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Correspondence  |   August 2008
Electrocardiographic ST-segment Depression: Confirm, Deny, or Artifact?
Author Affiliations & Notes
  • Santosh I. Patel, M.D., F.R.C.A.
    *
  • *Trafford General Hospital, Urmston, Manchester, United Kingdom.
Article Information
Correspondence
Correspondence   |   August 2008
Electrocardiographic ST-segment Depression: Confirm, Deny, or Artifact?
Anesthesiology 8 2008, Vol.109, 352. doi:10.1097/ALN.0b013e31817f8cbd
Anesthesiology 8 2008, Vol.109, 352. doi:10.1097/ALN.0b013e31817f8cbd
In Reply:—
We thank Dr. Wong for his kind comments and interest in our article1 and were interested to read the details of his case. We agree that the low-pass filter attenuates high-frequency components of the electrocardiograph (such as sharp R waves) and a high-pass filter can cause ST-segment distortion.2 We would also offer the observation that filters used within the monitor may cause artifactual ST-segment elevation, simulating infarction, as well as mimicking depression.3 
However, we would also not want to create a false sense of assurance, and would advocate that such ischemic changes should be taken seriously on the first instance, even in asymptomatic patients. The incidence of silent ischemia is sufficiently high, particularly in diabetic patients, to create appropriate concern in circumstances of observed ST-segment changes.
However, we suggest that simple measures such as looking for confirmatory changes in other leads, checking electrode placement, and confirming the appropriate mode on the monitor should be undertaken before initiating any drastic diagnostic or therapeutic interventions. This is analogous to the logic of auscultatory confirmation of rate change, as suggested by Dr. Wong.
We would also point out that monitors may differ in their sensitivity and specificity for detecting and displaying ST-segment changes, and within the same monitor, the difference between computerized on-line analysis and printout may be significant.4 
*Trafford General Hospital, Urmston, Manchester, United Kingdom.
References
Patel SI, Souter MJ: Equipment-related electrocardiographic artifacts. Anesthesiology 2008; 108:138–48Patel, SI Souter, MJ
Gregg RE, Zhou SH, Lindauer JM, Helfenbein ED, Giuliano KK: What is inside the electrocardiograph? J Electrocardiol 2008; 41:8–14Gregg, RE Zhou, SH Lindauer, JM Helfenbein, ED Giuliano, KK
Burri H, Sunthron H, Shah D: Simulation of anteroseptal myocardial infarction by electrocardiographic filters. J Electrocardiol 2006; 39:253–8Burri, H Sunthron, H Shah, D
Yang H: Intraoperative automated ST segment analysis: A reliable black box? Can J Anaesth 1996; 43:1041–51Yang, H