title: The importance of the P-waves in the differentiation of attenuation of the QRS voltage due to pericardial effusion versus due to peripheral edema.
abstract: BACKGROUND
  The cases of the 3 patients reported herein show the role of the P-waves in the differential diagnosis of the attenuated voltage of QRS complexes from pericardial effusion (PEREF) and from those resulting from peripheral edema (PERED) of varying pathophysiologic etiology.
  
  
  RESULTS
  Whereas the QRS complexes decrease similarly in these 2 conditions, the voltage of P-waves do not become attenuated in PEREF, but do so in PERED. The underlying mechanism preventing attenuation of the voltage of P-waves in PEREF is the lack of much fluid around the atria, particularly in the presence of less than massive PEREF (no local electrical short-circuiting influence), in contrast to the attenuating effect exerted to both ventricles and atria in patients with PERED, who as a result, show parallel decrease in the voltage of QRS complexes and P-waves.
  
  
  CONCLUSIONS
  Attenuation of the amplitude of the electrocardiogram QRS complexes occurs in both patients with PEREF and PERED; however, attenuation of the amplitude of the P-waves is seen only in patients with PERED, and this observation is useful in the differential diagnosis of these 2 clinical conditions.
authors.affiliation: Mount Sinai School of Medicine of the New York UniversityNew York, NY, USA.
authors.forename: John E
authors.initials: JE
authors.lastname: Madias
mesh_terms: D000368:Aged; D002305:Cardiac Tamponade / Q000175:diagnosis*; D003937:Diagnosis, Differential; D015150:Echocardiography, Doppler; D004489:Edema, Cardiac / Q000175:diagnosis*; D017097:Electric Impedance; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010490:Pericardial Effusion / Q000175:diagnosis*; D018570:Risk Assessment; D012494:Sampling Studies; D012680:Sensitivity and Specificity