Electrolyte Imbalances & ECG Changes Flashcards

What is the FIRST ECG change seen as serum potassium rises in progressive hyperkalemia?

Answer: Peaked T waves

Peaked T waves are the earliest manifestation of hyperkalemia, appearing before any conduction abnormalities such as PR prolongation or QRS widening.

A patient with end-stage renal disease presents with absent P waves and a widened QRS. The most likely cause is:

Answer: Severe hyperkalemia

Absent P waves and widened QRS in a renal failure patient indicate severe hyperkalemia impairing both atrial depolarization and ventricular conduction.

The QTc interval is most reliably prolonged in which electrolyte condition?

Answer: Hypocalcemia

Hypocalcemia specifically prolongs the ST segment (isoelectric portion), extending the QTc and increasing risk of torsades de pointes.

Which electrolyte imbalance is the first-line treatment target when a patient develops torsades de pointes?

Answer: Hypomagnesemia correction

IV magnesium sulfate is the first-line treatment for torsades de pointes; hypomagnesemia facilitates the QT prolongation that initiates this arrhythmia.

How does hyperkalemia progressively affect the PR interval on ECG?

Answer: Prolongs it beyond 200 ms

Hyperkalemia slows AV nodal conduction, causing PR interval prolongation that can progress to complete AV block if potassium continues to rise.

A patient on furosemide develops ST depression, T wave flattening, and prominent U waves. The most likely electrolyte cause is:

Answer: Hypokalemia

Loop diuretics like furosemide cause renal potassium wasting; hypokalemia classically produces ST depression, T wave flattening, and prominent U waves.

Which emergency medication stabilizes the cardiac membrane in hyperkalemia WITHOUT lowering the serum potassium level?

Answer: Calcium gluconate

Calcium gluconate directly antagonizes hyperkalemia's membrane effects within minutes, providing temporary cardiac protection without redistributing or removing potassium.