Beating-heart surgery avoids cardiopulmonary bypass

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1 Intraoperative Ischemia and Long-Term Events After Minimally Invasive Coronary Surgery Marco Zimarino, MD, Sabina Gallina, MD, Maria Di Fulvio, MD, Michele Di Mauro, MD, Gabriele Di Giammarco, MD, Raffaele De Caterina, MD, PhD, and Antonio Maria Calafiore, MD Department of Cardiology and Cardiac Surgery, G. D Annunzio University of Chieti, Chieti, Italy Background. Concern has been raised about the effects of prolonged left anterior descending (LAD) artery occlusion during minimally invasive direct coronary artery bypass graft surgery (MIDCABG). We sought to assess the impact of myocardial dysfunction during MIDCABG on long-term outcome and the protective role of collateral circulation on myocardial ischemia. Methods. Myocardial function was evaluated in 92 patients by intraoperative transesophageal echocardiography during MIDCABG. Results. Wall motion score index increased during LAD occlusion (p < 0.00l) and reverted after LAD reopening (p < versus occlusion and p not significant versus baseline). The change in wall motion score index (occlusion versus baseline) was higher in patients with multivessel disease (p < 0.05) and in patients with LAD Thrombolysis in Myocardial Infarction study classification flow grade 2 or less without collateral circulation (p < 0.05). Myocardial stunning was documented in 12 patients (13%). The 5-year adverse event rate (including death, myocardial infarction, and revascularization) was 12%. By multivariate Cox regression analysis, multivessel disease, but not perioperative ischemia or stunning, was the only predictor of event-free survival. Conclusions. During MIDCABG anterior wall dysfunction is transient, with prompt recovery after completion of the anastamosis in most cases; myocardial stunning can be documented in a minority of patients. Flow either antegrade or retrograde in the LAD territory plays a protective role against the development of ischemia. Multivessel disease, but not perioperative ischemia or stunning, predicts long-term event-free survival. (Ann Thorac Surg 2004;78:135 41) 2004 by The Society of Thoracic Surgeons Beating-heart surgery avoids cardiopulmonary bypass at the cost of prolonged myocardial ischemia [1]. Minimally invasive direct coronary artery bypass surgery (MIDCABG) permits anastamosis of the left internal mammary artery to the left anterior descending (LAD) coronary artery through a small left anterior thoracotomy without cardiopulmonary bypass [2]. Data on angiographic patency rates and survival after MIDCABG compare favorably with conventional surgery in experienced centers [3, 4]. Controversy exists, however, as to whether coronary occlusion during off-pump surgery results in clinically relevant myocardial ischemia [5, 6]. In the present study we used intraoperative transesophageal echocardiography (TEE) to assess the effects of prolonged LAD occlusion on myocardial dysfunction during MIDCABG, and evaluated the impact of myocardial ischemia on long-term outcome. We also sought to test the protective role of collateral circulation on myocardial ischemia in this setting. Accepted for publication Dec 2, Address reprint requests to Dr Zimarino, Ospedale San Camillo de Lellis, University of Chieti, Via Forlanini , Chieti, Italy; m.zimarino@unich.it. Material and Methods Study Population The study was approved by the local ethics committee, and written informed consent was obtained from all patients. Between April 1996 and April 1999, 770 patients underwent MIDCABG at our institution. Based on the limited availability of the cardiologists staff, of the echocardiographic system, or on the inability of the surgeon to request transesophageal echocardiography (TEE), intraoperative TEE was performed only in 100 cases. In 5 cases intraoperative TEE was judged not adequate for evaluation; in 3 cases transthoracic echocardiography (TTE) before MIDCABG was not available. Therefore, clinical records, angiography, intraoperative TEE, TTE before and 3 days after MIDCABG, and in-hospital outcomes were completely available from 92 patients (92%), who were the study population. Surgical Technique As previously described [2], the chest was opened through a left anterior small thoracotomy, ribs were retracted, and the pericardium was incised vertically. The left internal mammary artery was harvested and, in the majority of cases, skeletonized. After systemic heparinization (1 mg/kg), the left internal mammary artery was divided, injected with a papaverine solution and its flow and quality carefully evaluated. The LAD was then 2004 by The Society of Thoracic Surgeons /04/$30.00 Published by Elsevier Inc doi: /j.athoracsur

