR, which contributed to excellent early clinical outcomes.     

Multivessel off-pump coronary artery bypass grafting can be taught to trainee surgeons

BACKGROUND: Although Off-Pump Coronary Artery Bypass (OPCAB) surgery is being increasingly explored and practised in many cardiac units worldwide, there have been only few reports documenting the training of surgeons in this new technique. The purpose of this study was to address the reproducibility of the OPCAB in a unit where this technique is used extensively. METHODS: Registry data, notes, and charts of 64 patients who were operated on by four trainee cardiac surgeons over a period of thirteen months at Harefield Hospital, were reviewed retrospectively. These trainees were part of an accredited training program for cardiothoracic training and were trained by a single consultant trainer in a cardiac unit after it had an established recent experience in performing nonselective OPCAB for all in-coming patients. Five (7.8%) patients (with 17 distal anastomoses) consented and underwent early postoperative angiography to check the quality of the grafts and anastomoses. RESULTS: The mean age of the study patients was 65.6 and the mean Parsonnet score was 9.4. There was a mean of 2.9 grafts per patient and circumflex territory anastomoses were performed in 48 (75%) patients. No operation required conversion to Cardiopulmonary Bypass (CPB). Angiography of the five patients revealed 17 satisfactory (100%) distal anastomoses. CONCLUSION: With appropriate training, it is possible for trainees to learn OPCAB and perform multivessel revascularization in relatively high-risk patients with good results.     

Evaluation of brain injury after coronary artery bypass grafting. A prospective study using neuropsychological assessment and diffusion-weighted magnetic resonance imaging.

OBJECTIVE: Neurocognitive dysfunction is a common complication after cardiac surgery with cardiopulmonary bypass (CPB). Studies using magnetic resonance imaging (MRI) have demonstrated that new focal brain lesions can occur after coronary artery bypass grafting (CABG), even in patients without apparent neurological deficits. Diffusion-weighted MRI is superior to conventional MRI and allows for sensitive and early detection of ischemic brain lesions. We prospectively investigated cerebral injury early and 3 months after CABG using diffusion-weighted MRI and related the findings to clinical data and neurocognitive functions. METHODS: Twenty-nine patients [67.6+/-8.6 (52-85) years, 5 females] undergoing elective CABG with CPB were examined before surgery, at discharge and 3 months after surgery. A battery of standardized neuropsychological tests and questionnaires on depression and mood were administered. Conventional and diffusion-weighted MRI of the brain was performed and new lesions were analyzed. Clinical characteristics, neuropsychological test performance and radiographic data were collected and compared. RESULTS: There was no major neurological complication after CABG. Thirteen patients (45%) exhibited 32 new ischemic lesions on postoperative diffusion-weighted MRI. The lesions were small, rounded and equally dispersed in both hemispheres. Eight patients had at least two lesions. At discharge, significant deterioration of neuropsychological performance was observed in 6 of the 13 tests compared to baseline assessment. By 3 months postoperatively, 5 of the 6 tests returned to preoperative levels. Verbal learning ability, however, remained impaired. The presence of new focal brain lesions was not associated with impaired neuropsychological performance. There was also no correlation between clinical variables, intraoperative parameters and postoperative complications and MRI findings. CONCLUSIONS: Although neurocognitive decline after CABG is mostly transient, memory impairment can persist for months. New ischemic brain lesions on postoperative diffusion-weighted MRI do not appear to account for the persistent neurocognitive decline.     

Long-term cardiac survival after reoperative coronary artery bypass grafting.

OBJECTIVE: Despite advances in cardiac surgery, the risk of reoperative coronary artery bypass surgery (RECABG) still exceeds those of a primary myocardial revascularization and also the late results are not so favourable. In this study, long-term cardiac survival is analyzed. METHODS: We analyzed long-term cardiac survival of 466 patients who survived the first 6 months after a RECABG between January 1987 and December 1998. Actuarial survival estimates were calculated and pre- and peroperative variables were analyzed to identify predictors of long-term cardiac related mortality. RESULTS: Mean follow-up was 7.7 +/- 3.8 years (1-17 years), and follow-up was 95.6% complete. One-year cardiac survival was 98.2%, 5-year: 91.0%, 10-year: 78.7% and 14-year survival 60.2%. Cardiac survival was only significantly superior for patients under 65 years of age at the moment of the RECABG. Impaired left ventricular function was identified as the only independent predictor of late cardiac-related mortality. CONCLUSION: The long-term survival in patients undergoing RECABG is acceptable. Once patients survived the first 6 postoperative months, advanced age (>65 years) is affecting long-term cardiac survival and impaired left ventricular function is the only independent predictor of late cardiac mortality.     

