Q. Explain False Positive Tests?
As ST depression has been equated with CAD, patients with this finding who have less than a critical coronary narrowing has been called false positives. Upon careful scrutiny of these patients, however most are found to have some process or condition that could explain the repolarization abnormality. In a study of 95 patients with ST-segment depression and normal coronary arteries, it was found that only 13 per cent did not have any possible explanation.
Eriksson and Mybre followed up 36 men for 7 years with normal coronary arteries and ST depression. The incidence of cardiac events after seven years was the same in this group as in those who were found to have significant CAD. The investigators believe that many of these patients represent early myocardiopathies and that the ST-segment was due to abnormalities in the vasodilator reserve. It is now known that coronary atheromas that do not appear to be flow limiting may cause decreased perfusion and ischaemia. Thus, the term false positive ST depression should probably be abandoned and replaced with abnormal ST depression of unknown cause.