2 136 ZIMARINO ET AL Ann Thorac Surg INTRAOPERATIVE ISCHEMIA DURING MIDCABG 2004;78: occluded proximally and distally with the aid of a small piece of silicone tubing in order to avoid any direct compression. A mechanical stabilizer was used to reduce movements of the artery. The LAD was then incised, and the anastomosis with the left internal mammary artery performed. The MIDCABG was performed in 39 subjects (43%) with multivessel coronary artery disease as a functionally adequate myocardial revascularization: in 15 cases only minimal or no viable myocardium was detected in areas other than that supplied by the LAD, in 18 cases a diffuse disease of distal branches was present, and in 6 cases the disease of non-lad coronary arteries was judged not relevant. Coronary Angiography Coronary angiograms were reviewed by two independent observers (M.Z. and M.D.M.). The projection using the most severe coronary narrowing was selected. Using the guiding catheter as a calibration standard, a caliperassisted measurement of minimal lumen and reference diameters was performed, and the percent lumen diameter stenosis calculated [7]. Multivessel coronary disease was defined as more than 50% stenosis in one or more vessels remote from the LAD. The antegrade LAD flow was graded with the use of the Thrombolysis in Myocardial Infarction (TIMI) study classification without knowledge of patient data [8]. In brief, grade 0 no antegrade flow; grade 1 minimal incomplete perfusion of contrast medium beyond the point of occlusion; grade 2 (partial perfusion) complete but delayed perfusion of the distal LAD bed; grade 3 (complete perfusion) antegrade flow to the entire distal LAD bed at a normal rate. The angiographic collateral vessel filling was graded by visual analysis according to Rentrop and associates [9]: 0 absent collateral circulation; 1 filling of collateral vessels without any epicardial filling of the LAD; 2 partial epicardial filling of the LAD by collateral vessels; 3 complete epicardial filling of the LAD by collateral vessels. Grading of the antegrade LAD flow and collateral vessels was performed independently by the two angiographers, and a consensus was reached when they differed. Echocardiographic Imaging and Analysis All study patients underwent a complete TTE the day before surgery and on postoperative day-3 using an ATL Apogee Cx 200 (Interspec-ATL, Bothell, WA) with a 3.5 MHz probe. Intraoperative TEE was performed with a 5 MHz multiplane probe. The TEE imaging was performed after anesthesia induction (baseline), during the period of anastamosis (occlusion), and during maximum recovered wall motion within 60 minutes after the anastamosis was completed (recovery). The TEE imaging included the four-chamber, two-chamber, and long-axis views (in sequence) followed by the transgastric short- and long-axis views; the probe was manipulated in order to avoid foreshortening of the left ventricular apex. All TTE and TEE studies were reviewed off-line by two experienced echocardiographers (S.G. and M.D.F.) masked to patients data and to the study sequence. Concordance between independent readings by the two operators was previously tested (k 0.90 for TTE and 0.91 and for TEE). Regional wall motion was indexed according to the 16-segment model proposed by the American Society of Echocardiography [10, 11]: normal 1; hypokinetic 2; akinetic 3; and dyskinetic 4. Left ventricular wall motion score was obtained by adding the scores of all 16 segments. A wall motion score index (WMSI) was calculated by dividing the global score by the number of segments analyzed. According to this scoring system, a higher score indicates worse function. To quantify the amount of jeopardized myocardium, the variation between occlusion and baseline WMSI ( WMSI) was calculated. In cases where intraoperative TEE documented WMSI at recovery more than baseline, myocardial stunning was considered if function normalized at day 3 TTE [12]. Myocardial damage was defined if function was persistently deteriorated at day 3 TTE. Among the 1,472 myocardial segments identified at intraoperative TEE, 1,451 segments (98.6%) could be evaluated at each stage of the procedure; 21 segments (1.4%) were not adequate for wall motion analysis: apical septal, apical lateral, and apical anterior segments in 4 cases, mid lateral in 3 cases, and apical inferior, mid anterior, and basal anterior in 2 cases. Particular care was taken to avoid misinterpretation due to surgeon s manipulation of the