[Value of cardiac pacing in hypertrophic obstructive cardiomyopathy refractory to medical treatment].

Recent studies have shown that dual-chamber cardiac pacing could improve patients with hypertrophic obstructive cardiomyopathy resistant to medical treatment. After a brief historical review, the authors report the present status of this original therapeutic option. The results of different studies are in agreement and show that the functional improvement is associated with a large reduction of the intraventricular pressure gradient with permanent DDD pacing. Although the exact mechanism of the improvement remains unknown, all groups underline the importance of complete and permanent ventricular capture. This requires precise regulation of the atrioventricular delay which in most cases must be programmed at a value inferior to 90 ms, which compromises ventricular filling which is already abnormal under basal conditions. The inefficacy of pacing in some cases is explained by the necessity of selecting a very short atrioventricular delay which alters diastolic function and finally masks the benefits of ventricular capture. In this particular situation, the authors propose improving atrioventricular synchrony by pharmacological prolongation of the PR interval, or, when unsuccessful, by ablation of the atrioventricular junction. This attitude was adopted in 5 cases when pacing with an AVD programmed between 20 and 70 ms, provided only a partial haemodynamic result. Improved atrioventricular synchrony allowed selection of an AVD of 100 to 150 ms, so reducing the gradient by more than 70%, compared with 30% under the initial programming parameters. The authors conclude that a positive and sustained benefit of cardiac pacing can only be obtained by an individualised regulation of pacing parameters to optimize atrioventricular synchrony which seems to be the key element of success.