Hyperkalemia:
- Distinctive sequence of ECG changes affecting both depolarization (QRS) and repolarization (ST-T)
- First change: Narrowing and peaking of T-waves ('tented' or 'pinched' shape) and can become tall
Hyperkalemia:
- Further elevation: PR intervals become prolonged, P-waves may disappear. Will have intra-ventricular conduction delay, with widening of QRS complexes.
- Can lead to large, undulating (sine wave) pattern with asystole and cardiac death
Hyperkalemia ECG:
- Nice example from Life in the Fast Lane (litfl.com/hyperkalaemia-…)
- Can see: prolonged PR interval, broad QRS, and peaked T-waves
Hypokalemia:
- Produces distinctive changes in the ST-T complex; most common with ST-depressions with prominent U-waves and prolong repolarization
- U-waves may even exceed the height of the T-waves
- Can be challenging to measure the QT intervals
Hypokalemia EKG:
- Nice EKG from Life in the Fast Lane (litfl.com/hypokalaemia-e…)
- Note: Widespread ST depression and T wave inversion, Prominent U waves, Long QU interval
- Reported K~1.7
Hypercalcemia:
- Shortened QT interval is due to shortening of ST-segment.
- T-waves may appear to take off from the end of the QRS complex
- High Calcium can lead to coma/ death
Hypercalcemia EKG:
- Nice EKG from Life in the Fast Lane (litfl.com/hypercalcaemia…)
- Note hypercalcemia causing marked shortening of the QT interval (260ms)
Hypocalcemia:
- Lengthens or prolongs the QT intervals
- Example of a patient with prolonged QTc in the setting of hypoparathyoidism
Hypomagnesemia:
- Can be attributed to GI or renal losses (diuretic)
- Implicated in ventricular arrhythmias with acute MI and Torsade de Points
- Should have aggressive IV Magnesium replacement if needed
- EKG (litfl.com/hypomagnesaemi…) with an example of NSVT
***Not to use for clinical care, just educational material**
Thanks to these websites for the amazing graphics!
Inferior Wall Infarction:
- Diaphragmatic portion of the LV
- Will see changes in leads II, III, and aVF
- May produce abnormal Q-waves in these leads
- Generally caused by occlusion of the RCA; less commonly can occur with a left circumflex coronary obstruction
Posterior Infarction:
- Occurs on the posterior (back) surface of the LV
- May be difficult to diagnose because characteristic abnormal ST elevations may no appear in any of the 12 conventional leads
- Tall R-waves and ST depressions can occur in V1 and V2
Q-wave:
- Can occur in any lead; indicates that the electrical voltages are directed away from that particular lead
- With a transmural infarction, necrosis of heart muscle occurs in a localized area of the ventricle
- New Q-waves usually appear within first day of MI
Anterior Wall MI:
- Can see loss of normal R-wave progression in the chest leads (normally should have a progression of height of R-waves from V1-V6)
- In antero-septal infarct, will lose small r waves in V1-V2 (septal depolarization from left to right) and have QS in V1-V2
Myocardial Ischemia:
- One of the most important things to evaluate on EKG
- If severe narrowing/complete blockage of a coronary artery causes blood flow to become adequate, ischemia of the heart muscle develops
- Can be transient (angina pectoris) or more severe (necrosis & MI)
Myocardial Ischemia
- LV consists of an outer layer (epicardium/sub-epicardium) and inner layer (sub-endocardium)
- Can have limit of ischemia to the inner layer or can affect the entire thickness of the ventricular wall (transmural ischemia)
Fascicular Blocks:
- Left bundle branch system: sub-divided into an anterior & posterior fascicle.
- Hemi-block does not widen the QRS complex markedly (compared to a RBBB or LBBB)
Left Anterior Fascicular Block (LAFB):
- Diagnosed by finding of a left axis deviation (-45 degrees or more negative)
- Delayed activation of more superior & leftward position of the LV
- Isolated finding is non-specific; can be seen w/ HTN, AV disease, CAD, and aging
LBBB:
- Similar to a RBBB, produces a wide QRS and affects the early phase of depolarization
- Septum will depolarize from (right to left; instead of normal left to right).
- Will see the loss of septal r-wave in V1 and septal q-wave in V6
LBBB:
- V1: Negative QRS complex b/c the LV is still electrically predominant (initial depolarization is negative and remains negative in the right-sided chest lead) (W-shape)
- V6: Entirely positive R-wave ('M'- Pattern)
Ventricular Conduction:
- Normal electrical stimulus reaches ventricles from the atria through the AV node & His-Purkinje systems
- First part of heart to be depolarized is the left-side of the septum; then spreads to RV and LV by right & left bundles
- Normal QRS < 0.10 sec
RBBB:
- 1st phase of depolarization: Left side of septum is stimulated first (branch of left bundle); on a normal ECG produces a septal r-wave in V1 and small septal q-wave in V6. No impact with RBBB.
- 2nd phase: Simultaneous depolarization of LV and RV. No impact with RBBB.