Electrocardiographic Screening of Emphysema: Lead aVL or Leads III and I?

We read with great interest the recently published study by Lazovic et al. [1]. The study reiterates a very important yet neglected ECG observation of vertical P-axis, which can be effectively utilized as a quick bedside screening modality for chronic obstructive pulmonary disease (COPD)/emphysema [2-3]. Lazovic et al. utilized unipolar lead aVL alone for vertical P-wave screening instead of bipolar leads III and I or both criteria in combination, namely P-wave amplitude in lead III greater than in lead I or a negative P-wave in aVL [2].

In one of our recent studies, we found that lead aVL is less sensitive as compared to bipolar leads III and I for diagnosing vertical P-vector in COPD patients [4]. In an ideal theoretical setting, the P wave amplitude should be negative in aVL when the P wave amplitude in lead III is greater than in lead I (suggesting vertical P vector), but this was not found in a practical clinical setting, which could be possibly due to a commonly encountered variable/high skin resistance or poor surface contact at aVL producing a spurious “augmented” extremity (unipolar) lead abnormality. Thus, we recommend that one should consider using both leads III and I in combination with lead aVL for determination of vertical P-vector in patients with emphysema. Also, authors of this study have not specified the method employed for calculating the P-vector (automated vs. manual), but we believe they may have used automated readings to determine the correlation of Pvector with pulmonary function tests. In case when one considers to use manual P-vector readings which on some occasions may be more accurate than automated P-vectors, one would again have to use P-amplitudes in leads III and I. For these reasons, it may be best to use all three leads (I, III and aVL) for determination of vertical Pvector while screening for emphysema, as this would offer the highest sensitivity for its diagnosis.