|
Automated
Electrocardiograph ST Segment Trending Monitors: Accuracy in Detecting
Myocardial Ischemia.
Leung
JM, Voskanian A, Bellows WH, Pastor D. Anesth Analg. 1998;87:4-10
[ see
abstract below ]
Anyone who's bought EKG monitors in the last few years probably has some
version of automated ST segment analysis available on their new monitors.
Many of us make management decisions with this "on-line, real time" information.
But how good is that information? Dr. Leung and colleagues, well known
in the cardiac ischemia research world, attempt to answer part of that
question in this study.
ST segment monitors ("ST trending monitors") tracking leads II and V5
were compared to three-lead Holter monitors. Data obtained using both
types of analysis were read in a controlled fashion off-line (i.e. after
the fact). That means that the ability of automated ST segments monitors
to detect ischemia would be maximized compared to the way they are really
used (i.e. by glancing, following trends, misinterpreting or ignoring
them as the case may be).
Ninety-four patients were enrolled. Of those, thirty had ischemia. In
those thirty patients with ischemia, 42 ischemic episodes were noted using
the Holter monitors (which have been documented to catch almost all ischemic
episodes compared to 12-lead EKGs and TEE). 90% of those 42 ischemic episodes
were detected using automated ST segment analysis. Small R-waves predisposed
the ST trending monitors to missing true ischemia. In 33 cases, the ST
trend monitors noted ischemia where the Holter did not (i.e. false positives).
Large R-waves predisposed the ST trending monitors to such false positives.
Of the automated ST segment analysis devices, the Marquette monitor was
the best performer. Today's technology is good, but far from perfect.
Further advances need to be made for us all to be able to count on identifying
perioperative ischemia in real time on a reliable basis using automated
ST trend analysis.
Return to the Current
Literature Review Front Page , or read the abstract:
ABSTRACT
Continuous automated ST segment trending devices (ST trending monitors)
are included in most new operating room electrocardiography (ECG) monitors
to facilitate ischemia detection, but their efficacy is not well validated.
Therefore, we compared their accuracy with that of Holter ECG recorders
in detecting ST segment changes (both analyzed offline) in 94 patients undergoing
coronary artery bypass graft surgery. Holter ECG tapes were analyzed using
standard criteria for determining ECG ischemic episodes, which were compared
with those measured by the ST trending monitors. Overall, 42 ischemic episodes
were detected by using the Holter monitor in 30 patients. Of the 42 episodes,
38 (90%) were also detected by the ST trending monitors. Sixteen episodes
of ST segment deviation were detected by the ST trending monitors, but not
by the Holter. The sensitivity of the three ST trending monitors in detecting
ischemia was 75%, 78%, and 60% for the Marquette (Milwaukee, WI), Hewlett
Packard (Andover, MA), and Datex (Helsinki, Finland) monitors, respectively,
with a specificity of 89%, 71%, and 69% relative to the Holter. Compared
with the HP and Datex monitors, the Marquette monitor has the best agreement
with the Holter (K 0.64). Conditions in which ST trending monitors may be
inaccurate were identified and included the appearance of small R-wave amplitude,
drifting baseline, and during periods of conduction abnormalities and pacing.
We conclude that ST trending monitors have only moderate sensitivity and
specificity (<75% overall) in accurately detecting ECG ST segment changes
compared with Holter ECG recordings. Therefor, sole reliance on ST trending
monitors for the detection of myocardial ischemia may be insufficient. Implications:
Using Holter recordings as the reference standard for detection of intraoperative
ischemia, ST trending monitors were found to have overall sensitivity and
specificity of 74% and 73%, respectively. Several conditions contribute
to the inaccuracy of ST trending monitoring, and additional modification
of their performance is necessary to achieve better agreement with the Holter
analysis.
|
