Carotid sinus syndrome: acute hemodynamic evaluation of a dual chamber pacing mode.

Cardiac pacing is the treatment of choice in patients with carotid sinus syndrome (CSS). Three different pacing modes were tested in 20 patients (16 males, 4 females; mean age 75 +/- 9 years) with documented symptomatic CSS. Three carotid sinus massages (CSM) were performed in each supine patient successively paced in random order in: DDI--the reference pacing mode; DDD--automatic mode conversion (DDD/AMC) allowing automatic switching from AAI to DDD when AV block occurs; DDD/AMC plus atrial acceleration (DDD/AMC+acc); and OOO (CSM without pacing) to determine whether the vasodepressive effect was still present 10 minutes after the preceding CSM. Intraarterial blood pressure was continuously monitored. Results were expressed as the value of the mean systolic BP at T0 + 3 s + 6 s ... T0 + 30 s divided by the value of the mean systolic blood pressure prior to onset of CSM. The drop in arterial blood pressure was more severe in the DDI mode than in DDD/AMC (P < 0.001) and DDD/AMC+acc (P < 0.0001) in 20 patients. In the OOO mode, the drop in arterial blood pressure was most marked and greater than in the DDI mode (P < 0.0001). The average time between start of the CSM and onset of the drop in blood pressure was the same in the three dual chamber modes. We conclude that the DDD/AMC mode significantly improves the vasodepressor response to CSM compared to the DDI mode. There is a current trend favoring DDD/AMC+acc over DDD/AMC.