Prediction of improvement in regional left ventricular function after coronary artery bypass grafting: quantitative stress-redistribution 201Tl imaging in detection of myocardial viability

BACKGROUND: This study investigated the usefulness of quantitative assessment of Thallium-201 stress redistribution myocardial scintigraphy combined with quantitative assessment of regional left ventricular function using the centerline method for predicting of recovery regional left ventricular function following myocardial revascularization. METHODS: Twenty patients with chronic total obstruction of the proximal portion of left anterior descending artery and/or right coronary artery were studied. Percent Tl-uptake method was used to evaluate myocardial viability before CABG. Regional LV function was evaluated before and after CABG with the centerline method. The territory of LAD was defined by chords 10 to 58 and that of RCA was defined by chords 59 to 80 in the centerline method. The parameter of regional left ventricular function was the mean (SF-Av.)/SD of each LAD and RCA territory. RESULTS: In cases showing a % uptake value under 50%, the preoperative value of (SF-Av.)/SD was -3.18+/-0.74 and postoperative value was -2.63+/-0.8 1. The difference between these values was not significant. When the %uptake value over 50%, the preoperative value of (SF-Av.)/SD was -2.80+/-0.49 and the postoperative value was -2.27+/-0.28. The postoperative value was significantly higher than the preoperative value(p=0.007). CONCLUSIONS: Even in cases of severe left ventricular dysfunction, regional left ventricular function improved if the value of % uptake in the redistribution Thallium imaging was 50% or over. Quantitative analysis of myocardial scintigraphy combined with quantitative analysis of left ventriculography is a useful method for predicting recovery of regional left ventricular function following myocardial revascularization.     

Assessment of minimally invasive direct coronary artery bypass grafting of the left internal thoracic artery by means of magnetic resonance imaging

OBJECTIVES: We sought to evaluate graft patency, flow, and flow reserve in patients with minimally invasive direct coronary artery bypass surgery of internal thoracic artery grafts by a combined magnetic resonance protocol with a phase-contrast technique and magnetic resonance angiography. METHODS: At 1.5 T (Magnetom Sonata, Siemens), 30 symptomatic patients with 30 left internal thoracic artery grafts were examined 6 years after minimally invasive surgical intervention. Navigator-gated magnetic resonance angiography and contrast-enhanced FLASH-3D magnetic resonance angiography (0.2 mmol gadopentate-diethylene triamine pentetic acid [Gd-DTPA]/kg body weight) was used to assess bypass patency. Phase-contrast flow measurements with retrospective gating were performed in the internal thoracic artery grafts at rest and after stress induction with dipyridamole (0.57 mg/kg body weight). Graft patency was evaluated by means of multidetector computed tomography (Sensation 16, Siemens). RESULTS: Internal thoracic artery grafts were occluded in 5 of 30 patients. In 6 patients the anastomosis to the left anterior descending artery was highly stenotic (>70 % ) at multidetector computed tomography. In patients with regular grafts (multidetector computed tomography), a significant improvement of graft flow ( P < .001) and diastolic/systolic peak velocity ratio ( P < .001) after stress induction was detected. Magnetic resonance angiography combined with flow reserve measurements could differentiate between occluded-stenotic and regular minimally invasive direct coronary artery bypass grafts. CONCLUSIONS: Magnetic resonance imaging allows a combined assessment of bypass patency and flow with flow reserve in patients after the minimally invasive direct coronary artery bypass operation. The protocol of this study might be applicable for the evaluation of graft status in symptomatic patients after revascularization.     

