Diaphragmatic action potentials registered in the electrocardiogram: A clinical and experimental study

P-wave—like deflections followed by high-frequency minute oscillations were observed in the ECG of a 58-year-old obese woman with fever and erysipelas of the left leg. The phenomenon was present in vertical leads and was most prominent in those recorded from the vicinity of the diaphragm. It disappeared when the signs of diffuse inflammation of the leg subsided and reappeared when the patient rebreathed into a plastic bag. It was reasoned that the abnormal ventilatory load imposed by her obesity and the increased metabolic demand of the infectious disease may have caused an augmented electrical activity of the diaphragm and the appearance of this activity on the surface leads. In cats, strong diaphragmatic action potentials, which were produced by phrenic nerve stimulation, caused the appearance of similar P-wave-like deflections in the vertical leads of the ECG.