Electrocardiographic changes resulting from pericardial effusion drainage.

Electrocardiographic (ECG) changes resulting from drainage of pericardial effusion (PE) have not been systematically studied. In addition, because PE and peripheral edema produce voltage attenuation of the electrocardiogram, we aimed at exploring whether these 2 conditions could be differentiated by electrocardiogram. We previously showed that peripheral edema attenuates amplitudes of QRS complexes and P waves and published a case report showing that attenuation in PE involves QRS complexes but not P waves. Clinical, laboratory, and echocardiographic data and quantitative measurements of amplitudes of QRS complexes and P waves before and after pericardiocentesis in 43 patients were obtained. Although changes of QRS complexes before and after pericardiocentesis were statistically significant, they were not so for P waves. Other ECG measurements before and after pericardiocentesis did not show statistically significant changes, except for heart rate, which decreased, and PR interval and QRS duration, which increased after the procedure. In conclusion, pericardiocentesis results in augmentation of QRS complexes on electrocardiogram, whereas it does not affect amplitude of P waves; this differential from peripheral edema is attributed to the fact that PE around the atria is much less than around the ventricles, and thus alleviation of PE alters the voltage transfer dynamics to the body surface for the atria much less than it does for the ventricles.