Lower cardiac index and increased pulmonary backflow during exercise in adults with small unrepaired Atrial Septal Defects – an MRI study
Presented By:
Marie Maagaard, MD, PhD; Mathias Ahlstrup, MD; Nicolai Boutrup, MD; Sebastian Udholm, MD, PhD, DMSc; Jens Erik Nielsen-Kudsk, MD, DMSc; Steffen Ringgaard, MSc, PhD; Vibeke Hjortdal, MD, PhD, DMSc
Overview:
Objectives: A small, unrepaired atrial septal defect (ASD) is considered a benign lesion with good prognosis. Recently, clinical and register-based studies discovered increased long-term mortality and morbidity as well as impaired functional capacity in adults with small unrepaired ASDs when compared with their healthy peers. The nature of these findings is not fully understood and therefore, magnetic resonance imaging (MRI) was performed to evaluate cardiac function at rest and during exercise.
Methods: Adults with unrepaired ASDs – either open or spontaneously closed – and healthy controls underwent MRI at rest for the evaluation of cardiac chamber volumes and morphology with cine scans. Quantitative flow scans measured blood flow in the systemic and pulmonary circulation at rest and during increasing supine exercise.
Results: In total, 15 open ASDs with a mean age of 39±11years and 15 matched controls with a mean age of 38±12years were included, along with 20 spontaneously closed ASDs with a mean age of 36±13years and 20 controls with a mean age of 36±11years. Cardiac chamber volumes were comparable between groups and all within normal range. Flow measurements at rest were comparable between groups, and heart rates and workloads were comparable between groups during exercise. Shunt ratio for open ASDs was 1.2±0.2 and remained unchanged during exercise, whereas absolute blood flow through the shunt increased from rest being 0.9±0.9l/min to exercise being 2.1±1.8l/min. During exercise, open ASDs had a lower cardiac index than their controls (p<0.01) and reached 31% lower cardiac index at maximal exercise levels. At the end of the test, open ASDs had higher retrograde flow through the pulmonary artery, 0.8±0.3l/min/m2 compared to the controls 0.5±0.2l/min/m2, p<0.01.
Conclusion: Adults with a small, open ASD exhibit a markedly lower exercise capacity of 31% compared with their healthy peers. Furthermore, patients with open ASDs exhibit higher retrograde flow with increasing exercise compared with healthy controls. These findings may partly explain the lower functional capacity demonstrated previously. Still, the causes of the increased long-term morbidity in ASD patients remain undetermined and further research is warranted.
