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EKG
- Case Answer
Hypocalcemia
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Joseph
Bordelon, MD
His
electrolytes were unremarkable except for a serum calcium
of 4.3 (5.0 corrected) and an ionized calcium of 0.6.
Notice
the sinus bradycardia as well as the unusual T waves. Most
notable is the prolonged QT interval of 536 versus a normal
interval of 440-460.
Electrocardiographic
abnormalities that also result from hypocalcemia including
prolonged Q-T intervals and marked QRS and ST changes that
may mimic acute myocardial infarction or conduction abnormalities.
Ventricular arrhythmias are a rare complication of hypocalcemia,
although congestive heart failure corrected by return of
serum calcium to normal have been reported. In addition
to EKG alterations, hypocalcemia can have other familiar
clinical manifestations such as Chvostek's sign (tetany
that can be elicited by percussion of the facial nerve below
the zygoma, resulting in ispilateral contractions of the
facial muscle) or Trousseau's sign (painful carpal spasm
that can be illicited by 3 min of occlusive pressure with
a blood pressure cuff).
Treatment
includes intravenous administration of calcium gluconate
or chloride. DonŐt forget to check serum magnesium levels
as well as abnormal levels can frustrate your attempts to
correct the serum calcium. There is an extensive differential
diagnosis of hypocalcemia. However, in this patient, the
most likely cause was thought to be his chronic renal failure
which can impair 1-alpha hydroxylation of vitamin D metabolism.
The patient had also recently been started on phenytoin
which can induce cytochrome p450 activation and accelerate
hepatic metabolization of vitamin D to inactive products.
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