title: P-wave indices in patients with pulmonary emphysema: do P-terminal force and interatrial block have confounding effects?
abstract: BACKGROUND
  Pulmonary emphysema causes several electrocardiogram changes, and one of the most common and well known is on the frontal P-wave axis. P-axis verticalization (P-axis > 60°) serves as a quasidiagnostic indicator of emphysema. The correlation of P-axis verticalization with the radiological severity of emphysema and severity of chronic obstructive lung function have been previously investigated and well described in the literature. However, the correlation of P-axis verticalization in emphysema with other P-indices like P-terminal force in V1 (Ptf), amplitude of initial positive component of P-waves in V1 (i-PV1), and interatrial block (IAB) have not been well studied. Our current study was undertaken to investigate the effects of emphysema on these P-wave indices in correlation with the verticalization of the P-vector.
  
  
  METHODS
  Unselected, routinely recorded electrocardiograms of 170 hospitalized emphysema patients were studied. Significant Ptf (s-Ptf) was considered ≥40 mm.ms and was divided into two types based on the morphology of P-waves in V1: either a totally negative (-) P wave in V1 or a biphasic (+/-) P wave in V1.
  
  
  RESULTS
  s-Ptf correlated better with vertical P-vectors than nonvertical P-vectors (P = 0.03). s-Ptf also significantly correlated with IAB (P = 0.001); however, IAB and P-vector verticalization did not appear to have any significant correlation (P = 0.23). There was a very weak correlation between i-PV1 and frontal P-vector (r = 0.15; P = 0.047); however, no significant correlation was found between i-PV1 and P-amplitude in lead III (r = 0.07; P = 0.36).
  
  
  CONCLUSIONS
  We conclude that increased P-tf in emphysema may be due to downward right atrial position caused by right atrial displacement, and thus the common assumption that increased P-tf implies left atrial enlargement should be made with caution in patients with emphysema. Also, the lack of strong correlation between i-PV1 and P-amplitude in lead III or vertical P-vector may suggest the predominant role of downward right atrial distortion rather than right atrial enlargement in causing vertical P-vector in emphysema.
authors.affiliation: Department of Internal Medicine, University of Massachusetts Medical School, Plantation Street #813,Worcester, MA 01604, USA. lovids@hotmail.com
authors.forename: Lovely
authors.initials: L
authors.lastname: Chhabra
authors.forename: Vinod K
authors.initials: VK
authors.lastname: Chaubey
authors.forename: Chandrasekhar
authors.initials: C
authors.lastname: Kothagundla
authors.forename: Rishi
authors.initials: R
authors.lastname: Bajaj
authors.forename: Sudesh
authors.initials: S
authors.lastname: Kaul
authors.forename: David H
authors.initials: DH
authors.lastname: Spodick
mesh_terms: D000367:Age Factors; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000175:diagnosis* / Q000209:etiology; D005260:Female; D006325:Heart Atria / Q000503:physiopathology*; D006329:Heart Conduction System; D006801:Humans; D008297:Male; D008875:Middle Aged; D011656:Pulmonary Emphysema / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology; D012720:Severity of Illness Index; D013223:Statistics as Topic; D014672:Vectorcardiography / Q000379:methods*
keywords: P-axis; P-terminal force; emphysema; interatrial block; left atrial enlargement; vertical P-vector