nitinol and Heart-Diseases

In patients with non-valvular atrial fibrillation, efficacy of stroke prevention with oral anticoagulant therapy has been proved. Despite their high risk for thromboembolic events, there are substantial numbers of patients who are not candidates for long-term oral anticoagulant therapy, therefore the interest in alternative treatment strategies are in focus these days. The most common place within the heart for thrombus formation in patients with non-valvular atrial fibrillation is the left atrial appendage. Two devices specifically designed for percutaneous left atrial appendage closure are currently available in Europe: the WATCHMAN LAA system (Atritech, Inc) and the AMPLATZER Cardiac Plug (AGA Medical Corporation). Although present trial results (PLAATO, PROTECT AF) suggest that LAA closure may be performed at acceptable safety and it may reduce the long-term stroke risk, available data are still very limited. At present these procedures may be an acceptable alternative in selected high-risk patients with non-valvular atrial fibrillation who are not or suboptimal candidates for oral anticoagulant therapy. On 28. January, 2010 we performed the first three successful percutaneous left atrial appendage closure procedures in Gottsegen György Hungarian Institute of Cardiology in Hungary.

Topics: Administration, Oral; Aged; Alloys; Anticoagulants; Atrial Appendage; Atrial Fibrillation; Cardiac Surgical Procedures; Clinical Trials as Topic; Contraindications; Echocardiography, Transesophageal; Female; Heart Diseases; Humans; Hungary; Male; Middle Aged; Prosthesis Design; Radiography; Risk Assessment; Risk Factors; Septal Occluder Device; Stents; Stroke; Thoracoscopy; Thrombosis; Treatment Outcome

The field of interventional cardiovascular MRI is hampered by the unavailability of active guidewires that are both safe and conspicuous. Heating of conductive guidewires is difficult to predict in vivo and disruptive to measure using external probes. We describe a clinical-grade 0.035" (0.89 mm) guidewire for MRI right and left heart catheterization at 1.5 T that has an internal probe to monitor temperature in real-time, and that has both tip and shaft visibility as well as suitable flexibility.. The design has an internal fiberoptic temperature probe, as well as a distal solenoid to enhance tip visibility on a loopless antenna. We tested different tip-solenoid configurations to balance heating and signal profiles. We tested mechanical performance in vitro and in vivo in comparison with a popular clinical nitinol guidewire.. The solenoid displaced the point of maximal heating ("hot spot") from the tip to a more proximal location where it can be measured without impairing guidewire flexion. Probe pullback allowed creation of lengthwise guidewire temperature maps that allowed rapid evaluation of design prototypes. Distal-only solenoid attachment offered the best compromise between tip visibility and heating among design candidates. When fixed at the hot spot, the internal probe consistently reflected the maximum temperature compared external probes.Real-time temperature monitoring was performed during porcine left heart catheterization. Heating was negligible using normal operating parameters (flip angle, 45°; SAR, 1.01 W/kg); the temperature increased by 4.2°C only during high RF power mode (flip angle, 90°; SAR, 3.96 W/kg) and only when the guidewire was isolated from blood cooling effects by an introducer sheath. The tip flexibility and in vivo performance of the final guidewire design were similar to a popular commercial guidewire.. We integrated a fiberoptic temperature probe inside a 0.035" MRI guidewire. Real-time monitoring helps detect deleterious heating during use, without impairing mechanical guidewire operation, and without impairing MRI visibility. We therefore need not rely on prediction to ensure safe clinical operation. Future implementations may modulate specific absorption rate (SAR) based on temperature feedback.

Topics: Alloys; Animals; Cardiac Catheterization; Cardiac Catheters; Disease Models, Animal; Equipment Design; Heart Diseases; Magnetic Resonance Imaging, Cine; Magnetic Resonance Imaging, Interventional; Optical Fibers; Pliability; Swine; Temperature