in Which Leads Do You See ST Elevation/T Inversion. This Is Where the Ischemic Tissue Is

ECG

Measured from Lead 1

1. P wave
AV node: PR segment

2. Q

3. & 4. R

5. T (repolarization)

1.  Calibration / -  Calibration box should be 100mv (10mm)
2.  Rhythm / Sinus Rhythm definition:
-  P wave precedes each QRS complex
-  Rate is 60-100bpm
3.  Rate / 1500/mm between similar waves (ex. R-R’) [100bpm = 3 big boxes between R-R’]
Normal is 60-100bpm
4.  Waves & Intervals / P wave: Normal is upright, each one followed by QRS
PR interval: Normal is 120ms-200ms (3-5mm)
> 200ms (1 large square) is 1° AV block à sign of AV disease
(delayed conduction through AV node ex. Hypokalemia)
QRS duration: >120ms is widened QRS à indicates bundle branch block or MI
Bi-peaked Rs (R and R’) show conduction wave reaching R and L ventricles at different times
QT Interval: Should be shorter than half of total cycle length
Longer indicates conduction problem (ex. Hypocalcemia)
ST Segment: Should be at baseline (0mV) à Compare to PQ. Elevated in MI*
T wave: In MI, see T wave inversion*
5.  Mean Axis / Sum up vectors in different leads. Normal: Mean between -30° -90° (between I and aVF)
Deviation from this can indicate RVH (if in R quadrant) etc.

Localize ischemia

-  In which leads do you see ST elevation/T inversion. This is where the ischemic tissue is.

-  In stress test, inner vessels are compressed first causing transmural ischemia. Can locate occlusion.

-  Epicardium or transmural: ST segment ↑

-  Endocardium: ST segment ↓

ECG #1 Objectives

1.  Know where leads are.
2.  Know what transmural infarct looks like. / Epicardium or transmural: ST segment ↑
3.  Know what long PR interval indicates. / Sign of delayed conduction through AV node. 1° AV block (ex. Hypokalemia)
4.  Know where the infarct is. / See: Localize ischemia

Kosinski Objectives

1.  Understand that an electrophysiology study examines for heart arrhythmias and conduction system and not other components such as coronary arteries, valves

2.  Know that the PR segment on a 12 lead ECG represents conduction from the atria to the ventricles and is manifested as the AH and HV intervals on an electrophysiology study

3.  The most common arrhythmia in young patients is AV nodal re-entry and in older patients atrial fibrillation

4.  Most heart rhythm disturbances, but not all, can be cured by cardiac ablation

5.  Despite all the technology in evaluating a patient the history and physical exam remain extremely important

Atrioventricular Nodal Reentry Tachycardia (AVNT)

-  Most common cause of Paroxysmal supraventricular tachycardia (PSVT) in adults

-  Typical AVNRT accounts for 80% of cases

-  Is a reentrant arrhythmia (v. abnormal automaticity or triggered activity)

-  Circuit is confined to AV node and perinodal tissue

-  Requires presence of dual AV nodal physiology

o  i.e. presence of slow and fast pathways

-  Requires retrograde or VA conduction