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Ann Thorac Surg 2007;83:1035-1040
© 2007 The Society of Thoracic Surgeons
a Department of Cardiothoracic Surgery and Cardiothoracic Anesthesia, Tucson Heart Hospital, Tucson, Arizona
b Department of Cardiovascular Surgery, Anadolu Foundation Healthcare Systems/ Johns Hopkins Medicine Gebze, Kocaeli, Turkey
Accepted for publication October 6, 2006.
* Address correspondence to Dr Gurbuz, 4729 East Sunrise Dr, #153, Tucson, AZ 85718 (Email: atgurbuz{at}yahoo.com).
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Abstract |
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 Top Abstract IntroductionPatients and MethodsResultsCommentReferences |
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Methods: Routine ITEE was performed in 744 OPCAB patients performed over a five year period. Mean patient age was 69.1 ± 8.0 years. There were a high percentage of patients over 70 years (39%), diabetics (26%), poor left ventricular function (
35%) (31%), recent myocardial infarction (24%), unstable angina (15%), and preoperative intraaortic balloon pump (5.6%); mean graft number was 3.4.
Results: There was a major modification in intraoperative strategy in 117 patients (16%) and minor modification in 77 patients (10%) due to information available through the ITEE (total 26%). Graft revision was performed in 39 patients, graft construction was modified due to severe ascending aortic atherosclerosis in 31, and an intraoperative intraaortic balloon pump was placed due to previously underappreciated left ventricular dysfunction and new intraoperative left ventricular dysfunction in 37 patients. Ten patients were placed on cardiopulmonary bypass due to previously unknown intracardiac pathology (three atrial septal defect repairs and five valvular procedures, two others). Intracoronary shunts were placed due to new wall motion changes during anastomosis in 77 patients. There were two emergent conversions to cardiopulmonary bypass. There were no complications due to ITEE probe placement.
Conclusions: Intraoperative transesophageal echocardiography is a valuable adjunct and can result in a major change of surgical strategy in a significant number of patients when used routinely for OPCAB. It may also improve surgical outcome and add to the OPCAB benefits.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Routine ITEE during cardiac surgery was shown to reduce patient morbidity and improve patient outcome [4]. Intraoperative transesophageal echocardiography is especially beneficial in high-risk patients undergoing coronary artery bypass grafting (CABG). In one study, ITEE changed surgical management in 57% and anesthetic management in 73% of CABG patients [5].
There are only a few reports of ITEE performed during off-pump coronary artery bypass (OPCAB) [1, 6, 7]. These studies have concentrated mostly on guiding fluid administration, institution of vasopressors-inotropes or antiischemic therapy. Absence of cardiopulmonary bypass circuit during OPCAB requires close monitoring of hemodynamic parameters and quick decision making on the part of the surgical team. The ITEE may be more useful during OPCAB than on-pump CABG because it provides a variety of continuous real-time information during different stages of the operation. This study was undertaken to evaluate the impact of ITEE on intraoperative management of OPCAB patients.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Standard anesthesia induction with opiates was followed by inhalation anesthesia. Radial artery and central venous pressure monitoring was routinely used. Pulmonary artery catheters were inserted selectively at the discretion of the surgical team. Room temperature was adjusted to 27°C and heating pad and fluid warmers were standard. The electrocardiogram (ECG) was monitored continuously with two leads (II and V5). Surgical technique consisted of standard median sternotomy and pericardiotomy. Anticoagulation was achieved using full dose unfractionated porcine heparin (4 mg/kg; target activated clotting time, 350 to 400 seconds). The internal mammary artery and saphenous vein grafts were used as standard bypass conduits; radial arteries were used selectively. Distal anastomoses were constructed prior to proximal anastomoses when using vein grafts. Radial artery grafts were attached to internal thoracic arteries for inflow prior to distal coronary anastomoses. All patients received intravascular volume loading with crystalloids, as well as 4 grams of magnesium sulfate before the heart was displaced for graft construction.
