The Amplatzer Membranous VSD Occluder and the vulnerability of the atrioventricular conduction system

Transcatheter closure of ventricular septal defects with the Amplatzer Membranous VSD Occluder has yielded promising initial results, but disturbances of conduction, including complete heart block, have been reported. We report our experience with the Amplatzer occluder in 35 patients with a median age 4.5 years, the defects being sized angiographically at 4.4 plus or minus 1.1 millimetres, with a range from 3 to 8 millimetres, and the size of the occluder varying from 4 to 12 millimetres. Over a median follow-up of 2.5 years, the rate of complete closure was 87% and 91%, at 1 and 2 years respectively, while 2 patients required surgical closure of the defect subsequent to the insertion of the device. Persistent regurgitation across the tricuspid valve related to the occluder was observed in 3 patients, and in 6 patients across the aortic valve. Abnormalities of conduction related to the procedure were noted in 7 patients, one-fifth of the cohort. The disturbances were transient in 1 patient, but permanent in 6, in one of the latter progressing after 6 months from left bundle branch block to intermittent Mobitz II second-degree atrioventricular block in association with expansion of the occluder. We conclude that transcatheter closure of perimembranous ventricular septal defects with the Amplatzer occluder is effective with limited complications, but the incidence of immediate and progressive disturbances of conduction related to the proximity of conduction tissues to the rims of the occluder stress the importance of larger and longer studies to assess the safety of this procedure.