From the Guidelines
Causes of Large T Waves on an ECG
Large T waves on an electrocardiogram (ECG) are most commonly caused by hyperkalemia, an elevated level of potassium in the blood, which is a potentially life-threatening condition requiring immediate medical attention 1.
- Other potential causes include:
- Myocardial infarction (heart attack)
- Cardiac ischemia
- Certain medications, such as digitalis
Key Considerations for Hyperkalemia
In cases of suspected hyperkalemia, it is crucial to monitor the patient closely and consider administering calcium gluconate or calcium chloride to help stabilize cardiac membranes, along with other treatments aimed at reducing potassium levels, such as insulin and glucose, or diuretics 1.
- The presence of peaked T waves (tenting) on the ECG may be the first indicator of hyperkalemia, which can progress to more severe cardiac arrhythmias and arrest if left untreated 1.
- Renal failure and drug treatment are common causes of hyperkalemia, with severe cases often resulting from excessive IV potassium administration to a patient with renal insufficiency 1.
From the FDA Drug Label
The electrocardiogram should be monitored for any evidence of potassium toxicity (e.g., peaking of T waves) A large T wave on an electrocardiogram (ECG) can be caused by potassium toxicity, specifically hyperkalemia.
- Key factors that may contribute to this condition include:
- Electrolyte disturbances, such as high levels of potassium in the blood
- Digitalis overdosage, which can lead to a massive shift of potassium from inside to outside the cell, resulting in life-threatening hyperkalemia 2
From the Research
Causes of Large T Waves on an ECG
- Hyperkalemia: characterized by narrow-based and peaked T waves 3, 4
- Acute myocardial infarction (MI): broad-based T waves, also known as "hyperacute T waves" 3, 5, 6
- Acute cerebral events, including seizures: can cause transient giant T waves 3
- Cocaine toxicity: can cause giant T waves, as seen in a case report 3
- Memory T-waves: a rare cause of T-wave inversion, often seen in patients with previous episodes of ventricular tachycardia or pacemaker implantation 7
Characteristics of Large T Waves
- Hyperkalemia: peaked T waves, often narrow-based 3, 4
- Acute MI: broad-based T waves, often associated with ST-segment elevation 3, 5, 6
- Acute cerebral events: transient giant T waves, often without other ECG changes 3
- Memory T-waves: diffuse T-wave inversion, often with positive T wave in lead aVL and positive/isoelectric T wave in lead I 7