stabilizer: the placement of this device was indicated during tape recording, and the occlusion study was performed usually after the completion of the anastomosis and the stabilizer removal, before LAD reopening. Clinical Events and Follow-Up Major adverse cardiovascular events were defined as death, nonfatal myocardial infarction (prolonged chest pain with a documented rise in CK-MB 3 times the upper normal laboratory limit, or development of new Q waves), and all new revascularization procedures, whether percutaneous or surgical. All events were source-documented and adjudicated by consensus of two reviewers (G.V. and G.D.G). Clinical follow-up was carried-out on all 92 study patients (100%) by either telephone contacts or office visits within 1 month after MIDCABG and every 6 months thereafter up to 7 years. Statistical Analysis Continuous data were expressed as mean SD and compared by the Student t test. Discrete variables were expressed as counts and percentages and compared by the Fisher s exact test. Analysis of variance for repeated measures with the Bonferroni s correction for posthoc analyses tested differences in WMSI during baseline, occlusion, and recovery. Kaplan-Meier life-table analysis was used to calculate

3 Ann Thorac Surg ZIMARINO ET AL 2004;78: INTRAOPERATIVE ISCHEMIA DURING MIDCABG Table 1. Baseline Characteristics of the 770 Patients Who Underwent Minimally Invasive Direct Coronary Artery Bypass During Study Period With TEE n 92 (12%) Without TEE n 678 (88%) p Value Age (years) NS Sex (male) 80 (87%) 576 (85%) NS Family history 25 (27%) 196 (29%) NS Hypertension 66 (72%) 474 (70%) NS Diabetes 16 (17%) 101 (15%) NS mellitus Smoking 50 (54%) 352 (52%) NS Previous 45 (49%) 346 (51%) NS myocardial infarction Redo surgery 4 (4%) 34 (5%) NS Unstable 18 (20%) 156 (23%) NS angina Multivessel 39 (43%) 305 (45%) NS disease LAD TIMI flow (33%) 237 (35%) 2 12 (13%) 81 (12%) NS 3 49 (53%) 360 (53%) Ejection fraction (%) NS LAD left anterior descending artery; NS not significant; TEE transesophageal echocardiography; TIMI Thrombolysis in Myocardial Infarction study classification. event-free survival, and significance was here tested by the log-rank test. Cox multivariate regression analysis was used to model independent predictors of long-term major adverse cardiac events. Variables included in the model were age, sex, diabetes, hypertension, previous myocardial infarction, previous CABG, unstable angina, multivessel disease, left ventricular ejection fraction, WMSI, and the presence of myocardial stunning or damage after MIDCABG. Statistical analysis was performed with the use of the 137 SPSS package (release 7.5 version; SPSS, Chicago, IL). Significance was established at the level of p less than 0.05 except for posthoc analyses (p /3). Results Patient Characteristics Clinical and angiographic characteristics of the entire population of patients undergoing MIDCABG at our institution during the study period are reported in Table 1. There were no significant differences between patients undergoing MIDCABG with TEE (our study population) versus subjects undergoing MIDCABG without intraoperative TEE. Among the 92 patients who were part of our study population, LAD reference and minimal lumen diameter were mm and mm; mean diameter stenosis was 81% 17%. The TIMI flow grade was 0 to 1 in 31 patients (33%), 2 in 12 patients (13%), and 3 in 49 patients (53%). Collateral circulation was coded as grade 1 in 10 (11%); grade 2 in 22 (24%); and grade 3 in 5 patients (5%). Procedural Results The LAD occlusion lasted 22 6 minutes. Myocardial dysfunction occurred minutes after LAD occlusion; myocardial recovery was noted minute after the completion of the anastomosis. No patient needed hemodynamic support with drugs or intraortic balloon pump during MIDCABG nor thereafter during the hospital stay. Peak CK and CK-MB release were IU/mL and IU/mL, respectively. Overall Wall Motion Analysis The WMSI increased from at baseline to during occlusion (p 0.001), indicating a deterioration of left ventricular function during occlusion. The WMSI completely reverted after LAD opening ( , p versus occlusion; p not significant versus baseline). When compared with both baseline and recovery, wall motion score during occlusion was significantly worse during occlusion in mid anteroseptal, mid septal, Fig 1. Left ventricular wall motion score (WMS) before (baseline triangles), during (occlusion squares), and after (recovery circles) left anterior descending coronary artery occlusion in the 16 segments of the patient population studied. *p (Ant-Sept antero-septal; Post posterior.)

