Fetal cardiac interventions: rationale, risk and benefit

Pre-intervention myocardial stress is a good predictor of aortic valvoluplasty outcome for fetal critical aortic stenosis and evolving HLHS

Fetal critical aortic stenosis with evolving hypoplastic left heart syndrome (CAS-eHLHS) causes biomechanical and functional aberrations, leading to a high risk of progression to hypoplastic left heart syndrome (HLHS) at birth. Fetal aortic valvuloplasty (FAV) can resolve outflow obstruction and may reduce progression risk. However, it is currently difficult to accurately predict which patients will respond to the intervention and become functionally biventricular (BV) at birth, as opposed to becoming functionally univentricular (UV). This prediction is important for patient selection, parental counselling, and surgical planning. Therefore, we investigated whether biomechanics parameters from pre-FAV image-based computations could robustly distinguish between CAS-eHLHS cases with BV or UV outcomes in a retrospective cohort. To do so we performed image-based finite element biomechanics modelling of nine CAS-eHLHS cases undergoing intervention and six healthy fetal control hearts, and found that a biomechanical parameter, peak systolic myofibre stress, showed a uniquely large difference between BV and UV cases, which had a larger magnitude effect than echocardiography parameters. A simplified equation was derived for quick and easy estimation of myofibre stress from echo measurements via principal component analysis. When tested on a retrospective cohort of 37 CAS-eHLHS cases, the parameter outperformed other parameters in predicting UV versus BV outcomes, and thus has a high potential of improving outcome predictions, if incorporated into patient selection procedures. Physiologically, high myocardial stresses likely indicate a healthier myocardium that can withstand high stresses and resist pathological remodelling, which can explain why it is a good predictor of BV outcomes. KEY POINTS: Predicting the morphological birth outcomes (univentricular versus biventricular) of fetal aortic valvuloplasty for fetal aortic stenosis with evolving HLHS is important for accurate patient selection, parental counselling and management decisions. Computational simulations show that a biomechanics parameter, pre-intervention peak systolic myofibre stress, is uniquely robust in distinguishing between such outcomes, outperforming all echo parameters. An empirical equation was developed to quickly compute peak systolic myofibre stress from routine echo measurements and was the best predictor of outcomes among a wide range of parameters tested.

[Fetal aortic valvuloplasty in critical aortic stenosis: indication, technique and postnatal outcomes]

Aortic stenosis is a complex heart disease that involves the aortic valve and the left ventricle. Impairment of the left ventricle, abnormalities in its size, systolic and diastolic function determine the postnatal outcomes in the same way as the aortic valve. In the most severe forms, the left ventricle cannot provide systemic circulation at birth and the physiology is that of hypoplastic left heart syndrome. Fetal aortic valvuloplasty has been developed in the 90s to prevent in utero progression of aortic stenosis to hypoplastic left heart syndrome. In the present article, the most recently reported data about indications, procedure details and postnatal outcomes were reviewed.

Fluid Mechanics of Fetal Left Ventricle During Aortic Stenosis with Evolving Hypoplastic Left Heart Syndrome

In cases of fetal aortic stenosis and evolving Hypoplastic Left Heart Syndrome (feHLHS), aortic stenosis is associated with specific abnormalities such as retrograde or bidirectional systolic transverse arch flow. Many cases progressed to hypoplastic left heart syndrome (HLHS) malformation at birth, but fetal aortic valvuloplasty can prevent the progression in many cases. Since both disease and intervention involve drastic changes to the biomechanical environment, in-vivo biomechanics likely play a role in inducing and preventing disease progression. However, the fluid mechanics of feHLHS is not well-characterized. Here, we conduct patient-specific echocardiography-based flow simulations of normal and feHLHS left ventricles (LV), to understand the essential fluid dynamics distinction between the two cohorts. We found high variability across feHLHS cases, but also the following unifying features. Firstly, feHLHS diastole mitral inflow was in the form of a narrowed and fast jet that impinged onto the apical region, rather than a wide and gentle inflow in normal LVs. This was likely due to a malformed mitral valve with impaired opening dynamics. This altered inflow caused elevated vorticity dynamics and wall shear stresses (WSS) and reduced oscillatory shear index at the apical zone rather than mid-ventricle. Secondly, feHLHS LV also featured elevated systolic and diastolic energy losses, intraventricular pressure gradients, and vortex formation numbers, suggesting energy inefficiency of flow and additional burden on the LV. Thirdly, feHLHS LV had poor blood turnover, suggesting a hypoxic environment, which could be associated with endocardial fibroelastosis that is often observed in these patients.