Brain magnetic resonance angiography-based strategy for stroke reduction in coronary artery bypass grafting

We have been using magnetic resonance angiography (MRA) preoperatively to identify patients at increased risk of stroke in coronary artery bypass grafting (CABG). Based upon the intracranial MRA findings, either the off-pump or the on-pump procedure was selected. We report the results of our MRA-based strategy of CABG in 140 consecutive patients. Intracranial arterial lesions were found in 90 patients (64%). The most affected arteries were internal carotid (48%), followed by vertebral (18%) and middle cerebral (16%). Using the MRA score describing the severity of intracranial atherosclerosis, 35 patients with a score of > or = 5 underwent off-pump, while 105 patients with a score of < 5 underwent on-pump CABG. In the off-pump group, the patient age was older, the incidence of abnormal preoperative brain CT was higher, and the MRA score was higher (6.0+/-1.1 vs. 1.2+/-1.3 points) than in the on-pump groups. Even though the risk was higher in the off-pump group, the clinical outcomes were not significantly different, including the hospital mortality and the incidence of stroke and additional coronary intervention. In conclusion, the brain MRA-based selection of off-pump CABG can contribute to prevention of stroke in neurologically high-risk patients.     

体外循环和非体外循环冠状动脉旁路术围手术期心肌损伤程度的对比研究

目的　对比研究常规体外循环下冠状动脉旁路术 (CCABG)和非体外循环心脏跳动下冠状动脉旁路术 (OPCAB)围手术期心肌肌钙蛋白I(cTnI)动态变化规律 ,以明确心肌损伤的程度。方法　 5 9例不稳定心绞痛患者 ,射血分数 (EF) 0 35～ 0 5 6 ,其中 34例行OPCAB ,患者平均年龄 (5 9 1± 1 7)岁 ,平均搭桥数 1 0～ 5 0支 ,平均 (2 90± 0 8)支 ;2 5例行CCABG ,患者平均年龄 (5 6 5± 1 8)岁。搭桥数 2 0～ 5 0支 ,平均 (3 2± 0 7)支。分别在术前 ,术后第 8、2 4、48、72、96、12 0h时 ,采集患者静脉血标本 ,离心后取血浆测定cTnI值。cTnI的测定采用自动双抗体夹心酶联免疫荧光测定法 ,仪器检测灵敏度cTnI 0 35 μg/L。　 结果　术前 2组患者cTnI差异无显著性意义 (P >0 0 5 )。OPCAB手术组cTnI值在术后观察期内均低于CCABG组 ,差异有显著性意义 (t=1 9432 ,P =0 0 0 7)。全组患者无死亡 ,均痊愈出院。　结论　cTnI是诊断心肌损伤的良好指标。OPCAB手术心肌损伤程度显著低于CCABG手术。     

Pericardial cardiac troponin I release after coronary artery bypass grafting.

Pericardial fluid can reflect the composition of cardiac interstitium in myocardial ischemia. This study investigated the hypothesis that pericardial cardiac troponin I (CTnI) measurements could be a more accurate marker of perioperative myocardial infarction (MI) than serum CTnI after coronary artery bypass grafting (CABG). Postoperative arterial and pericardial blood samples were taken in 102 subjects undergoing elective CABG allocated to one of three groups according to the 12-lead electrocardiogram (ECG) abnormalities observed during the first postoperative 24 h: Group 1 = normal ECG; Group 2 = nonspecific ECG abnormalities; and Group 3 = perioperative Q-wave MI. Peak pericardial CTnI concentrations were much higher than peak serum concentrations in all subjects and significantly greater in Group 3 than in Groups 1 and 2 (1,318 +/- 1,810 ng/mL vs 367 +/- 339 ng/mL and 558 +/- 608 ng/mL, respectively; P < 0.01). However, no significant difference between groups occurred at any time for pericardial/serum CTnI ratios, indicating that time courses of CTnI were not different in pericardial fluid and serum. A significant correlation was found between serum and pericardial CTnI concentrations (R = 0.70, P < 0.001). Pericardial CTnI was not more accurate than serum CTnI in predicting Q-wave MI as shown by the low value of the area under the receiver-operator characteristic curve (= 0.71). Peak and early pericardial CTnI were also not accurate in predicting an increase of serum CTnI greater than a cutoff value of 19 ng/mL. Thus, pericardial CTnI measurements were less useful than serum CTnI measurements in the diagnosis of perioperative MI after CABG. IMPLICATIONS: Although cardiac troponin I concentrations were much higher in pericardial fluid than in serum and significantly increased in subjects who experienced perioperative Q-wave myocardial infarction, pericardial cardiac troponin I measurements were of less value than serum cardiac troponin I measurements for the diagnosis of perioperative myocardial infarction after coronary artery bypass grafting and cannot be recommended in routine clinical practice.