Tim Phalen – 10/13/09

STEMI vs. Non STEMI – STEMI is ultimate candidate for reperfusion therapy – non STE-MI – much higher mortality rate.

Is the early part of the ST segment elevated – 1mm elevated at beginning – at J point only (J point elevation)

Pick one good segment – pick one where T-P matches that of T-P before it –pick a steady baseline

Notch in ST segment – not always BBB – Not STEMI

Always use the T-P segment to measure elevation

aVR – Looks from top at chamber of Left ventricle – not used because we can’t localize the injury. Also looking at endocardial tissue – wont have same meaning or significance

Evolution of AMI

• Ischemia – Endocardial Hypoxia – St Depression – T wave inversion
• Injury – Epicardial Hypoxia – causes ST Elevations – being that the epicardial cells have a rich blood supply – must be an occlusion.
• Hyperacute Phase -  T waves – Tall & peaked – first change – may give illusion of a wide based t wave (vs hyperkalemia) – Tall = in limb leads elevations of  >5mm – in chest leads more >10mm – Peaked = don’t want to sit on it
• Acute Phase -
• Pathological Q wave – =>.04 – or greater than 1/3 of R wave. –Age undetermined
• A normal 12 lead does not rule out an AMI

Reciprocal Leads

• II III aVF vs. I aVL, V-Leads
• Inferior wall MI – single most likely reciprocal lead is aVL
  • Some MIs start with reciprocals and then show elevations

More than 50% of ST Elevations are not caused by AMI – called STEMI imposters (first 3 make up 80%)

• LVH – Primary cause is HTN
  • increased QRS amplitude – variety of formulas exist – read the interpretation – machine does the math. (Or – look at v1 – from baseline to most negative deflection – count mm – then look at v5 and v6 and count the tallest. add depth of v1 to highest of v5 or v6 – if over 35 you have LVH (if under age 35 use 53mm)
• BBB – Primary cause is aging process
  • Widens the QRS complex – QRS Dur. >0.12 sec (120ms)
• Ventricular Rhythms including paced
  • Widens the QRS complex – QRS Dur. >0.12 sec (120ms)
• Benign Early Repolarization (BER)
  • ST elevations often in lateral leads and lead II
  • Tall peaked T waves – and tall QRS
  • Fishhook ST segment
  • Young healthy male (20-40 years, +African Americans)
  • does not typically produce reciprocal changes
• Pericarditis (epicardium may be inflamed too)
  • May be in all leads
  • May be in leads not grouped anatomically
  • sharp pain
  • localize with a finger
  • positional – prefer leaning forward
  • radiates to base of neck or shoulder blade
  • might hear friction rub on auscultation
  • does not typically produce reciprocal changes

5 step analysis

• 1. Rate & rhythm
  2. Waveform analysis
     1. st segment
     2. T wave
     3. Q wave
  3. Suspected STEMI
     1. location
  4. Additional considerations
     1. voltage criteria for LVH
     2. QRS width
     3. Reciprocal leads
  5. STEMI Decision
     1. Definitely NOT a STEMI
     2. Definite STEMI
     3. Definite Maybe – EMS needs a plan for definite maybes – Transmit ECGs to ER for consult.

see www.ecgsolutions.com

Right and Posterior Leads

• • Inferior wall MI – most likely RCA – 40% of time will also have a Right Ventricular MI – Add v3r through v6r (at minimum look at v4r)
  • Anywhere else – Most likely LCA -
  • Posterior wall MI – reciprocal changes in v1- v4 (reciprocal q wave would manifest with taller R waves, sometimes)– indicative changes in V7, v8 and v9 (keep going around back – posterior axiallary mid scapular, just left of spine)

BBB Recognition

• forget the notch
• suspect with wide QRS
• normal sinus, a-fib, or any sinus rhythm – suspect BBB
• v1 – back off j point – which direction is tail end of QRS – RBBB – points up – LBBB turns down
• LBBB – new onset – indication for reperfusion – (Sgarbossa criteria)
  • Normally BBBs produce discordant QRS-ST (direction of QRS is in opposition to ST)
  • Both in same direction in any one lead – infarct.
  • If you have LBBB with concordant (both downward) QRS & ST depressions – suspect MI if it occurs in V1 or V2 or V3
  • More than 5mm of elevation from baseline to j point – suspect MI in any one lead
• Serial EKGs – changes are hallmark of AMI