Cardiac displacement was achieved using deep pericardial sutures between the left inferior pulmonary vein and the inferior vena cava. We did not use gauze pads in the pericardium as not to obliterate TEE views. The operating room table was positioned in a steep Trendelenburg position and rotated to the right for grafting lateral and posterior wall vessels. Anterior coronary arteries were grafted first, followed by lateral and inferior wall vessels in this order. Arterial blood gases and activated clotting time were monitored every 30 minutes. Intraluminal shunts were utilized when there was hemodynamic deterioration or with the appearance of new segmental wall motion abnormalities (SWMA) on the TEE after coronary occlusion.
Hemodynamic instability was defined as intraoperative hypotension (mean arterial pressure < 60 mm Hg) or significant bradycardia leading to hypotension as well as all tachyarrhythmias with hemodynamic deterioration for a duration of two minutes or longer. Inotropic support was used when intraoperative hypotension was unresponsive to fluid administration and simple positioning maneuvers.
An intraaortic balloon pump (IABP) was inserted in the beginning of the procedure if there was previously underappreciated severe left ventricular dysfunction or with deteriorating hemodynamic status unresponsive to fluid administration and a moderate amount of inotropic support for a period of 5 minutes and concomitant left ventricular dysfunction on ITEE.
The criteria for conversion to cardiopulmonary bypass were significant hemodynamic instability and ventricular arrhythmias unresponsive to medications and IABP. Graft flow was evaluated using a hand-held Doppler device. Graft revision was performed when there was poor diastolic flow augmentation in the conduits, together with new segmental wall motion changes on the TEE. Ischemia on the ECG was defined as ST segment changes lasting greater than one minute (either horizontal or downsloping ST depression 
1 mm or horizontal ST elevation 1 mm occurring 60 mseconds after the J point).
The TEE was performed by three cardiac anesthesiologists during the study period. Two of the three received extensive training and were certified by the American Board of Echocardiography. The third had extensive practical experience in ITEE.
The TEE probe was placed after induction of anesthesia prior to draping. Continuous ITEE monitoring was performed using a 9 mm multiplane 5 MHz probe (Acuson TE V5-Ms; Acuson Corp, Mountain View, CA). Midesophageal and transgastric short axis and long axis views were used to evaluate global and regional left ventricular wall motion, intracardiac volume status, mitral valve competence, right ventricular function and tricuspid valve, aortic valve for stenosis and regurgitation, as well as ascending and descending thoracic aortas.
Left ventricular function was evaluated in 16 segments as recommended by the American Society of Echocardiography Council on Intraoperative Echocardiography [8].
Each segment was graded according to endocardial movement and wall thickening during the cardiac cycle [9]. Grades ranging from 1 to 5 were assigned for each segment; 1 and 2 being normal and 3 to 5 being abnormal.
An episode of ischemia was defined as a worsening of wall motion in any segment by two or more scores lasting more than one minute. Available images were stored every 10 minutes and compared throughout the procedure.
The ascending aorta and aortic arch were evaluated with upper esophageal views. Aortic atherosclerosis was classified according to the plaque size and mobility as reported by Katz and colleagues [10]. Surgical strategy was modified whenever there were protruding atheromas, due to the high risk of associated perioperative cerebrovascular events reported in these patients [11].
Perioperative myocardial infarction was defined as an increase in cardiac specific troponin (>3.9 µg/L at 24 hours or 3.4 µg/L at 48 hours) after surgery with or without new Q waves on the ECG. Perioperative cerebrovascular events were defined as new onset neurologic deficit lasting 24 hours or longer with associated changes in the cerebral magnetic resonance imaging.
