Understanding the Causes of Brady Disrythmias

Contributor: Dylan Luyten MD

Educational Pearls:

What is a Bradyarrhythmia?

• Also known as a bradyarrhythmia, it is an irregular heart rate that is also slow (below 60 beats per minute).

What can cause it?

• Complete heart block AKA third-degree AV block; identified on ECG by a wide QRS, and complete dissociation between the atrial and ventricular rhythms with the ventricular being much slower. Treat with a pacemaker.

• Medication overdose, especially beta blockers. Many other drugs can slow the heart as well including: opioids, clonidine, digitalis, amiodarone, diltiazem, and verapamil to name a few.

• Electrolyte abnormalities, specifically hyperkalemia. Hypokalemia, hypocalcemia, and hypomagnesemia can also cause bradyarrhythmias.

• Myocardial infarction. Either by damaging the AV node or the conduction system itself or by triggering a process called Reperfusion Bradycardia.

• Hypothermia. Bradycardia is generally a sign of severe or advanced hypothermia.

References

1. Jurkovicová O, Cagán S. Reperfúzne arytmie [Reperfusion arrhythmias]. Bratisl Lek Listy. 1998 Mar-Apr;99(3-4):162-71. Slovak. PMID: 9919746.

2. Simmons T, Blazar E. Synergistic Bradycardia from Beta Blockers, Hyperkalemia, and Renal Failure. J Emerg Med. 2019 Aug;57(2):e41-e44. doi: 10.1016/j.jemermed.2019.03.039. Epub 2019 May 30. PMID: 31155316.

3. Wung SF. Bradyarrhythmias: Clinical Presentation, Diagnosis, and Management. Crit Care Nurs Clin North Am. 2016 Sep;28(3):297-308. doi: 10.1016/j.cnc.2016.04.003. Epub 2016 Jun 22. PMID: 27484658.

Summarized by Jeffrey Olson MS2 | Edited by Meg Joyce & Jorge Chalit, OMSII