1. ECG Lecture
Scott Ewing, D.O.
March 23, 2006

2. Question #1
The patient is an elderly man who presented to the emergency ward with dizziness and new renal failure

4. Hyperkalemia Hyperkalemia (7.6 mEq/L) secondary to renal failure
Findings consistent with severe hyperkalemia
Widening of the QRS complex
Peaking of the T waves
Prolongation of the PR interval and flattening of the P waves
If left untreated, the ECG will progress to a sinusoidal pattern and eventually asystole with subsequent hemodynamic collapse and death

5. Question #2 A 65-year-old man
What should you do before calling cardiology fellow for a "hyperacute myocardial infarction" here?

7. Hyperkalemia
Classic hyperkalemia with tall peaked T waves, along with PR prolongation and underlying left ventricular hypertrophy (LVH) (patient has renal disease with hypertension)
Note QRS prolongation also seen with moderate-severe hyperkalemia
Potassium here was 9.6mEq/L
Not all tall positive T waves are "hyperacute“
The latter term should be reserved for increased T wave positivity secondary to transmural ischemia
Major clues include narrowness (tenting) of T waves along with other findings noted above

8. Question #3 This ECG is most consistent with which diagnosis?
Acute anterior myocardial infarction
Accelerated idioventricular rhythm
Marked hyperkalemia
Marked hypercalcemia
Systemic hypothermia

10. Hyperkalemia The K+ was 10.5 mEq/L in a patient with renal failure
Note the wide QRS complexes with no evident P waves
CK was normal and ST elevations were likely due to hyperkalemia. (Note: The apparent spike after the second QRS complex is an artifact.)

11. Question #4 A 38-yr-old woman
What does the ECG show and what is the differential diagnosis?

13. Hypokalemia
Sinus bradycardia with diffuse T wave flattening or inversions and markedly prominent U waves
Best seen in leads V2 and V3
Most common causes
Hypokalemia (K+ here was 2.4 mEq/L)
Drugs such as quinidine, phenothiazines, tricyclics
Patients with hereditary long QT syndromes may show a similar finding
This pattern is of great importance because it identifies patients at high risk of torsade de pointes type of polymorphic ventricular tachycardia

14. Question #5 30-yr-old man with diarrhea, not on medication
What waveform is prominent?
What is the diagnosis?

16. Hypokalemia
There are very (!) prominent U waves with Q-T(U) prolongation
He had severe hypokalemia (1.5 mEq/L) due to diarrhea
Calcium was normal, as was magnesium (remember pure hypocalemia prolongs ST segment primarily but doesn't give large U waves.)
Obviously, this acquired-type long-QT(U) syndrome puts subject at risk for torsade de pointes which he fortunately did not have before coming to hospital

17. Hyperkalemia
ECG changes have a sequential progression of effects, which roughly correlate with the potassium level
ECG findings may be observed as follows:
Early changes include peaked T waves, shortened QT interval, and ST segment depression
Followed by bundle branch blocks causing a widening of the QRS complex, increases in the PR interval, and decreased amplitude of the P wave
These changes reverse with appropriate treatment
Without treatment, the P wave eventually disappears and the QRS morphology widens to resemble a sine wave. Ventricular fibrillation or asystole follows.
ECG findings generally correlate with the potassium level, but potentially life-threatening arrhythmias can occur without warning at almost any level of hyperkalemia.

18. Hypokalemia ECG findings may be observed as follows
Flattening of the T wave, which is the earliest change
A "U wave" then develops, associated with ST-T wave flattening and sometimes slight ST depression
ST depression is more  noticeable and the U wave increases in amplitude until ultimately the U wave overtakes the T wave.
At this point distinguishing between the T wave and U wave may be almost impossible ("Q-U" prolongation).