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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• [email protected]• Powerpoints, articles, calculators, Oh My!• EKG reference cards