RESUMO
BACKGROUND: It is unclear whether the presence of a vertical P-wave axis on electrocardiogram modifies the association of COPD with mortality. OBJECTIVE: To examine the association and interaction of abnormal P-wave axis and COPD with mortality. STUDY DESIGN AND METHODS: The analysis included 7359 with ECG data from the Third National Health and Nutrition Examination Survey (NHANES-III) who were free of cardiovascular disease (CVD) at enrollment. Abnormal P-wave axis (aPWA) was defined as values above 75°. COPD was self-reported as either a diagnosis of emphysema or chronic bronchitis. National Death Index was used to identify the date of death and cause of death. Using multivariable Cox proportional hazard analysis, we examined the association of COPD with all-cause mortality by aPWA status. RESULTS: Over a median follow-up of 14 years, 2435 deaths occurred. Participants with concomitant presence of aPWA and COPD experienced higher death rates (73.9 per 1000 person-years (PY)) compared to either COPD or aPWA alone (36.4 per 1000 PY and 31.1 per 1000 PY), respectively. In multivariable-adjusted models, a stronger association between COPD and mortality was noted in the presence compared to the absence of aPWA (HR 95% CI): 1.71 (1.37-2.13) vs. 1.22(1.00-1.49), respectively (interaction P-value = 0.02). Similarly, a stronger association between aPWA and mortality was observed in the presence compared to the absence of COPD (HR 95% CI): 1.66(1.26-2.19) vs. 1.18(1.06-1.31), respectively (interaction P-value = 0.02). Similar higher death rates and mortality risk was observed when spirometry-confirmed COPD and aPWA were present together than in isolation. CONCLUSION: The concomitant presence of aPWA and COPD leads to a significantly higher mortality rate compared to the presence either COPD or aPWA alone as a clinical variable. P-wave axis, reported routinely on ECG printout, can potentially identify patients with COPD who need intensive control of risk factors and disease management.