Fetal Cardiac Interventions-Polish Experience from "Zero" to the Third World Largest Program

This article presents the technical aspects of the Polish fetal cardiac interventions (FCI) program, including preparation of the team and modifications in the technique of the procedure that aim to increase its safety for the mother and the fetus. Over 9 years, 128 FCI in 113 fetuses have been performed: 94 balloon aortic valvuloplasties (fBAV), 14 balloon atrioseptoplasties (fBAS) with stent (BAS+), 5 balloon atrioseptoplasties without stent placement (BAS-), and 15 fetal pulmonary valvuloplasties (fBPS). The technical success rate ranged from 80% (BAS-) to 89% (fBAV), while the procedure-related death rate (defined as death within 72 hours following the procedure) ranged from 7% (fBAV and fBPV) to 20% (BAS). There were 98 live births after all FCI (3 pregnancies continue). Median gestational age at delivery was 39 weeks in our center and 38 weeks in other centers.

Organ Dynamics and Hemodynamic of the Whole HH25 Avian Embryonic Heart, Revealed by Ultrasound Biomicroscopy, Boundary Tracking, and Flow Simulations

Congenital heart malformations occur to substantial number of pregnancies. Studies showed that abnormal flow biomechanical environments could lead to malformations, making it important to understand the biomechanical environment of the developing heart. We performed 4D high-frequency ultrasound scans of chick embryonic hearts at HH25 to study the biomechanics of the whole heart (atria and ventricle). A novel and high-fidelity motion estimation technique, based on temporal motion model and non-rigid image registration algorithm, allowed automatic tracking of fluid-structure boundaries from scan images, and supported flow simulations. Results demonstrated that atrial appendages were the most contractile portion of the atria, having disproportionately high contribution to atrial blood pumping for its volume in the atria. However, the atria played a small role in blood pumping compared to the ventricle, as it had much lower ejection energy expenditure, and as the ventricle appeared to be able to draw inflow from the veins directly during late diastole. Spatially and temporally averaged wall shear stresses (WSS) for various cardiac structures were 0.062–0.068 Pa, but spatial-averaged WSS could be as high as 0.54 Pa in the RV. WSS was especially elevated at the atrial inlet, atrioventricular junction, regions near to the outflow tract, and at dividing lines between the left and right atrium and left and right side of the ventricle, where septation had begun and the lumen had narrowed. Elevated WSS could serve as biomechanics stimulation for proper growth and development.

Perinatal outcomes and intrauterine complications following fetal intervention for congenital heart disease: systematic review and meta-analysis of observational studies

OBJECTIVE

To assess perinatal outcomes and intrauterine complications following fetal intervention for congenital heart disease (CHD).

METHODS

A systematic review and meta-analysis were performed following an electronic search of PubMed and Scopus databases (last searched August 2015). Perinatal outcomes that were assessed included fetal death, live birth, preterm delivery < 37 weeks' gestation and neonatal death. Intrauterine complications that were assessed included bradycardia requiring treatment and hemopericardium requiring drainage. Estimated proportions were reported as mean (95% CI). Inconsistency was assessed using the I² statistic.

