[Predicting the risk of atrioventricular conduction lesions after percutaneous septal ablation for obstructive hypertrophic cardiomyopathy].

Background And Introduction: Damage to the AV conduction system is a frequent complication of percutaneous septal ablation (PTSMA) that needs early and reliable identification of those patients (pts.) at risk for complete heart block (CHB) and subsequent pacemaker implantation.

Methods And Results: In the first 39 pts. who underwent PTSMA in 1996, AV conduction recovery needed up to 11 days. One pt. suffered from unexpected CHB after 9 days. Seven pts. who needed a DDD pacemaker (DDD-PM) were compared to those without conduction disturbances. A score was established which identified all DDD-PM candidates retrospectively if they presented with >12 score points. In the following 137 consecutive pts. treated in 1997 and 1998, this score was applied prospectively, and again correctly identified all candidates for a DDD-PM. In addition, a low risk group was identified with <8 score points. From 1999 on, the score was applied in routine clinical decision-making in 120 consecutive pts. with respect to DDD-PM implantation. All low risk pts. (<8 points) remained free from bradycardias, while 2/54 pts. (4%) of the intermediate risk group, and 20/23 pts. (87%) of the high risk group had to undergo DDD-PM implantation. Pts. with a first-degree AV block or those with a right bundle branch block at baseline had no excess risk, while 50% of the pts. with a left bundle branch block (LBBB) needed a DDD-PM.

Conclusions: Based on pre-interventional data and careful monitoring of the first 48 hours after PTSMA, identification of pts. at risk for CHB and subsequent DDD-PM implantation seems to be possible. Pts. with a score <8 seem to be at low, those with >12 points at high risk. In the remaining cases watchful waiting with prolonged monitoring may allow AV conduction to recover, thus, reducing the number of unnecessary DDD-PM implantations. In cases with LBBB at baseline, however, implantation of a DDD-PM should be considered first-line therapy.