Grading of Ischemic Response in Stress Echocardiography

Abstract

The relationship between the data obtained from provocative tests and the angiographically assessed coronary artery disease is usually expressed in terms of sensitivity and specificity. The need for a dichotomous (yes or no) classification of both the results of provocative tests and coronary angiography has at least three important limitations. Coronary artery disease is not an all or nothing condition: a binary classification requires arbitrary threshold criteria and creates artificial distinctions in coronary artery disease that, in actuality, shows a continuous spectrum of severity [1]. Sensitivity and specificity values tend to be affected by the disease distribution in the study population: a sample distribution with a high frequency of mild disease will be placed centrally near the threshold values where scatter is more likely to lower sensitivity and specificity [2]. Percentage diameter narrowing is not an adequate standard to quantify stenosis severity in clinical studies [3]: in unselected populations, this anatomic parameter has a poor correlation with the coronary flow reserve (see Chap. 2). Thus, coronary artery disease is a complex phenomenon which cannot be described adequately by means of a simple “normality versus disease” code; there are, in fact, significant differences as regards the degree and the extent of coronary artery disease, carrying important implications for both the therapeutic and the prognostic side. A stress test should therefore not only predict the presence/absence of coronary disease, but also stratify the disease severity. Accordingly, the diagnosis of myocardial ischemia by stress echocardiography should be delimited by time/space coordinates which represent: the circumferential (horizontal) extent of ischemia (x axis); the transmural (vertical) depth of ischemia (y axis); the ischemia-free stress time (i.e., the time from the start of the stress to the appearance of ischemia) (z axis) (Fig. 1).

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... but time is time, and passes by though sages disagree

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