4 138 ZIMARINO ET AL Ann Thorac Surg INTRAOPERATIVE ISCHEMIA DURING MIDCABG 2004;78: Taking into account both antegrade and retrograde flow in the LAD territory, WMSI was significantly higher among patients with TIMI flow grade 2 or more and absent collateral circulation when compared with subjects with either TIMI flow grade 3 or the presence of significant (Rentrop 1) collateral circulation (p 0.05; Fig 3). Fig 2. Changes in left ventricular wall motion score index ( WMSI) in patients with single left anterior descending (LAD) and multivessel disease (MVD). apical septal, apical lateral, and apical anterior segments (Fig 1). There was no significant deterioration in wall motion in any of the other segments throughout the study, even in patients with multivessel disease. In 54 patients (59%), a deterioration of contractile function during occlusion occurred in two or more myocardial segments. Delta wall motion score index (occlusion versus baseline) was higher (indicating worse intraoperative left ventricular dysfunction) among patients with multivessel coronary artery disease when compared with those with just LAD disease (p 0.05; Fig 2). Delta wall motion score index was similar among patients with LAD TIMI flow grade 0 to 1 ( ) and those with TIMI flow grade 2 or more ( , p not significant). Delta wall motion score index did not differ between subjects with and without collateral circulation ( versus , respectively, p not significant). Fig 3. Changes in left ventricular wall motion score index ( WMSI) in patients with different flow status in the left anterior descending artery territory. (CC collateral circulation; TIMI thrombolysis in myocardial infarction classification). Myocardial Stunning When compared with baseline, WMSI decreased after LAD reopening in 29 patients (32%), was unchanged in 51 patients (55%), and increased in the remaining 12 patients (13%). Overall, 27 myocardial segments (1.8%) were identified as deteriorated at the end of MIDCABG: mid anteroseptal in 5 cases; basal anteroseptal, mid anterior, apical anterior, and apical septal in 3 cases; posterobasal septal, mid lateral, and apical lateral in 2 cases; and basal anterior, mid posteroseptal, mid posterior, and apical inferior in 1 case. In the subjects with increased WMSI at recovery, TTE performed on postoperative day 3 showed no additional segmental wall motion abnormality compared with preoperative findings, suggesting myocardial stunning. When compared with preoperative findings, no patient with myocardial damage (worsened myocardial function at day 3 TTE) was identified. Baseline characteristics in patients with myocardial stunning were similar to the overall population; multivessel disease was present in 6 of 13 patients (46%, p not significant versus patients without myocardial stunning). The LAD occlusion time was 23 8 minutes, similar to the remaining patients (22 7 minutes, p not significant). Subjects in this cohort showed a larger amount of jeopardized myocardium during MIDCABG: WMSI was significantly higher ( ) when compared with patients showing a normalized or improved myocardial function at the end of surgery ( , p 0.001). Peak CK-MB release was 24 9 IU/mL, similar to subjects with myocardial recovering early after MIDCABG (29 27 IU/mL, p not significant). In-Hospital Outcome There were no in-hospital deaths. Three patients (3.3%) had a myocardial infarction during the hospital stay; in none of them persistent myocardial dysfunction at the end of MIDCABG (recovery WMSI greater than baseline) was detected. These patients underwent diagnostic angiography the following week. In 2 of them a coronary angioplasty was performed, with stent implantation in the right coronary artery in 1, and in the circumflex artery in the other. One patient had a patent left internal mammary artery and a previously stenotic proximal LAD was found occluded; the remaining coronary circulation was normal. One patient with postoperative graft bleeding required an emergency open thoracotomy, but total patency of the conduit was found during repeat surgery by Doppler and 3 days later confirmed by angiography. Atrial fibrillation developed in 5 of 88 patients with preoperative sinus rhythm (6%); subjects who had atrial fibrillation had similar baseline and procedural charac-

