Rational Basis of Stress Echocardiography

When a stress echocardiography test result is positive, myocardial ischemia is present. The presence of regional dysfunction requires ischemia, and – in the words of John Ross Jr. – the very definition of ischemia requires an alteration of myocardial function: “Ischemia is a reduction in myocardial blood flow sufficient to cause a decrease in myocardial contraction.” In this definition, however, one must consider that “decrease in myocardial contraction” is not synonymous with “reduction in visually assessed regional systolic thickening,” which expresses only one dimension (radial strain) of the complex three-dimensional event of myocardial contraction. The latter also includes circumferential and longitudinal strain, all contributing to changes in ejection fraction and to the pump function. In addition, systolic thickening is evaluated in a subjective and qualitative, not objective and quantitative, way and reflects the average transmural function, without discriminating between the subendocardium (highly vulnerable to ischemia) and subepicardium (more resistant to ischemia). The clinical world is not the experimental laboratory, stress echocardiography is not equivalent to implanted sonomicrometry, and therefore the fundamental parameter of regional systolic thickening on two-dimensional echocardiography should be integrated with information derived from clinical presentation, patient specificity, and information provided by other markers of ischemia.