The effect of dual chamber pacing on left ventricular peak dp/dt, and influence of ventricular pacing site and intravenous metoprolol administration.

The aim of this study is to evaluate the influence of atrioventricular dela y (AVD), ventricular pacing site and adjuncted beta-blocker therapy on the effect of temporary dual chamber (DDD) pacing on the left ventricular (LV) peak dp/dt. Peak dp/dt and other LV pressure parameters were measured befor e and during DDD pacing in 15 patients (5 female) following their diagnosti c cardiac catheterisation procedures. Their mean age and LV ejection fracti on was 56+10 years and 64+13 % respectively. Three series of pacing were do ne: In the Ist, 2nd and 3rd series the ventricular electrode was placed to the outflow tract of the right ventricle (RV), to the RV apex, and again to the RV apex but 5 minutes after IV 15 mg metoprolol infusion. At each seri es, DDD pacing was started at 30 ms AVD and it was increased 10 ms every 20 s until reaching 150 ms. Results were compared with their initial values a nd the values of the same steps in the other series. In all three series LV dp/dt decreased significantly after DDD pacing (p<0.05). Increasing of AVD diminished this effect. There were no significant differences between the measurements obtained in the Ist and 2nd series, however measurements obtai ned in the 3rd series were significantly lower than the others at all steps (p<0.05). It is concluded that DDD pacing reduces the LV peak dp/dt. Pacin g of the ventricle form RV outflow tract or apex does not change this effec t. Negative inotropic effects of DDD pacing and the beta-blocking therapy ( metoprolol) seems to be independent of each other but additive.