5 Ann Thorac Surg ZIMARINO ET AL 2004;78: INTRAOPERATIVE ISCHEMIA DURING MIDCABG 139 Fig 4. Six-year actuarial Kaplan-Meier event-free survival curves according to the extent of coronary artery disease. Solid line indicates patients with single left anterior descending (LAD) disease; dashed line indicates patients with multivessel disease (MVD). The number of patients surviving without death, myocardial infarction or revascularization procedures (major adverse cardiac events [MACE]) at each 1-year interval is shown. teristics when compared with the remaining patients with preoperative sinus rhythm. Follow-Up The mean follow-up was months (range, 41 to 86; median, 63). During the follow-up, 3 patients died. One patient experienced recurrent chest pain 4 months after MIDCABG; angiography showed an occluded left internal mammary artery, and a percutaneous angioplasty with stent deployment in the LAD was performed. One patient underwent stent implantation on the left circumflex and the right coronary artery 30 months after surgery. After 5 years, follow-up was completed in 65 patients (71%). The overall survival was 95%; major adverse cardiac events were documented in 8 subjects (12%). The actuarial event-free survival was similar in patients with postoperative myocardial stunning (92% 8%) compared with patients with myocardial function found unchanged or improved after MIDCABG (91% 3%, p not significant). The 5-year actuarial event-free rate for patients with a relevant amount of jeopardized myocardium during MIDCABG (at least 2 ischemic myocardial segments, WMSI 0.125) was similar to patients with minimal ischemia during MIDCABG (91 4 versus 92% 4%, p not significant). The probability of event-free survival was significantly lower for patients with multivessel disease (82% 6%), when compared with subjects with isolated LAD disease (98% 2%, p ; Fig 4). The result of the Cox proportional hazard regression model including 11 possibly explanatory variables demonstrated that multivessel disease remained a significant independent risk factor for the occurrence of adverse events during 5 years of follow-up, with a hazard ratio of 9.8 (95% confidence interval, 1.2 to 80, p ). Comment This study shows that anterior wall dysfunction during MIDCABG does occur, but is transient and reversible. While a decrease in anterior wall motion was the rule during LAD occlusion, 13% of patients had persistent anterior wall dysfunction 60 minutes after LAD reopening, with a complete recovery of anterior wall function after 3 days. Thus, the present study documents that LAD flow or collateral circulation to the LAD territory is associated with lesser detrimental changes in left ventricular function during MIDCABG. Also, we have here documented that the presence of multivessel coronary artery disease significantly affects both the extension of intraoperative ischemia and long-term event-free survival. Myocardial Ischemia and LAD Flow Intraoperative TEE documented that myocardial dysfunction in patients submitted to MIDCABG is confined to distal LAD territories. This may be because of the presence of developed collaterals in more than one third of patients and to the distal location of the occlusion site. As already reported by Brown and colleagues [5] in a small series of patients, systolic dysfunction was more significant with lesser degrees of coronary artery stenosis, implicating lesser development of collateral circulation or of preconditioning. Our data extend these observations, showing that anterior wall motion worsened if impaired antegrade flow was present before the operation or if collaterals were poorly developed. In a series of 17 patients undergoing MIDCABG for severe LAD stenosis, ischemic preconditioning with brief episodes of coronary occlusion failed to preserve myocardium from the development of ischemia during the anastomosis [13]. It therefore appears that chronic physiologic adaptations of the coronary circulation to the stenosis exert a better protection on myocardial systolic function than the induction of transient ischemia during surgery. Recently, Menon and associates [14] tested the effectiveness of temporary intraluminal shunting during MIDCABG: this technique prevented myocardium from systolic dysfunction, that lasted 30 minutes after removal of the occlusive system was completely reversible. We

