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Nonlinear association between P-wave axis and lung function in adult population with COPD: evidence from a
Na Zhang1, Jijing Wang1, Guihua Zhao1
1Department of Cardiopulmonary Function, Henan Provincial People's Hospital of Zhengzhou University, Zhengzhou, Henan, China.
Objective:
This study aims to explore the correlation between the electrical axis of the P wave and lung function indicators in patients with chronic obstructive pulmonary disease (COPD) and the prognostic value of the P wave electrical axis in COPD.
Methods:
A retrospective analysis was performed on data from 407 participants at Henan Provincial People's Hospital, Northeast Henan Hospital. Participants were categorized into control group (n = 206) and COPD group (n = 201). The COPD group was further divided into five subgroups (mild, moderate, moderate-severe, severe, and very severe) according to the percentage of predicted FEV1 (FEV1% pred). The study employed multiple linear and logistic regression analysis, restricted cubic splines (RCS) analysis, and subgroup analyses to examine the correlation between the P wave electrical axis and ventilation indicators.
Results:
COPD patients were older, predominantly male, and had higher smoking prevalence than controls (all P < 0.001). The analysis showed higher heart rate (81.3 ± 16.7 vs. 73.0 ± 12.3 bpm, P < 0.001) and P-wave axis (64.2 ± 21.9° vs. 41.5 ± 18.4°, P < 0.001) in COPD patients. Univariate linear regression demonstrated significant negative correlations between P-wave axis and pulmonary function indicators: FEV1 (β = -9.24, P < 0.001) and FEF75% (β = -14.72, P < 0.001). Logistic regression analysis showed that the P-wave axis was independently and positively associated with the risk of COPD (OR = 1.05, P < 0.001). The RCS analysis further suggests a non-linear pattern "J-shaped", between P-wave axis and COPD risk, and beyond a specific threshold, at 61.9°, risk increased more sharply above this threshold. Notably, the steep upward trend of risk for P-wave axis > 75° was limited by sparse sample distribution and only for exploratory reference. Additionally, subgroup analysis indicates a stronger association in males than females (OR = 1.06, P < 0.05). Subgroup results should be interpreted cautiously due to reduced statistical power within small stratified populations.
Conclusion:
The P-wave axis is closely associated with pulmonary function and COPD risk, exhibiting a nonlinear "J-shaped" relationship with 61.9° (95%CI: 61.5°, 62.4°) inflection point.
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