Device closure of atrial septal defects using the CardioSEAL/STARFlex devices
An atrial septal defect (ASD) results in left to right shunting with resultant right heart volume overload, increased pulmonary flow, increased pulmonary vascular shear stress, and, in up to 25% of patients, the development of pulmonary hypertension in young to middle adult years.1,2 The vast majority of patients are diagnosed in childhood on routine physical examination due to an audible pulmonary flow murmur associated with the increased volume through the pulmonary valve. Approximately 3-5% will have symptoms in childhood of increased respiratory effort, frequent respiratory infections, and even failure to thrive, even as early as a few months.3 More commonly, symptoms develop in young to middle adult years as insidious mild exercise intolerance. Some adult patients will present with atrial arrhythmias due to right atrium (RA) dilation, most typically PACs but occasionally atrial flutter or fibrillation. Paradoxical embolus-related stroke or TIA is a precipitating event for some. Many adult patients are diagnosed incidentally when evaluated for palpitations or chest pains unrelated to the ASD. Once an ASD has been diagnosed a complete
transthoracic echocardiogram should be performed to evaluate the suitability of device closure. This includes specific attention to the pulmonary vein drainage as well as the size and location of the defect, including tissue rims to the AV valves, inferior vena cava (IVC), right pulmonary veins, aortic valve, and roof of the atrium. If the transthoracic study is inadequate to delineate these structures then transesophageal echo should be performed. The CardioSEAL/STARFlex device system is effective at closing defects of 22 mm diameter (balloon occlusion) if all rims are present, and ≤20 mm diameter if there is absence of the aortic knob rim. A device to occlusion diameter of >2:1 is preferred. Patients with inadequate AV valve, IVC, atrial roof, and pulmonary vein rims can not be effectively closed with the CardioSEAL/STARFlex devices. If patients have a history of frequent palpitations a 24-hour Holter moniter should be performed prior
to device closure. If an accessory pathway tachycardia exists, and ablation may be beneficial, it should be performed prior to closure of the septal defect for ease of access to the left atrium. Preprocedural evaluation includes a CBC with dif-
ferential and type and screen for children with the addition of lytes, BUN, Cr, PT, PTT, INR, and glucose for adults. Patients begin 81 mg aspirin (5 mg/kg if <16 kg) daily 3 days before the procedure.The catheterization is performed as an outpatient procedure for the majority, with admission the morning of the procedure and discharge 6 hours after completion. The procedures are performed under moderate conscious sedation. Fluoroscopic and echocardiographic guidance are used for ASD assessment and device positioning. If patients are < 4 years of age transthoracic echo usually suffices; older patients require an additional venous sheath for intracardiac echocardiography. Some operators still prefer general anesthesia with transesophageal echocardiography. The CardioSEAL/STARFlex device system consists
of the device and the delivery catheter system. The device comprises two metal MP35N frameworks, each covered by a polyester fabric patch and, in the case of the STARFlex device, a Nitinol centering spring (Figure 18.1). From the proximal umbrella frame a pin extends at 90° to the device for attachment to the delivery catheter system. The Nitinol microsprings are attached between the two frameworks at the umbrella tips to align the device centrally within the defect.The devices come in sizes of 17, 23, 28, 33, and 40 mm diameter. The delivery system consists of a loading tube that facilitates folding of the umbrellas flat with attachment to the delivery catheter/cable (Figure 18.2). The handle on the delivery catheter has a button slide that opens the forceps tip of the cable that locks onto the pin on the proximal frame of the device. A slot in the forceps tip allows free movement of the device independent of the cable to facilitate alignment with the atrial septum. Once the device is loaded into the loading tube and attached to the delivery catheter, the loading tube is inserted through the back bleed valve of the long sheath and the device advanced through the long sheath by pushing the delivery catheter.