Redbud Medical Systems, Inc.
Custom-made beds for Supine bike stress
echo, Post treadmill imaging exercise echo, & Resting echo
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400
500
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[ The following is excerpted, with permission, from the Manual for Stress Echo by Larry DeBord. ]
Criteria for the Correctly Acquired Systolic Loop
Triggering issues are less important in diagnosing the sickest of the sick or the wellest of the well. Triple vessel disease and 90% stenoses of proximal LADs are easy to identify, and the normally augmenting heart of a twenty-year old soccer player can be correctly read even with a poor study. But identifying the subtle, transient wall motion abnormalities that may identify those patients in the early stages of CAD requires that the clinician exert maximum effort in every aspect of the exam, no matter how small. Single vessel disease, especially isolated circumflex disease can be very difficult to detect. Inappropriate triggering can mask these lesions.
Failure to capture end-systole can make a heart look hypokinetic. The observation that more contraction takes place in early systole than in late systole does not permit omission of the final moments of contraction.
Including too much diastole at the end of the loop, exaggerates the heartÂ’s contractility. This is particularly true if resting systole spans seven frames, but exercise systole spans only three.
If the resting and exercise loops do not begin at the same moment in the cardiac cycle, they are not easily and accurately compared. End diastolic volumes cannot be compared. If the resting loop is correctly triggered and the LV walls begin moving inward in frame #2, but the exercise loop is triggered early, frames 1, 2, and 3 are diastolic, and the walls do not begin moving inward until frame #4, the exercising walls may appear, artifactually, to be slow. If frame #1 captures too early, end systole may not be acquired.
Stress echo conferences often include (not by design) examples of triggering at its worst - loops with one or two frames of end-systole and the remainder showing diastole. This defeats the purpose of the frame grabber which is to isolate systole for identification of systolic abnormalities.
Summary of the Ideally Captured Systolic Loop
Frame #1 should be acquired during isovolumic contraction, that is, after the R-wave but before mechanical systole, before the endocardium begins moving inward, and before the aortic valve has opened. In Frame #1 the aortic valve should be closed. If the aortic valve is open in Frame #1, acquisition is late by an unknown quantity. If the aortic valve does not open until the third or fourth frame, acquisition began early - in diastole. In the extreme case of early triggering, the mitral valve will still be open.
Frame #2 should show the aortic valve open and the endocardium moving inward as mechanical systole begins.
Frames #3, #4, #5, #6 and #7 should show the myocardium continuing to thicken and to progress inward.
- Frame #8, ideally, should record the final instant of systole, when the endocardium has traveled inward to its limit. But in reality, in order to be assured that end systole, is captured, Frame #8 should record the first moment of diastole, the first moment of relaxation, showing the endocardium moving outward very slightly and the aortic valve closing. LV Chamber size should be smaller than that in frame #1.
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Email: sales@redbudmedical.com Web address: http://www.redbudmedical.comContent revised: January 24, 2004