This study aims to investigate the safety and efficacy of transcatheter microguidewire drilling (TMD) for transseptal left atrial access in patients with abnormal atrial septal morphology.

Despite the widespread application and decades of experience, Brockenbrough-needle transseptal puncture still risks cardiac perforations and secondary pericardial effusion/tamponade, especially in patients with abnormal atrial septal morphology. To facilitate atrial septal crossing, different methods and devices have been developed, including radiofrequency energy, excimer laser, SafeSept wire and so on. However, these are still limited by availability and cost, and the advantages might be further offset by the potential risks. In addition, these methods are performed mainly with the linear insertion technique, which might result in less forward-force to penetrate atrial septum and displacement of needle-tip. Therefore, it is necessary to develop a safe, available and low-cost transseptal procedure for these patients.

Through a Brockenbrough needle, the hard "back-end" of the microguidewire (0.014-inch) has the potential to drill through the atrial septum with ease. Compared with a standard linear insertion technique, the penetration might be improved and less force is required with the bidirectional rotation technique, and the related risks might be reduced with the modified TSP due to the thin microguidewire. After the passage of the needle, the soft-end of microguidewire can be introduced into left pulmonary superior vein, which can become a safe rail for the introduction of puncture dilator/sheath.

In this study, we examined the effectiveness and safety of microguidewire-assisted TSP for patients with complex atrial septum.

Inclusion Criteria: 1) Patients with atrial septal aneurysm (a bulging of the atrial septum of at least 10 mm beyond the plane of the atrial septum into either the right or left atrium); 2) Or patients with previous multiple transseptal punctures (≧2); 3) Or patients with thickened atrial septum (thickness ≧3 mm); 4) Or patients with enlarged right atrium (≧ 6 cm) and diminished left atrium (< 3 cm); 5) Or patients with prior mitral valve surgery; 6) Or patients with atrial baffles.

Exclusion Criteria: 1) Associated atrial septal defect or patent foramen ovale; 2) Associated interrupted inferior vena cava; 3) Presence of implanted cardiac devices; 4) Echocardiographic evidence of intracardiac thrombus, mass, tumor or vegetation; 5) Thromboembolic events within the last 6 months; 6) Patients unable to grant informed, written consent.