CAROTID-SINUS SYNDROME - ACUTE HEMODYNAMIC EVALUATION OF A DUAL-CHAMBER PACING MODE

Cardiac pacing is the treatment of choice in patients with carotid sin us syndrome (CSS). Three different pacing modes were tested in 20 pati ents (16 males, 4 females; mean age 75 +/- 9 years) with documented sy mptomatic CSS. Three carotid sinus messages (CSM) were performed in ea ch supine patient successively paced in random order in: DDI-the refer ence pacing mode; DDD-automatic mode conversion (DDD/AMC) allowing aut omatic switching from AAI to DDD when AV block occurs; DDD/AMC plus at rial acceleration (DDD/AMC + ace); and OOO (CSM without pacing) to det ermine whether the vasodepressive effect was still present 10 minutes after the preceding CSM. Intraarterial blood pressure Mras continuousl y monitored. Results were expressed as the value of the mean systolic BP at TO + 3 s + 6 s... TO + 30 s divided by the value of the mean sys tolic 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) a nd DDD/ RMC + ace (P < 0.0001) in 20 patients. In the OOO mode, the dr op 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 tile three dual c hamber 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 + tree over DDD/AMC.