Recording Intrinsic Nerve Activity at the Sinoatrial Node in Normal Dogs with High-density Mapping.

Background - It is known that autonomic nerve activity controls the sinus rate. However, the coupling between local nerve activity and electrical activation at the sinoatrial node (SAN) remains unclear. We hypothesized that we would be able to record nerve activity at the SAN to investigate if right stellate ganglion (RSG) activation can increase the local intrinsic nerve activity, accelerate sinus rate, and change the earliest activation sites (EASs). Methods - High-density mapping of the epicardial surface of the right atrium (RA) including the SAN was performed in 6 dogs during stimulation of the RSG, and after RSG stellectomy. A radiotransmitter was implanted into 3 additional dogs to record RSG and local nerve activity at the SAN. Results - Heart rate accelerated from 108±4 bpm at baseline to 125±7 bpm after RSG stimulation (P=0.001), and to 132±7 bpm after apamin injection (P<0.001). Both electrical RSG stimulation and apamin injection induced local nerve activity at the SAN with the average amplitudes of 3.60±0.72 µV and 3.86±0.56 µV, respectively. RSG stellectomy eliminated the local nerve activity and decreased the heart rate. In ambulatory dogs, local nerve activity at the SAN had a significantly higher average Pearson correlation to heart rate (0.72±0.02, P=0.001) than RSG nerve activity to HR (0.45±0.04 P=0.001). Conclusions - Local intrinsic nerve activity can be recorded at the SAN. Short bursts of these local nerve activities are present before each atrial activation during heart rate acceleration induced by stimulation of the right stellate ganglion.