RESULTS

An electronic search identified 2279 records, of which 29 studies (11 retrospective cohort and 18 case reports) were considered eligible for analysis. Fetal death after treatment of CHD by aortic valvuloplasty was reported in three studies, with a rate of 31% (95% CI, 9-60%), after pulmonary valvuloplasty in one study, with a rate of 25% (95% CI, 10-49%), after septoplasty in one study, with a rate of 14% (95% CI, 6-28%) and after pericardiocentesis and/or pericardioamniotic shunt placement in 24 studies, with a rate of 29% (95% CI, 18-41%). Bradycardia requiring treatment was reported after aortic valvuloplasty in two studies, with a rate of 52% (95% CI, 16-87%), after pulmonary valvuloplasty in one study, with a rate of 44% (95% CI, 23-67%), and after septoplasty in one study, with a rate of 27% (95% CI, 15-43%).

CONCLUSIONS

Current evidence on the effectiveness of prenatal intervention for CHD derives mostly from case reports and a few larger series; no study was randomized. Although the results of the meta-analysis are encouraging in terms of perinatal survival, they should be interpreted with caution when comparing with procedures performed after delivery. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Tissue Doppler imaging in fetuses with aortic stenosis and evolving hypoplastic left heart syndrome before and after fetal aortic valvuloplasty

OBJECTIVES

Fetal aortic valvuloplasty can improve filling and reduce afterload of the left ventricle in critical aortic stenosis. Success of an intrauterine intervention is currently measured by technical success, clinical survival and eventual postnatal biventricular physiology. In the present study we investigated the use of tissue Doppler imaging (TDI) to evaluate changes in ventricular function assessed before and after prenatal aortic valvuloplasty.

METHODS

Between October 2008 and December 2012, cardiac function was assessed by TDI before and after intervention in 23 fetuses that underwent technically successful valvuloplasty for critical aortic stenosis and in which postnatal outcome was known. The measurements were transformed into gestational age-independent Z-scores where appropriate.

RESULTS

Mean ± SD gestational age at intervention was 27.5 ± 3.1 weeks. Of the 23 fetuses, 14 had biventricular outcome. Before intervention all left ventricular (LV) TDI-derived parameters and mitral annular plane systolic excursion (MAPSE) were severely abnormal. It was possible to demonstrate considerably improved cardiac function after technically successful valvuloplasty. Among fetuses with postnatal biventricular outcome, TDI-derived LV myocardial peak velocity during early diastole (E') and myocardial peak velocity during systole in the ejection phase (S') significantly increased, E'/myocardial peak velocity during late diastole with atrial contraction (A') increased towards normal values, and LV transmitral-to-mitral-annular diastolic velocity ratio (E/E') and myocardial performance index (MPI') decreased but remained abnormally elevated. In addition, right ventricular A', S' and MPI' significantly improved after intervention.

CONCLUSION

Technically successful fetal aortic valvuloplasty led to significantly improved myocardial performance. It was possible to use TDI to detect distinct changes in ventricular function and TDI-derived parameters correlated with a biventricular outcome after birth. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Fetal intervention for critical aortic stenosis: advances, research and postnatal follow-up

PURPOSE OF REVIEW

Fetal aortic valvuloplasty is intended to alter the natural history of aortic stenosis evolving to hypoplastic left heart syndrome. The most recently reported data and advances on this procedure were reviewed.

RECENT FINDINGS

The highlights of the latest experience are the advances in further understanding of the prenatal and postnatal natural history of this disease, and the way in which fetal aortic valvuloplasty impacts on it, the identification of new predictors of biventricular outcome, and the report of postnatal survival of intervened patients. Recently reported short-term and middle-term results are encouraging. Experimental research on procedural aspects is ongoing, with no definite results. Multicenter studies are also ongoing.

SUMMARY

In recent years, there have been advances in the understanding of the prenatal and postnatal process of aortic stenosis evolving to hypoplastic left heart syndrome and the effects of fetal aortic valvuloplasty, as well as the need of adequate postnatal therapeutic strategies for these patients. Procedural aspects are being studied with animal models, but still need far more experience before human application. Long-term results are still to be discovered, and multicenter studies may provide a new perspective. Continuing research is mandatory so that ultimately fetal heart intervention finds its place among the therapeutic resources for congenital heart disease.