Ann Thorac Surg 1997;63:1144
© 1997 The Society of Thoracic Surgeons
Invited Commentary
Invited Commentary
Pedro J. del Nido, MD
Department of Cardiac Surgery, Harvard Medical School, Children's Hospital, 300 Longwood Ave, Boston, MA 02115
See also page 1138.
Mechanical circulatory support systems designed for children must surmount obstacles not present for systems designed for adults. In children, the large range in patient size, faster heart rates, and anatomic variability require that support systems be capable of achieving a wide range of flows and accept a variety of cannula sizes. Simple miniaturization of existing adult devices has proved to be a significant engineering challenge; therefore, new devices designed specifically for children offer the best hope of successful clinical application. Due to development costs and the potentially larger application in adult patients, few manufacturers have expressed interest in pediatric support systems despite the need for such devices. Consequently, mechanical circulatory support in children is most frequently achieved with either a standard roller pump and bladder box such as with an extracorporeal membrane oxygenator or a centrifugal pump with a smaller pump head. Both of these systems are nonpulsatile, and durability remains a problem with the centrifugal pump.
The MEDOS HIA-VAD described by Konertz and colleagues therefore represents a significant step forward toward the elusive goal of a small, portable, or even implantable ventricular assist device with sufficient durability to be used for chronic support in children. The MEDOS HIA-VAD pulsatile system has several design features, in addition to its multiple sizes, that make it attractive. The clear outer plastic design, three-leaflet polyurethane valves, and ability to achieve pulse rates up to 180/min are distinct advantages. The preliminary results reported by Konertz and colleagues with 4 of 6 children surviving long term are encouraging and comparable if not better than the 40% to 50% survival reported by most centers with extracorporeal membrane oxygenation or centrifugal pump support in children. Also, the ability to wean from ventilatory support and even extubate older children is of prime importance and gives the hope that such a device may be effective for chronic support, particularly for children awaiting transplantation.
The continued need for anticoagulation with heparin and the report of a thromboembolism developing in 1 child despite the anticoagulation regimen underscores the need for further refinements to this very promising new type of ventricular assist system. Incorporation of heparin bonding of the bladder and valve may help to overcome these problems. Nevertheless, the preliminary results with this type of pneumatic assist device designed specifically for pediatric use are sufficiently encouraging that a wider study with a larger cohort of patients is certainly indicated.
Related Article
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Clinical Experience With the MEDOS HIA-VAD System in Infants and Children: A Preliminary Report
- Wolfgang Konertz, Holger Hotz, Martin Schneider, Mathias Redlin, and Helmut Reul
Ann. Thorac. Surg. 1997 63: 1138-1144.
[Abstract]
[Full Text]
