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Ann Thorac Surg 2004;78:579-583
© 2004 The Society of Thoracic Surgeons

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Original article: cardiovascular

Impact of intraoperative transesophageal echocardiography in patients undergoing valve replacement

^a The Dan Sheingarten Echocardiography Unit and Valvular Clinic, Department of Cardiology, Rabin Medical Center, Beilinson Campus, Petah Tiqva, affiliated With the Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel
^b The Department of Cardiothoracic Surgery, Rabin Medical Center, Beilinson Campus, Petah Tiqva, affiliated with the Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel

Accepted for publication February 18, 2004.

^* Address reprint requests to Dr Shapira, Echocardiography and Valvular Clinic, The Department of Cardiology, Rabin Medical Center, Beilinson Campus, Petah-Tiqva, 49100, Israel
e-mail: yshapira{at}post.tau.ac.il

	Abstract

Top Abstract Introduction Patients and methods Statistical analysis Results Comment References

 
BACKGROUND: The role of intraoperative transesophageal echocardiography (IOTEE) in valve replacement surgery is not well established. The aim of this study was to explore the impact of immediate postpump IOTEE in valve replacement surgery at a single tertiary medical center.

METHODS: The departmental database was screened for valve replacement operations (mechanical or bioprosthetic valves) performed during a 55-month period that were succeeded by immediate postpump IOTEE. Data was gathered regarding the impact of IOTEE on the immediate postoperative course.

RESULTS: The study group included 417 patients (44.8% male, 55.2% female, age 65.2 ± 13.9 years). Prepump IOTEE was performed in 352 patients (84.4%). A single valve was replaced in 336 patients (80.6%) and two or more valves were replaced in 81 patients (19.4%). Overall 501 valves were inserted: mitral, 237 (131 mechanical, 106 biological); aortic, 221 (89 mechanical, 132 biological); tricuspid, 43 (2 mechanical, 41 biological). Unexpected pathologic echocardiographic findings on postpump IOTEE necessitated immediate surgical correction in 15 patients (3.6%): perivalvular leak in 8 patients (4 mitral, 4 aortic), immobilized leaflet in 4 patients (3 mitral, 1 tricuspid), coronary obstruction by an aortic bioprosthesis in 2 patients, and incompetent xenograft in 1 patient. Prolonged removal of air was necessary in 45 patients (10.8%). In 47 patients (11.3%) the postpump IOTEE contributed to the evaluation of difficult weaning from the bypass pump and to its appropriate therapeutic management (volume expansion, inotropic agents, vasodilators, or mechanical assistance).

CONCLUSIONS: Immediate postpump IOTEE is an important diagnostic and therapeutic role in valve replacement surgery and should be widely implemented.

	Introduction

Top Abstract Introduction Patients and methods Statistical analysis Results Comment References

 
Intraoperative transesophageal echocardiography (IOTEE) is a valuable tool with regard to cardiac surgery. The preoperative TEE assessment can introduce important modifications of the surgical plan and the postpump assessment can provide quality control of the surgical result including the efficiency of the removal of air and the hemodynamic status in terms of effective intravascular volume and biventricular contraction.

The role of IOTEE in valve repair surgery and complex congenital lesions is well established as summarized in the American Society of Anesthesiologists (ASA) and the Society of Cardiovascular Anesthesiologists (SCA) Task Force on Transesophageal Echocardiography [1]. However its routine application in valve replacement surgery is less clear and was graded by the Task Force as category II (ie, supported by weaker evidence and expert consensus). Recent studies provided additional data on the importance of IOTEE in valve replacement operations with an emphasis on the prepump data [2–8]. Nevertheless the American College of Cardiology/American Heart Association (ACC/AHA) Task Force, in its 2003 update for the clinical application of echocardiography, considered IOTEE in valve replacement as only class IIA indication, namely, a condition for which there is conflicting evidence and/or a divergence of opinion about the usefulness and/or efficacy of the procedure, but the weight of evidence and/or opinion is in favor of its usefulness and/or efficacy [9]. The role of postpump IOTEE has not been sufficiently stressed in the literature. The present study summarizes the impact of IOTEE in a tertiary referral medical center in patients referred for valve replacement surgery with an emphasis on the postpump assessment.

	Patients and methods

Top Abstract Introduction Patients and methods Statistical analysis Results Comment References

 
We reviewed the departmental database for all patients who underwent elective or urgent valve replacement surgery between January 1, 1999 and July 31, 2003 followed by immediate postpump IOTEE. Patients were eligible if at least one valve was replaced during surgery (whether preplanned, advised post-IOTEE, or as a bailout after a failed valvular repair procedure) and immediate postpump IOTEE was performed.

