Hajsadeghi Shokoufeh, Chitsazan Mitra, Miresmail Seyed Javad
Department of Cardiology, School of Medicine, Tehran University of Medical Sciences, Iran.
Acta Med Iran. 2011;49(12):824-7.
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.
长期以来，体表心电图（ECG）一直是检测代谢紊乱的一种有用方法。然而，当患者同时存在多种代谢异常时，可能难以辨别确切的紊乱情况。尽管常见电解质紊乱的“经典”心电图特征已有详细描述，但多种并发的电解质紊乱可能导致心电图异常，这些异常可能不易被检测到。这份心电图报告涉及一名60岁男性，他出现全身乏力、虚弱、上腹部疼痛、厌食、恶心以及极度高钙血症（血清总钙和离子钙水平分别为20.5mg/dL和12.02mg/dl）、低钾血症和低镁血症，同时伴有甲状旁腺激素升高（1160pg/ml）以及血清维生素D水平正常（97ng/ml）。原发性甲状旁腺功能亢进的这种罕见表现形式在文献中被称为甲状旁腺危象。甲状旁腺危象是多种电解质异常的一种紧急形式，表现为危及生命的高钙血症以及同时存在的低钾血症和低镁血症；后两者被认为是钙对肾小管的利尿作用所致。我们患者独特的心电图模式最初被误诊为QT校正（QTc）间期延长伴T波高耸，这种情况在甲状旁腺危象患者中已有多次报道，与我们的患者情况相符。但进一步检查发现，QTc间期不仅没有延长，反而如高钙血症对心电图的影响所预期的那样缩短了。患者心电图的确切模式（图1）可如下解读：（1）T波低平，（2）U波明显，（3）T波下降支延长，使其与下一个U波重叠，（4）ST段几乎消失，（5）QT校正间期缩短。总之，应当强调的是，当T波和U波之间仅由很短的一段间隔分开时，它们可能会模仿QT间期延长的表现。然而，更多的检查能够明确确切的心电图模式，尤其是在多种电解质紊乱的情况下，此时“经典”的心电图模式并不常见。
