2.2 Statistical analysis
Normality distribution of quantitative variables was confirmed with the Kolmogorov-Smirnov test. Quantitative variables following a normal distribution are expressed as mean values ± standard deviation. Qualitative variables are expressed using frequencies and percentages. For independent variables that followed a normal distribution, we used the Student t-test . Qualitative variables were compared using the chi-square and McNemar tests. Only p values <0.05 were considered statistically significant. Multivariate analysis with logistic regression (backward stepwise) was used to determine whether the association between sinus and paced P-wave duration and AHRE was influenced by the baseline group characteristics (confounding factors). The covariates included were left atrial diameter (SI) and CHA2DS2-VASc score. The magnitude of the effects was expressed in odds ratio (OR) and 95% confidence interval (95% CI). Data were collected in Excel and imported into IBM SPSS (Armonk, New York) (version 25.0 for Windows) for statistical analysis.
RESULTS
Between July 2014 and December 2017, we included 220 patients (61% male, age 75 ± 10 years) with a CIED implanted in our center (Fundación Jiménez Diaz, Madrid, Spain; dual-chamber PM 96%, ICD 2%, and CRT 4%). The reasons for implantation were sinus node disease (30%), advanced AV block (52%), and different types of conduction disorders symptomatic with syncope (18%). Patients were divided into two groups depending on the presence of AHRE during device interrogation. Clinical characteristics of the patients included in both groups can be seen in Table 1.
After a mean follow-up of 59±25 months, 46% of the patients presented AHRE on device interrogation. Half of the episodes had a duration of between 1 h and 12 h (50%) and 21% of them were > 24 h. The age of the patients with AHRE was significantly higher (77 ± 8 vs 74 ± 10 years; p = 0.028). There were also significant differences in the CHA2DS2-VASc scale (3.7 ± 1.5 vs 3.3 ± 1.5; p = 0.02) and the SI diameter of the LA (53 ± 7 vs. 49 ± 6 mm; p = 0.017).