In vitro hemodynamic performance of a blood pump for self-powered venous assist in univentricular hearts

Univentricular heart anomalies represent a group of severe congenital heart defects necessitating early surgical intervention in infancy. The Fontan procedure, the final stage of single-ventricle palliation, establishes a serial connection between systemic and pulmonary circulation by channeling venous return to the lungs. The absence of the subpulmonary ventricle in this peculiar circulation progressively eventuates in failure, primarily due to chronic elevation in inferior vena cava (IVC) pressure. This study experimentally validates the effectiveness of an intracorporeally-powered venous ejector pump (VEP) in reducing IVC pressure in Fontan patients. The VEP exploits a fraction of aortic flow to create a jet-venturi effect for the IVC, negating the external power requirement and driveline infections. An invitro Fontan mock-up circulation loop is developed and the impact of VEP design parameters and physiological conditions is assessed using both idealized and patient-specific total cavopulmonary connection (TCPC) phantoms. The VEP performance in reducing IVC pressure exhibited an inverse relationship with the cardiac output and extra-cardiac conduit (ECC) size and a proportional relationship with the transpulmonary pressure gradient (TPG) and mean arterial pressure (MAP). The ideal VEP with fail-safe features provided an IVC pressure drop of 1.82 ± 0.49, 2.45 ± 0.54, and 3.12 ± 0.43 mm Hg for TPG values of 6, 8, and 10 mm Hg, respectively, averaged over all ECC sizes and cardiac outputs. Furthermore, the arterial oxygen saturation was consistently maintained above 85% during full-assist mode. These results emphasize the potential utility of the VEP to mitigate elevated venous pressure in Fontan patients.

In Silico Evaluation of a Self-powered Venous Ejector Pump for Fontan Patients

PURPOSE

The Fontan circulation carries a dismal prognosis in the long term due to its peculiar physiology and lack of a subpulmonic ventricle. Although it is multifactorial, elevated IVC pressure is accepted to be the primary cause of Fontan's high mortality and morbidity. This study presents a self-powered venous ejector pump (VEP) that can be used to lower the high IVC venous pressure in single-ventricle patients.

METHODS

A self-powered venous assist device that exploits the high-energy aortic flow to lower IVC pressure is designed. The proposed design is clinically feasible, simple in structure, and is powered intracorporeally. The device's performance in reducing IVC pressure is assessed by conducting comprehensive computational fluid dynamics simulations in idealized total cavopulmonary connections with different offsets. The device was finally applied to complex 3D reconstructed patient-specific TCPC models to validate its performance.

RESULTS

The assist device provided a significant IVC pressure drop of more than 3.2 mm Hg in both idealized and patient-specific geometries, while maintaining a high systemic oxygen saturation of more than 90%. The simulations revealed no significant caval pressure rise (< 0.1 mm Hg) and sufficient systemic oxygen saturation (> 84%) in the event of device failure, demonstrating its fail-safe feature.

CONCLUSIONS

A self-powered venous assist with promising in silico performance in improving Fontan hemodynamics is proposed. Due to its passive nature, the device has the potential to provide palliation for the growing population of patients with failing Fontan.

Mechanisms of exercise-induced pulmonary hypertension in patients with cardiac septal defects

The objective of this study was to investigate mechanisms of exercise-induced pulmonary hypertension in patients with congenital cardiac septal defects. This was a randomized, placebo controlled, crossover drug trial in a single national pediatric cardiology centre that performs congenital cardiac defect surgery. There were 14 patients with cardiac septal defects and known exercise-induced pulmonary hypertension. The intervention consisted of 50 mg oral sildenafil versus placebo. Measurements included supine bicycle exercise echocardiography and oxygen uptake. The outcome measure was right-ventricular systolic pressure as estimated by Doppler tracings of tricuspid regurgitant jet as well as systolic and diastolic longitudinal myocardial velocities by color tissue Doppler echocardiography. Sildenafil did not change exercise right-ventricular systolic pressure during exercise; however, decreased systemic systolic pressure was seen. Enhanced biventricular longitudinal function with sildenafil compared with placebo was indicated by greater tissue Doppler velocities and displacement measurements during exercise. Finally, a less steep increase of right-ventricular pressure during exercise was associated with greater left-ventricular diastolic myocardial tissue Doppler velocity. Exercise-induced pulmonary hypertension in cardiac septal defects does not seem to have a pulmonary vasoconstrictive component, but it may be related to left-ventricular filling pressure. Furthermore, sildenafil improved biventricular systolic performance in this patient group, possibly related to decreased systemic afterload.

Motor and social development in 6-month-old children with congenital heart defects

OBJECTIVE

To assess whether the development of children with varying severity of congenital heart defect (CHD) differs from that of children without CHD at age 6 months.

STUDY DESIGN

A total of 236 children with CHD were compared with 61 032 children from the Norwegian Mother and Child Cohort Study conducted by the Norwegian Institute of Public Health. Diagnostic and treatment information was retrieved from a nationwide CHD registry. Four groups of CHD were distinguished: mild (n = 92), moderate (n = 50), severe (n = 70), and CHD with comorbidity (n = 24). At child age 6 months, the children's mothers reported on motor and social development by using the Mother and Child Questionnaire.

RESULTS

After adjusting for confounders (ie, birth weight), severe CHD increased the odds of gross motor impairment (odds ratio [OR], 3.78; 95% CI, 1.97-7.25) and fine motor impairment (OR, 2.04; 95% CI, 0.96-4.33). CHD with co-morbidity (eg, intestinal malformations) increased the odds of gross motor impairment (OR, 3.00; 95% CI, 0.95-9.51), fine motor impairment (OR, 5.47; 95% CI, 2.03-14.74), and social impairment (OR, 3.43; 95% CI, 1.40-8.41).

CONCLUSION

Increased odds of motor impairment are present already in infancy in severe CHD and CHD with comorbidity. CHD with comorbidity increases the odds of social impairment.

Treatment of patients with Eisenmenger's syndrome with Bosentan

We treated prospectively 14 patients with Eisenmenger's syndrome, with a mean age of 10 years, ranging from 3 to 18 years. Treatment continued for 12 months, and demonstrated a lasting symptomatic improvement, but no improvement in terms of mean saturation of oxygen over 24 hours. Exercise capacity, as judged by peak uptake of oxygen, worsened in the six patients able to perform a treadmill test. The symptomatic benefit from dual blockage of endothelin receptors in these patients may be due to mechanisms other than selective pulmonary vasodilatation alone.

Natriuretic peptides as markers of patent ductus arteriosus in preterm infants

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HTR polymer facial implants: a five-year clinical experience

Forty-three patients at two different international sites underwent onlay facial augmentation of the malar, paranasal, and chin regions using 61 HTR polymer preformed implants. All implants were placed intraorally and rigidly fixed with a titanium screw. Over postoperative periods ranging from two to five years, one implant was removed because of infection. Two other implants in patients with rheumatic and connective tissue disease were removed because of persistent pain and erythema. Another peri-implant infection was treated successfully without removal. One-year postoperative radiographs in patients with chin implants demonstrated no underlying bone resorption. This porous polymeric material appears to offer clinical results comparable to other alloplastic materials for onlay facial skeletal augmentation.