All IOTEE studies were performed by one of four cardiologists (YS, MV, DEW, AS), experienced in IOTEE, using a 3.7/5 or 4/7 MHz multiplane transducer (Hewlett-Packard, Andover, MA) or a 6T Vingmed Ultrasound (General Electrical, Harten, Norway). For sonography we used Hewlett-Packard Sonos 1000 or 2000, Agilent 5500 scanners, or a Vivid 3 Premium digital cardiovascular ultrasound scanner (General Electrical, Tirat HaCarmel, Israel). Every study was recorded on a super-VHS tape.

The TEE probes were introduced by anesthesiologists after the induction of general anesthesia. The preoperative study was performed before initiation of the cardiopulmonary bypass usually while the chest was already open. The postpump study was performed by the same cardiologist immediately after spontaneous circulation was resumed and was terminated at optimization of hemodynamics. The IOTEE procedure was performed according to the ASE/SCA guidelines [10]. It included a systematic evaluation of all the valves in multiple acquisition angles, cardiac chamber size and function, exclusion of intracardiac masses, and evaluation of the thoracic aorta. Intracardiac air bubbles were defined as small, discrete, highly moveable echogenic dots. Pooled air was defined as a strongly echogenic line or area adjacent to the wall usually at the highest level of each chamber.

	Statistical analysis

Top Abstract Introduction Patients and methods Statistical analysis Results Comment References

 
Numeric values are reported as mean ± standard deviation or as a proportion of the sample size. Categorical variables were compared with the ² test.

	Results

Top Abstract Introduction Patients and methods Statistical analysis Results Comment References

 
The study group consisted of 417 patients (186 male [44.6%] and 231 female [55.4%]) aged 65.2 ± 13.9 years (range 23–92 years) (Table 1). IOTEE was performed in both the prepump and postpump phase in 352 patients (84.4%) and only in the postpump phase in 65 patients (15.6%). The most frequent additional procedures included coronary artery bypass grafting (CABG) (29.7%), tricuspid annuloplasty (20.4%), and cooled-tip radio-frequency ablation of atrial fibrillation (6.5%). Overall 501 valves were inserted. The breakdown of valve type and position is depicted in Table 2.

Of the 237 patients undergoing MVR, 9 patients experienced immediate postpump perivalvular leak (3.8%), 4 patients (1.7%) were less than moderate, and 5 patients (2.1%) were moderate. Four patients with a moderate leak underwent immediate repair of the leak. In 1 patient with a very long bypass time and a heavily calcified mitral annulus, the surgeon opted against a second pump run. There were no perivalvular leaks in the tricuspid prostheses.

Impaired left ventricular function attributed to compromised ostial left main flow in patients undergoing AVR with bioprosthetic valves occurred in 2 patients. In the first patient a 21-mm Shelhigh valve (Shelhigh Inc, Union, NJ) was replaced by a 19 mm mitroflow valve (Sulzer Carbomedics, Inc, Austin, TX) and left ventricular function recovered with uneventful outcome. In the second patient a 21-mm mitroflow valve was replaced by a 19-mm mitroflow valve resulting in resumption of coronary flow and improved left ventricular function. However the patient died within 24 hours because of low cardiac output.

Of 133 patients with mechanical valves in atrioventricular valve position, immobilized leaflet was noted in 4 of them (3%). Three patients exhibited interference of prosthetic leaflet motion by tissue remnants (2 in the mitral valve position and 1 in a tricuspid valve situated in a systemic atrioventricular position in a patient with corrected transposition). The fourth case was attributed to the use of biological glue in a patient with complicated infective endocarditis. In all 4 patients the tissue remnants were cleared and the valves were reoriented leading to resumption of normal function. There was a single case of moderate intravalvular regurgitation of a newly implanted mitral bioprosthesis (Perimount; Edwards Lifesciences, Irvine, CA). The valve had to be immediately replaced by a mechanical valve.

Intracavitary air was carefully monitored during weaning from the cardiopulmonary bypass machine. Attempts at air removal were continued until there was no pooled air and the microbubbles either disappeared or were reduced to very few. Prolonged air removal (ie, extension of the bypass time only to assure clearance of air) was required in 45 patients (10.8%). The procedure usually consisted of leaving the antegrade cardioplegia site open and placing the patient in the Trendelenburg position. Occasionally air was evacuated by left ventricular apical needle application.

