Atrial septal defect (ASD) accounts for 10% of all congenital heart lesions and represent the third most congenital cardiac defect seen in adults1. This lesion is sometimes associated with the development of pulmonary arterial hypertension (PAH), right ventricular volume overload, congestive heart failure and atrial arrhythmias 1.

Surgical closure of the defect aims at relieving the heart and pulmonary circulation from the haemodynamic burden. Although patients benefit from surgical occlusion of the defect, they still have cardiovascular morbidity after the operation 1. A new technique using the Amplatzer septal occluder was developed for the transcatheter closure of ASD 1234. This device is simple in construction, easy to deploy, and can be withdrawn and repositioned many times. It carries the advantages of fewer complications, avoidance of cardioplegia and cardiopulmonary bypass, shorter hospitalization, reduced need for blood products, and less patient discomfort. Although satisfactory results have been reported with transcatheter closure of ASD, there are some complications in this procedure. The type and rate of complications are different among different devices. Chessa et al 4 reported the embolization/malposition was the most common complication. Arrhythmias were the next most common complications. The other complications included right iliac vein dissection; groin hematoma, retropharynx hemorrhage.

ANP, a cardiac neurohormone secreted in the right atrium in response to increased right atrial pressure as well as volume loads 56. It is an important regulator of the sodium and volume homeostasis7. It may be elevated in patients with congenital and acquired heart disease 8.

The present study was designed to evaluate the correlation between plasma ANP concentrations and PAP and right ventricular volume overload, and to investigate the changes in plasma ANP concentrations in patients with ASD during transcatheter closure of defects.

Transcatheter closure of ASD and three-dimensional echocardiographic examinations were successfully performed in all patients, achieving a complete occlusion 3 days postoperatively in 100% of patients, and there were no complications, such as arrhythmia, embolization, or cardiac tamponade after the procedure. All patients had a single device implanted. The sizes of occluder were from 11 to 40 mm. The acquisition time of the echocardiographic data ranged from 8 to 10 minutes. Off-line image processing and analysis required on average 45 minutes.

Previous studies evaluated the RV geometric change response to transcatheter closure of ASD by the measurement of a single RV dimension in a long- or short-axis view, or both 31213. RV dimension does not adequately reflect the complex geometry of the right ventricle, and there are no clear landmarks to ensure that this dimension is measured in the same anatomic location across serial studies. We used a three-dimensional echocardiographic volumetry to calculate RV volumes. This model might offer even more accurate assessment of right-sided chamber volumes. Thus, the measurement of RV volumes in this study allowed much more confidence than the measurement of a simple linear dimension.

In this study, we showed that (1) plasma ANP concentrations were elevated in patients with ASD regardless of the presence of PAH, (2) plasma ANP concentrations were correlated positively with PAP, RVEDV and RVESV; and correlated negatively with RVEF, and (3) after transcatheter closure of ASD, plasma ANP concentrations were markedly decreased, the RVEDV, RVESV decreased and the RVEF increased markedly.

These findings are consistent with previous reports on ANP that showed a positive correlation between plasma ANP concentrations and Qp/Qs and a positive correlation between plasma ANP and PAP in patients with different types of congenital heart disease, including ASD 51415.

ANP is a 28 amino acid peptide and produced primarily in the cardiac atria 8, stimulated by atrial stretch, for example, volume overloading. ANP is a biologically active peptide with natriuretic and diuretic activities. In our study, plasma ANP concentrations were correlated positively with PAP and RVEDV in patients with ASD. These results imply that ANP may be released in response to right heart volume overload caused by the left-to right shunt in patients with ASD. Possible pathophysiologic significance of ANP increase in patients with ASD may relate to their pulmonary vasodilative effect. Increased ANP concentrations in patients with ASD correlated positively with PAP may play an important role in protecting the pulmonary bed.

In the last 50 years cardiac catheterization has changed its primary role from a diagnostic to that of a therapeutic procedure. Most recently, ASD transcatheter occlusion techniques have become an alternative to surgical procedure using cardiopulmonary bypass 4. Our study showed that the plasma ANP concentrations decreased markedly at 3 days after transcatheter closure and there was a significant decrease in right ventricular volume by 3 days after transcatheter closure. Muta et al 16 demonstrated that the plasma ANP concentrations at 1 month after ASD closure decreased and were similar to control values. Schussler et al 17 demonstrated right ventricular volumes decreased by 22%, 30%, and 41% at 1 day, 1 month, and 6 months, respectively, after successful transcatheter closure of large ASDs. Right atrial areas decreased by 5%, 23%, and 26%, respectively, over the same time. Presumably, the early reduction in right heart size is secondary to removal of the left-to-right shunt and reduction of pro-load 3. Right ventricular volumes continued to improve for up to 6 months, suggesting an ongoing remodeling process 17. The mechanism of ANP decreases may reflect a reduction of volume overload of right heart.

Although it became readily apparent that 3DE provides more accurate and reliable measurements of right ventricular volume and function, the complex image acquisition and off-line data processing have limited the use of 3DE in daily clinical practice.

The ASD was found to be associated with increased right ventricular volume, pulmonary arterial hypertension and was accompanied by increased plasma ANP concentrations, probably due to long-standing atrial stretch, when compared with controls. The change in plasma ANP concentrations may reflect changes in cardiac load during transcatheter closure of ASD. Thus plasma ANP concentrations can reflect pressure and volume loads to the pulmonary artery and right ventricle, and may be helpful in identifying patients with ASD and pulmonary arterial hypertension that demands early intervention.

JDD, GSM and FXL participated to the design of the study. JDD and GSM were responsible for collection of data and drafting of manuscript. JDD performed the statistical analysis and revised the manuscript critically for important intellectual content. YYH and XLZ performed three-dimensional echocardiography, BL and JDD carried out immunoradiometric assay. All authors read and approved the final manuscript.