PROLONGED QT

Question 1

DDX

Answer 1

Hypokalemia
Hypomagnesemia
Hypocalcemia
Acute MI
Elevated Intracranial Pressure
Drugs with Sodium Channel Blocking Effect (TCA, Quinidine etc.)
Hypothermia
Congenital Prolonged QT

Question 2

HYPOKALEMIA

Answer 2

Increased P wave amplitude
Prolongation of PR interval
Widespread ST depression and T wave flattening/inversion
Prominent U waves (best seen in the precordial leads V2-V3)
Apparent long QT interval due to fusion of T and U waves (= long QU interval)

Question 3

HYPOMAGNESEMIA

Answer 3

Prolonged PR interval
Prolonged QT interval
Atrial and ventricular ectopy
Predisposition to ventricular tachycardia and torsades de pointes

Question 4

SODIUM CHANNEL BLOCKER TOXICITY (TCA)

Answer 4

Tachycardia
R-wave amplitude in aVR ≥3 mm
Rightward axis
QRS Widening
QT Prolongation
Possible Brugada Pattern