The present study was undertaken to determine if leads CM5, CC5, and V5 are
equally sensitive in detecting ST segment depression with exercise or hyperventilation
in apparently normal males. Seven physically active men (29.4 + 2.9 yrs, 180.9 + 2.5
cm, 77.9 + 3.4 kg, x±SEM), free of risk factors for heart disease, were initially found
to have J point (J0) depression with mild exercise in lead V5. Simultaneous ECG
recordings from CM5, CC5 and V5 during seated rest (REST), immediately post-moderate
exercise (IPE), and after 30 s of hyperventilation (HVT). ECG signals were
manually evaluated for ST segment depression at the J point and 60 ms and 80 ms
past the J point (J60, J80). None of the three leads differed in their ability to detect ST
segment changes. With exercise, J0 was significantly (P<.05) reduced compared to
REST; neither J60 nor J80 differed from REST. HVT reduced J0 significantly but not
J60 or J80 Exercise provoked greater reductions than HVT. These data suggest that,
in apparently healthy adult males, these three ECG leads are equally able to detect J
point changes with exercise and hyperventilation, but exercise results in a relatively
greater downward ST segment shift than does hyperventilation.