ECG Changes in Hyponatremia
Hyponatremia can cause ECG changes including P-wave alternans, QT interval prolongation, and atrioventricular conduction abnormalities. 1, 2, 3
Common ECG Findings in Hyponatremia
- P-wave alternans (alternating P-wave configuration) has been observed in patients with hyponatremia, which resolves after correction of sodium levels 2
- QT interval prolongation can occur, increasing the risk of ventricular arrhythmias 1
- Second-degree or complete atrioventricular (AV) block may develop during or shortly after episodes of severe hyponatremia 3
- Conversion from first-degree to second-degree AV block has been observed in patients with underlying cardiac disease during hyponatremic states 3
Severity and Clinical Correlation
- The severity of ECG changes typically correlates with the degree and rapidity of hyponatremia development 4
- Patients with acute hyponatremia (developing over less than 48 hours) are more likely to be symptomatic even at moderate sodium levels 4
- Seizures are more common when serum sodium levels fall below 121 mmol/L 4
- In patients with heart failure, hyponatremia is associated with increased risk of arrhythmias and poor outcomes 5
Monitoring Recommendations
- The American Heart Association recommends continuous ECG monitoring for patients with moderate to severe electrolyte imbalances 1
- Patients with abnormal baseline ECG findings, cardiac comorbidities, or those receiving treatments that may cause electrolyte shifts require closer monitoring 1
- Careful attention should be paid to other electrolyte abnormalities that may coexist with hyponatremia, as they can exacerbate ECG changes 1
Special Considerations
- Hyponatremia in the setting of heart failure requires careful management, as inappropriate fluid administration can worsen the condition 5
- In patients with subarachnoid hemorrhage, hyponatremia is associated with increased rates of cerebral ischemia and poor outcomes at 3 months 4
- Cardiac conduction defects may be more pronounced in patients with underlying heart disease or those taking medications that affect cardiac conduction 3
Treatment Implications
- Correction of hyponatremia typically leads to resolution of ECG abnormalities 2
- The rate of sodium correction should be carefully controlled to avoid osmotic demyelination syndrome 4
- In patients with heart failure, treatment approach differs based on whether hyponatremia is hypervolemic (from congestion) or hypovolemic (from excessive diuresis) 5
While the primary focus in managing hyponatremia is correcting the underlying sodium imbalance, monitoring for cardiac conduction abnormalities is essential, especially in patients with pre-existing cardiac disease or those taking medications that affect cardiac conduction.