Assessment of long-term cardiac adaptation in adult patients with type II atrial septal defect : A cardiovascular magnetic resonance (CMR) study

Left Ventricular Diastolic Function in Children with Atrial Septal Defects Improves After Closure by Means of Increased Hydraulic Force

Hydraulic force aids diastolic filling of the left ventricle (LV) by facilitating basal movement of the atrioventricular plane. The short-axis atrioventricular area difference (AVAD) determines direction and magnitude of this force. Patients with atrial septal defect (ASD) have reduced LV filling due to the left-to-right shunt across the atrial septum and thus potentially altered hydraulic force. The aims were therefore to use cardiac magnetic resonance images to assess whether AVAD and thus the hydraulic force differ in children with ASD compared to healthy children, and if it improves after ASD closure. Twenty-two children with ASD underwent cardiac magnetic resonance before ASD closure. Of these 22 children, 17 of them repeated their examination also after ASD closure. Twelve controls were included. Left atrial and ventricular areas were delineated in short-axis images, and AVAD was defined as the largest ventricular area minus the largest atrial area at each time frame and normalized to body height (AVADi). At end diastole AVADi was positive in all participants, suggesting a force acting towards the atrium assisting the diastolic movement of the atrioventricular plane; however, lower in children both before (6.3 cm2/m [5.2-8.0]; p < 0.0001) and after ASD closure (8.7 cm2/m [6.6-8.5]; p = 0.0003) compared to controls (12.2 cm2/m [11.3-13.9]). Left ventricular diastolic function improves after ASD closure in children by means of improved hydraulic force assessed by AVAD. Although AVADi improved after ASD closure, it was still lower than in controls, indicating diastolic abnormality even after ASD closure. In patients where AVADi is low, ASD closure may help avoid diastolic function deterioration and improve outcome. This could likely be important also in patients with small shunt volumes, especially if they are younger, who currently do not undergo ASD closure. Changes in clinical routine may be considered pending larger outcome studies.

Arrhythmic Risk and Treatment after Transcatheter Atrial Septal Defect Closure

Atrial septal defect (ASD) represents the most common congenital heart defect identified in adulthood. Atrial and ventricular geometric remodeling due to intracardiac shunt increase the risk of arrhythmias, especially atrial fibrillation (AF). Clinical, echocardiography, electrocardiogram, and device-related predictors may be used to assess the risk of atrial arrhythmias after ASD closure. The underlying mechanisms in these patients are complex and at least in part independent of the structural remodeling secondary to hemodynamic overload. Device closure of the ASD itself and its timing impact future arrhythmia risk, as well as posing a challenge for when transseptal puncture is required. Sudden cardiac death (SCD) risk is higher than in the general population and an implantable cardioverter-defibrillator (ICD) may be indicated in selected cases.

Haemodynamic left-ventricular changes during dobutamine stress in patients with atrial septal defect assessed with magnetic resonance imaging-based pressure-volume loops

BACKGROUND

Atrial septal defect (ASD) results in a left-to-right shunt causing right-ventricular (RV) volume overload and decreased cardiac output from the left ventricle. Pressure-volume (PV) loops enable comprehensive assessment of ventricular function and might increase understanding of the pathophysiology of ASD. The aim of this study was to investigate if left-ventricular (LV) haemodynamic response to stress in patients with ASD differs from controls.

MATERIAL AND METHODS

Patients with ASD (n = 18, age 51 ± 18) and healthy controls (n = 16, age 35 ± 13) underwent cardiac magnetic resonance (CMR) and brachial cuff pressure measurements at rest and during dobutamine stress. An in-house, validated method was used to compute PV loops.

RESULTS

Patients had lower stroke work, potential energy and external power at rest than controls (p < 0.001; p < 0.05; p < 0.05). Stroke work and external power increased and potential energy decreased during stress in patients (p < 0.05; p < 0.0001; p < 0.01) and controls (p < 0.0001; p < 0.001; p < 0.01). Contractility and arterial elastance at rest were higher in patients than controls (p < 0.01; p < 0.01). Contractility increased during stress in both groups (p < 0.0001; p < 0.001). There was no difference between patients and controls in arterio-ventricular coupling.

CONCLUSION

LV haemodynamic response to stress can be assessed using noninvasive PV loops derived from CMR and brachial blood pressure. Patients with ASD had normal LV energy efficiency, in contrast to other patient groups with decreased cardiac output. Data suggest that patients with ASD had an increased inotropic level at rest with high contractility and heart rate but were able to respond with a further increase during stress, albeit to not as high a cardiac output as controls.

In Vitro Pressure Measurements Across an Interatrial Shunt for HFpEF Treatment

PURPOSE

Preserved ejection fraction heart failure (HFpEF) can be treated by installing a shunt in the interatrial septum, which relieves excess pressure in the left atrium by allowing blood to flow from left to right. This technique has proven effective in clinical trials, but the details of the flow through the shunted heart are not well understood. The current study aims to collect quantitative data on the relationship between pressure and flow rate in such shunts.

METHODS

An in vitro, shunted double atrium flow phantom was fabricated and used to investigate the relationship between pressure drop and flow across an interatrial shunt. Flow rate was controlled and the resulting pressure drop across the shunt was measured for a variety of flow cases, including steady and pulsatile flow, flow rate waveforms typical of healthy and failing hearts, and low and high heart rates.

RESULTS

The results show a positive relationship between shunt flow rate and pressure drop which is more pronounced in steady flow than in pulsatile flow. Increasing heart rate increases the time-averaged pressure drop across the shunt but not the maximum pressure drop. For steady-flow cases, large changes in pressure drop resulting from moderate changes in flow rate suggest a flow regime transition during parts of the cardiac cycle. Comparison of time-averaged pulsatile flow pressure measurements with steady-flow measurements and two analytical plate-orifice models suggests that none approximate pulsatile flow accurately.

CONCLUSIONS

The flow rate/pressure drop relationship across an in vitro model of an interatrial shunt has been measured for a variety of physiologically relevant cases. Among other things, the results suggest that steady flow approximations to the heart's pulsatile flow should be used with caution and simplified theoretical models do not approximate the flow rate/pressure drop relationship accurately.

Quantification of Myocardial Deformation Applying CMR-Feature-Tracking-All About the Left Ventricle?

Purpose of Review

Cardiac magnetic resonance-feature-tracking (CMR-FT)-based deformation analyses are key tools of cardiovascular imaging and applications in heart failure (HF) diagnostics are expanding. In this review, we outline the current range of application with diagnostic and prognostic implications and provide perspectives on future trends of this technique.

Recent Findings

By applying CMR-FT in different cardiovascular diseases, increasing evidence proves CMR-FT-derived parameters as powerful diagnostic and prognostic imaging biomarkers within the HF continuum partly outperforming traditional clinical values like left ventricular ejection fraction. Importantly, HF diagnostics and deformation analyses by CMR-FT are feasible far beyond sole left ventricular performance evaluation underlining the holistic nature and accuracy of this imaging approach.

Summary

As an established and continuously evolving technique with strong prognostic implications, CMR-FT deformation analyses enable comprehensive cardiac performance quantification of all cardiac chambers.