Which of the following ECG findings indicate the presence of hypokalemia?

SCTIMST Staff Nurse - 2016

Medical & Surgical Nursing

Easy

Appeared in: SCTIMST Staff Nurse - 2016

Explanation

Hypokalemia (low potassium) causes characteristic ECG changes, including ST-segment depression.
As potassium levels fall, ventricular repolarization is altered, leading to a depressed ST segment, often accompanied by T-wave flattening and prominent U waves.
The provided image clearly demonstrates ST-segment depression, a hallmark sign of hypokalemia.
This finding is distinct from the changes seen in hyperkalemia, which include tall, peaked T waves and a widened QRS complex.

Option A: Tall, peaked T waves are a classic sign of hyperkalemia (high potassium), not hypokalemia. This change is one of the earliest indicators of elevated potassium levels.
Option B: Widening of the QRS complex is a sign of moderate to severe hyperkalemia, reflecting slowed intraventricular conduction. It is not associated with hypokalemia.
Option C: A prolonged PR interval indicates a delay in conduction from the atria to the ventricles (first-degree AV block) and is typically seen in hyperkalemia, not hypokalemia.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain ECG interpretation for electrolyte imbalances, specifically hypokalemia as background academic context rather than a clinical decision trigger.
Prompt recognition of ECG changes related to potassium imbalances is a critical nursing skill, as both hypokalemia and hyperkalemia can cause life-threatening cardiac arrhythmias.
Nurses must be aware of the safety protocols for IV potassium administration: it must always be diluted, infused via a pump (never gravity), and never given as a bolus or IV push, as this can cause fatal cardiac arrest.
What if? If the patient's ECG showed tall, peaked T-waves and they were also taking an ACE inhibitor and a potassium-sparing diuretic, the nurse's priority would be to suspect hyperkalemia, hold the medications, notify the provider, and anticipate orders for calcium gluconate and insulin/dextrose.

How to Approach the Question

First, identify the core concept of the question, which is linking an ECG finding to a specific electrolyte imbalance (hypokalemia).
Recall the characteristic ECG changes for both hypokalemia and hyperkalemia. A helpful mnemonic is that in hypokalemia, everything goes 'down' or 'flat' (ST depression, flat T wave), while in hyperkalemia, things go 'up' or 'wide' (peaked T wave, wide QRS).
Analyze the provided image. Observe the depressed ST segment, the flattened T wave, and the prominent U wave, which are all classic signs of hypokalemia.
Evaluate each option against your knowledge and the visual evidence. Option A (Tall, peak T wave), B (Widening of QRS), and C (Prolonged PR interval) are all associated with hyperkalemia.
Conclude that ST segment depression is the only option listed that correctly indicates hypokalemia.

Concept Tested & Keywords

Concept Tested: ECG interpretation for electrolyte imbalances, specifically hypokalemia.
Stem keywords: ECG findings, hypokalemia
Lead-in keywords: Which

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E6 Medicine Harrison 22e Part 1 pp. 1915-1917, 1911-1913

E6 Gynecology Williams p. 64-85