Effect of electrocardiographic P-wave axis on mortality.

Although P-wave axis is routinely reported on the printouts of most contemporary electrocardiograms, the prognostic significance of its abnormality has not been systematically evaluated. We examined the association between abnormal P-wave axis and cardiovascular and all-cause mortality in 7,501 participants (53% women, mean age 59 years) from the United States Third National Health and Nutrition Examination Survey. P-wave axis of 0° to 75° was considered normal. Participants were linked to the National Death Index to identify the underlying cause of death listed on the death certificates using the International Classification of Disease. During a median follow-up of 13.8 years, a total of 2,541 deaths occurred; of which 1,077 were due to a cardiovascular cause. Abnormal P-wave axis was associated with 55% increased risk of all-cause mortality (hazard ratio [HR] 1.55, 95% confidence interval [CI] 1.43 to 1.69, p <0.01) and 41% increased risk of cardiovascular mortality (HR 1.41, 95% CI 1.24 to 1.62, p <0.01). After adjustment for age, gender, race/ethnicity, diabetes, systolic blood pressure, body mass index, smoking status, total/high-density lipoprotein cholesterol ratio, previous cardiovascular disease, chronic obstructive pulmonary disease, bronchial asthma, heart rate, and use of antiarrhythmic or atrioventricular nodal blocking drugs, the risk of mortality remained significantly high (HR 1.24 95% CI 1.13 to 1.36, p <0.01 for all-cause mortality and HR 1.19 95% CI 1.03 to 1.38, p = 0.02 for cardiovascular mortality) and was consistent across several subgroups of the participants. In conclusion, abnormal P-wave axis is associated with an increased risk of death, findings that call for attention to this routinely reported finding on contemporary electrocardiographic machines.