Changes in blood volume shunting in patients with atrial septal defects: assessment of heart function with cardiovascular magnetic resonance during dobutamine stress

Abstract

BackgroundThe purpose of this study was to determine the effect of stress on left-to-right shunting in patients with atrial septal defect (ASD) and to investigate if the degree of shunting, cardiac output (CO), and right ventricular (RV) volumes are related to exercise capacity.MethodsTwenty-six patients with a secundum ASD and 16 healthy volunteers were studied with rest/stress cardiac magnetic resonance using 20 µg/kg/min dobutamine and 0.25–0.75 mg atropine to quantify CO, pulmonary to systemic flow ratio (QP/QS), and left ventricular (LV) and RV volumes. Peak oxygen uptake (VO2peak) was determined on ergospirometry.ResultsIn patients with ASD the QP/QS decreased from 2.0 ± 0.2 at rest to 1.5 ± 0.1 (P < 0.001) during dobutamine stress (n = 20) and shunt volume per heartbeat decreased from 70 ± 9 to 38 ± 9 mL (P < 0.001). However, absolute shunt volume per minute was unchanged (5.1 ± 0.8 vs. 4.5 ± 1.0 L/min, P = 0.32) explained by a higher increase in systemic CO during stress (90 ± 11%) compared with pulmonary CO (43 ± 7%, P < 0.001). In ASD patients, VO2peak correlated with aortic CO during stress (r = 0.77) and QP/QS at rest (r = −0.48) but not during stress (P = 0.09). VO2peak did not correlate with RV volumes in patients.ConclusionPulmonary to systemic flow ratio and shunt volume per heartbeat decrease during stress in ASD patients. This may be explained by an enhanced LV diastolic function during stress and may have implications to detect disturbances in LV compliance in ASD patients. A high systemic CO during stress is a strong predictor of exercise capacity.

A new vessel segmentation algorithm for robust blood flow quantification from two‐dimensional phase‐contrast magnetic resonance images

“…Two-dimensional PC-MR data of the ascending aorta from 17 healthy volunteers and 154 patients with heart failure (defined as left ventricular ejection fraction below 40%) were retrospectively included from a previous study of cardiac index (Carlsson et al, 2012). Two-dimensional PC-MR data of the pulmonary artery from 35 healthy volunteers and 25 patients with atrial septal defects were also included from a previous study of atrial septal shunt volumes (Stephensen et al, 2016). Vessel shape constraints and optimized algorithm parameters were extracted from 40 data sets, 20 from the ascending aorta group (10 healthy volunteers) and 20 from the pulmonary artery group (10 healthy volunteers).…”

Alterations in ventricular pumping in patients with atrial septal defect at rest, during dobutamine stress and after defect closure

“…During dobutamine stress, left‐to‐right shunting volume decreased which resulted in more balanced stroke volumes in the left and right ventricle (Stephensen et al ., ) and a larger increase in systemic compared to pulmonary cardiac index. Thus, during dobutamine stress, there was a greater increase in trans‐mitral flow compared to trans‐septal flow.…”

“…Furthermore, it is not known how increased workload affects longitudinal pumping in patients with ASD. Administration of dobutamine–atropine lowers the left‐to‐right shunt in ASD patients and subsequently the degree of RV volume overload (Stephensen et al ., ). Thus, studies in ASD patients with dobutamine–atropine may elucidate if the mechanisms of altered RV pumping physiology in the volume‐overloaded state is caused by the RV dilatation itself or if the different aetiologies of RV dilatation lead to different responses in pumping physiology.…”

Left ventricular dispersion as a parameter for augmented left ventricular stroke volume in patients with atrial septal defect following transcatheter closure

“…In addition, the left‐to‐right shunt also causes inadequate left ventricular (LV) diastolic filling and reduced LV end‐diastolic volume due to right ventricular (RV) dilatation, leading to left‐sided heart failure because of insufficient LV stroke volume (LVSV) to maintain the blood flow necessary to meet the body's needs. In addition, a recent study showed that exercise capacity such as peak oxygen uptake, which is often used as a marker of the impact of the ASD after surgical or transcatheter ASD closure, correlates strongly with systemic cardiac output at rest and during low‐dose dobutamine stress in patients with ASD . Transcatheter closure of the ASD currently is widely considered to be the first‐choice therapeutic option due to its clear‐cut functional, safety, and social advantages .…”

“…In addition, a recent study showed that exercise capacity such as peak oxygen uptake, which is often used as a marker of the impact of the ASD after surgical or transcatheter ASD closure, 3,4 correlates strongly with systemic cardiac output at rest and during low-dose dobutamine stress in patients with ASD. 5 Transcatheter closure of the ASD currently is widely considered to be the first-choice therapeutic option due to its clear-cut functional, safety, and social advantages. 6,7 Moreover, ASD closure results in normalized LV and RV geometry, and can increase LVSV.…”