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Results |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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We were able to place the TEE probe in all patients. Baseline TEE was performed after induction of anesthesia before incision. The ITEE revealed previously unknown intracardiac pathology in 10 patients (1.3%). There were three atrial septal defects (two secundum defects and one patent foramen ovale with bidirectional shunt). Significant mitral valve regurgitation (grade 3-4) was diagnosed with ITEE in four patients (three due to ischemic regurgitation and one due to posterior leaflet chord rupture) and one patient had significant aortic valve insufficiency. All atrial septal defects were repaired under cardiopulmonary bypass. Mitral valve repair with annuloplasty alone (three patients) and quadrangular posterior leaflet resection in addition to annuloplasty (one patient) were performed in four patients with mitral valve insufficiency. The aortic valve was replaced in the fifth patient. There was an underappreciated anterior left ventricular aneurysm in one patient. This was repaired using an endoaneursymorraphy technique. Another patient had a previously undiagnosed ascending aortic aneurysm (confirmed to be 5.6 cm in diameter by ITEE measurement), which was resected and replaced with a Dacron tube graft. These intracardiac defects were either diagnosed entirely using TEE (atrial septal defects and valvular abnormalities) and or confirmed (left ventricular aneurysm and ascending aortic aneurysm) by ITEE.
The IABP was placed in the beginning of the procedure in 24 patients (3.2%) with severe left ventricular dysfunction, which was underestimated preoperatively. The ITEE was used to identify atherosclerosis of the ascending aorta and aortic arch (when visible) in all patients. There was normal aortic endothelium in 592 patients, intimal thickening without protruding atheromas in 99, and sessile atheromas protruding less then 5 mm into the aortic lumen in 22 patients. Severe aortic atherosclerosis (sessile atheroma protruding more than 5 mm into the aortic lumen and atheromas with a mobile component) was identified in 31 patients (4.1%). Graft construction was modified in this last group and a no-touch aorta technique was used to avoid ascending aortic manipulation. Complete arterial revascularization was performed in all of these 31 patients using internal thoracic arteries (left in 20 and bilateral in 11 patients) and radial arteries (unilateral in 24 and bilateral in 7 patients). All 31 patients underwent a no-touch aorta technique. There were no perioperative cerebrovascular accidents or myocardial infarctions in these patients.
Intracoronary shunts were placed in 77 patients (10.3%) (122 anastomoses) due to the appearance of new SWMA on ITEE and hemodynamic deterioration during distal graft construction. We were able to complete 112 of the 122 anastomoses (64 patients) with the help of shunts without additional interventions. Emergent IABP was initiated in the remaining 13 patients with persistent hemodynamic deterioration and new onset severe left ventricular dysfunction despite inotropic support. There were two emergent conversions to cardiopulmonary bypass due to continuing instability after insertion of the IABP.
Wall motion was evaluated before and after each distal anastomosis and at the completion of the procedure. A new SWMA appeared in 247 patients during grafting. The SWMA reversed in 208 patients shortly after completion of anastomosis; however, it persisted until the end of procedure in 39 patients. Graft revision was performed in all 39 patients. There was anastomotic narrowing in 15, thrombus in eight, and kinking of graft at touchdown site in four grafts. There were no technical abnormalities in 12 grafts. The SWMA reversal occurred in 31 patients after graft revision and SWMA persisted in eight patients despite graft revision. All of these patients had enzyme elevations consistent with intraoperative myocardial infarction and four died in the perioperative period. Myocardial injury in these patients was attributed to intracoronary embolization of air or atherosclerotic debris.
There was decreased or absent graft flow with intraoperative Doppler evaluation in 46 patients (51 grafts). The ITEE revealed normal wall motion in seven patients. Decreased flow was attributed to graft spasm in two patients (both radial artery grafts used to bypass the circumflex coronary branches) and poor distal runoff in five patients (three totally occluded right coronary branches and two small-size diagonal branches). The remaining 39 patients underwent graft revision (see above).
