Can hypokalemia (low potassium levels) cause ST depression?

From the Guidelines

Yes, hypokalemia can cause ST depression on an electrocardiogram (ECG). When serum potassium falls below the normal range, it affects cardiac electrical activity by altering the resting membrane potential of cardiac cells, leading to disruptions in the normal repolarization process of the heart, which can manifest as ST segment depression on an ECG, along with other changes like flattened T waves, prominent U waves, and prolonged QT intervals 1. The severity of ECG changes typically correlates with the degree of potassium depletion, with more pronounced changes occurring when potassium levels fall below 3.0 mEq/L.

Some key points to consider in the management of hypokalemia include:

• The classification of hypokalemia as mild (3.0–3.5 mEq/L), moderate (2.5–2.9 mEq/L), or severe (<2.5 mEq/L) 1
• The importance of maintaining a potassium level of at least 4 mEq/L in patients with heart failure 1
• The potential for hypokalemia to cause a variety of arrhythmias, including first or second-degree atrioventricular block, atrial fibrillation, and ventricular arrhythmias such as premature ventricular contractions, ventricular tachycardia, and torsades de pointes 1

It's also worth noting that diuretics can cause hypokalemia, which may result in muscle fatigue, ventricular ectopy, and rarely, ST-segment depression 1. However, the most recent and highest quality study on this topic is from 2017, which provides more comprehensive guidance on the management of hypokalemia and its effects on the ECG 1.

In terms of treatment, potassium replacement therapy is recommended, either oral or intravenous depending on severity, with the goal of restoring normal levels (typically 4.0-4.5 mEq/L). For mild hypokalemia (>3.0 mEq/L), oral potassium chloride supplements of 40-100 mEq/day divided into multiple doses are usually sufficient. For severe cases (<2.5 mEq/L) or those with cardiac manifestations, intravenous replacement at rates not exceeding 10-20 mEq/hour is recommended to prevent dangerous overcorrection.

From the FDA Drug Label

Potassium depletion may produce weakness, fatigue, disturbances of cardiac rhythm (primarily ectopic beats), prominent U-waves in the electrocardiogram, and in advanced cases, flaccid paralysis and/or impaired ability to concentrate urine The answer is yes, hypokalemia can cause ST depression is not directly stated, however disturbances of cardiac rhythm and prominent U-waves in the electrocardiogram are mentioned as effects of potassium depletion, which can be associated with ST depression. 2

From the Research

Hypokalemia and ST Depression

• Hypokalemia, or low potassium levels, can cause various electrocardiography (ECG) abnormalities, including ST depression 3, 4.
• Severe hypokalemia can lead to life-threatening cardiac conduction disturbances and neuromuscular dysfunction, making it essential to determine the need for urgent treatment through a combination of history, physical examination, laboratory, and ECG findings 4.
• The relationship between hypokalemia and ST depression is supported by studies that highlight the importance of potassium homeostasis in maintaining normal cardiac function 5.
• Hypokalemia can be caused by decreased intake, renal losses, gastrointestinal losses, or transcellular shifts, and its treatment involves addressing the underlying cause and replenishing potassium levels 3, 6.

Electrocardiography Abnormalities

• Electrocardiography can identify cardiac conduction disturbances, but may not always correlate with serum potassium levels 3, 4.
• ECG changes, including ST depression, can be indicative of severe hypokalemia and require urgent treatment 4.
• The use of intravenous calcium, insulin, and other medications may be necessary to manage hyperkalemic ECG changes and prevent cardiac conduction disturbances 3, 4.

Clinical Management

• Clinical management of hypokalemia should focus on establishing the underlying cause and alleviating the primary disorder 5.
• Treatment of hypokalemia involves oral or intravenous potassium supplementation, and addressing the underlying cause of the disorder 3, 4, 6.
• Prevention of hypokalemia is also crucial, particularly in patients at risk, such as the elderly, women, and those with edematous states or using diuretics 7.