Sharpen Your Calipers - Dr. Littmann

The Role of the ECG in Acute Nontraumatic BLE Weakness
 
Acute bilateral lower extremity paralysis

1. The differential diagnosis of acute nontraumatic bilateral weakness is broad
2. Most causes have unique manifestations and symptoms
3. The two most common cluster of causes of acute nontraumatic BLE weakness without significant associated symptoms: spinal cord disease and periodic paralysis
4. Patients with periodic paralysis have unique ECG manifestations

 
Hypokalemic periodic paralysis
I. Familial hypokalemic periodic paralysis

1. Mostly Caucasian men
2. First attack at age <25
3. Most patients have family history
4. Most patients have repetitive attacks

II. Thyrotoxic hypokalemic periodic paralysis

1. Mostly Asian and Latino men
2. First attack later (20s – 30s)
3. Attacks only occur when hyperthyroid
4. No family history of periodic paralysis
5. Hyperthyroidism frequently indolent, easy to miss the diagnosis

III. Common ECG manifestations of thyrotoxic hypokalemic periodic paralysis

1. Large distant U waves frequently reaching the next P waves
2. Tall QRS complexes
3. Slight PR prolongation
4. Terminal notching of QRS complexes in anterior chest leads (rsR’ pattern)

IV. Emergency treatment of thyrotoxic hypokalemic periodic paralysis

1. Propranolol
2. Use caution with potassium replacement

 
Hyperkalemic paralysis

1. Almost always acquired and/or iatrogenic
2. Only occurs with severe, extreme hyperkalemia
3. Wide bizarre QRS complexes, sine-wave appearance
4. Usually no P waves present
5. Most patients do not have PEA

 
ECG signs of severe hyperkalemia

1. The more severe the hyperkalemia, the less you can expect peaking of the T waves
2. Widened QRS complexes, new axis shifts
3. Widened QRS complexes with ST-segment elevation in V1-V2
4. Widened QRS complexes with the Brugada pattern in V1-V2
5. Double counting of heart rate by the ECG interpretation software
6. Sine-wave appearance

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