The ITEE was also used to measure left ventricular dimension and changes in the preload during the procedure. Fluid administration was guided mainly with ITEE rather than pulmonary artery catheters in our institution. This practice was done in every case and therefore was not classified as a modification of intraoperative strategy.
A summary of intraoperative changes due to ITEE data is given in Table 2.
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Patient complaints attributed to TEE probe placement were sore throat and odynophagia in 91 patients and were resolved with symptomatic treatment. There were no dental, oropharyngeal, esophageal, or gastric injuries due to ITEE.
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Patients undergoing CABG today are older and have more comorbidities. There are also an increasing number of patients with a history of adverse cardiac events, cerebrovascular accidents, renal failure, and percutaneous coronary interventions in the past. The OPCAB has been shown to decrease morbidity and mortality in this high-risk patient population [13]. This technique, however, requires constant monitoring of cardiac function and systemic perfusion by the surgical team. The absence of cardiopulmonary bypass circuit requires prompt intervention by the surgeon and the anesthesiologist should there be a deterioration in hemodynamic parameters or cardiac function. Standard monitoring techniques such as electrocardiography, arterial pressure, central venous pressure, and(or) pulmonary arterial pressure provide valuable information during OPCAB. While some of these parameters change immediately with cardiac positioning or ischemia, other changes like ECG and pulmonary artery pressures are usually delayed or absent despite ongoing ischemia [14]. Intraoperative transesophageal echocardiography is a valuable adjunct and can overcome the limitations of these traditional monitoring modalities during OPCAB.
Information provided by ITEE starts during the baseline examination before sternotomy. Cardiac valves, cardiac septa, and ascending aortas are visualized with accuracy using TEE. The identification of previously unknown intracardiac pathology with ITEE is common and is reported in 5.6% of patients in one study [4]. Therefore, ITEE may impact intraoperative decisions regarding additional procedures, some that may require use of a cardiopulmonary bypass circuit. In this study, ITEE identified previously unrecognized intracardiac pathology in 10 patients (1.3%) and all had a major modification of the planned surgical procedure.
It has been shown that as many as 13% of patients over 50 years old undergoing cardiac surgery will have significant atherosclerotic disease of the ascending aorta [15]. Digital palpation can only detect aortic calcification and fails to identify patients with soft mobile or protruding atheromas. Proximal and mid-ascending aortas, as well as the descending thoracic aorta, can be clearly visualized by ITEE. The distal ascending aorta and proximal aortic arch cannot be visualized due to the interposed trachea and esophagus. Studies have shown that atheromas in the descending thoracic aorta [16], as well as the ascending aorta and arch [10, 17], are strong independent risk factors for stroke after CABG. This is usually due to dislodgement of the atheromatous material during aortic manipulation. The ITEE may modify operative strategy, and a no-touch aorta technique with composite arterial grafting can be used for these patients as was done with 31 patients in the present study. We were able to avoid postoperative neurologic events in these patients. This was demonstrated previously by others [18]. The advantage of avoiding cannulation and the ability to use a no-touch technique for the aorta were particular advantages of OPCAB combined with ITEE. None of the six patients with permanent neurologic deficits in this study had protruding atheromas detected on ITEE.
Intraoperative transesophageal echocardiography also provides important data during graft construction in OPCAB. It can be used to identify the etiology of hemodynamic derangement, new intraoperative arrhythmias due to ischemia, and to determine degree of aortic atherosclerosis.
