Nonpulsatile total left ventricular support in pediatric patients

Development and Initial in Vivo Testing of a New Hydraulic Drive System (Paedipump) for Circulatory Support in Infants

The main limitation in the use of circulatory support in children is the lack of an adequate system with regard to size and pumping capacity Recently, two pneumatically driven ventricular support systems with low volume chambers for use in a pediatric population became available. We have developed a hydraulic drive system with an advantageous exact control of the stroke volume. The system enables two different modes of operation: the full-empty and the filled-empty modes. In both cases the ventricle is empty at the end of systole.

This new system was tested in experimental animals (6 pigs, body weight 9.5–14.0 kg) with normal and reduced left ventricular function (MAP<45 mmHg). A 25 ml ventricle (HIA-Medos) was implanted. The full-empty and the filled-empty mode used led to a significant load reduction, both in animals with normal and impaired cardiac function. Plasma lactate levels, pH-values and total body 0 2 consumption were in the normal range during circulatory support indicating adequate organ perfusion.

Results showed that sufficient ventricular support was achieved during all pumping modes due to the possibility of controlling and modifying the stroke volume of the hydraulically driven support system employed according to necessity. This is a promising feature for its future application in infants with congenital or acquired heart diseases.

Evaluation of a pulsatile pediatric ventricular assist device in an acute right heart failure model

BACKGROUND

The development of pulsatile ventricular assist devices for children has been limited mainly by size constraints. The purpose of this study was to evaluate the MEDOS trileaflet-valved, pulsatile, pediatric right ventricular assist device (stroke volume = 9 mL) in a neonatal lamb model of acute right ventricular failure.

METHODS

Right ventricular failure was induced in ten 3-week-old lambs (8.6 kg) by right ventriculotomy and disruption of the tricuspid valve. Control group 1 (n = 5) had no mechanical support whereas experimental group 2 (n = 5) had right ventricular assist device support for 6 hours. The following hemodynamic parameters were measured in all animals: heart rate and right atrial, pulmonary arterial, left atrial, and systemic arterial pressures. Cardiac output was measured by an electromagnetic flow probe placed on the pulmonary artery.

RESULTS

All results are expressed as mean +/- standard deviation and analyzed by Student's t test. A p value less than 0.05 was considered statistically significant. Base-line measurements were not significantly different between groups and included systemic arterial pressure, 80.6 +/- 12.7 mm Hg; right atrial pressure, 4.6 +/- 1.6 mm Hg; mean pulmonary arterial pressure, 15.6 +/- 4.2 mm Hg; left atrial pressure, 4.8 +/- 0.8 mm Hg; and cardiac output, 1.4 +/- 0.2 L/min. Right ventricular injury produced hemodynamics compatible with right ventricular failure in both groups: mean systemic arterial pressure, 38.8 +/- 10.4 mm Hg; right atrial pressure, 16.8 +/- 2.3 mm Hg; left atrial pressure, 1.4 +/- 0.5 mm Hg; and cardiac output, 0.6 +/- 0.1 L/min. All group 1 animals died at a mean of 71.4 +/- 9.4 minutes after the operation. All group 2 animals survived the duration of study. Hemodynamic parameters were recorded at 2, 4, and 6 hours on and off pump, and were significantly improved at all time points: mean systemic arterial pressure, 68.0 +/- 13.0 mm Hg; right atrial pressure, 8.2 +/- 2.3 mm Hg; left atrial pressure, 6.4 +/- 2.1 mm Hg; and cardiac output, 1.0 +/- 0.2 L/min.

CONCLUSIONS

The results demonstrate the successful creation of a right ventricular failure model and its salvage by a miniaturized, pulsatile right ventricular assist device. The small size of this device makes its use possible even in small neonates.

Extracorporeal membrane oxygenation for cardiac support in children

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) support for cardiac failure has been used in children since 1981 at the Children's Hospital in Pittsburgh. Most children required support after cardiac operations. Recently, however, a larger number of patients with decompensated cardiomyopathy or myocarditis have been supported with ECMO, which was used as a bridge to transplantation in most.

METHODS

From 1981 to 1994, 68 children were placed on ECMO for cardiac support.

RESULTS

The overall survival for the entire time period was 38%, with the more recent experience survival increased to 47%. In 14 children, ECMO was used as a bridge to transplantation, with 9 children receiving a heart transplant and 7 long-term survivors. Extracorporeal membrane oxygenation has also been used to resuscitate 11 children after sudden cardiac arrest, with a long-term survival of 53%.

CONCLUSIONS

We conclude that ECMO support for severe cardiac failure is effective. Patient selection and the use of heart transplantation for intractable heart failure have improved the overall survival.