Secundum atrial septal defect in the adult. Clinical, haemodynamic and electrophysiological aspects.

Atrial septal defect (ASD) is the most common congenital heart malformation diagnosed in adult life. In this thesis important clinical, haemodynamic and electrophysiological aspects of ASD in the adult are explored.

The diagnostic accuracy of magnetic resonance velocity mapping (MRvm)in calculating the pulmonary/systemic flow ratio (QP/QS)was assessed (I). The mean and maximal error by MRvm was 1±1% and ≤4% respectively in the whole range of different QP/QS and repeatability showed a difference of 1±5%. Interobserver variability was four times higher for radionuclide angiography than MRvm, 16% vs. 4%, demonstrating the superiority of MRvm.

Atrial electrophysiological properties before and 8±6 months after ASD closure were examined by means of high-resolution orthogonal P-wave signal-averaged ECG (II and III). P-wave duration was significantly longer in ASD patients than in controls and overall, it was not significantly affected by ASD closure. P-wave duration did not relate to echocardiographic atrial sizes, suggesting atrial conduction delay which seems more or less irreversible in middle-aged ASD patients.

The remodelling potential and its speed were investigated by repeated echocardiograms before and during the 1st year after ASD closure (IV). Right ventricular and right atrial sizes as well as the pulmonary pressure levels were markedly reduced after ASD closure and became normal in a majority of the patients. In contrast, the left atrial size did not change and remained abnormal in 44%. When changes occurred they came early.

Outcome of ASD closure was compared to medical management 6 and 30 years after the initial assessment (V). Closure of the defect was superior to medical management in terms of functional class, heart size and pulmonary pressure in the intermediate term. Early ASD closure also seemed beneficial in terms of late cardiovascular morbidity and mortality, in spite of a high frequency of late ASD closure, after the intermediate exam, in the medically managed group. In summary, the findings favour timely closure of the ASD if to reduce the risk of late mortality and morbidity.