Hemodynamic compromise during OPCAB is due mainly to cardiac positioning and placement of stabilizing platforms on the heart. However, regional and global ischemia may occur during graft construction due to temporary occlusion of the coronary arteries. Standard intraoperative ECG uses extremity leads due to the inability to place precordial leads at the time of sternotomy. However, this modality fails to detect 75% of the new intraoperative ischemia and subsequent myocardial infarction [19]. The ECG is not a sensitive method to detect subendocardial ischemia and has limited value in patients with conduction defects and paced rhythms. New segmental wall motion abnormalities during bypass surgery are a sensitive indicator of myocardial ischemia. The ITEE can accurately detect segmental wall motion abnormalities seconds after the onset of ischemia [19]. It has been demonstrated that post-bypass regional wall motion abnormalities may be predictive of adverse cardiac outcomes after coronary artery bypass surgery [20]. Similarly, four of the eight patients with persistent new SWMA in this study died in the perioperative period. Therefore, prompt identification and swift intervention for intraoperative myocardial ischemia with ITEE play a significant role in improving early OPCAB outcome.
We did not use pulmonary artery catheters in OPCAB patients. Fluid administration and cardiac function were guided according to data provided by ITEE. We believe that ITEE provided accurate information regarding intracardiac volume status during OPCAB. During OPCAB, cardiac displacement and compression of cardiac chambers distort pulmonary artery catheter numbers. Moreover, pulmonary capillary wedge pressure (PCWP) may not reflect left ventricular end diastolic pressures accurately in patients with coronary artery disease due to changing ventricular compliance during revascularization [21]. It has also been shown that cardiac dislocation during OPCAB will increase the central venous pressure by right ventricular outflow tract obstruction, and decrease or not change the mean pulmonary artery pressure or PCWP [22]. Therefore, pulmonary artery catheters are not ideal in assessing cardiac filling pressures during OPCAB. The ITEE provides real-time information about left ventricular dimensions and therefore is a better guide for fluid administration during OPCAB. Although ITEE was the sole modality to determine intracardiac volumes and the need for fluid administration, we did not include this as one of the changes in surgical strategy.
In this study, ITEE resulted in a change of the planned operative strategy in 16% of patients. Most of these changes were critical surgical decisions (ie, conversion to on-pump, IABP placement, changing grafting strategy due to severe aortic atherosclerosis, or graft revision). Intracoronary shunts were placed based on the ITEE data in another 10% of patients. In a series of on-pump CABG patients, ITEE changed the intraoperative management in 17% patients [23]. However, it was used mainly to guide fluid administration and antiischemic therapy. It resulted in a critical change in surgical procedure in only 3% of patients. In another study, routine use of ITEE for on-pump CABG was found "valuable" or "essential" in 12% of patients and "informative" in 22% [24]. In a high-risk on-pump CABG population, ITEE resulted in a major alteration in surgical management in 33% of patients and at least one major anesthetic-hemodynamic change in 51% of patients [5]. The ITEE in this context emerges as an additional tool for monitoring and management in today’s high-risk CABG patients. It also serves to combine the advantages of advanced intraoperative monitoring and avoiding cardiopulmonary bypass during OPCAB, and hence may have an impact on perioperative morbidity and mortality.
The ITEE resulted in a major change of surgical strategy in almost twice as many OPCAB patients compared with on-pump CABG patients in previously published studies. This is probably due to the fact that there is a major difference in the conduct of operation between on-pump CABG and OPCAB. Off-pump coronary artery bypass graft surgery requires constant and close monitoring of hemodynamic parameters and requires frequent and prompt interventions by the surgical team; ITEE becomes an invaluable adjunct guiding these interventions. Therefore, ITEE can be integrated into OPCAB to increase benefits and further improve results of this technique.
Although there might be a marginal increased intraoperative cost due to ITEE, this technique may also reduce hospital cost by improving early postoperative complications. However, we have found no published cost-benefit studies evaluating financial impact of ITEE during OPCAB.
The ITEE associated complications are rare and are reported in the range of 0% to 0.5% in different series [1, 25]. Most are oropharyngeal, esophageal, and gastric injuries due to direct trauma from the TEE probe. The most frequent complaint experienced by patients after ITEE is sore throat or odynophagia (0.1%). Only a few of these patients experience dysphagia or frank esophageal injury. This latter complication is fortunately rare and was reported to be 0.01% in one series [25].
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References |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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