Biventricular endocardial pacing and not MSP was superior to conventional CRT, but was highly site specific. Within individuals, however, different methods of stimulation are optimal and may need to be tailored to the underlying substrate.

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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, echocar-diography 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.

Aims Pre‐clinical work suggests that upper thoracic spinal cord stimulation (SCS) may have therapeutic effects in the treatment of heart failure (HF). We therefore aim to assess the safety and feasibility of SCS in HF patients. Methods and results A prospective, randomized, double‐blind, crossover pilot study was conducted in symptomatic HF patients receiving optimal medical therapy. Patients were implanted with an SCS system and randomized to an SCS‐ACTIVE, delivered at 90% paraesthesia threshold, or an SCS‐INACTIVE phase for 3 months, followed by a 1‐month washout period and crossover to the alternative phase. The safety of SCS therapy was assessed by death and cardiac events. Implantable cardioverter defibrillator (ICD) function in the presence of SCS was tested by defibrillation testing during SCS system implant and review of real‐time and stored electrograms during follow‐up. The efficacy of SCS therapy was assessed by changes in patient symptoms, LV function, and BNP level. Nine patients were investigated. In all cases, ICD sensing, detection, and therapy delivery were unaffected by SCS. During follow‐up, one patient died and one was hospitalized for HF while in the SCS‐INACTIVE phase, and two patients had HF hospitalizations during the SCS‐ACTIVE phase. Symptoms were improved in the majority of patients with SCS, while markers of cardiac structure and function were, in aggregate, unchanged. Conclusion This study shows that an SCS system can be safely implanted in patients with advanced HF and that the SCS system does not interfere with ICD function.

Cardiac resynchronization therapy (CRT) restores synchrony in heart failure patients. However, a significant proportion of patients implanted with CRT devices do not realize any benefit from CRT. Placing a left ventricular (LV) lead at the sites of electrical or mechanical delay has been advocated to maximize response to CRT, but there is currently no technique described to measure mechanical delay in real-time. We describe a novel technique that can be used intraoperatively to assess mechanical and electrical activation of the coronary sinus for guidance of LV pacing site optimization during CRT implantation.