In 47 patients (11.3%) the postpump IOTEE contributed to the evaluation of difficult weaning from the bypass machine and thereby to the proper choice of therapeutic measures (volume expansion, inotropic agents, vasodilators, or mechanical assistance). Findings included isolated left ventricular failure in 24 patients (5.8%), isolated right ventricular failure in 12 patients (2.9%), biventricular failure in 7 patients (1.7%), dynamic LV outflow tract obstruction in 4 patients (1%), and hypovolemia in 3 patients (0.7%). Eighty-five of the patients who underwent prepump IOTEE (24.1%) experienced some degree of left ventricular dysfunction (mild—23, moderate—36, severe—26). In the 62 patients with prepump moderate or severe left ventricular dysfunction, postpump IOTEE was useful in handling pharmacological and mechanical support in 20 patients compared with 27 patients who experienced normal or mildly impaired left ventricular dysfunction (32.3% vs 9.3%, p < 10^–4).

An intraaortic balloon pump (IABP) was inserted in 7 patients (1.7%) and IOTEE was used to monitor its precise location. In the study period there was 1 patient in which failure to introduce the TEE probe occurred and 1 patient experienced postoperative upper gastrointestinal bleeding caused by esophageal laceration.

	Comment

Top Abstract Introduction Patients and methods Statistical analysis Results Comment References

 
The present study underscores the importance of postpump IOTEE in valve replacement operations. We focused on hard end points, namely, prosthetic valve malfunction and impaired coronary flow due to the valves, both of which required a second pump run. Without the use of IOTEE a considerable portion of our patients would have experienced a complicated course including a prolonged hospital stay and a redo operation shortly after the index procedure. In some cases the outcome might have been fatal.

There are several benefits of postpump IOTEE. That is, it may prevent excess mortality and morbidity associated with hemodynamic compromise due to leaflet immobilization or perivalvular leak, cerebral and coronary ischemia due to retained air, and profound hemolysis due to perivalvular leak; it provides documentation of the appropriateness of surgery, including the removal of air measures and normality of valve function to avoid future claims of carelessness; it may reduce costs associated with prolonged hospital stay, redo surgery, and medical treatment of morbid complications; and it provides the surgeon and the anesthesiologist data on biventricular function and volume and exclusion of dynamic LVOT obstruction and therefore guides pharmacotherapy, volume handling, and mechanical assistance including IABP indication and location. Some of these advantages are further discussed below.

Perivalvular leak may be associated with considerable morbidity dictated by the degree of regurgitation and the intensity of intravascular hemolysis. Small jets are not infrequent and their incidence may reach 17.6% post-AVR and 22.6% post-MVR [11]. These leaks usually remain unchanged or disappear at follow-up [11]. In the immediate postpump phase, it is important to wait for the reversal of anticoagulation by protamine after which the size of the perivalvular jets may be halved [12]. Only large jets should be addressed bearing in mind the consequences of a second pump run in the particular patient. In our sample the rate of perivalvular leak was lower than in earlier studies (10% for AVR, 3.8% for MVR), possibly because we addressed only considerable jets and/or those that did not abolish after protamine infusion. Click and associates [5] noted 18 cases of perivalvular leak among 411 patients with MVR and among 844 patients with AVR (aortic replacement or repair) which account for 1.4% of these operations. In 10 of their patients the leakage was repaired after a second pump run. Fujii and associates [8] noted 1 such case (in the mitral position) among 136 patients (0.7%).

Nonthrombotic valve block is rare in patients undergoing valve replacement with bileaflet valves [4–8, 13–15]. Click and associates [5] identified three malfunctioning prostheses (no mention of valve position) among 1255 patients undergoing MVR or AVR (0.2%), some in which the aortic valves were repaired, not replaced. Fujii and associates [8] noted one such case (in the mitral position) among 136 patients (0.7%). In other studies including several hundred patients, this complication was not observed at all [4, 6, 7]. The rather high rate of mechanical valve malfunction in the atrioventricular position in the present study (3%) probably reflects our attempts to preserve parts of the native valves.

We noted two patients who experienced iatrogenic coronary obstruction in our series, both involving biological aortic valves whose struts interfered with coronary flow. Coronary obstruction after valve replacement is rare and usually occurs several months postoperatively. It is attributed to direct coronary cannulation [16, 17] or an oversized valve [18]. In our patients there was no use of direct coronary cannulation, the obstruction was instantaneous, and it was relieved with valve re-replacement. We did not find similar reports in the literature.