6 140 ZIMARINO ET AL Ann Thorac Surg INTRAOPERATIVE ISCHEMIA DURING MIDCABG 2004;78: deliberately tried to minimize the manipulation of LAD artery, however, as iatrogenic lesions are not so infrequently documented after MIDCABG [15]. Myocardial Stunning Postoperative stunning commonly occurs after cardiac surgery [16, 17]. In our study, myocardial stunning was identified in a minority of cases (1.8% of segments analyzed and 13% of patients) and was associated with a larger amount of jeopardized myocardium, indicating that recovery after MIDCABG needs more than 1 hour to be completed, when transient ischemia is of sufficient magnitude. However, myocardial stunning had no impact on either in-hospital or long-term outcome. That lack of impact might be due to the limited number of patients studied, in a relatively low-risk population, in which only eight major adverse cardiac events were recorded, mainly revascularization procedures in territories other than LAD artery. This issue needs verification in a larger population. MIDCABG in Patients With Multivessel Disease The leading indication for MIDCABG surgery is singlevessel disease with chronic occlusion or recurrent restenosis of the LAD artery. Promising results obtained after the initial experience encouraged the inclusion of patients with multivessel disease and significant concurrent medical illnesses for whom cardiopulmonary bypass entails a relevant risk [3, 4]. Whenever feasible, off-pump CABG reduces in-hospital morbidity without affecting midterm outcome compared with traditional surgery with cardiopulmonary bypass [18]. A strategy of functional revascularization with MIDCABG conceptually differs from complete anatomical bypass grafting. Our results show that patients with multivessel disease develop a larger amount of transient ischemia during surgery compared with patients with single LAD disease, without increased in-hospital complications. During the follow-up, however, the extent of coronary artery disease was the only determinant of adverse outcome. Limitations We acknowledge several limitations of the current study: intraoperative TEE was performed in a selected series of patients; however, baseline clinical and angiographic characteristics of our study patients were comparable to our overall MIDCABG population. Data are also lacking on the correlation between preexisting inducible ischemia and the extent of myocardial dysfunction during MIDCABG; this gap of knowledge needs to be addressed by further studies. Another limitation is that troponin enzymes were not systematically available at the time of the study. Myocardial contrast echocardiography is more accurate than coronary angiography in the detection of collateral circulation [19] and could have added insights into the mechanism of protection against ischemia. Also, the metabolic effects of coronary occlusion were not assessed in the present study. The use of a measure of systolic function more sensitive than WMSI, such as absolute (in mm) or percent myocardial thickening could have further detailed the analysis. Moreover, the study did not address diastolic dysfunction, which may precede and persist longer than systolic dysfunction accompanying acute ischemia. The limited number of the study population could be responsible for a beta error, preventing the detection of additional risk factors (such as the extent of transient ischemia) for long-term adverse events. Therefore, although our study population is representative of a larger cohort, enthusiastic reports of the final outcomes of this surgical technique must be viewed cautiously and compared with those of conventional surgery in a larger population only after adjustment for baseline variables [20]. In conclusion, within durations of ischemia of the LAD territory limited to 30 minutes, MIDCABG does not apparently cause persistent wall motion abnormalities. Although myocardial stunning can be documented in a minority of patients, this is transient. Intraoperative TEE can document a depression of contractile