Littmann sign in hyperkalemia: double counting of heart rate

Computer-Estimated Heart Rate vs True Heart Rate—Be Aware of the Software

“…In severely ill patients, heart rate overcounting by computerized software, especially in combination with wide QRS complexes, is a strong indication of possible severe hyperkalemia. [1][2][3]…”

“…9 Recently, it was found that overcounting of the heart rate by ECG interpretation software, especially when combined with wide QRS complexes, can also be an indication of severe hyperkalemia. [1][2][3] The cause of hyperkalemic heart rate double counting is uncertain, but it is most likely due to software not being able to distinguish between widened QRS complexes and tall T waves. The present case strongly supports this hypothesis because during cardiac arrest, both the QRS complexes and the T waves were marked as ventricular complexes (Figure , B).…”

“…Double counting of the heart rate has been seen with different ECG systems using a variety of computer algorithms. [1][2][3] Overcounting of the heart rate is not fully specific for the diagnosis of hyperkalemia given that pacemaker spikes, artifact, tall P waves, and physiologically tall T waves too can be mistaken for QRS complexes. However, in a severely ill patient, heart rate overcounting, especially when combined with QRS complex widening, should prompt consideration of severe hyperkalemia.…”

Wide QRS complex rhythm with pulseless electrical activity

“…3 Pulseless electrical activity associated with a wide QRS complex and marked axis deviation, as in this patient, is usually the result of a metabolic abnormality, most often hyperkalemia 3 ; additional indicators of severe hyperkalemia include ST-segment elevation in the anterior chest leads (including the Brugada pattern 4 ) and, as in this patient, "double counting" of the heart rate by the interpretation software (FIGURE 1). 5,6 Based on the suspicion of a metabolic cause, the serum potassium was tested and was 8.9 mmol/L (reference range 3.5-5.0). The patient was given intravenous calcium, sodium bicarbonate, glucose, and insulin, and 2 hours later the serum potassium had decreased to 7.1 mmol/L.…”

The Littmann sign: An indication of hyperkalemia

“…Their automated interpretation program was limited to GE‐Marquette system when the rate was measured, but Tomcsányi et al. found that this “Littmann sign” could be observed in another ECG recording by a different manufacturer (Schiller) . The exact cause of the double count has been unclear.…”