Do peaked T waves on an electrocardiogram (ECG) indicate dehydration?

Peaked T Waves on ECG Indicate Hyperkalemia, Not Dehydration

Peaked T waves on an electrocardiogram (ECG) are a characteristic sign of hyperkalemia, not dehydration. 1 According to the American Heart Association guidelines, as hyperkalemia progresses, the T wave often becomes peaked when serum potassium levels reach 5.5-6.5 mmol/L.

ECG Changes in Hyperkalemia

Hyperkalemia causes a predictable progression of ECG changes as potassium levels rise:

1. Mild hyperkalemia (5.5-6.4 mmol/L):

   • Peaked/tented T waves (early and most common sign) 2
   • Narrow-based, symmetrical, and tall T waves 1

2. Moderate hyperkalemia (6.5-8.0 mmol/L):

   • Prolonged PR interval
   • Flattened P waves
   • QRS widening 2

3. Severe hyperkalemia (>8.0 mmol/L):

   • Sine wave pattern
   • Ventricular fibrillation
   • Asystole or pulseless electrical activity 1

T Wave Morphology in Hyperkalemia

The American College of Cardiology guidelines describe normal T wave amplitude in lead V2 as 1.0-1.4 mV in men and 0.7-1.0 mV in women 1. In hyperkalemia, T waves become:

• Taller than normal
• More symmetrical
• Narrow-based with a sharp peak 2

The terminal T wave angle (Tta) has been shown to be a useful predictor of hyperkalemia, with an optimal cutoff angle of 66.20° (sensitivity 67.3%, specificity 73.8%) 3.

Limitations of T Wave Changes as Hyperkalemia Indicators

It's important to note that:

1. ECG manifestations of hyperkalemia vary among individuals and may not be predictable 1
2. T wave changes alone have limited sensitivity and specificity for detecting hyperkalemia 4
3. In patients with acute kidney injury, T wave changes are poor predictors of serum potassium levels 4

Dehydration and ECG Changes

Dehydration itself does not directly cause peaked T waves. Instead, dehydration may lead to:

• Sinus tachycardia
• Low QRS voltage
• ST segment changes

However, severe dehydration can cause pre-renal acute kidney injury, which may lead to hyperkalemia and subsequent T wave changes 1.

Clinical Implications

When peaked T waves are observed on an ECG:

1. Immediate action: Check serum potassium levels
2. Cardiac monitoring: Continuous monitoring is essential if hyperkalemia is suspected 2
3. Treatment considerations: Based on potassium level and ECG changes:
   • Calcium gluconate for membrane stabilization
   • Insulin with glucose to shift potassium intracellularly
   • Potassium binders for removal 2

Common Pitfalls

1. Misattribution: Attributing peaked T waves to dehydration rather than hyperkalemia can delay appropriate treatment
2. Overlooking other causes: Other conditions that can cause T wave changes include:
   • Myocardial ischemia
   • Left ventricular hypertrophy
   • Early repolarization
   • Cerebrovascular events 1
3. Relying solely on ECG: ECG changes may not always correlate with serum potassium levels, especially in patients with acute kidney injury 4

In conclusion, peaked T waves on ECG are a characteristic sign of hyperkalemia, not dehydration. When observed, prompt evaluation of serum potassium levels is warranted to guide appropriate management.