ST Segment – The Thing You Can’t Miss

Nick SparacinoCardiology Study Group

ST Segment

• J-Point to beginning of T wave

• Isoelectric in limb leads in 75% of “normal” EKG

• Up to 90% of all EKG’s have some ST elevation precordially

• >1mm elevation abnormal

• Any depression abnormal

Baseline? I don’t need no stinking baseline!

•Three potentially isoelectric portions• PR, ST, TP• PR can be unreliable,

particularly if pericarditis is on differential• Generally use TP• None can be completely

relied on with standard EKG

Mechanism of ischemic/injurious ST Changes

• 2 “phases” of electrical activity • Ischemic tissue depolarizes and repolarizes

less vigorously than healthy tissue

How does that make the squiggly line change?

Location, Location, Location

Where’s the lesion?

Where’s the lesion?

Where is the lesion? What is your mgmt?

Early Repolarization

• Traditionally considered benign• 1-5% of general population• More common with young males, African Americans• Large T waves, concave ST contour, no other evidence of

LVH or other causes• Mimics hyperkalemia• 2008 NEJM found 2.1 HR for SCD!

Early Repolarization

LVH

• Covered in last installment• High points: Estes-Romhilt is best criteria• Look for big QRS, negative P in V1, clinical history of

htn, stim abuse

Digoxin

• Derangements in Na/Ca movement produces changes in action potential

• Causes characteristic “scooped” inverted ST-T• Looks like check-mark

Wellen’s Sign

• 1996 Wellen described a series of acute proximal LAD lesions with no ST elevation or troponin rise

• Biphasic anterior T waves the only unifying feature• A case was missed by one of us at the VA recently – can’t lean on trops!

Pericarditis

• Diffuse ST elevation• Look at PR interval!

What do you do?

Brugada• Most well known of a series of

inherited ion channel pathologies

• Produce a characteristic pattern of precordial ST elevation

• 3 described types, type 1 is the classic

• Very high J point, smoothly descends to an inverted T

• High risk of sudden cardiac death• Most common in southeast

Asian males – up to .5-1% in a Japanese study

Neurologic insult

• Most often described with strokes• Trauma, tumor, metabolic derangements

When in doubt

• Call for help!• Fellow residents, senior

residents, chiefs, fellows, IM attendings, cards attendings

• “Better to wake someone up than put someone to sleep”

• Practice!

Over to you, Mo

• www.goodsamcsg.wikispaces.com• Cardiostudy@gmail.com• Powerpoints, articles, calculators, Oh My!• EKG reference cards