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CON: Transesophageal Echocardiography Should Be Routinely Used In All Patients Undergoing Cardiac Surgery

Michael P. Fee, MD
University of Nebraska Medical Center

TEE has provided us with endless pictures, but has not been shown to improve outcomes. Throughout the literature, myocardial ischemia has been linked to segmental wall motion abnormalities (SWMA). Unfortunately, many situations not related to ischemia can also cause SWMA. These include impaired systolic function, altered conduction, myocardial stunning, myocarditis and acute changes in loading. Wall motion is not symmetrical in normal subjects; therefore abnormalities are best diagnosed as changes from baseline. Probe manipulation, to increase the number of segments visualized, will alter baseline imaging and may affect wall motion assessment. Even experienced operators have difficulties recognizing changes in regional wall motion abnormalities due to ischemia. Comparing five experienced anesthesiologists, Bergquist et al reported that sensitivity of echocardiographic ischemia detection ranges from 50% - 100% and specificity ranges from 67% to 82%1.

Some contend that TEE is a vital guide for decisions in cardiac surgery. Bergquist et al found that only 17% of clinical interventions were decided predominantly by TEE. Only 30% of fluid administration decisions were influenced by TEE alone. Also, 25% of real-time vs off-line interpretations of ejection fraction area estimates varied by greater than 10%2. Such estimations are based on planimetry, which is sensitive to probe positioning and edge recognition, and is not an exact technology. Non-perpendicular cuts and/or poor border detection can yield errant information. Doppler estimation of cardiac output has not correlated well with thermodilution techniques3.

A large study involving all cardiac cases at one institution indicated the incidence of unsuspected prebypass TEE findings of major significance in CABG surgeries to be 4.9%. If one removes ischemia-induced acute hemodynamic instability (most likely obvious without TEE) and the assessment of IABP requirement (corresponding to high PA pressures and low CI), the true TEE impact drops to less than 2% of all CABG cases. The examiners had experience with over 500 previous TEE examinations, yet concordance with off-line readings by cardiologists was only 87%,4 too late to do anything but second guess the decisions made in the OR.

Advanced TEE training is recommended when valve surgery decisions are to be guided by TEE5. Valvular competence is judged on regurgitant flow. Unfortunately, TEE measures flow velocity. To determine flow from flow velocity requires a Newtonian fluid, a straight, rigid vessel and laminar flow, none of which occurs in the heart. Most importantly, an exact perpendicular cross-sectional area of the orifice is needed, which is not possible with TEE. Those scary red colors indicate high flow velocity, but the actual regurgitant volume flow may be low.

Current recommendations suggest a basic level of training for all situations where TEE is used5. Rafferty et al report in 846 consecutive cases involving 26 anesthesiologists, that their abilities to obtain 2D images and color flow Doppler were rated as poor in 15.2% and 20.3% respectively6. These inadequate images were disproportionately associated with 4 of the 26 attendings. In Bergquist's study, usable images ranged from 38% to 84%1.

If the number of inexperienced examiners increases, what affect will false positives or false negatives have on outcomes? Do TEE's actually present a hazard to patients? Although small, the risk of esophageal and upper airway injury exists. Will TEE cause a distraction from important information needed to be monitored? A novel study by Weinger et al showed caregivers' response time to a random red light 10 times slower when performing TEE than during monitor observation7.

Lack of positive outcome data, difficulty obtaining meaningful information, and training constraints would persuade one to limit TEE. Certainly there are useful applications of TEE but we cannot recommend global use of TEE in all cardiac cases.

REFERENCES

  1. Bergquist BD, Leung JM, Bellows WH: Transesophageal Echocardiography in Myocardial Revascularization: I. Accuracy of Intraoperative Real-Time interpretation. Anesthesia and Analgesia 1996;82:1132-8
  2. Bergquist BD, Bellows WH, Leung JM: Transesophageal Echocardiography in Myocardial Revascularization: II. Influence on Intraoperative Decision Making. Anesthesia and Analgesia 1996;82:1139-45
  3. Muhiudeen IA, Kuecherer HF, Lee E, Cahalan MK, Schiller NB. Intraoperative Estimation of Cardiac Output by Transesophageal Pulsed Doppler Echocardiography. Anesthesiology 1991;74:9-14
  4. Mishra M, Chauhan R, Sharma KK, Dhar A, Bhise M, Dhole S, Omar A, Kasliwal RR, Trehan N. Real-Time Intraoperative Transesophageal Echocardiography-How Useful? Experience of 5,016 Cases. J Cardiothorac Vasc Anesth 1998;12:625-632
  5. Thys DM, Abel M, Bollen BA, Cahalan MK, Curling P, Dean RJ, Paulus D, Pearlman AS, Roizen MF, Smith J, Stewart WJ, Woolf SH: Practice Guidelines for Perioperative Transesophageal Echocardiography: A Report by the American Society of Anethesiologists and the Society of Cardiovascular Anesthesiologists Task Force on Transesophageal Echocardiography: Anesthesiology 1996;84: 986-1006
  6. Rafferty T, LaMantia KR, Davis E, Phillips D, Harris S, Carter J, Ezekowitz M, McCloskey G, Godek H, Kraker P, Jaeger D, Kopriva C, Barash P. Quality Assurance for Intraoperative Transesophageal Echocardiography Monitoring: A Report of 846 Procedures. Anesth Analg 1993;76: 228-32
  7. Weinger MB, Herndon OW, Gaba DM: The Effect of Electronic Record Keeping and Transesophageal Echocardiography on Task Distribution, Workload, and Vigilance During Cardiac Anesthesia. Anesthesiology 1997;87:144-56



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