Human fetal hearts with tetralogy of Fallot have altered fluid dynamics and forces.

Studies have suggested the effect of blood flow forces in pathogenesis and progression of some congenital heart malformations. It is therefore of interest to study the fluid mechanic environment of the malformed prenatal heart, such as the tetralogy of Fallot (TOF), especially when little is known about fetal TOF. In this study, we performed patient-specific ultrasound-based flow simulations of three TOF and seven normal human fetal hearts. TOF right ventricles (RVs) had smaller end-diastolic volumes (EDVs) but similar stroke volumes (SVs), whereas TOF left ventricles (LVs) had similar EDVs but slightly increased SVs compared with normal ventricles. Simulations showed that TOF ventricles had elevated systolic intraventricular pressure gradient (IVPG) and required additional energy for ejection but IVPG elevations were considered to be mild relative to arterial pressure. TOF RVs and LVs had similar pressures because of equalization via ventricular septal defect (VSD). Furthermore, relative to normal, TOF RVs had increased diastolic wall shear stresses (WSS) but TOF LVs were not. This was caused by high tricuspid inflow that exceeded RV SV, leading to right-to-left shunting and chaotic flow with enhanced vorticity interaction with the wall to elevate WSS. Two of the three TOF RVs but none of the LVs had increased thickness. As pressure elevations were mild, we hypothesized that pressure and WSS elevation could play a role in the RV thickening, among other causative factors. Finally, the endocardium surrounding the VSD consistently experienced high WSS because of RV-to-LV flow shunt and high flow rate through the over-riding aorta. NEW & NOTEWORTHY Blood flow forces are thought to cause congenital heart malformations and influence disease progression. We performed novel investigations of intracardiac fluid mechanics of tetralogy of Fallot (TOF) human fetal hearts and found essential differences from normal hearts. The TOF right ventricle (RV) and left ventricle had similar and elevated pressure but only the TOF RV had elevated wall shear stress because of elevated tricuspid inflow, and this may contribute to the observed RV thickening. TOF hearts also expended more energy for ejection.

Fluid mechanics of human fetal right ventricles from image-based computational fluid dynamics using 4D clinical ultrasound scans.

There are 0.6-1.9% of US children who were born with congenital heart malformations. Clinical and animal studies suggest that abnormal blood flow forces might play a role in causing these malformation, highlighting the importance of understanding the fetal cardiovascular fluid mechanics. We performed computational fluid dynamics simulations of the right ventricles, based on four-dimensional ultrasound scans of three 20-wk-old normal human fetuses, to characterize their flow and energy dynamics. Peak intraventricular pressure gradients were found to be 0.2-0.9 mmHg during systole, and 0.1-0.2 mmHg during diastole. Diastolic wall shear stresses were found to be around 1 Pa, which could elevate to 2-4 Pa during systole in the outflow tract. Fetal right ventricles have complex flow patterns featuring two interacting diastolic vortex rings, formed during diastolic E wave and A wave. These rings persisted through the end of systole and elevated wall shear stresses in their proximity. They were observed to conserve ∼25.0% of peak diastolic kinetic energy to be carried over into the subsequent systole. However, this carried-over kinetic energy did not significantly alter the work done by the heart for ejection. Thus, while diastolic vortexes played a significant role in determining spatial patterns and magnitudes of diastolic wall shear stresses, they did not have significant influence on systolic ejection. Our results can serve as a baseline for future comparison with diseased hearts.

Coronary manifestations of Kawasaki Disease in computed tomography coronary angiography.

Coronary arteritis in Kawasaki disease can lead to serious complications such myocardial infarction and sudden death. The identification of coronary manifestations with a method that is minimally invasive and of low radiation exposure is therefore important in paediatric patients with Kawasaki disease. Coronary CT angiography can be an attractive alternative to invasive coronary angiography. This paper describes imaging techniques for coronary CT angiography in pediatric patients and demonstrates the spectrum of cardiovascular manifestations in patients with Kawasaki disease.

Peristaltic-Like Motion of the Human Fetal Right Ventricle and its Effects on Fluid Dynamics and Energy Dynamics.

In both adult human and canine, the cardiac right ventricle (RV) is known to exhibit a peristaltic-like motion, where RV sinus (inflow region) contracts first and the infundibulum (outflow region) later, in a wave-like contraction motion. The delay in contraction between the sinus and infundibulum averaged at 15% of the cardiac cycle and was estimated to produce an intra-ventricular pressure difference of 15 mmHg. However, whether such a contractile motion occurs in human fetuses as well, its effects on hemodynamics remains unknown, and are the subject of the current study. Hemodynamic studies of fetal hearts are important as previous works showed that healthy cardiac development is sensitive to fluid mechanical forces. We performed 4D clinical ultrasound imaging on eight 20-weeks old human fetuses. In five fetal RVs, peristaltic-like contractile motion from the sinus to infundibulum ("forward peristaltic-like motion") was observed, but in one RV, peristaltic-like motion was observed from the infundibulum to sinus ("reversed peristaltic-like motion"), and two RVs contraction delay could not be determined due to poor regression fit. Next, we performed dynamic-mesh computational fluid dynamics simulations with varying extents of peristaltic-like motions for three of the eight RVs. Results showed that the peristaltic-like motion did not affect flow patterns significantly, but had significant influence on energy dynamics: increasing extent of forward peristaltic-like motion reduced the energy required for movement of fluid out of the heart during systolic ejection, while increasing extent of reversed peristaltic-like motion increased the required energy. It is currently unclear whether the peristaltic-like motion is an adaptation to reduce physiological energy expenditure, or merely an artefact of the cardiac developmental process.

Aortopulmonary window: a single institution surgical experience.

BACKGROUND: Aortopulmonary window is a rare cardiac anomaly. We report our experience with this rare lesion and highlight the criteria for treating this defect without the use of cardiopulmonary bypass. METHODS: From May 2007 to April 2012, 10 patients, aged 1 to 10 months and weighing 3.4 to 5.5 kg, were operated on by a single surgeon using both off-pump and standard techniques. All patients underwent preoperative and postoperative echocardiographic assessment, and were followed up with clinical examinations and echocardiography. RESULTS: There was no operative death and all patients were alive at the last follow-up. No major morbidities were noted. Two cases were operated on off-pump and they had shorter intensive care unit stays. All patients were in New York Heart Association class I on follow-up, with no residual shunt noted in follow-up echocardiograms. CONCLUSIONS: The surgical closure of aortopulmonary window carries a low surgical risk. Early surgical closure prevents the development of pulmonary vascular disease and achieves good immediate and long-term outcomes. Off-pump repair techniques, when used judiciously, have a place in the treatment of this defect.