Background: Patients with atrial septal defect (ASD) have an increased risk for atrial fibrillation (AF). Previously it was shown that maximum P wave duration and P wave dispersion in 12-lead surface electrocardiograms are significantly increased in individuals with a history of paroxysmal AF. We studied P maximum and P dispersion in adult patients with ASD during normal sinus rhythm. In addition, the impact of surgical closure of ASD on these variables within 1 year after surgery was evaluated.
Methods: Thirty-four patients (21 women, 13 men; mean age: 35 +/- 11 years) operated on for ostium secundum type ASD and 24 age-matched healthy subjects (13 women, 11 men; mean age: 37 +/- 10 years) were investigated. P maximum, P minimum, and P dispersion (maximum - minimum P wave duration) were measured from the 12-lead surface electrocardiography.
Results: P maximum was found to be significantly longer in patients with ASD as compared to controls (115.2 +/- 9 vs 99.3 +/- 14 ms; P < 0.0001). In addition, P dispersion of the patients was significantly higher than controls (37 +/- 9 vs 29.8 +/- 10 ms; P = 0.003). P minimum was not different between the two groups (P = 0.074). After surgical repair of ASD, 10 patients (29%) experienced one or more episodes of paroxysmal AF. Patients with postoperative AF were older (45 +/- 6 vs 30 +/- 10 years; P = 0.001), and had a higher preoperative pulmonary artery peak systolic pressure as compared to those without postoperative AF (51 +/- 11 vs 31 +/- 9 mmHg; P < 0.0001). No significant difference in the pulmonary-to-systemic flow ratio was observed preoperatively between the two groups (P = 0.56). P maximum and P dispersion were significantly higher in patients with postoperative paroxysmal AF at baseline and at postoperative first month, sixth month, and first year as compared to those without it (for P maximum P = 0.027, P = 0.014, P = 0.001, P < 0.0001, respectively; for P dispersion P = 0.037, P = 0.026, P = 0.001, P < 0.0001, respectively). In addition, in patients with postoperative AF, no significant changes were detected in both of these P wave indices during postoperative follow-up. However, in the other group, P maximum and P dispersion were found to be significantly decreased at postoperative 6 months and 1 year as compared to baseline. P minimum was similar throughout the postoperative follow-up as compared to baseline in both groups.
Conclusions: Mechanical and electrical changes in atrial myocardium may cause greater P maximum and P dispersion in patients with ASD. Surgical closure of the ASD can regress these pathological changes of atrial myocardium with a result in decreased P maximum and P dispersion. However, higher P maximum and P dispersion at baseline, which have not decreased after surgery, may be associated with postoperative paroxysmal AF, especially for older patients.