Ryan Rooke

Spinal cord stimulation protects against atrial fibrillation induced by tachypacing

BACKGROUND Spinal cord stimulation (SCS) has been shown to modulate atrial electrophysiology and confer protection against ischemia and ventricular arrhythmias in animal models. OBJECTIVE To determine whether SCS reduces the susceptibility to atrial fibrillation (AF) induced by tachypacing (TP). METHODS In 21 canines, upper thoracic SCS systems and custom cardiac pacing systems were implanted. Right atrial and left atrial effective refractory periods were measured at baseline and after 15 minutes of SCS. Following recovery in a subset of canines, pacemakers were turned on to induce AF by alternately delivering TP and searching for AF. Canines were randomized to no SCS therapy (CTL) or intermittent SCS therapy on the initiation of TP (EARLY) or after 8 weeks of TP (LATE). AF burden (percent AF relative to total sense time) and AF inducibility (percentage of TP periods resulting in AF) were monitored weekly. After 15 weeks, echocardiography and histology were performed. RESULTS Effective refractory periods increased by 21 ± 14 ms (P = .001) in the left atrium and 29 ± 12 ms (P = .002) in the right atrium after acute SCS. AF burden was reduced for 11 weeks in EARLY compared with CTL (P <.05) animals. AF inducibility remained lower by week 15 in EARLY compared with CTL animals (32% ± 10% vs 91% ± 6%; P <.05). AF burden and inducibility were not significantly different between LATE and CTL animals. There were no structural differences among any groups. CONCLUSIONS SCS prolonged atrial effective refractory periods and reduced AF burden and inducibility in a canine AF model induced by TP. These data suggest that SCS may represent a treatment option for AF.

Multicenter clinical experience with an atrial lead designed to minimize far-field R-wave sensing

AIMS To evaluate a novel atrial lead designed to reduce far-field sensing. METHODS AND RESULTS Sixty-three patients with standard pacing indications were randomized to receive an OptiSense 1699T (St Jude Medical, USA) or conventional pacing lead in the right atrium. Post-implant follow-up was conducted for all patients at 90 days and for a subset at 360 days. Standard electrical parameters were measured. Thresholds of sensing were determined for far-field ventricular signals. The number of inappropriate mode switches was determined from the stored intracardiac electrogram (IEGM). At 90 days, an IEGM Holter recorded 24 h of IEGM. With atrial sensitivity programmed at 0.3 mV, no far-field sensing occurred in the OptiSense group, but it did occur in 20% and 30% of the control group at 90 and 360 days, respectively. Inappropriate mode switching was observed in 4% of the OptiSense group in contrast to 23% of the control group. The IEGM Holter found no far-field sensing in the OptiSense group, but did find 83 023 far-field events from 22% of control patients. The standard electrical parameters of the OptiSense leads were acceptable. CONCLUSION The OptiSense lead reduced ventricular far-field sensing in the atrium while maintaining satisfactory pacing and sensing performance, resulting in less inappropriate mode switch.