function in the anterior territory, to an extent related to the severity of coronary artery disease and the degree of epicardial coronary flow. Long-term events, however, are not related to the severity of transient ischemia during LAD occlusion. A reduced long-term event-free survival was related to the extent of coronary artery disease, thus constituting a strong argument for complete revascularization at the time of the initial bypass surgery. Larger studies are needed to ascertain the effectiveness of MIDCABG as a functional revascularization in patients with multivessel coronary artery disease compared with traditional bypass surgery. References 1. Benetti FJ, Naselli G, Wood M, et al. Direct myocardial revascularization without extracorporeal circulation: experience in 700 patients. 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7 Ann Thorac Surg ZIMARINO ET AL 2004;78: INTRAOPERATIVE ISCHEMIA DURING MIDCABG 141 occlusion by an angioplasty balloon in human subjects. J Am Coll Cardiol 1985;5: Schiller NB, Shah PM, Crawford M, et al, for the American Society of Echocardiography Committee on Standards Subcommittee on Quantitation of Two-Dimensional Echocardiograms. Recommendations for quantitation of the left ventricle by two-dimensional echocardiography. J Am Soc Echocardiogr 1989;2: ASE/SCA. ASE/SCA guidelines for performing a comprehensive intraoperative multiplane transesophageal echocardiography examination. Recommendations of the American Society of Echocardiography Council for Intraoperative Echocardiography and the Society of Cardiovascular Anesthesiologists Task Force for Certification in Perioperative Transesophageal Echocardiography. Anesth Analg 1999;89: Braunwald E, Kloner RA. The stunned myocardium: prolonged, post-ischemic ventricular dysfunction. Circulation 1982;66: Malkowski MJ, Kramer CM, Parvizi ST, et al. Transient ischemia does not limit subsequent ischemic regional dysfunction in humans: a transesophageal echocardiographic study during minimally invasive coronary artery bypass surgery. J Am Coll Cardiol 1998;31: Menon AK, Albes JM, Oberhoff M, et al. Occlusion versus shunting during MIDCAB: effects on left ventricular function and quality of anastomosis. Ann Thorac Surg 2002;73: Alessandrini F, Gaudino M, Glieca F, et al. Lesions of the target vessel during minimally invasive myocardial revascularization. Ann Thorac Surg 1997;64: Kloner RA, Jennings RB. Consequences of brief ischemia: stunning, preconditioning, and their clinical implications part I. Circulation 2001;104: Kloner RA, Jennings RB. Consequences of brief ischemia: stunning, preconditioning, and their clinical implications part II. Circulation 2001;104: Angelini GD, Taylor FC, Reeves FC, Ascione R. Early and midterm outcome after off-pump and on-pump surgery in Beating Heart Against Cardioplegic Arrest Studies (BHA- CAS 1 and 2): a pooled analysis of two randomised controlled trials. Lancet 2002;359: Sakata Y, Kodama K, Adachi T, et al. Comparison of myocardial contrast echocardiography and coronary angiography for assessing the acute protective effect of collateral recruitment during occlusion of the left anterior descending coronary artery at the time of elective angioplasty. Am J Cardiol 1997;79: Tamis-Holland LE, Homel P, Durani M, et al. Atrial fibrillation after minimally invasive direct coronary artery bypass surgery. J Am Coll Cardiol 2000;36: Notice From the American Board of Thoracic Surgery Regarding Trainees and Candidates for Certification Who Are Called to Military Service Related to the War on Terrorism The Board appreciates the concern of those who have received emergency calls to military service. They may be assured that the Board will exercise the same sympathetic consideration as was given to candidates in recognition of their special contributions to their country during the Vietnam conflict and the Persian Gulf conflict with regard to applications, examinations, and interruption of training. If you have any questions about how this might affect you, please call the Board office at (312) Timothy J. Gardner, MD Chairman The American Board of Thoracic Surgery 2004 by The Society of Thoracic Surgeons Ann Thorac Surg 2004;78: /04/$30.00 Published by Elsevier Inc