A Rare Electrocardiographic Manifestation of a Rare Form of Multiple Electrolyte Disturbances: Hyperparathyroid Crisis

Abstract

The surface electrocardiogram (ECG) has been used as a useful method for detection of metabolic disturbances for a long time. However, it may be difficult to distinguish the exact disturbance when more than one metabolic abnormality exists in a patient simultaneously. Although, "classic" ECG characterizations of common electrolyte disturbances are well described, multiple concurrent electrolyte disturbances may lead to ECG abnormalities that may not be easily detectable. This ECG concerns a 60-year-old male presented with general fatigue, weakness, epigastric pain, anorexia, nausea and extreme hypercalcemia (serum total and ionized calcium levels 20.5 mg/dL and 12.02 mg/dl, respectively), hypokalemia and hypomagnesemia associated with elevated parathyroid hormone (1160 pg/ml) and normal serum vitamin D level (97 ng/ml) . This rare manifestation of primary hyperparathyroidism has been named hyperparathyroid crisis in the literature. Hyperparathyroid crisis is an emergency form of multiple electrolyte abnormalities that manifest as a life-threatening hypercalcemia and simultaneous hypokalemia and hypomagnesemia; these two later are believed to be caused by diuretic effect of calcium on the renal tubules. The unique pattern of ECG in our patient first was misdiagnosed as prominent T waves with prolongation of the QT corrected (QTc) interval, which has been reported several times in patients with hyperparathyroidism crisis, compatible with our patient. But more investigation revealed that, the QTc interval not only is not prolonged, it is shortened as it is expected from the effect of hypercalcemia on electrocardiogram. The exact pattern of the patient`s ECG (figure 1) can be interpreted as it follows: (1) Flattening of the T wave, (2) a prominent U wave, (3) prolongation of the descending limb of the T wave such that it overlapped with the next U wave (4) virtual absence of ST segment and (5) shortening of the QT corrected interval. In conclusion, it should be emphasized when the T and U waves are separated by a very short segment they can mimic the appearance of a prolonged QT interval. However, more investigation can demonstrate the exact electrocardiographic pattern especially in multiple electrolyte disturbances, when "classic" ECG patterns are not expectable.