Comparison of atrial electromechanical coupling interval and P-wave dispersion in non-dipper versus dipper hypertensive subjects

Background. The lack of nocturnal BP fall less than 10% of the daytime, called non-dipper hypertension, is associated with increased cardiovascular morbidity and mortality. The aim of our study was to investigate atrial conduction time in patients with non-dipper hypertension using electromechanical coupling interval and P-wave dispersion (PWD), measured with the surface electrocardiogram and tissue Doppler echocardiographic imaging (TDI). Methods. Age-and sex-matched 43 dipper hypertensive patients (19 male, 24 female, mean age: 53.9 +/- 10.5 years), 40 non-dipper patients (18 male, 22 female, mean age 54.3 +/- 9.6 years) and 46 healthy subjects (22 male, 24 female, mean age: 52.8 +/- 9.6 years) were included in the study. The difference between the maximum and minimum P-wave durations was calculated and defined as PWD. Atrial electromechanical coupling (PA), inter-atrial and intra-atrial electromechanical delays were measured with TDI. Results. PWD was significantly higher in patients with non-dippers compared with dippers (p < 0.02) and controls (p < 0.001). The inter-atrial conduction time was delayed in non-dippers compared with dippers (p < 0.01) and controls (p < 0.001). There was a positive correlation between left atrial (LA) diameter and inter-atrial conduction times (r = 0.46, p < 0.001). LA diameter was also correlated with PWD (r = 0.44, p < 0.001). Conclusion. The patients with non-dipper hypertension have higher P-wave duration, PWD and delayed inter-atrial electromechanical coupling intervals compared with those of dippers and controls. This indicates that these subjects may be more prone to atrial rhythm disturbances.