ABSTRACT
Devices CardioSEAL® and StarFLEX® are descendants of the original Clamshell® device. Clamshell consisted of two mirror-image umbrella-like square patches of polyester connected at their hubs. The metal framework was constructed of stainless steel wires radiating from the central hub to each of the four corners of the patch with a midpoint coil in the wire rib to achieve angulation, tension, and flexibility. The fabric was sewn to the stainless steel rib skeleton. Each square patch was rotated 45° relative to its opposing counterpart. When deployed, each side of the device was concave toward the septum, and the rib coils increased the closing tension at the corners. This device suffered, however, from a high rate of wire rib fractures due to metal fatigue and/or corrosion. Clamshell® was succeeded by CardioSEAL®, which substituted MP35N alloy for the stainless steel ribs and incorporated two tandem coil hinges in each rib. Bench testing and accumulated clinical experience have confirmed a dramatic reduction in rib fracture rate. This device is the version currently available in the United States (Figure 32.1). STARFlex® represents a further modification of this technology. It consists of a CardioSEAL® and includes nitinol springs that connect the edges of the opposing sides of the device. These springs traverse the defect such that, when each side of the device is deployed, they are stretched under tension (Figure 32.2). This tension serves two purposes: (1) it draws the edges of each side of the device more firmly and securely against the septum, and (2) it causes the device to self-center, ensuring more symmetric coverage over the entrance to and exit from the patent foramen ovale (PFO). These two effects result in a higher rate of immediate and complete defect closure and in the ability to close a somewhat larger defect with a somewhat smaller device.
