This 10 July 2017 Article by Amal Mattu in Western Journal of Emergency Medicine warns that hyperkalemia might be a cause of bradycardia and to consider calcium in resistant bradycardia.
The obvious answer to the question posed in the title is “yes,” but the actual ECG findings that predict adverse events are apparently not well known to many physicians. I was reminded of this fact repeatedly this past year, when I was sent three different cases to review in which patients had cardiac arrest due to hyperkalemia, and in none of the cases was hyperkalemia recognized on the initial ECG. The reason was simple: We all have been taught a myth that peaked T-waves are the most common and important finding on the ECG of a patient with hyperkalemia. In none of the three cases were prominent peaked T-waves present. Instead, all three cases had bradycardia that failed to respond to atropine or (in one case) pacing before arrest.
In this study, published in the Western Journal of Emergency Medicine, Durfey and colleagues evaluated the ECGs of patients with hyperkalemia (potassium levels ≥ 6.5 mEq/L) over a 5-year period and correlated the findings with the occurrence of short-term adverse events (development of symptomatic arrhythmias, cardiac arrest, or death within 6 hours). Short-term adverse outcomes occurred in 15% of patients, all of whom had abnormalities on the initial ECG, but the most common ECG finding of hyperkalemia in these patients was not peaked T-waves. In fact, peaked T-waves were found to have no correlation with short-term adverse effects. In contrast, the finding that was associated with the highest relative risk for an adverse outcome by far was bradycardia (heart rate < 50 beats/min) (relative risk [RR], 12.29), followed by junctional rhythm (RR, 7.46) and QRS prolongation (RR, 4.74).
Anecdotally, we have also repeatedly found that bradycardia is a very common finding in patients with critical hyperkalemia, and the presence of peaked T-waves is quite variable. These bradycardias are often irregular, lack P-waves, and appear somewhat bizarre. Furthermore, typical advanced cardiac life support (ACLS) recommendations for bradycardia (atropine and pacing) will frequently be ineffective in these patients.
The key point here is that physicians must remember hyperkalemia as a potential cause of bradycardia, and when ACLS is not working for these patients, remember to give calcium or sodium bicarbonate