Meticulous air removal, guided by IOTEE, is an integral part of valve surgery in our center. Almost 11% of our patients experienced prolonged air removal, which usually added 5–10 minutes to the bypass time but reached 15–20 minutes in selected cases. In the absence of a control group of patients who did not undergo IOTEE, we cannot assess the impact of air removal on outcome in terms of neurologic integrity and protection from myocardial ischemia. There is some evidence, however, that pooled air may be associated with myocardial ischemia and conduction abnormalities [19]. The association between microbubbles that are not pooled and adverse events is less obvious [20], but it has not been thoroughly and systematically investigated since the mid-1980s.

The postpump IOTEE provided useful hemodynamic data on myocardial contractility and volume status. Patients with preexisting left ventricular dysfunction of at least moderate degree had more than threefold chance of obtaining useful data, compared with those with normal or mildly impaired left ventricular function. Some of the hemodynamic information may also be readily appreciated by analyzing intracardiac pressure curves and/or by direct visualization of the heart and great vessels by the surgeon. It is therefore difficult to assess the unique contribution of IOTEE to the hemodynamic puzzle. The most obvious role of IOTEE in this respect was in the diagnosis of dynamic left ventricular outflow tract (LVOT) obstruction that is usually caused by combined overzealous catecholamine infusion in an empty heart. We noted this phenomenon in 1% of our patients. Click and associates [5] identified dynamic LVOT obstruction in 27 out of 3245 patients (0.8%) after a variety of operations. A second pump run was requested in only 5 patients and decreasing inotropic agents and/or volume expansion in 22 patients solved the problem. IOTEE is also a very useful tool for validating the appropriate location of IABP. It was used for this purpose in all the patients who required this device.

The rate of second pump run varies among reports. Click and associates [5] noted new postpump data in 5.9% of patients undergoing MVR and 4.7% of patients undergoing AVR. However the precise data on valve replacement could not be elicited, because valve repair and replacement were not reported separately in this regard. Fujii and associates [8] reported 4 cases of second pump run among 136 patients (2.9%) because of stuck mitral valve, incompetent mitral xenograft, perivalvular leak (aortic), and free-floating calcium after AVR (1 patient each). Ionescu and associates [6] reported a single case of second pump run caused by mitral valve dehiscence among 300 patients undergoing valve replacement (0.3%) and Norwangi and associates [7] did not have any cases among 383 patients undergoing AVR (38 with MVR as well). In our study the rate of second pump run was 3.6% which is in accordance with the other studies.

Obviously the contribution of the prepump IOTEE cannot be ignored. However this was not the aim of the current study. A complete prepump study was conducted in 84.4% of our patients. It affected the therapeutic decision in 29.3% of operations. However its particular role in the decision tree (along with the referring cardiologist and surgeon) for each patient could not always be elicited.

The cost-effectiveness and economic impact of IOTEE are subject to the local facilities and pricing multiplied by the complication rates. Assessment of the facilities should include the presence or absence of an ultrasound scanner, probes, dedicated cardiology service, staff training, and salaries. The complications should be priced according to added hospital stay, reoperation rates, and further hospitalizations due to untreated prosthetic valve malfunction. An additional factor may be the monetary consequences of negligence claims in cases where IOTEE was not performed. In their analysis of valve replacement operations, Ionescu and associates [6] concluded that IOTEE was cost-effective only if it could be provided without major capital investment [6]. However their calculations were based on very few adverse events (3 patients with preoperative added data and 2 patients with postoperative complications among 300 patients). Because the rate of second pump run in large-scale studies is approximately 3%–6%, there is an economic rationale for introducing an IOTEE service even if it requires de novo construction.

This study did not include a control group. Therefore we were unable to compare the surgical outcome of the study patients with another group in an identical setup without IOTEE. However we believe that in light of the obvious contribution of IOTEE in the present study, conducting a randomized controlled investigation might be ethically inappropriate.

An inherent limitation of our study is the uncertainty regarding the actual influence of IOTEE findings on clinical outcome in certain end points. For example, it could not be determined whether prolonged IOTEE-guided air removal decreased the incidence of neurologic injury or not.

In conclusion, the postpump IOTEE elaborates extremely valuable data in valve replacement surgery and is highly recommended as an integral diagnostic modality in the procedure.

	References

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Ehud Raanani Eitan Snir Bernardo A. Vidne Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Shapira, Y. Articles by Sagie, A. Search for Related Content PubMed PubMed Citation Articles by Shapira, Y. Articles by Sagie, A. Related Collections Valve disease