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Two Cases of Severe Hyperkalemia with Atypical Electrocardiographic Manifestations Chonbuk National University Medical School, Department of Internal Medicine Kyung Pyo Kang, Sik Lee, Min Hee Lee, Won Kim, Sung Kwang Park, Sung Kyew Kang
Introduction § Hyperkalemia is one of the most common electrolyte abnormalities affecting the electrocardiographic changes. § It is also the more common acute life-threatening metabolic emergencies seen in the medical department.
Narrowing & peaking T wave (tented T) Diminution of P-wave amplitude PR interval ↑ Widening QRS interval, Sinewave, Ventricular fibrillation, Cardiac arrest
Introduction § Serum potassium levels higher than 8 mmol/L (severe hyperkalemia) are almost invariably associated with ECG abnormalities. § However, minimal or atypical ECG changes have been observed in some cases of severe hyperkalemia. § In this report, we describe two cases of severe hyperkalemia (K+ ≥ 8 mmol/L) in which the ECGs showed atypical changes.
Case 1 § 66/female § C. C: generalized, progressive weakness, fever, and myalgia over the past 7 days. § P/Ex: an acutely ill appearance and there was an eschar on her neck. She had moderate tenderness in the upper abdomen. § Laboratory findings: BUN 66 mg/dl, creatinine 3. 95 mg/dl, K+ 8. 5 mmol/L, Na+ 121 mmol/L, HCO 3 - 21. 3 mmol/L, Ca 2+ 0. 85 mmol/L, Scrub typhus Ab (+) 1: 320 § Impression: 1. Scrub typhus 2. Acute renal failure
ECG K+ : 8. 5 mmol/L Ventricular rate 51 bpm, PR interval 184 ms, QRS duration 92 ms, QT/QTc 452/414 ms, sinus bradycardia, and nonspecific ST and T wave changes
Case 2 § 41/male § C. C: abdominal pain and diarrhea over the past 5 days. § Past history: MPGN, TB pleurisy, and cerebral infarction. § P/Ex: an acutely ill appearance and he had abdominal tenderness. § Laboratory findings: BUN 41 mg/dl, creatinine 7. 12 mg/dl, K+ 8. 2 mmol/L, Na+ 137 mmol/L, HCO 3 - 23. 6 mmol/L, Ca 2+ 0. 84 mmol/L § Impression 1. ESRD 2. MPGN
ECG K+ : 8. 2 mmol/L Ventricular rate 101 bpm, PR interval 148 ms, QRS duration 84 ms, QT/QTc 344/441 ms, and sinus tachycardia
Discussion I § Potassium plays an important role in maintaining the electrical potential across the cellular membrane, as well as in depolarization and repolarization of the myocyte.
Discussion II § With the increased extracellular concentration of potassium, transmembrane permeability is increased, causing an influx of potassium into the cells. § There is alteration of the transmembrane potential gradient, a decrease in magnitude of the resting potential, and a decrease in velocity of phase 0 of the action potential. § The potassium influx causes a shortening of the action potential and results in delayed conduction between the myocytes. J Emerg Med 27: 153 -160, 2004
Discussion III § The lack of ECG changes 1) The rate of change of serum potassium concentration 2) Hypernatremia 3) Hypercalcemia 4) Baseline ECG changes such as LVH, intraventricular conduction delay, and myocardial ischemia Am J Kidney Dis 7: 461 -465, 1986 J Electrocardiol 32: 45 -49, 1999
Conclusion § Our two cases have the lack of correlation between severe hyperkalemia and ECG findings. § Physicians should be aware that the ECG is not always a reliable indicator of severe hyperkalemia.