Exercise Stress Laboratories in the Future What Should their Capabilities Be?

Тhe current issue of this journal contains information from Guiney et al demonstrating the ability of thallium (Tl) myocardial scintigraphy to differentiate false-positive from true-positive ECC responses that are indicative of myocardial ischemia during exercise. That report emphasizes the usefulness of 201T1 in identifying the presence of anatomically (and presumably physiologically) important coronary artery luminal diameter narrowing. It is important to differentiate true- from false-positive ECG responses indicative of myocardial ischemia, since there is a relatively high frequency of false-positive tests in women, in persons taking digoxin, in those with ventricular hypertrophy, in persons with electrolyte or cardiac conduction abnormalities, and in those with abnormal ECGs preceding exercise.

During the past several years, the sensitivity of rest and maximal exercise 201Tl scintigrams in the recognition of anatomically important coronary artery disease has been 70 to 80 percent, with a specificity of approximately 90 percent 2,8 More recently, quantitative measurements of regional ventricular mTl uptake, “reperfusion” ^Tl imaging,4 the insistence on obtaining images within five minutes after the injection of mTl9 and assuring maximal exercise effort have improved the sensitivity to 85 to 90 percent in several centers. 5»6

The correct recognition of physiologically important coronary disease is critical in the evaluation, management, and predicting prognosis in patients with chest pain and ischemic heart disease Canadian Pharmacy viagra. Relatively noninvasive methodology, such as T1 myocardial scintigraphy, that allow the identification of functionally important coronary disease represent an important development in the diagnostic capabilities of the cardiologist.

In addition to the study by Guiney et al, others have also shown that the combination of 201P myocardial scintigraphy and ECG monitoring during stress testing is better than either alone in detecting the presence of anatomically important coronary artery stenoses.8»9 Therefore, if used properly and with experience and contemporary methodology, 201T1 myocardial scintigraphy can be a valuable and relatively noninvasive diagnostic tool in evaluating chest pain.

However, myocardial imaging techniques can also make other important contributions to assessing the presence or absence of physiologically important coronary artery disease. Borer and associates have demonstrated that measurements of left ventricular ejection fraction at rest and during exercise help identify those persons with important ischemic heart disease. We have suggested that measurements of left ventricular end-systolic volume and of systemic arterial systolic blood pressure/left ventricular end-systolic volume ratio (TP/V index”) are also useful means of identifying physiologically important ischemic heart disease.Our approach was suggested by the earlier efforts of Suga and Sagawa demonstrating that alterations in the P/V index provide a means to assess changes in contractility.

Estimates of alterations in regional ventricular wall motion from rest to exercise should also provide important clues to the presence of functionally important coronary artery disease and help to differentiate cardiomyopathy with global ventricular dysfunction from the segmental ventricular alterations typical of ischemic heart disease.We believe that future developments will also emphasize alterations in segmental diastolic function and systolic wall thickening in the differentiation of functionally important ischemic heart disease from cardiomyopathies. In patients with ischemic heart disease, functional studies that evaluate regional ventricular alterations potentially allow one not only to determine that ischemic heart disease exists, but also to assess the functional impact of coronary artery disease on global and regional ventricular function. This should also have prognostic significance.