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ST Segment – The Thing You Can’t Miss. Nick Sparacino Cardiology 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.
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ST Segment – The Thing You Can’t Miss Nick Sparacino Cardiology 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
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!
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!
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