Massive carbamazepine overdose (> 50mg/kg) is associated with cardiotoxicity due to fast sodium channel blockade. ECG changes are not usually as dramatic as those seen in TCA overdose.
ECG features of Carbamazepine Cardiotoxicity
ECG Examples
Example 1a
- This first ECG was taken several hours after massive carbamazepine overdose (150-200 mg/kg), by which time the patient was beginning to manifest clinical signs of cardiotoxicity (hypotension requiring noradrenaline).
- Carbamazepine level around that time was 33 mg/L.
- There is subtle ECG evidence of fast sodium channel blockade: Note the QRS widening (135 ms), 1st degree heart block (PR 240ms) and small secondary R wave in aVR.
Example 1b
- This second ECG was taken several hours after intubation and treatment with hyperventilation (to pH 7.50) and haemofiltration.
- Carbamazepine level is now down to 17 mg/L and haemodynamic instability has resolved.
- Note the QRS duration and PR interval have now normalised, while the secondary R wave in aVR has reduced in amplitude.
Example 2
- This ECG demonstrates more obvious cardiotoxicity following a massive carbamazepine overdose.
- QRS complexes are broad and there is a large R’ wave in aVR.
Advanced Reading
Online
Textbooks
- Zimmerman FH. ECG Core Curriculum. 2023
- Mattu A, Berberian J, Brady WJ. Emergency ECGs: Case-Based Review and Interpretations, 2022
- Straus DG, Schocken DD. Marriott’s Practical Electrocardiography 13e, 2021
- Brady WJ, Lipinski MJ et al. Electrocardiogram in Clinical Medicine. 1e, 2020
- Mattu A, Tabas JA, Brady WJ. Electrocardiography in Emergency, Acute, and Critical Care. 2e, 2019
- Hampton J, Adlam D. The ECG Made Practical 7e, 2019
- Kühn P, Lang C, Wiesbauer F. ECG Mastery: The Simplest Way to Learn the ECG. 2015
- Grauer K. ECG Pocket Brain (Expanded) 6e, 2014
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric 6e, 2008
- Chan TC. ECG in Emergency Medicine and Acute Care 1e, 2004
LITFL Further Reading
Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |
MBBS DDU (Emergency) CCPU. Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Co-creator of the LITFL ECG Library. Twitter: @rob_buttner