In Reply.—Hypoxia, acidosis, hyperkalemia, or hypocalcemia are various metabolic imbalances that may play a contributing role in the genesis of a 2:1 heart block.
Our patient was monitored carefully and frequently by obtaining blood gases and electrolyte determinations. The laboratory results demonstrated neither hypoxia nor acidosis at the time the arrhythmia was demonstrated on the ECG. Furthermore, the serum potassium level was normal in our patient. Dr Chan's suggestion that the serum potassium level in our patient was elevated is erroneous because the value of 6.5 mEq/L is within the range of normal (5.3 to 8.9 mEq/L)1 for this infant at her age.
We acknowledge the fact that potassium does play an important role in myocardial repolarization.
Cellular function is determined by a state of balance between various electrolytes. A state of imbalance perhaps best summarizes the electrolyte status of our patient.
Newborns are perhaps more likely to
FISHBEIN J, HEBERT L. Relative Role of Hypocalcemia in 2:1 Heart Block-Reply. Am J Dis Child. 1982;136(10):953. doi:10.1001/archpedi.1982.03970460082023