New insights in measurement of myocardial ischemia.
Myocardial ischemia may be defined as myocellular dysfunction resulting from hypoxia usually due to limited coronary blood flow. The methods commonly used to make a diagnosis of myocardial ischemia employ either clinical findings (e.g., angina, myocardial infarction) or signals from laboratory tests. Since ischemia is often clinically silent and since clinical events related to ischemia may be catastrophic (i.e., myocardial infarction and sudden death), physicians are dependent on tests using various targeted signals. These signals, however, do not actually provide quantitative measurements of the degree of ischemia or related myocardial dysfunction. Nevertheless, the functional abnormalities reflected by these signals can identify patients at high or low risk for adverse outcomes related to ischemia. So, in this sense, these signals can be used to support the diagnosis of ischemia as well as evaluate its importance in a given patient. The most commonly used signal is an ST-segment shift evident on the electrocardiogram (ECG). When this is horizontal or downsloping and > or = 10 mm, this is often, but not always, due to myocardial ischemia. Although assessment of the exercise-stress ECG offers several advantages over assessment of the resting ECG, the standard Bruce protocol is associated with notable shortcomings that become apparent when an attempt is made to assess the effects of a treatment on the ST-segment signal. These might be surmounted by use of a continuous ramp-type protocol. Ambulatory ECG monitoring is growing in importance in the wake of increasing awareness of the different daily life circumstances that are associated with ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)
Pepine
C J
CJ
University of Florida College of Medicine, Gainesville 32610-0277.
D004562:Electrocardiography; D005080:Exercise Test; D006801:Humans; D017202:Myocardial Ischemia / Q000175:diagnosis*