THE BEST HEART SPECIALIST S IN YELAHANKA
There are two aspects to report: depression and elevation.
The ST segment is said to be abnormal if it slopes down 1 mm or more from the J point—the
end of the QRS complex (downsloping depression)—or is depressed 1 mm or more horizontally
(plane depression). Depression of the J point itself may be normal, especially during exercise,
but this upsloping ST depression should return to the isoelectric line within 0.08 seconds.
The isoelectric line is defined as the PR or TP segment of the ECG . ST depression may
be due to ischaemia, the effect of digoxin, hypertrophy and so on.
ST elevation of up to 3 mm may be normal in V leads (especially the right), and up to 1 mm
may be normal in limb leads. This ST elevation is called early repolarisation syndrome or pattern.
Otherwise ST elevation may mean an acute myocardial infarction where it is
said to represent a current of injury. Pericarditis also causes ST elevation but unlike infarction
is usually associated with concave upwards elevation. hypertrophy and
conduction defects like LBBB can be associated with ST elevation in leads where the QRS is
The T wave is always inverted in lead aVR and often in L3 and V1–V2, and in aVL if the R wave
is less than 5 mm tall. Inversion and flattening are common and non-specific findings. Deep
(> 5 mm) symmetrical and persistent (days to weeks) inversion is consistent with infarction;
broad, ‘giant’ inversion may follow syncope from any cause including cerebrovascular accidents.
Like the ST segment, the T wave tends to be directed opposite to the main QRS deflection in
conduction defects (e.g. LBBB), VEBs or ventricular hypertrophy (where it
is described as secondary ST/T changes or strain pattern).
Tall peaked T waves are most often seen as a reciprocal change to inferior or posterior infarcts.
They are classically seen in patients with hyperkalaemia. Broader large T waves are seen in early
(‘hyperacute’) infarction and sometimes in cerebrovascular accidents. While not diagnostic
by themselves (T waves never are), when they are associated with modest ST elevation (especially
in V3) and reciprocal depression in the inferior leads, they indicate infarction or ischaemia. When
these changes evolve over time they are even more specific for infarction
A U wave may be prominent in patients with hypokalaemia, LVH and bradycardia. Isolated