Vertical P-wave axis: the electrocardiographic synonym for pulmonary emphysema and its severity

The correlation between vertical P-wave axis (P-axis > 60°) and pulmonary emphysema was investigated on a very large controlled series to see if P-axis verticalisation as lone criterion can be effectively used to screen emphysema in general population. Correlation between degrees of P-axis verticalisation and the severity of the obstructive lung disease (as per global initiative for chronic obstructive lung disease [GOLD] criteria) was also studied to see if this criterion can be used for gross quantification of the chronic obstructive pulmonary disease (COPD) in routine clinical practice.

Around 6500 unselected, routine electrocardiograms (ECGs) were reviewed which yielded 600 ECGs with vertical P-axis in sinus rhythm. 635 ECGs from the same continuum were selected with P-axis ≤60° matched for patient's age and sex serving as controls. Charts were reviewed for the diagnosis of COPD and emphysema based on medical history, pulmonary function tests, and imaging studies.

Prevalence of emphysema in patients with vertical P-axis was strikingly higher than in the control group: 85% vs 4.4%. The sensitivity and specificity of vertical P-axis for diagnosing emphysema was 94.76% and 86.47%, respectively. Vertical P-axis and forced expiratory volume (FEV1) were inversely correlated (Pearson correlation coefficient=-0.683). Prevalence of severe COPD was strikingly higher in patients with P-axis > 75° as compared to the group with P-axis 60°-75°: 96.3% vs 4.6%. Close to 80% of the emphysema patients with P-axis > 85° had very severe disease (FEV1 < 30%).

P-axis verticalisation is highly effective for screening emphysema and degree of verticalisation provides a gross quantification of the disease.